A fasciculation "muscle twitch" is a small, local, involuntary muscle contraction (twitching) visible under the skin arising from the spontaneous discharge of a bundle of skeletal muscle fibers. Fasciculations have a variety of causes, the majority of which are benign, but can also be due to disease of the motor neurons.
Fasciculations with Suxemethonium:
There are two phases to the blocking effect of suxamethonium. The first is due to the prolonged stimulation of the acetylcholine receptor results first in disorganized muscle contractions (fasciculations), as the acetylcholine receptors are stimulated. On stimulation, the acetylcholine receptor becomes a general ion channel, so there is a high flux of potassium out of the cell, and of sodium into the cell, resulting in an endplate potential less than the action potential. So, after the initial firing, the cell remains refractory.
Fiberoptic endotracheal intubation is a useful technique in a number of situations. It can be used when the patient's neck cannot be manipulated, as when the cervical spine is not stable. It can also be used when it is not possible to visualize the vocal cords because a straight line view cannot be established from the mouth to the larynx. Fiberoptic intubation can be performed either awake or under general anesthesia and it can be performed either as the initial management of a patient known to have a difficult airway, or as a backup technique after direct laryngoscopy has been unsuccessful.
While the sniffing position is required for most direct laryngoscopies, it is not essential for fiberoptic guided intubation. The chin lift and jaw thrust manoeuvers, and protrusion of the tongue, move the soft tissues and improve the view through the fiberscope. These manoeuvers also help to prevent airway obstruction in the sedated patient. Fiberoptic bronchoscopy requires a clear visual pathway. Blood and secretions prevent visualation of the laryngeal structures. Administration of an antisialogogue – (a remedy against excessive salivation) prior to the start of the procedure is therefore essential. In the
Fiberoptic intubation (cont).
average adult patient, 0.2 mg of glycopyrrolate given intramuscularly one hour prior to bronchoscopy is satisfactory. If the patient arrives with no premedication, the glycopyrrolate should be given as soon as possible.
Repeated airway manipulation causes oedema and bleeding, both of which impair visualation through the bronchoscope. The possibility of a fiberoptic technique should therefore be kept in mind, and employed before blood and secretions have rendered this technique unusable.
A quivering, vibratory movement of muscle fibres, irregular contractions of e.g. atrium /
Denoting the fine rapid contractions or twitchings of fibres or of small groups of fibres in skeletal or cardiac muscle.
Insoluble protein involved in blood clotting. When an injury occurs fibrin is deposited around the wound in the form of a mesh, which dries and hardens, so that bleeding stops. Fibrin is developed in the blood from a soluble protein, fibrinogen. The conversion of fibrinogen to fibrin is the final stage in blood clotting. Platelets, a type of cell found in blood, release the enzyme thrombin when they come into contact with damaged tissue, and the formation of fibrin then occurs. Calcium, vitamin K, and a variety of enzymes called factors are also necessary for efficient blood clotting.
Fibrin is a protein involved in the clotting of blood. It is a fibrillar protein that is polymerised (bonding "single units" together) to form a "mesh" that forms a haemostatic plug or clot. Fibrin is made from its zymogen fibrinogen, a soluble plasma glycoprotein (a bio-molecule composed of a protein and a carbohydrate) that is synthesised by the liver. Processes in the coagulation cascade activate the zymogen prothrombin to the serine protease thrombin, which is responsible for converting fibrinogen into fibrin. Fibrin is then cross linked by factor XIII to form a clot.
Fibrinolysis is the process where a fibrin clot, the product of coagulation, is broken down. Its main enzyme, plasmin, cuts the fibrin mesh at various places, leading to the production of circulating fragments that are cleared by other proteinases or by the kidney and liver after healing has taken place.
Fresh Frozen Plasma.
Fresh frozen plasma (FFP) is defined as the fluid portion of one unit of human blood that has been centrifuged(spins liquid samples at high speed), separated, and frozen solid at -18° C (or colder) within 6 hours of collection. FFP contains the labile as well as the stable components of the coagulation, fibrinolytic and complement systems; the proteins that maintain oncotic pressure ( within tissues as opposed to within the plasma ) and modulate immunity; and other proteins that
Fresh Frozen Plasma (cont).
have diverse activities. In addition, fats, carbohydrates and minerals are present in concentrations similar to those in circulation. Although well-defined indications exist for the use of FFP in single or multiple coagulation deficiencies, indications for many of its other uses may be empiric (guided by practical experience rather than precepts or theory). Fresh frozen plasma" (FFP) is prepared from a single unit of blood. It is frozen after collection and can be stored for one year from date of collection. FFP contains all of the coagulation factors and proteins present in the original unit of blood. It is used to treat coagulopathies ( defect of the mechanism of blood clotting ) from warfarin overdose, liver disease, or dilutional coagulopathy. FFP which has been stored more than the standard length of time is re-classified as simply "frozen plasma," which is identical except that the coagulation factors are no longer considered completely viable.
The major function of the respiratory system is gas exchange. As gas exchange occurs, the acid-base balance of the body is maintained as part of homeostasis. If proper ventilation is not maintained two opposing conditions could occur: 1) respiratory acidosis, a life threatening condition, and 2) respiratory alkalosis. Upon inhalation, gas exchange occurs at the alveoli, the tiny sacs which are the basic functional component of the lungs. The alveolar walls are extremely thin (approx. 0.2 micro-metres), and are permeable-(that can be permeated or penetrated, especially by liquids or gases) to gases. The alveoli are lined with pulmonary capillaries, the walls of which are also thin enough to permit gas exchange. All gases diffuse from the alveolar air to the blood in the pulmonary capillaries, as carbon dioxide diffuses in the opposite direction, from capillary blood to alveolar air. At this point, the pulmonary blood is oxygen-rich, and the lungs are holding carbon dioxide. Exhalation follows, thereby ridding the body of the carbon dioxide and completing the cycle of respiration. In an average resting adult, the lungs take up about 250ml of oxygen every minute while excreting about 200ml of carbon dioxide. During an average breath, an adult will exchange from 500 ml to 700 ml of air. This average breath capacity is called tidal volume.
a state of total unconsciousness resulting from general anaesthetic drugs. A variety of drugs are given to the patient that have different effects with the overall aim of ensuring unconsciousness, amnesia and analgesia. The anaesthetist selects the optimal technique for any given patient and procedure.
General anaesthesia is a complex procedure involving:
• Pre-anaesthetic assessment.
• Induction,Narcosis-(sleep),Paralysis–(muscle relaxants) and Analgesia-(pain relief - drugs).
• Maintanence of anaesthesia (Isoflurane, Propofol infusion, and fluid management)
• Reversal of anaesthesia
• Recovery and Postoperative pain relief.
Prior to surgery, the anaesthetist interviews the patient to determine the best combination and drugs and dosages and the degree of how much monitoring is required to ensure a safe and effective procedure. Pertinent information is the patient's age, weight, medical history, current medications, previous anaesthetics, and fasting time. Usually, the patients are required to fill out this information on a separate form during the pre-operative evaluation. Depending on the existing medical conditions reported, the anaesthetist will review this information with the patient either during his pre-operative evaluation or on the day of his surgery.
An important aspect of this assessment is that of the patient's airway, involving inspection of the mouth opening and visualisation of the soft tissues of the pharynx. The condition of teeth and location of dental crowns and caps are checked, neck flexibility and head extension observed. If an endotracheal tube is indicated and airway management is deemed difficult, then alternative placement methods such as fiberoptic intubation may be used.
Anaesthetists may give a pre-medication by injection or by mouth anywhere from a couple of hours to a couple of minutes before the onset of surgery to induce drowsiness and relaxation. The most common drugs used for pre-medication are benzodiazepines such as midazolam.
The general anaesthetic is administered in either the operating theatre itself or an anaesthetic room. General anaesthesia can be induced by intravenous (IV) injection, or breathing a volatile anaesthetic through a facemask (inhalational induction). Onset of anaesthesia is faster with IV injection than with inhalation, taking about 10-20 seconds to induce total unconsciousness. This has the advantage of avoiding the excitatory phase of anaesthesia (see below), and thus reduces complications related to induction of anaesthesia. An inhalational induction may be chosen by the anaesthetist where IV access is difficult to obtain, where difficulty maintaining the airway is anticipated, or due to patient preference (eg. children). Commonly used IV induction agents include propofol, sodium thiopental, etomidate, and ketamine. The most commonly-used agent for inhalational induction is sevoflurane because it causes less irritation than other inhaled gases.
The duration of action of IV induction agents is generally 5 to 10 minutes, after which time spontaneous recovery of consciousness will occur. In order to prolong anaesthesia for the required duration (usually the duration of surgery), anaesthesia must be maintained. Usually this is achieved by allowing the patient to breathe a carefully controlled mixture of oxygen, nitrous oxide, and a volatile anaesthetic agent. This is transferred to the patient's brain via the lungs and the bloodstream, and the patient remains unconscious. Inhaled agents are frequently supplemented by intravenous anesthetics, such as opioids (usually fentanyl or a fentanyl derivative) and sedative-hypnotics (usually propofol or midazolam). At the end of surgery the volatile anaethetic is discontinued. Recovery of consciousness occurs when the concentration of anaesthetic in the brain drops below a certain level (usually within 1 to 30 minutes depending upon the duration of surgery).
In the 1990s a novel method of maintaining anaesthesia was developed in Glasgow, UK. Called Total IntraVenous Anaesthesia (TIVA), this involves using a computer controlled syringe driver (pump) to infuse propofol throughout the duration of surgery, removing the need for a volatile anaesthetic. Purported advantages include faster recovery from anaesthesia, reduced incidence of post-operative nausea and vomiting, and absence of a trigger for malignant hyperthermia.
Other medications will occasionally be given to anaesthetised patients to treat side effects or prevent complications. These medications include antihypertensives to treat high blood pressure, drugs like ephedrine and phenylephrine to treat low blood pressure, drugs like albuterol to treat asthma or laryngospasm/bronchospasm, and drugs like adrenaline or diphenhydramine to treat allergic reactions. Sometimes glucocorticoids or antibiotics are given to prevent inflammation and infection, respectively.
The induction of paralysis with a neuromuscular blocker is an integral part of modern anaesthesia. The first drug used for this purpose was curare, introduced in the 1940s, which has now been superseded by drugs with fewer side effects and generally shorter duration of action. Paralysis allows surgery within major body cavities, eg. abdomen and thorax without the need for very deep anaesthesia, and is also used to facilitate endotracheal intubation.
Acetylcholine, the natural neurotransmitter substance at the neuromuscular junction, causes muscles to contract when it is released from nerve endings. Muscle relaxants work by preventing acetylcholine from attaching to its receptor.
Paralysis of the muscles of respiration, ie. the diaphragm and intercostal muscles of the chest requires that some form of artificial respiration be implemented. As the muscles of the larynx are also paralysed, the airway usually needs to be protected by means of an endotracheal tube.
Monitoring of paralysis is most easily provided by means of a peripheral nerve stimulator. This device intermittently sends short electrical pulses through the skin over a peripheral nerve while the contraction of a muscle supplied by that nerve is observed. The effects of muscle relaxants are commonly reversed at the termination of surgery by anticholinesterase drugs.
Examples of skeletal muscle relaxants in use today are pancuronium, rocuronium, vecuronium, atracurium, mivacurium, and succinylcholine (see drugs).
With the loss of consciousness caused by general anaesthesia, there is loss of protective airway reflexes (such as coughing), loss of airway patency and sometimes loss of a regular breathing pattern due to the effect of anaesthetics, opioids, or muscle relaxants. To maintain an open airway and regulate breathing within acceptable parameters, some form of "breathing tube" is inserted in the airway after the patient is unconscious. To enable mechanical ventilation, an endotracheal tube is often used (intubation), although there are alternative devices such as face masks or laryngeal mask airways.
Monitoring involves the use of several technologies to allow for a controlled induction of, maintenance of and emergence from general anaesthesia.
1. Continuous Electrocardiography (ECG): The placement of electrodes which monitor heart rate and rhythm. This may also help the anaesthetist to identify early signs of heart ischemia.
2. Continuous pulse oximetry (SpO2): The placement of this device (usually on one of the fingers) allows for early detection of a fall in a patient's haemoglobin saturation with oxygen (hypoxemia).
3. Blood Pressure Monitoring (NIBP or IBP): There are two methods of measuring the patient's blood pressure. The first, and most common, is called non-invasive blood pressure (NIBP) monitoring. This involves placing a blood pressure cuff around the patient's arm, forearm or leg. A blood pressure machine takes blood pressure readings at regular, preset intervals throughout the surgery. The second method is called invasive blood pressure (IBP) monitoring. This method is reserved for patients with significant heart or lung disease, the critically ill, major surgery such as cardiac or transplant surgery, or when large blood losses are expected. The invasive blood pressure monitoring technique involves placing a special type of plastic cannula in the patient's artery - usually at the wrist or in the groin.
4. Agent concentration measurement - Common anaesthetic machines have meters to measure the percent of inhalational anaesthetic agent used (e.g. sevoflurane, isoflurane, desflurane, halothane etc).
5. Low oxygen alarm - Almost all circuits have a backup alarm in case the oxygen delivery to the patient becomes compromised. This warns if the fraction of inspired oxygen drops lower than room air (21%) and allows the anaesthetist to take immediate remedial action.
6. Circuit disconnect alarm - indicates failure of circuit to achieve a given pressure during mechanical ventilation.
7. Carbon dioxide measurement (capnography)- measures the amount of carbon dioxide expired by the patient's lungs. It allows the anaesthetist to assess the adequacy of ventilation.
8. Temperature measurement to discern hypothermia or fever, and to aid early detection of malignant hyperthermia.
9. EEG or other system to verify depth of anaesthesia may also be used. This reduces the likelihood that a patient will be mentally awake, although unable to move because of the paralytic agents. It also reduces the likelihood of a patient receiving significantly more amnesic drugs than actually necessary to do the job.
Stages of anaesthesia:
Stage 1: anaesthesia, also known as the "induction," is the period between the initial administration of the induction medications and loss of consciousness. During this stage the patient progresses from analgesia without amnesia to analgesia with amnesia. Patients can carry on a conversation at the time.
Stage 2: anaesthesia, also known as the "excitement stage," is the period following loss of consciousness and marked by excited and delirious activity. During this stage, respirations and heart rate may become irregular. In addition, there may be uncontrolled movements, vomiting, breath holding,
General anaesthesia (cont).
and pupillary dilation. Since the combination of spastic movements, vomiting, and irregular respirations may lead to airway compromise, rapidly acting drugs are used to minimize time in this stage and reach stage 3 as fast as possible.
Stage 3: Surgical Anesthesia. During this stage, the skeletal muscles relax, and the patient's breathing becomes regular. Eye movements slow, then stop, and surgery can begin.
Stage 4: anaesthesia, also known as "overdose," is the stage where too much medication has been given and the patient has severe brain stem or medullary depression. This results in a cessation of respiration and potential cardiovascular collapse. This stage is lethal without cardiovascular and respiratory support.
The anaesthesia concludes with a management plan for postoperative pain relief. This may be in the form of regional analgesia, oral, transdermal or parenteral medication. Minor surgical procedures are amenable to oral pain relief medications such as paracetamol and NSAIDS such as ibuprofen. Moderate levels of pain require the addition of mild opiates such as codeine.
Major surgical procedures may require a combination of modalities to confer adequate pain relief. Parenteral methods include Patient Controlled Analgesia System (PCAS) involving morphine, a strong opiate. Here, the patient presses a button to activate a pump containing morphine. This administers a preset dose of the drug. As the pump is programmed not to exceed a safe amount of the drug, the patient cannot self administer a toxic dose.
Overall, the mortality rate for general anaesthesia is about five deaths per million anaesthetic administrations. Death during anaesthesia is most commonly related to surgical factors or pre-existing medical conditions. These include major haemorrhage, sepsis, and organ failure (eg. heart, lungs, kidneys, liver). Common causes of death directly related to anaesthesia include:
• aspiration of stomach contents.
• suffocation (due to inadequate airway management).
• allergic reactions to anaesthesia (specifically and not limited to anti-nausea agents) and other deadly genetic predispositions.
• human error.
• equipment failure.
Tested after fasting:( normal range)= 70 - 110 mg/dL.
Our body's primary source of energy takes the form of glucose. This type of sugar comes from digesting carbohydrates into a chemical that we can easily convert to energy. When glucose levels in the bloodstream aren't properly regulated, one can develop a serious condition, such as diabetes. We get most of our glucose from digesting the sugar and starch in carbohydrates. Our digestive system, using bile and enzymes, breaks down the starch and sugar in these foods into glucose. This functional form of energy then gets absorbed through the small intestine into the bloodstream. There, a chemical known as insulin, excreted by the pancreas, meets the glucose. Together, they can enter cells in muscles and the brain, allowing glucose to power activities like lifting a book or remembering a phone number.
The form in which carbohydrate is stored in the liver and muscle.As a carbohydrate meal is eaten and digested, blood glucose levels rise, and the pancreas secretes insulin. Glucose from the portal vein enters the liver cells (hepatocytes). Insulin acts on the hepatocytes to stimulate the action of several enzymes, including glycogen synthase(an enzyme which converts excess glucose residues). Glucose molecules are added to the chains of glycogen as long as both insulin and glucose remain plentiful. In this postprandial or "fed" state, the liver takes in more glucose from the blood than it releases After a meal has been digested and glucose levels begin to fall, insulin secretion is reduced, and glycogen synthesis stops.
In biology, compound containing a sugar and a non-sugar unit. Many glycosides occur naturally, for example, digitalis is a preparation of dried and powdered foxglove leaves that contains a mixture of cardiac glycosides. One of its constituents, digoxin, is used in the treatment of congestive heart failure and cardiac arrhythmias.
Cardiac glycosides are drugs used in the treatment of congestive heart failure and cardiac arrhythmia, e.g. Digoxin. Cardiac glycosides increase the force of myocardial contraction and reduce conductivity within the atrioventricular (AV) node. Digoxin is the most commonly used cardiac glycoside. Cardiac glycosides are most useful in the treatment of supraventricular tachycardias, especially for controlling ventricular response in persistent atrial fibrillation. For management of atrial fibrillation the maintenance dose of the cardiac glycoside can usually be determined by the ventricular rate at rest, which should not be allowed to fall below 60 beats per minute except in special circumstances, e.g. with the concomitant administration of a beta-blocker.
Graft: Healthy skin, bone, or other tissue taken from one part of the body to replace diseased or injured tissue removed from another part of the body. In medicine, grafting is a surgical procedure to transplant tissue without a blood supply. The implanted tissue must obtain a blood supply from the new vascular bed or otherwise die.
The haematocrit (Ht or HCT) and packed cell volume (PCV) are measures of the proportion of blood volume that is occupied by red blood cells. It is normally 45 ± 7 (38-52%) for males and 42 ± 5 (37-47%) for females. The haematocrit is considered an integral part of a person's complete blood count or CBC results along with the haemoglobin concentration, white blood cell count, and platelet count.
In medicine, haemodialysis is a method for removing waste products such as potassium and urea, as well as free water from the blood when the kidneys are incapable of this (i.e. in renal failure). It is a form of renal dialysis and is therefore a renal replacement therapy.
In medicine, haemodialysis is a method for removing waste products such as potassium and urea, as well as free water from the blood when the kidneys are incapable of this (i.e. in renal failure). It is a form of renal dialysis and is therefore a renal replacement therapy-(see hemofiltration).
Haemodialysis is typically conducted in an undedicated facility, either a special room in a hospital or a clinic (with specialized nurses and technicians) that specializes in haemodialysis. Although less typical, dialysis can also be done in a patient's home as home hemodialysis
Haemodynamics.( haemodynamically ).
Haemodynamics is a medical term for the dynamic regulation of the blood flow in the brain. It is the principle on which functional magnetic resonance imaging (M.R.I) is based.
Neurons, like all other cells, require energy to function. This energy is supplied in the form of glucose and oxygen (the oxygen being carried in haemoglobin). The blood supply of the brain is dynamically regulated to give active neural assemblies more energy whilst inactive assemblies receive less energy.
In medicine, haemofiltration, is a renal replacement therapy-(see below) similar to haemodialysis which is used almost exclusively in the intensive care setting. Thus, it is almost always used for acute renal failure. It is a slow continuous therapy in which sessions usually last between 12 to 24 hours and are usually performed daily. During haemofiltration, a patient's blood is passed through a set of tubing (a filtration circuit) via a machine to a semipermeable membrane (the filter) where waste products and water are removed. Replacement fluid is added and the blood is returned to the patient.
As in dialysis, in haemofiltration one achieves movement of solutes across a semi-permeable membrane. However, solute movement with haemofiltration is governed by convection rather than by diffusion. With haemofiltration, dialysate is not used. Instead, a positive hydrostatic pressure drives water and solutes across the filter membrane from the blood compartment to the filtrate compartment, from which it is drained. Solutes, both small and large, get dragged through the membrane at a similar rate by the flow of water that has been engendered by the hydrostatic pressure. So convection overcomes the reduced removal rate of larger solutes (due to their slow speed of diffusion) seen in haemodialysis.
Renal replacement therapy is a term used to encompass life-supporting treatments for renal failure.
• peritoneal dialysis-( is a method for removing waste such as urea and potassium from the blood, as well as excess fluid, when the kidneys are incapable of this (i.e. in renal failure). It is a form of renal dialysis, and is thus a renal replacement therapy).
• haemofiltration and
• renal transplantation.
These treatments do not cure kidney disease; they are palliative-(relieving or soothing the symptoms of a disease or disorder without effecting a cure) treatments.
Male: 13 - 18 gm/dL ,Female: 12 - 15 gm/dL
A drop of blood contains millions of red blood cells, or erythrocytes. These specialised cells are like flattened discs, which gives them a much greater surface area with which to exchange oxygen and carbon dioxide in the lungs and with body cells. Red blood cells are able to carry oxygen so efficiently because of a special protein inside them: haemoglobin. In fact, it is the haemoglobin that is responsible for the colour of the red blood cell. Haemoglobin contains a haem prosthetic group that has an iron atom at its centre. When the iron is bound to oxygen, the haem group is red in colour (oxy haemeoglobin), and when it lacks oxygen (deoxygenated form) it is blue-red. As blood passes through the lungs, the haemoglobin picks up oxygen because of the increased oxygen pressure in the capillaries of the lungs, and can then release this oxygen to body cells where the oxygen pressure in the tissues is lower. In addition, the red blood cells can pick up the waste product, carbon dioxide, some of which is carried by the haemoglobin (at a different site from where it carries the oxygen), while the rest is dissolved in the plasma. The high carbon dioxide levels in the tissues lowers the pH, and the binding of haemoglobin to carbon dioxide causes a conformational change that facilitates the release of oxygen. The carbon dioxide is then released once the red blood cells reach the lungs.
Haemoglobin is composed of four polypeptide chains, which in adults consist of two alpha (a) globin chains and two beta (b) globin chains (i.e. a2b2). Each polypeptide has a haem prosthetic group attached, where each haem can bind one oxygen molecule - so there are four haem groups per haemoglobin molecule that together bind four oxygen molecules.
Haemolysis; from the Latin Haemo-, Greek Αἷμα meaning blood, -lysis, meaning to break open— is the breaking open of red blood cells and the release of haemoglobin into the surrounding fluid.
Bleeding, technically known Haemorrhage is the loss of blood from the circulatory system. Bleeding can occur internally, where blood leaks from blood vessels inside the body or externally, either through a natural opening such as vagina, mouth or rectum, or through a break in the skin. The complete loss of blood is referred to as exsanguination .The average human has around 7 to 8% of their body weight made up of blood. This equates to an average of around 5 litres of blood (5.3 quarts) in a 70kg (154 lbs) man. The circulating blood volume is approximately 70 ml / kg of ideal body weight. Thus the average 70 kg male has approximately 5000 ml (5.3 quarts) of circulating blood. Loss of 10-15% of
total blood volume can be endured without clinical sequelae-(a pathological condition resulting from a disease, injury, or other trauma) in a healthy person, and blood donation typically takes 8-10% of the donor's blood volume. The human body generates blood at a rate of about 2 litres (2.1 quarts) per week. The technique of blood transfusion is used to replace severe quantities of lost blood.
Haemostat / Haemostasis.
A drug or remedy for arresting haemorrhage.( haemostatic ). Haemostasis can refer to the physiologic process whereby bleeding is halted. Stopped bleeding is commonly referred to, however, as coagulation, but coagulation is only one type of haemostatic process.
When a blood vessel is wounded, several steps occur to staunch the flow of blood, namely:
• Vasoconstriction constricts the blood vessel, minimizing vessel diameter and slowing bleeding.
• Primary haemostasis occurs, wherein platelets, one of the formed elements of the blood, bind to collagen in the exposed walls of the blood vessel to form a haemostatic plug within seconds after an injury.
• Secondary haemostasis or coagulation occurs. This involves a complex cascade of coagulation factors, ultimately resulting in the transformation of fibrinogen, a blood protein, into polymerized-(a large molecular mass ) fibrin, making a clot. This process takes several minutes.
• The clot attracts and stimulates the growth of fibroblasts and smooth muscle cells within the vessel wall, and begins the repair process which ultimately results in the dissolution of the clot (fibrinolysis).
Disorders of haemostasis can be roughly divided into platelet disorders, such as idiopathic thrombocytopenic purpura-(a low platelet count -(thrombocytopenia-of no known cause (idiopathic), and disorders of coagulation, such as haemophilia. Haemostasis may also refer to the complex interaction between vessels, platelets, coagulation factors, coagulation inhibitors and fibrinolytic proteins to maintain the blood within the vascular compartment in a fluid state. The objective of the haemostatic system is to preserve intravascular integrity by achieving a balance between haemorrhage and thrombosis.
A haemothorax is a condition that results from blood accumulating in the pleural cavity. Its cause is usually traumatic, from a blunt or penetrating injury to the thorax, resulting in a rupture of either of the serous membrane lining the thorax and covering the lungs. This rupture allows blood to spill into the pleural space, equalizing the pressures between it and the lungs. Blood loss may be massive in people with these conditions, as each side of the thorax can hold 30%-40% of a person's blood volume. If left untreated, the condition can progress to a point where the blood accumulation begins to put pressure on the mediastinum and the trachea, effectively limiting the amount of diastolic filling of the ventricles and deviating the trachea to the unaffected side.
Signs and symptoms
• Tachypnoea. (Greek: "rapid breathing") is characterized by rapid breathing and is not identical with hyperventilation - tachypnoea may be necessary for a sufficient gas-exchange of the body, for example after exercise, in which case it is not hyperventilation.
• Dyspnoea. (Pronounced disp-nee-ah, from the Latin dyspnoea, Greek dyspnoia from dyspnoos, shortness of breath) or short of breath (SOB) is perceived difficulty breathing or painful breathing.
• Cyanosis. (see Cyanosis).
• Decreased or absent breath sounds on affected side.
• Tracheal deviation.
• Dull resonance on percussion.
• Unequal chest rise.
• Tachycardia. (see Tachycardia)
• Hypotension. (see Hypotension)
• Pale, cool, clammy skin.
• Possibly subcutaneous air.
• Narrowing pulse pressure.
A haemothorax is managed by removing the source of bleeding and by draining the blood already in the thoracic cavity. Blood in the cavity can be removed by inserting a drain (chest tube, drain) in a procedure called a tube thoracostomy. Patients should recover swiftly after this. However, if the cause is rupture of the aorta in high energy trauma, the intervention by a thoracic surgeon is mandatory.
The half-life of a quantity, subject to exponential decay, is the time required for the quantity to decay to half of its initial value. The concept originated in the study of radioactive decay, but applies to many other fields as well, including phenomena which are described by non-exponential decays. The term half-life was coined in 1907, but it was always referred to as half-life period. It was not until the early 1950s that the word period was dropped from the name.
Harmonic scalpel: This medical device uses ultrasonic energy to vibrate its blade at 55,000 cycles per second. Invisible to the naked eye, the vibration transfers energy to the tissue, providing simultaneous cutting and coagulation. The temperature of the surrounding tissue reaches 80 degrees Celsius. Proponents of this procedure assert that the end result is precise cutting with minimal thermal damage.
The heart is a muscular organ responsible for pumping blood through the blood vessels by repeated, rhythmic contractions.The term cardiac (as in cardiology) means "related to the heart" and comes from the Greek καρδία, kardia, for "heart." The heart is composed of cardiac muscle, an involuntary muscle tissue which is found only within this organ. The average human heart beating at 72 BPM, will beat approximately 2.5 billion times during a lifetime of 66 years.
In the human body, the heart is usually situated in the middle of the thorax with the largest part of the heart slightly to the left underneath the breastbone (sternum). The heart is usually felt to be on the left side because the left heart (left ventricle) is stronger (it pumps to all body parts). The left lung is smaller than the right lung because the heart occupies more of the left hemi-thorax. The heart is enclosed by a sac known as the pericardium and is surrounded by the lungs. The pericardium is a double membrane structure containing a serous fluid to reduce friction during heart contractions. The mediastinum, a subdivision of the thoracic cavity, is the name of the heart cavity.
The function of the right side of the heart is to collect de-oxygenated blood, in the right atrium, from the body and pump it, via the right ventricle, into the lungs (pulmonary circulation) so that carbon dioxide can be dropped off and oxygen picked up (gas exchange). This happens through a passive process called diffusion - (the process whereby particles of liquids, gases, or solids intermingle as the result of their spontaneous movement caused by thermal agitation and in dissolved substances move from a region of higher to one of lower concentration). The left side collects oxygenated blood from the lungs into the left atrium. From the left atrium the blood moves to the left ventricle which pumps it out to the body. On both sides, the lower ventricles are thicker and stronger than the upper atria. The muscle wall surrounding the left ventricle is thicker than the wall surrounding the right ventricle due to the higher force needed to pump the blood through the systemic circulation.
Starting in the right atrium, the blood flows through the tricuspid valve to the right ventricle. Here it is pumped out the pulmonary semi-lunar valve and travels through the pulmonary artery to the lungs. From there, blood flows back through the pulmonary vein to the left atrium. It then travels through the bicuspid valve to the left ventricle and on to through the aortic semi-lunar valve to the aorta. The aorta forks, and the blood is divided between major arteries which supply the upper and lower body. The blood travels the arteries to the smaller arterioles, then finally to the tiny capillaries which feed each cell. The (relatively) deoxygenated blood then travels to the venules, which coalesce into veins, then to the inferior and superior vena cavae and finally back to the right atrium where the process began.
Heart failure (see congestive heart failure).
The treatment of chronic heart failure aims to relieve symptoms, improve exercise tolerance, reduce the incidence of acute exacerbations, and reduce mortality. An ACE inhibitor, titrated to a ‘target dose’ (or the maximum tolerated dose if lower), generally achieves these aims; a diuretic is also necessary in most patients to reduce symptoms of fluid overload. Digoxin improves symptoms and exercise tolerance and reduces hospitalisation due to acute exacerbations but it does not reduce mortality. Drug treatment of chronic systolic heart failure is covered below; optimal management of diastolic heart failure is less certain but digoxin should probably be avoided.
Heart rate is a term used to describe the frequency of the cardiac cycle. It is considered one of the four vital signs. Usually it is calculated as the number of contractions (heart beats) of the heart in one minute and expressed as "beats per minute" (bpm). See "Heart" for information on embryofetal heart rates. The heart beats up to 120 times per minute in childhood. When resting, the adult human heart beats at about 70 bpm (males) and 75 bpm (females), but this rate varies among people. However, the resting heart rate can be significantly lower in athletes. The infant/neonatal rate of heartbeat is around 130-150 bpm, the toddler's about 100–130 bpm, the older child's about 90–110 bpm, and the adolescent's about 80–100 bpm. The pulse is the most straightforward way of measuring the heart rate, but it can be deceptive when some heart beats do not have much cardiac output. In these cases (as happens in some arrhythmias), the heart rate may be considerably higher than the pulse rate.
The heart has four chambers. The top two are called the atria. The bottom two are called the ventricles. The heart's "natural" pacemaker is called the sinoatrial (SA) node or sinus node. It's a small mass of specialized cells in the heart's right atrium. It produces electrical impulses that make your heart beat. For your heart to beat properly, the signal must travel from the SA node down a
specific path to reach the ventricles. As the signal goes from the atria to the ventricles, it passes through specialized conducting tissue called the atrio-ventricular (AV) node. On an electrocardiogram (ECG), a portion of the graph called the P wave shows the impulse passing through the atria. Another portion of the graph, the QRS wave, shows the impulse passing through the ventricles. As long as the impulse is transmitted normally, the heart pumps and beats at a regular pace.
Sometimes the signal from the heart's upper to lower chambers is impaired or doesn't transmit. This is "heart block" or "AV block." This does not mean that the blood flow or blood vessels are blocked.
Heart block is classified according to the level of impairment — first-degree heart block, second-degree heart block or third-degree (complete) heart block.
First-degree heart block.
First-degree heart block, or first-degree AV block, is when the electrical impulse moves through the AV node more slowly than normal. The time it takes for the impulse to get from the atria to the ventricles (the PR interval) should be less than about 0.2 seconds. If it takes longer than this, it's called first-degree heart block.
Heart rate and rhythm are normal, and there may be nothing wrong with the heart.
Certain heart medicines such as digitalis can slow conduction of the impulse from the atria to the ventricles and cause first-degree AV block. Also, well-trained athletes may have it .Generally, no treatment is necessary for first-degree heart block.
First-degree atrioventricular block
• sinus rhythm with a prolonged PQ (PR) interval (> 0,2 s)
Second-degree heart block.
In this condition, some signals from the atria don't reach the ventricles. This causes "dropped beats." On an ECG, the P wave isn't followed by the QRS wave, because the ventricles weren't activated. There are two types:
Type I second-degree heart block, or Mobitz Type I, or Wenckebach's AV block. Electrical impulses are delayed more and more with each heartbeat until a beat is skipped. This condition is not too serious but sometimes causes dizziness and/or other symptoms.
Second-degree atrioventricular block Mobitz I (Wenckebach AV block)
• P waves are present and appear in a regular rhythm
• there is a progressive lengthening of the PR interval until a blocked P wave occurs
• QRS complexes do not appear in a regular rhythm
• the longest interval between two QRS complexes is shorter than a double P-P interval
• there is a 3:2 conduction block on the recording
Type II second-degree heart block, or Mobitz Type II. This is less common than Type I but generally more serious. Because electrical impulses can't reach the ventricles, an abnormally slow heartbeat may result. In some cases a pacemaker is needed.
Second-degree atrioventricular block Mobitz II
• P waves are present and appear in a regular rhythm
• P waves precede each QRS complex in a regular interval, until one or several QRS complexes are blocked
• QRS complexes do not appear in a regular rhythm
• the interval between two QRS complexes is a multiple of a P-P interval
Third-degree or complete heart block.
Complete heart block (complete AV block) means that the heart's electrical signal doesn't pass from the upper to the lower chambers. When this occurs, an independent pacemaker in the lower chambers takes over. The ventricles can contract and pump blood, but at a slower rate than that of the atrial pacemaker.
These impulses are called functional or ventricular scope beats. They're usually very slow and can't generate the signals needed to maintain full functioning of the heart muscle. On the ECG, there's no normal relationship between the P and the QRS waves.
Complete heart block is most often caused in adults by heart disease or as a side effect of drug toxicity. Heart block also can be present at — or even before — birth. (This is called congenital heart block.) It also may result from an injury to the electrical conduction system during heart surgery. Complete heart
Heart Block (cont).
block may be a medical emergency with potentially severe symptoms and a serious risk of cardiac arrest (sudden cardiac death). If a pacemaker can't be implanted immediately, a temporary pacemaker might be used to keep the heart pumping until surgery can be performed.
Third-degree atrioventricular block
• P waves, if present, appear in a regular rhythm
• nevertheless the patient can have a different atrial rhythm (e.g., atrial fibrillation)
• QRS complexes appear in an independent regular rhythm different from the rhythm of the P waves (atrioventricular dissociation)
• the rate of the QRS complexes is below 60 beats per minute
The rhythm of the heart is normally determined by a pacemaker site called the sinoatrial (SA) node located in the posterior wall of the right atrium near the superior vena cava. The SA node consists of specialized cells that undergo spontaneous generation of action potentials at a rate of 100-110 action potentials ("beats") per minute. This intrinsic rhythm is strongly influenced by autonomic nerves, with the vagus nerve being dominant over sympathetic influences at rest. This "vagal tone" brings the resting heart rate down to 60-80 beats/minute. The normal range for sinus rhythm is 60-100 beats/minute. Sinus rates below this range are termed sinus bradycardia and sinus rates above this range are termed sinus tachycardia.
The sinus rhythm normally controls both atrial and ventricular rhythm. Action potentials generated by the SA node spread throughout the atria, depolarizing this tissue and causing atrial contraction. The impulse then travels into the ventricles via the atrio-ventricular node (AV node). Specialized conduction pathways (bundle branches and Purkinje fibers) within the ventricle rapidly conduct the wave of depolarization throughout the ventricles to elicit ventricular contraction. Therefore, normal cardiac rhythm is controlled by the bodie’s natural pacemaker activity of the SA node.
Hepatic (see Liver).
The bundle of His is a collection of heart muscle cells specialized for electrical conduction that transmits the electrical impulses from the AV node (located between the atria and the ventricles) to the point of the apex of the fascicular( small bundle ) branches. The fascicular branches then lead to the Purkinje fibers which innervate the ventricles, causing the cardiac muscle of the ventricles to contract at a paced interval. These specialized muscle fibres in the heart were named after the Swiss cardiologist Wilhelm His, Jr., who discovered them in 1893. The fibers of the Bundle of His allow electrical conduction to occur more easily and quickly than typical cardiac muscle. They are an important part of the electrical conduction system of the heart as they transmit the impulse from the AV node (the ventricular pacemaker) to the rest of the heart. The bundle of His branches into the three bundle branches: the right, left anterior and left posterior bundle branches that run along the inter-ventricular septum. The bundles give rise to thin filaments known as Purkinje fibers. These fibers distribute the impulse to the ventricular muscle. Together, the bundle branches and Purkinje network
comprise the ventricular conduction system. It takes about 0.03-0.04s for the impulse to travel from the bundle of His to the ventricular muscle.
Histamine: Substance that plays a major role in many allergic reactions. Histamine dilates blood vessels and makes the vessel walls abnormally permeable-( the capacity of a blood vessel wall to pass through small molecules (ions, water, nutrients).
Homeostasis is that property of either an open system or a closed system, especially a living organism, which regulates its internal environment so as to maintain a stable, constant condition. Multiple dynamic equilibrium adjustments, controlled by interrelated regulation mechanisms, make homeostasis possible. The term was coined in 1932 by Walter Bradford Cannon from the Greek homoios (same, like, resembling) and stasis (to stand, posture).
A hormone (from Greek όρμή - "to set in motion") is a chemical messenger from one cell (or group of cells) to another. All multi-cellular organisms produce hormones (including plants). The function of hormones is to serve as a signal to the target cells; the action of hormones is determined by the pattern of secretion and the signal transduction of the receiving tissue. The best-known animal hormones are those produced by endocrine glands of vertebrate animals, but hormones are produced by nearly every organ system and tissue type in a multi-cellular organism. Endocrine hormone molecules are secreted (released) directly into the bloodstream, while exocrine hormones are secreted directly into a duct -(a circumscribed channel leading from an exocrine gland or organ)., and from the duct they either flow into the bloodstream or they flow from cell to cell by diffusion in a process known as paracrine signalling-(paracrine signaling- a form of cell signaling in which the target cell is close to ("para" = alongside of or next to, but this strict prefix definition is not meticulously followed ) the signal releasing cell)..
Hydrogen is a chemical element represented by the symbol H and an atomic number of 1. At standard temperature and pressure it is a colorless, odorless, nonmetallic, tasteless, highly flammable diatomic gas (H2). With an atomic mass of 1.00794 g/mol, hydrogen is the lightest element. Hydrogen is the most abundant of the chemical elements, constituting roughly 75% of the universe's elemental mass. Hydrogen can form compounds with most elements and is present in water and most organic compounds. It plays a particularly important role in acid-base chemistry, in which many reactions involve the exchange of protons between soluble molecules.
Hydrogen ion is a general term for all ions of hydrogen and its isotopes-( any of the several different forms of an element).
Hydrolysis is a chemical reaction or process in which a chemical compound reacts with water. This is the type of reaction that is used to break down polymers-(molecules with large molecular mass). Water is added in this reaction.
Hypertension, commonly referred to as "high blood pressure", is a medical condition in which the blood pressure is chronically elevated. While it is formally called arterial hypertension, the word "hypertension" without a qualifier usually refers to arterial hypertension. Hypertension has been associated with a higher risk of heart attack or stroke.
Hyperthermia (hyperpyrexia), in its advanced state referred to as heat stroke or sunstroke, is an acute condition which occurs when the body produces or absorbs more heat than it can dissipate. Body temperatures above 40°C (104 °F) are life-threatening.
Hypertrophy is the increase of the size of an organ or in a select area of the tissue. It should be distinguished from hyperplasia which occurs due to cell division increasing the number of cells while their size stays the same; hypertrophy occurs due to an increase in the size of cells, while the number stays the same.
In medicine, hyperventilation (or over-breathing) is the state of breathing faster and/or deeper than necessary, thereby reducing the carbon dioxide concentration of the blood below normal. This is in contrast to hyperpnea, where the increased breathing is required to meet demand, as during and following exercise or when the body lacks oxygen (hypoxia), for instance in high altitude or as a result of anaemia.
Hypotension is abnormally low blood pressure. Normal blood pressure is a reading of less than 120/80 mmHg (mmHg = millimeters of mercury, a unit for measuring pressure). Hypotension is blood pressure that is lower than 90/60 mmHg.
Hypothermia is a condition where the normal body temperature of 37°C (98.6°F) drops below 35° (95°F).
Hypermagnesaemia occurs in patients with acute or chronic renal failure given antacids or laxatives containing magnesium. It can be induced by enemas containing magnesium. Symptoms and signs include neurological and cardiovascular depression, weakness, respiratory paralysis and cardiac conduction defects. Treatment requires the cessation of any magnesium therapy. Calcium, insulin and dextrose may be given to counteract the plasma magnesium levels. Dialysis may be required in patients with severe renal failure.
Hypertonic In biology, a hypertonic cell environment has a higher concentration of solutes than inside the animal or plant cell. The ability of a solution to change the shape or tone of cells by altering their internal water volume is called tonicity (tono = tension). In a hypertonic environment, osmotic pressure causes water to flow out of the cell. If enough water is removed in this way, the cytoplasm will have such a small concentration of water that the cell has difficulty functioning.
A cell that is in a hypertonic environment has a higher concentration of solute in the environment than in the inside of the cell, making the net flow of water out of the cell. A cell in a hypotonic environment has a lower concentration of solute in the environment than in the inside of the cell, making the net flow of water into the cell and eventually causing cell lysis –(to separate) refers to the death of a cell by breaking of the cellular membrane.
Hypertrophic cardiomyopathy, or HCM, is a disease of the myocardium (the muscle of the heart) in which a portion of the myocardium is hypertrophied (thickened) without any obvious cause. Though perhaps most famous as a leading cause of sudden cardiac death in young athletes. HCM's more important significance is as a cause of sudden unexpected cardiac death in any age group and as a cause of disabling cardiac symptoms.
A cardiomyopathy is any disease that primarily affects the muscle of the heart. In HCM, the normal alignment of muscle cells is disrupted, a phenomenon known as myocardial disarray. HCM also causes disruptions of the electrical functions of the heart. HCM is believed to be due to a mutation in one of many genes that results in a mutated myosin heavy chain, one of the components of the myocyte (the muscle cell of the heart). Depending on the degree of obstruction of the outflow of blood from the left ventricle of the heart, HCM can be defined as obstructive or non-obstructive.
HCM is also known as idiopathic - (unknown cause) hypertrophic subaortic stenosis (IHSS) and hypertrophic obstructive cardiomyopathy (HOCM). A non-obstructive variant of HCM is apical hypertrophic cardiomyopathy , which is also known as nonobstructive hypertrophic cardiomyopathy and Japanese variant hypertrophic cardiomyopathy (since the first cases described were all in individuals of Japanese descent).
Hypomagnesemia is an electrolyte disturbance in which there is an abnormally low level of magnesium in the blood. Usually a serum level less than 0.6 mmol/l is used as reference. It must be noted that hypomagnesemia is not equal to magnesium deficiency. Hypomagnesemia can be present without magnesium deficiency and vice versa. Deficiency of magnesium causes among others cardiac arrhythmia and increased irritability of the nervous system with tetany. It may result from a number of conditions including inadequate intake of magnesium, chronic diarrhea, malabsorption, alcoholism, chronic stress, diuretic use and other disorders. The prefix hypo- means low (contrast with hyper-, meaning high). The middle magnes refers to magnesium. The end portion of the word, -emia, means 'in the blood' (note, however, that hypomagnesemia is usually indicative of a systemic magnesium deficit).
In biology, a hypotonic solution has the lower osmotic pressure of two fluids and also describes a cell environment with a lower concentration of solutes than the cytoplasm of the cell. Given a cell placed in a hypotonic environment, osmosis causes a net flow of water into the cell, causing swelling and expansion. This swelling can cause the cell to burst. Solutions and cell environments are also described, in terms of osmotic pressure, as being either, hypotonic, hypertonic or isotonic.
also known as respiratory depression, occurs when ventilation is inadequate to perform needed gas exchange. It generally causes an increased concentration of carbon dioxide (hypercapnia) and respiratory acidosis. It can be caused by medical conditions, by holding one's breath, or by drugs, typically when taken in overdose. Hypoventilation may be dangerous for those with sleep apnoea.
is a state of decreased blood volume; decrease in volume of blood plasma. Severe hypovolaemia leads to hypovolaemic shock. Shock is a serious medical condition where the tissue perfusion is insufficient to meet demand for oxygen and nutrients. This hypoperfusional state is a life-threatening medical emergency and one of the leading causes of death for critically ill people. This primary cause may lead to many other medical emergencies, such as hypoxia or cardiac arrest. A low blood volume can result in multiple organ failure, erectile dysfunction, kidney damage and failure, brain damage, coma and death (desanguination). Desanguination refers to a state of being, resulting from a massive loss of blood.
Hypoxia literally means "deficient in oxygen." It can refer to:
Hypoxia (medical), a shortage of oxygen in the body.
Hypoxaemia is the reduction of oxygen specifically in the blood; anoxia is when there is no oxygen available at all.
Environmental hypoxia, a condition in high altitudes such as mountains where the reduced partial pressure of oxygen available leads to hypoxia.
Ischaemia, a restriction in blood supply (oxygen supply) to an organ or section of the body, generally due to constriction or blocking of blood vessels.
The process resulting in a macroscopic-(is visible to the naked eye ) area of necrotic tissue in some organ caused by loss of adequate blood supply. Supplying arteries may be blocked from within by some obstruction (e.g. a blood clot or fatty cholesterol deposit), or may be mechanically compressed or ruptured by trauma.
Colonization of a host organism by a foreign species. In an infection, the infecting organism seeks to utilize the host's resources to multiply (usually at the expense of the host). The infecting organism- (in Greek organon = instrument), or pathogen-( a biological agent that causes disease or illness to its host), interferes with the normal functioning of the host and can lead to chronic wounds, gangrene, loss of an infected limb, and even death. The host's response to infection is inflammation- (Latin, inflammatio, to set on fire). Colloquially, a pathogen is usually considered a microscopic organism though the definition is broader, including bacteria-(unicellular microorganisms), parasites-( is one version of symbiosis ("living together"), viruses-( (from the Latin noun virus, meaning toxin or poison), prions-( an infectious agent composed only of protein ) A symbiosis between parasite and host, whereby the relationship is beneficial for the former but detrimental to the latter, is characterised as parasitism. The branch of medicine that focuses on infections and pathogens is infectious disease.
Inflammation: (Latin, inflammatio, to set on fire) is the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. It is a protective attempt by the organism to remove the injurious stimuli as well as initiate the healing process for the tissue. Inflammation is not a synonym for infection. Even in cases where inflammation is caused by infection it is incorrect to use the terms as synonyms: infection is caused by an exogenous-(from the Greek words "exo" and "gen", meaning "outside" and "production") pathogen, while inflammation is the response of the organism to the pathogen.
A standard intravenous IV infusion set consists of a pre-filled, sterile container (glass bottle, plastic bottle or plastic bag) of fluids with an attached drip chamber which allows the fluid to flow one drop at a time, making it easy to see the flow rate (and also reducing air bubbles); a long sterile tube with a clamp to regulate or stop the flow; a connector to attach to the access device; and connectors to allow "piggybacking" of another infusion set onto the same line, e.g., adding a dose of antibiotics to a continuous fluid drip.
An infusion pump allows precise control over the flow rate and total amount delivered, but in cases where a change in the flow rate would not have serious consequences, or if pumps are not available, the drip is often left to flow simply by placing the bag above the level of the patient and using the clamp to regulate the rate; this is a gravity drip.
A rapid infuser can be used if the patient requires a high flow rate and the IV access device is of a large enough diameter to accommodate it. This is either an inflatable cuff placed around the fluid bag to force the fluid into the patient or a similar electrical device that may also heat the fluid being infused.
An inotrope is an agent which increases or decreases the force or energy of muscular contractions. Negatively inotropic agents weaken the force of muscular contractions. Positively inotropic agents increase the strength of muscular contraction .Most commonly, the inotropic state is used in reference to various drugs that affect the strength of contraction of heart muscle (myocardial contractility). However, it can also refer to pathological conditions. For example, ventricular hypertrophy can increase inotropic state, while myocardial infarction can decrease it. One of the most important factors affecting inotropic state is the level of calcium in the cytoplasm. Positive inotropes usually increase the level, while negative inotropes decrease it. However, not all drugs involve calcium release, and among those which do, the mechanism for manipulating the calcium level can vary from drug to drug.
International Normalized Ratio (INR).
The prothrombin time (PT) and its derived measures of prothrombin ratio (PR) and international normalized ratio (INR) are measures of the extrinsic ( not essential or inherent ) pathway of coagulation. They are used to determine the clotting tendency of blood, in the measure of warfarin-(anticoagulant medication ) dosage, liver damage and vitamin K-(Vitamin K denotes a group of lipophilic-( fat-liking), and hydrophobic-(water in Greek hydro- and for fear phobos refers to the physical property of a molecule (known as a hydrophobe) that is repelled from a mass of water ), vitamins that are needed for the posttranslational modification of certain proteins, mostly required for blood coagulation status. The reference range for prothrombin time is usually around 12-15 seconds; the normal range for the INR is 0.8-1.2. PT measures factors II, V, VII, X and fibrinogen. It is used in conjunction with the activated partial thromboplastin time (aPTT) which measures the intrinsic ( of or relating to the essential nature of a thing; inherent ) pathway.
Intramuscular injection is the injection of a substance directly into a muscle. In medicine, it is one of several alternative methods for the administration of medications. It is used for particular forms of medication that are administered in small amounts. Depending on the chemical properties of the drug,
Intramuscular injection (cont).
the medication may either be absorbed fairly quickly or more gradually. Intramuscular injections are often given in the deltoid-(a muscle in the shoulder), vastus lateralis - (is the largest part of the Quadriceps femoris-(leg), ventrogluteal and dorsogluteal muscles-( The gluteal muscles are the three muscles that make up the human buttocks). When the gluteal muscles are used, injections should be made on the upper, outer quadrant of the buttock to avoid damaging the sciatic nerve.
Thrombocytopenia (low platelet counts) and coagulopathy (bleeding tendency) are contraindications for intramuscular injections, as they may lead to haematomas.
In medicine, intubation refers to the placement of a tube into an external or internal orifice of the body. Although the term can refer to endoscopic procedures, it is most often used to denote tracheal intubation. Tracheal intubation is the placement of a flexible plastic tube into the trachea to protect the patient's airway and provide a means of mechanical ventilation. The most common tracheal intubation is orotracheal intubation where, with the assistance of a laryngoscope -(larynx+scope) is a medical instrument that is used to obtain a view of the glottis – ( the space between the vocal cords is called the glottis), an endotracheal tube is passed through the mouth, larynx, and vocal cords, into the trachea. A bulb is then inflated near the distal tip of the tube to help secure it in place and protect the airway from blood, vomit, and secretions. Another possibility is nasotracheal intubation where a tube is passed through the nose, larynx, vocal cords, and trachea.
Ionised - converted totally or partly into ions.
An ion is an atom or group of bonded atoms which have lost or gained one or more electrons, making them negatively or positively charged. An ion consisting of a single atom is called a monatomic ion. A negatively charged ion, which has more electrons in its electron shells than it has protons in its nuclei, is known as an anion- (pronounced; an-eye-on) due to its attraction to anodes. A positively-charged ion, which has fewer electrons than protons, is known as a cation- (pronounced; cat-eye-on) due to its attraction to cathodes. A polyatomic anion that contains oxygen is sometimes known as an oxyanion.
Ion channels are pore-forming proteins that help to establish and control the small voltage gradient across the plasma membrane of all living cells by allowing the flow of ions down their electrochemical gradient. They are present in the membranes that surround all biological cells.
Isotonic literally translates to equal tension. The term is used in several different contexts. Isotonic solution bears the same chemical resemblance of the body’s blood, plasma and tears. All fluids in the body have a certain concentration, referred to as osmotic pressure. The body’s common osmotic pressure, which is isotonic, allows a consistent maintenance of body tissues. In order for a substance to be absorbed and used in the body’s metabolism, it must be transported in an isotonic state.
Effect of different solutions on blood cells:
Cells have a semipermeable membrane that allows the diffusion (flow) of water, but not the dissolved compounds such as salt ions (solutes). Water diffuses across the membrane in direction of the higher concentrated solution in a process called osmosis, thereby generating osmotic pressure if the inside concentration is higher. Under isotonic conditions the concentrations of impermeable solutes, the osmolality, is the same inside and outside the cell and there is no osmotic pressure. A medium of lower osmolality is called hypotonic and one of higher osmolality is called hypertonic.
Isotopes- (Greek for "at the same place") are any of the several different forms of an element each having different atomic mass (mass number). Isotopes of an element have nuclei with the same number of protons (the same atomic number) but different numbers of neutrons. Therefore, isotopes have different mass numbers, which give the total number of nucleons—the number of protons plus neutrons.
In cell biology, molecular biology and related fields, the word intracellular means "inside the cell". It is used in contrast to extra-cellular- (outside the cell).
Intravenous therapy or IV therapy is the giving of liquid substances directly into a vein. It can be intermittent or continuous; continuous administration is called an intravenous drip. The word intravenous simply means "within a vein", but is most commonly used to refer to IV therapy. Compared with other routes of administration, the intravenous route is the fastest way to deliver fluids and medications throughout the body. Some medications, as well as blood transfusions, can only be given intravenously.
An infusion pump or perfusor infuses fluids, medication or nutrients into a patient's circulatory system. It is generally used intravenously, although subcutaneous, arterial and epidural infusions are occasionally used. Infusion pumps can administer fluids in ways that would be impractically expensive or unreliable if performed manually by nursing staff. For example, they can administer as little as 0.1 mL per hour injections (too small for a drip), injections every minute, injections with repeated boluses requested by the patient, up to maximum number per hour (e.g. in patient-controlled analgesia), or fluids whose volumes vary by the time of day.
Because they can also produce quite high but controlled pressures, they can inject controlled amounts of fluids subcutaneously (beneath the skin), or epidurally (just within the surface of the central nervous system- a very popular local spinal anaesthesia for childbirth).
Ischaemia is a condition in which the blood flow (and thus oxygen) is restricted to a part of the body. Cardiac ischemia is the name for lack of blood flow and oxygen to the heart muscle. It's the term given to heart problems caused by narrowed heart arteries. When arteries are narrowed, less blood and
oxygen reaches the heart muscle. This is also called coronary artery disease and coronary heart disease. This can ultimately lead to heart attack.
Ischemia often causes chest pain or discomfort known as angina pectoris( chest ).
Jet ventilation is a special type of mechanical ventilation for surgical operations in the airway. Jet ventilation (JV) is characterized by the insufflation-(Latin insufflatio "blowing on or into") of gas portions with high velocity into the airway. The latter has to be open to the atmosphere in order to allow an unhindered gas egress and therefore to avoid overdistention (barotrauma) of the lungs.
Barotrauma is physical damage to body tissues caused by a difference in pressure between an air space inside or beside the body and the surrounding gas or liquid.
Indications: The rationale for JV is its property of being administered without an endotracheal tube, thus not requiring an airtight sealing of the airway. This feature allows maintenance of a sufficient gas exchange while the airway can be accessed, examined and operated with a rigid bronchoscope. Another advantage of this ventilation method during the use of surgical laser beams, is the avoidance of inflammable tubing material, as is usually applied for conventional intermittent positive pressure ventilation. JV can be applied either by simple manual devices or sophisticated electronically operated ventilators with various choices for ventilation settings as well as measuerement and display of applied and resulting parameters. A ventilation frequency below 1 Hz is called "low frequency jet ventilation" while above 1 Hz it is a "high frequency jet ventilation".
Procedure: The connection between the ventilator and the patient's airway can be established via a translaryngeal jet catheter (translaryngeal-infraglottic access), directly through the skin of the anterior neck into the trachea (transtracheal-infraglottic access) or through a nozzle which is located proximally and above the vocal cords (supraglottic access). Common ventilation settings in an adult patient are:
• oxygen concentration: 30-100%.
• driving pressure: 0.8-4 bar.
• ventilation frequency: 150 cycles per minute.
• I:E ratio of 1.0.
Complications: Complications of JV may comprise hypoxaemia, hypercapnia, surgical emphysema and pneumothorax.
The kidneys are organs that filter wastes (such as urea) from the blood and excrete them, along with water, as urine. The medical field that studies the kidneys and diseases of the kidney is called nephrology. The prefix nephro- meaning kidney is from the Ancient Greek word nephros (νεφρός); the adjective renal meaning related to the kidney is from Latin rēnēs, meaning kidneys. In humans, the kidneys are located in the posterior part of the abdomen. There is one on each side of the spine; the right kidney sits just below the liver, the left below the diaphragm and adjacent to the spleen. Above each kidney is an adrenal gland (also called the suprarenal gland). The asymmetry within the abdominal cavity caused by the liver results in the right kidney being slightly lower than the left one while the left kidney is located slightly more medial. The kidneys are retroperitoneal. They are approximately at the vertebral level T12 to L3. The upper parts of the kidneys are partially protected by the eleventh and twelfth ribs, and each whole kidney is surrounded by two layers of fat (the perirenal and pararenal fat) which help to cushion it.
Each kidney receives its blood supply from the renal artery, two of which branch from the abdominal aorta. The basic functional unit of the kidney is the nephron, of which there are more than a million within the cortex and medulla of each normal adult human kidney. Nephrons regulate water and soluble matter (especially electrolytes) in the body by first filtering the blood under pressure, and then reabsorbing some necessary fluid and molecules back into the blood while secreting other, unneeded molecules.
The kidneys excrete a variety of waste products produced by metabolism, including the nitrogenous wastes: urea (from protein catabolism) and uric acid (from nucleic acid metabolism) and water. The kidney is one of the major organs involved in whole-body homeostasis. Among its homeostatic functions are acid-base balance, regulation of electrolyte concentrations, control of blood volume, and regulation of blood pressure. The kidneys secrete a variety of hormones, and is one of the major organs involved in whole-body homeostasis.
Lactate (lactic acid)
Venous: 4.5 - 19.8 mg/dL, Arterial: 4.5 - 14.4 mg/dL .
Lactic acid is mainly produced in muscle cells and red blood cells. It forms when the body breaks down carbohydrates to use for energy during times of low oxygen levels. Your body's oxygen level might drop during intense exercise or if you have an infection or disease. A blood test can be done to measure the amount of lactic acid in the blood. This test is usually done to diagnose lactic acidosis. Abnormal results suggest that body tissues are not getting enough oxygen.
Conditions associated with increased lactic acid levels include:
• Hypoxia seen in shock
• Congestive heart failure
• Hepatic (liver) problems
• Ischemia (not enough oxygenated blood getting to a certain area)
• Lung disease .
Lactic acidosis is when lactic acid builds ups in the blood stream faster than it can be removed. Lactic acid is produced when oxygen levels in the body drop. The most common cause is intensive exercise. However, it can also be caused by certain diseases, such as sepsis, respiratory failure, AIDS, cancer, and kidney failure. The primary treatment for lactic acidosis is correcting the underlying medical problem that causes the condition.
A laryngoscope (larynx+scope) is a medical instrument that is used to obtain a view of the glottis– (the space between the vocal cords is called the glottis).
A rigid laryngoscope is used for direct laryngoscopy. It consists of a handle (incorporating a battery) and a blade with a light source.
Direct laryngoscopy is done with the patient lying on his or her back; the larygoscope is inserted into the mouth to push away the tongue and lift the epiglottis - (is a lid-like flap of elastic cartilage tissue covered with a mucus membrane, attached to the root of the tongue. It projects obliquely upwards behind the tongue and the hyoid bone. so that a view of the glottis – (the space between the vocal cords is called the glottis).is possible. This procedure is most often employed in tracheal intubation. It is painful and extremely uncomfortable and is usually not done in conscious patients. One of the main complications when using a laryngoscope is dental damage to the patients upper teeth.It is performed to facilitate endotracheal intubation as part of a general anesthetic or cardiopulmonary resuscitation following a cardiac arrest.
In medicine, laryngospasm is an uncontrolled/involuntary muscular contraction (spasm) of the laryngeal cords. The condition typically lasts less than 30 or 60 seconds, and causes a partial blocking of breathing in, while breathing out remains easier. It may be triggered when the voice box or the area of the windpipe below the voicebox detects the entry of water or other substance. It is characterized by a high pitched scream-like sound, and might be frightening for some to witness. Some people suffer from frequent laryngospasms, whether awake or asleep. In an ear, nose and throat practice, it is typically seen in people who have silent reflux disease. It is also a well known, infrequent but serious post-surgery complication.
Etiology - (the study of the cause or origin of a disease).
It is a complication associated with anaesthesia. The spasm can happen often without any provocation, but tends to occur after tracheal extubation.
Treatment: Laryngospasm in the operating room is treated by hyperextending the patient's head and administering mechanical ventilations with 100% oxygen. In more serious cases it may require intubation. If orotracheal intubation is not possible a cricothyroidotomy-(see below) is done to create an airway. In ear, nose and throat practices, it is treated by examining the patient pre-op and reassuring the patient that laryngospasm resolves. Sometimes reflux-(abnormal flowing back of gastric contents) medication is used to reduce the acidity in the stomach.
A cricothyroidotomy, or emergency airway puncture) is an emergency incision through the skin and cricothyroid membrane to secure a patient's airway during certain emergency situations. A cricothyrotomy is usually performed by emergency physicians, surgeons, or paramedics as a last resort when control of the airway by usual means (an endotracheal tube through the mouth) have failed or are not feasible.
The larynx (plural larynges), colloquially known as the voicebox, is an organ in the neck of mammals involved in protection of the trachea and sound production. The larynx houses the vocal folds, and is situated just below where the tract of the pharynx-(the pharynx (plural: pharynges) is the part of the neck and throat situated immediately posterior to the mouth and nasal cavity, and cranial, or superior, to the oesophagus, larynx, and trachea) splits into the trachea and the oesophagus-( or gullet is an organ in vertebrates which consists of a muscular tube through which food passes from the pharynx to the stomach). Sound is generated in the larynx, and that is where pitch and volume are manipulated. The strength of expiration from the lungs also contributes to loudness, and is necessary for the vocal folds to produce speech.
Left Atrial Radio-Frequency (RF) Ablation L.A.R.F.
Intra-operative left atrial radiofrequency (RF) ablation recently has been suggested as an effective surgical treatment for atrial fibrillation (AF). Left atrial radiofrequency ablation (RFA) during mitral valve surgery for continuous atrial fibrillation significantly improves postoperative sinus rhythm. Radiofrequency ablation (RFA) for atrial fibrillation is typically carried out in patients undergoing concomitant- (occurring together) open heart surgery (often mitral valve replacement or repair). The procedure uses thermal damage, rather than incisions, to block impulse conduction. The heat generated coagulates the heart tissue, forming linear scars or lesions that disrupt the transmission of the abnormal electrical impulses. The procedure may be carried out on both atria or on the left atrium only. It can be performed from within or outside the atrium.
Leukocytes (see White blood cells ).
White blood cells or leukocytes are cells of the immune system which defend the body against both infectious disease and foreign materials. Several different and diverse types of leukocytes exist, but they are all produced and derived from a pluripotent ( "having more than one potential outcome") cell in the bone marrow known as a haematopoietic stem cell. Leukocytes are found throughout the body, including the blood and lymphatic system. The number of leukocytes in the blood is often an indicator of disease. There are normally between 4×109 and 11×109 white blood cells in a litre of blood, making up approximately 1% of blood in a healthy adult. In conditions such as leukaemia the number of leukocytes is higher than normal, and in leukopenia this number is much lower.
In biochemistry, a ligand (latin- ligare = to bind) is a molecule that is able to bind to and form a complex with a bio-molecule to serve a biological purpose.
The lung is the essential respiration organ in air-breathing vertebrates, the most primitive being the lungfish. Its principal function is to transport oxygen from the atmosphere into the bloodstream, and to excrete carbon dioxide from the bloodstream into the atmosphere. This exchange of gases is accomplished in the mosaic of specialized cells that form millions of tiny, exceptionally thin-walled air sacs called alveoli. The lungs also have non respiratory functions. Medical terms related to the lung often begin with pulmo-, from the Latin pulmonarius ("of the lungs"), or with pneumo- (from Greek πνεύμω "lung").
Human respiratory system.
Energy production from aerobic-( "requiring air", i.e, oxygen) respiration requires oxygen and produces carbon dioxide as a by-product, creating a need for an efficient means of oxygen delivery to cells and excretion of carbon dioxide from cells. In air-breathing vertebrates, respiration occurs in a series of steps. Air is brought into the animal via the airways — in reptiles, birds and mammals this often consists of the nose; the pharynx; the larynx; the trachea (also called the windpipe); the bronchi and bronchioles; and the terminal branches of the respiratory tree. The lungs of mammals are a rich lattice of alveoli, which provide an enormous surface area for gas exchange. A network of fine capillaries allows transport of blood over the surface of alveoli. Oxygen from the air inside the alveoli diffuses into the bloodstream, and carbon dioxide diffuses from the blood to the alveoli, both across thin alveolar membranes. The drawing and expulsion of air is driven by muscular action; in early tetrapods, air was driven into the lungs by the pharyngeal muscles, whereas in reptiles, birds and mammals a more complicated musculoskeletal system is used. In the mammal, a large muscle, the diaphragm (in addition to the internal inter-costal muscles), drive ventilation by periodically altering the intra-thoracic volume and pressure; by increasing volume and thus decreasing pressure, air flows into the airways down a pressure gradient, and by reducing volume and increasing pressure, the reverse occurs. During normal breathing, expiration is passive and no muscles are contracted (the diaphragm relaxes). Another name for this inspiration and expulsion of air is ventilation. Vital capacity is the maximum volume of air that a
person can exhale after maximum inhalation. A person's vital capacity can be measured by a spirometer (an apparatus for measuring the volume of air inspired and expired by the lungs ,spirometry). In combination with other physiological measurements, the vital capacity can help make a diagnosis of underlying lung disease.
Non respiratory functions
In addition to respiratory functions such as gas exchange and regulation of hydrogen ion concentration, the lungs also:
• influence the concentration of biologically active substances and drugs used in medicine in arterial blood
• filter out small blood clots formed in veins
• serve as a physical layer of soft, shock-absorbent protection for the heart, which the lungs flank and nearly enclose.
• filter out gas micro-bubbles occurring in the venous blood stream during SCUBA diving decompression.
The lungs of mammals have a spongy texture and are honeycombed with epithelium having a much larger surface area in total than the outer surface area of the lung itself. The lungs of humans are typical of this type of lung.
In humans, it is the two main bronchi (produced by the bifurcation of the trachea) that enter the roots of the lungs. The bronchi continue to divide within the lung, and after multiple divisions, give rise to bronchioles. The bronchial tree continues branching until it reaches the level of terminal bronchioles, which lead to alveolar sacks. Alveolar sacs are made up of clusters of alveoli, like individual grapes within a bunch. The individual alveoli are tightly wrapped in blood vessels, and it is here that gas exchange actually occurs. Deoxygenated blood from the heart is pumped through the pulmonary artery to the lungs, where oxygen diffuses into blood and is exchanged for carbon dioxide in the hemoglobin of the erythrocytes. The oxygen-rich blood returns to the heart via the pulmonary veins to be pumped back into systemic circulation.
Lung cancer is a disease where tissue in the lung grows out of control. This leads to invasion of adjacent tissue and infiltration beyond the lungs metastasis-( sometimes abbreviated mets, is the transfer of a disease from one organ or part to another organ or part not directly connected with it. Only malignant tumor cells have the capacity to metastasize). Lung cancer, the most common cause of cancer-related death in men and the second most common in women, is responsible for 1.3 million deaths worldwide annually. The most common symptoms are shortness of breath, cough (including coughing up blood), and weight loss. The main types of lung cancer are small cell lung cancer and non-small cell lung cancer. This distinction is important because non-small cell lung cancer is sometimes treated with surgery, while small cell cancer is not. Also, small cell lung cancer usually responds better to chemotherapy. Chemotherapy is the use of chemical substances to treat disease. In its modern-day use, it refers primarily to cytotoxic drugs used to treat cancer. Cytotoxicity is the quality of being toxic to cells.
The most significant risk factor for developing lung cancer is long-term exposure to inhaled carcinogens, especially tobacco smoke. The occurrence of lung cancer in non-smokers, who account for less than
10% of cases, appears to be due to a combination of genetic factors. Radon gas, asbestos, and air pollution may also contribute to the development of lung cancer. Lung cancer is often seen on chest x-ray and CT scan. The diagnosis is confirmed with a biopsy. This is usually performed via bronchoscopy or CT-guided biopsy. Treatment and prognosis depend upon the histological type of cancer, the stage (degree of spread), and the patient's performance status. Possible treatments include surgery, chemotherapy, and radiotherapy. Even with treatment, the overall five-year survival rate is 14%
Malignant hyperthermia (MH or MHS for "malignant hyperthermia syndrome", or "malignant hyperpyrexia due to anesthesia") is a rare life-threatening condition that is triggered by exposure to drugs used for general anaesthesia, such as volatile anaesthetics or the depolarizing muscle relaxant suxamethonium chloride. In susceptible individuals, these drugs can induce a drastic and uncontrolled increase in skeletal muscle oxidative metabolism which overwhelms the body's capacity to supply oxygen, remove carbon dioxide, and regulate body temperature, eventually leading to circulatory collapse and death if untreated. MH is often inherited as an autosomal dominant disorder, for which there are at least 6 loci of interest. MH is phenotypically and genetically related to central core disease (CCD), an autosomal dominant disorder characterized both by MH symptoms and myopathy.
Signs, symptoms and diagnosis:
The phenomenon presents with muscular rigidity, followed by a hypermetabolic state with increased oxygen consumption, increased carbon dioxide production (hypercarbia), metabolic acidosis, tachycardia, and an increase in body temperature (hyperthermia) at a rate of up to ~2°C per hour. This is followed by a breakdown of muscle cells (rhabdomyolysis), which release their contents such as myoglobin, creatine kinase (CK/CPK is an enzyme expressed by various tissue types) and potassium, into the bloodstream.
Halothane, a once popular but now rarely used volatile anaesthetic, has been linked to a large proportion of cases, however, all halogenated volatile anaesthetics are potential triggers of malignant hyperthermia. Suxamethonium, a neuromuscular blocking agent, is also a trigger for MH. MH does not occur with every exposure to triggering agents, and susceptible patients may undergo multiple uneventful episodes of anaesthesia before developing an episode of MH. The symptoms usually develop within one hour after exposure to trigger substances, but may even occur several hours later in rare instances.
The standard procedure to test persons suspected of being susceptible is the "caffeine-halothane contracture test", CHCT. A muscle biopsy is carried out at an approved research center, under local anesthesia. The fresh biopsy is bathed in solutions containing caffeine or halothane and observed for contraction; under good conditions, the sensitivity is 97% and the specificity 78%. Negative biopsies are not definitive, so any patient who is suspected of MH by their medical history or that of blood relatives is generally treated with non-triggering anesthetics even if the biopsy was negative. Some researchers advocate the use of the "calcium-induced calcium release" test in addition to the CHCT to make the test more specific.
There is also a protocol for investigating people with a family history of MH, where first-line genetic screening of RYR1 mutations is one of the options.
In anaesthesiology, the Mallampati score, also Mallampati classification, is used to predict the ease of intubation. It is determined by looking at the anatomy of the oral cavity; specifically, it is based on the visibility of the base of uvula, faucial pillars and soft palate.
Mammary (Internal Thoracic) artery harvest
The choice of conduits is highly surgeon and institution dependent. Typically, the left internal thoracic artery (LITA) (previously referred to as left internal mammary artery or LIMA) is grafted to the Left Anterior Descending artery - (see coronary heart desease) and a combination of other arteries and veins is used for other coronary arteries. The right internal thoracic artery (RITA), the great saphenous vein from the leg and the radial artery from the forearm are frequently used. The right gastroepiploic artery from the stomach is infrequently used given the difficult mobilization from the abdomen.
The Maze Procedure is a surgical procedure that cures atrial fibrillation by interrupting the electrical impulses that cause the abnormal heart rhythm. The surgery involves the placement of incisions in both atria. When the incisions heal, scar tissue forms and prevents the abnormal electrical impulses from passing through the heart. Simple in concept, the Maze Procedure works essentially by creating blocks that the electrical impulses can not cross. In so doing, it corrects all the major problems associated with atrial fibrillation: it stops the atrial arrhythmia, it restores normal rhythm between the atria and the ventricles, and it preserves the ability of the atria to contract on its own.
In medicine, mechanical ventilation is a method to mechanically assist or replace spontaneous
breathing when patients cannot do so on their own, and must be done so after invasive intubation with an endotracheal or tracheostomy tube through which air is directly delivered In many cases, mechanical ventilation is used in acute settings such as in the ITU for a short period of time during a serious illness. For some patients who have certain chronic illnesses that require long-term ventilation assistance, they are also able to do so at home or other nursing/rehabilitation institution with the help of respiratory therapists and physicians. The main form of mechanical ventilation currently is positive pressure ventilation, which works by increasing the pressure in the patient's airway and thus forcing additional air into the lungs. This is in contrast to the more historically common negative pressure ventilators (for example, the "iron lung") that create a negative pressure environment around the patient's chest, thus sucking air into the lungs. Although often a life-saving technique, mechanical ventilation carries many potential complications including pneumothorax, airway injury, alveolar damage, and ventilator-associated pneumonia, among others. Accordingly it is generally weaned off or to minimal settings as soon as possible.
Positive-pressure ventilators work by increasing the patient's airway pressure through an endotracheal or tracheostomy tube. The positive pressure allows air to flow into the airway until the ventilator breath is terminated. Subsequently, the airway pressure drops to zero, and the elastic recoil of the chest wall and lungs push the tidal volume -- the breath -- out through passive exhalation.
Mediastinoscopy is a surgical procedure that enables visualization of the contents of the mediastinum, usually for the purpose of obtaining a biopsy. Mediastinoscopy is often used for staging of lymph nodes of lung cancer or for diagnosing other conditions effecting structures in the mediastinum such as sarcoidosis or lymphoma. Mediastinoscopy involves making an incision approximately 1 cm above the supra-sternal notch of the sternum, or breast bone. The scope may provide direct visualization or may be attached to a video monitor. Mediastinoscopy provides access to mediastinal lymph node levels 2, 4, and 7.
• Sarcoidosis, also called sarcoid (from the greek 'sark' and 'oid' meaning "flesh-like"), is an immune system disorder characterised by non-caseating-( caseation (literally: turning to cheese) is a form of necrosis) granulomas (small inflammatory nodules) that most commonly arises in young adults. The cause of the disease is still unknown. Virtually any organ can be affected; however, granulomas most often appear in the lungs or the lymph nodes.
• Lymphoma is a type of cancer that originates in lymphocytes-( types of cancer that affect blood, bone marrow and lymph nodes). There are many types of lymphoma. Lymphomas are part of the broad group of diseases called haematological neoplasms-( types of cancer that affect blood, bone marrow and lymph nodes ).
In the 19th and 20th centuries the affliction was called Hodgkin's Disease, as it was discovered by Thomas Hodgkin in 1832. Colloquially, lymphoma is broadly categorized as Hodgkin's lymphoma and non-Hodgkin lymphoma (all other types of lymphoma).
The mediastinum is a non-delineated (delineated =represented accurately or precisely ) group of structures in the thorax (chest), surrounded by loose connective tissue. It is the central compartment of the thoracic cavity. It contains the heart, the great vessels of the heart, oesophagus, trachea, thymus, and lymph nodes of the central chest. The mediastinum lies between the right and left pleuræ in and near the median sagittal plane-( a sagittal plane divides the body into sinister and dexter, left and right) portions of the chest. It extends from the sternum in front to the vertebral-( irregular bones that make
up the spinal column) column behind, and contains all the thoracic viscera except the lungs. It may be divided for purposes of description into two parts:
• an upper portion, above the upper level of the pericardium, which is named the superior mediastinum;
• and a lower portion, below the upper level of the pericardium. This lower portion is again subdivided into three parts,
o that in front of the pericardium, the anterior mediastinum;
o that containing the pericardium and its contents, the middle mediastinum;
o and that behind the pericardium, the posterior mediastinum.
It is surrounded by the chest wall anteriorly-(Latin ante; before),the lungs laterally- (Latin lateralis; "to the side") and the spine posteriorly-(Latin post; after).. It is continuous with the loose connective tissue of the neck, and extends inferiorly onto the diaphragm. Note that clinical radiologists and anatomists categorize the mediastinum in slightly different ways.
Medulla in general means the inner part, and derives from the Latin word for 'marrow'. In medicine it is contrasted to the cortex (outer layer) .The innermost part of an organ, particularly the kidneys, lymph glands and suprarenal glands.
Metobolite / Metobolic.
Metabolites are the intermediates and products of metabolism. The term metabolite is usually restricted to small molecules. A primary metabolite is directly involved in the normal growth, development, and reproduction. A secondary metabolite is not directly involved in those processes, but usually has important ecological function. Examples include antibiotics and pigments.
Mitral Valve Repair/Replacement.
Mitral valve replacement is a cardiac surgery procedure in which a patient’s mitral valve is replaced by a different valve. Mitral valve replacement is typically performed robotically or manually, when the valve becomes too tight (mitral valve stenosis) for blood to flow into the left ventricle, or too loose (mitral valve regurgitation) in which case blood can leak into the left atrium and back up into the lung. Some individuals have a combination of mitral valve stenosis and mitral valve regurgitation or simply one or the other. A mitral valve replacement/repair is performed to treat severe cases of mitral valve prolapse-("to fall out of place."), heart valve stenosis, or other valvular diseases. Since a mitral valve replacement is an open heart surgical procedure, it requires placing the patient on cardiopulmonary bypass to stop blood flow through the heart when it is opened up. A mitral valve replacement is necessary when the valve doesn’t open or close completely. When the valve narrows or is stenotic the valve doesn’t let blood flow easily into the heart causing the blood to "back up" and pressure to build up in the lungs. This is dangerous because when the leaflets in the valve don’t meet correctly, blood may leak backwards into the lungs each time the heart pumps. If blood leaks backwards, the heart has to pump harder in order to push the same amount of blood forward. This is known as volume overload. The heart may compensate for this overload for many months or even years but eventually the heart begins to fail and patients show symptoms of shortness of breath or fatigue.
Causes: Mitral valve problems are mainly caused from simple wear and tear that causes part of the valve mechanism to fail. Rheumatic fever may also damage the mitral valve causing stenosis or regurgitation, and occasionally the mitral valve is damaged by infection or bacterial endocarditis. Coronary artery disease is also what may cause the mitral valve to leak.
Symptoms: Some symptoms of patients that need mitral valve repair or replacement include: sensations of feeling the heart beat, chest pain, hard to breathe especially after activity, fatigue, coughing, and shortness of breath while lying flat. These symptoms may develop slowly or the patient my not have any symptoms at all.
Options: Some surgeons will first recommend repairing the valve instead of replacement, but if the patient is not a good candidate then they must replace the valve. Many mitral valves can be repaired, especially if the leak is due to wear and tear. When the valve is too damaged to repair, the valve must be replaced with an artificial valve. There are some advantages to repairing a mitral valve versus replacement it. Some of these advantages are; a lower mortality at the time of operation (1-2% for repair versus 6-8% for replacement), a significantly lower risk of stroke, and a lower rate of infection, improved long-term survival with mitral valve repair. After mitral valve repair, blood thinners are not required, in contrast to the life-long requirement for blood thinners after mechanical mitral valve replacement.
In medicine, the term morbidity can refer to
• the state of being diseased (from Latin morbidus: sick, unhealthy),
• the degree or severity of a disease,
• the prevalence of a disease: the total number of cases in a particular population at a particular point in time,
• the incidence of a disease: the number of new cases in a particular population during a particular time interval.
• disability irrespective of cause (e.g., disability caused by accidents).
The term morbidity rate can refer either to the incidence rate or to the prevalence rate of a disease. Compare this with the mortality rate of a condition, which is the number of people dying during a given time interval, divided by the total number of people in the population.
Mortality may refer to:
• The quality of being mortal, i.e. susceptible to death.
• Mortality rate, a measure of the number of deaths in some population.
In vertebrates, the term motor neuron classically applies to neurons located in the central nervous system (CNS) which project their axons outside the CNS and directly or indirectly control muscles.
Muscarine, L-(+)-muscarine, is a natural product found in certain mushrooms, particularly in Inocybe and Clitocybe species, such as the deadly C. dealbata. It was the first parasympathomimetic substance ever studied and causes profound activation of the peripheral parasympathetic nervous system that may end in convulsions and death. Muscarine has no effects on the central nervous system because it does not cross the blood-brain barrier due to its positively charged (polar) nitrogen atom. Muscarine mimics the action of the neurotransmitter acetylcholine at metabotropic receptors that are also known under the name muscarinic acetylcholine receptors.
Muscle (from Latin musculus "little mouse") is contractile tissue of the body. It is classified as skeletal, cardiac, or smooth muscle, and its function is to produce force and cause motion, either locomotion or movement within internal organs. Much of muscle contraction occurs without conscious thought and is necessary for survival, like the contraction of the heart, or peristalsis (which pushes food through the digestive system). Voluntary muscle contraction is used to move the body, and can be finely controlled, like movements of the eye, or gross movements like the quadriceps muscle of the thigh.
There are three general types of muscle tissues:
• Skeletal muscle (voluntary and involuntary) contractions
• Cardiac muscle (involuntary) contractions
• Smooth muscle (involuntary) contractions.
Muscle Relaxant / Neuromuscular blocking drugs.
A muscle relaxant is a drug which decreases the tone of a muscle. Neuromuscular-blocking drugs block neuromuscular transmission at the neuromuscular junction, causing paralysis of the affected skeletal muscles. This is accomplished either by acting pre-synaptically-( see below ) via the inhibition of acetylcholine (ACh) synthesis or release, or by acting post-synaptically at the acetylcholine receptor. While there are drugs that act pre-synaptically (such as botulin toxin and tetrodotoxin), the clinically-relevant drugs work post-synaptically.
Clinically, neuromuscular block is used as an adjunct to anesthesia to induce paralysis, so that surgery can be carried out with less complications. Because neuromuscular block may paralyze muscles required for breathing, mechanical ventilation should be available to maintain adequate respiration. These drugs fall into two groups:
• Non-depolarizing blocking agents: These agents constitute the majority of the clinically-relevant neuromuscular blockers. They act by blocking the binding of ACh to its receptors, and in some cases, they also directly block the ionotropic activity of the ACh receptors.
• Depolarizing blocking agents: These agents act by depolarizing the plasma membrane of the skeletal muscle fiber. This persistent depolarization makes the muscle fiber resistant to further stimulation by ACh.
Chemical synapses are specialized junctions through which the cells of the nervous system signal to each other and to non-neuronal cells such as those in muscles or glands.
Myocardia / myocardium.
Myocardium is the muscular middle layer of the wall of the heart. It is composed of spontaneously contracting cardiac muscle fibres which allow the heart to contract. Myo, meaning “muscle”, cardia, meaning “ heart “.
Myocardial rupture is a laceration or tearing of the walls of the ventricles or atria of the heart, of the interatrial or interventricular septum, of the papillary muscles - (of the heart serve to limit the movements of the mitral and tricuspid valves) or chordae tendineae – (are cord-like tendons that connect the papillary muscles to the tricuspid valve and the mitral valve in the heart.) or of one of the valves of the heart. It is most commonly seen as a serious sequelae of an acute myocardial infarction (heart attack).
Etiology = (The science and study of the causes or origins of disease).
The most common cause of myocardial rupture is a recent myocardial infarction, with the rupture typically occurring three to five days after infarction. Other causes of rupture include cardiac trauma, endocarditis (infection of the heart), cardiac tumours, infiltrative diseases of the heart, and aortic dissection.
Risk factors for rupture after an acute myocardial infarction include female gender, advanced age of the individual, and a low body mass index. Other presenting signs associated with myocardial rupture include a pericardial friction rub, sluggish flow in the coronary artery after it is opened, the left anterior descending artery being the cause of the acute MI, and delay of revascularization greater than 2 hours.
In medicine (cardiology), myocarditis is inflammation of the myocardium, the muscular part of the heart. It is generally due to infection (viral or bacterial). It may present with chest pain, rapid signs of heart failure, or sudden death.
The signs and symptoms associated with myocardits are varied, and relate either to the actual inflammation of the myocardium, or the weakness of the heart muscle that is secondary to the inflammation. Signs and symptoms of myocarditis include:
• Chest pain (often described as "stabbing" in character).
• Congestive heart failure (leading to oedema, breathlessness and hepatic congestion).
• Palpitations (due to arrhythmias).
• Sudden death (in young adults, myocarditis causes up to 20% of all cases of sudden death).
• Fever (especially when infectious, e.g. in rheumatic fever).
Since myocarditis is often due to a viral illness, many patients give a history of symptoms consistent with a recent viral infection, including fever, diarrhoea, joint pains, and easy fatigueability. Myocarditis is often associated with pericarditis, and many patients present with signs and symptoms that suggest concurrent myocarditis and pericarditis.
Myo, meaning "muscle", cyte, indicating "cell".
In medicine, a myopathy is a neuromuscular disease in which the muscle fibers do not function for any one of many reasons, resulting in muscular weakness. "Myopathy" simply means muscle disease (myo- Greek μυσ "muscle" + -pathy Greek "suffering"). This meaning implies that the primary defect is within the muscle, as opposed to the nerves ("neuropathies" or "neurogenic" disorders) or elsewhere (e.g., the brain etc.). Muscle cramps, stiffness, and spasm can also be associated with myopathy.
A myxoma (Myxo- = Latin for mucous) is the most common primary tumuor of the heart. Myxomas are usually located in either the left or right atrium of the heart; about 86 percent occur in the left atrium.
Myxomas are typically pedunculated – (an anatomical stalk or stem, such as the stalklike base to which a tumour is attached to normal tissue), with a stalk that is attached to the interatrial septum – (is the wall of tissue that separates the right and left atria of the heart). The most common location for attachment of the stalk is the fossa ovalis – (is an embryonic remnant of the foramen ovale, which normally closes shortly after birth) region of the interatrial septum.
The phrase "myxomatous degeneration" refers to the process in which connective tissue becomes filled with mucous – (a slippery secretion of the lining of various membranes in the body).
About 71% of myxomas occur in the heart, 41% on the skin, and 7% in the oral cavity (usually on the palate).
Narcosis, the unconsciousness induced by a narcotic drug.
The term narcotic is believed to have been coined by Galen (Greek physician), to refer to agents that benumb or deaden, causing loss of feeling or paralysis. The term is based on the Greek word ναρκωσις (narcosis), the term used by Hippocrates for the process of benumbing or the benumbed state. Galen listed mandrake root, and poppy juice (i.e. opium) as the chief examples. Narcotic refers to opium, opium derivatives, and their semi-synthetic or fully synthetic substitutes "as well as cocaine and coca leaves," which although classified as "narcotics". Controlled Substances Act (CSA), are chemically not narcotics. Contrary to popular belief, marijuana is not a narcotic.
Necrosis (in Greek Νεκρός = Dead) is the name given to accidental death of cells and living tissue.
For many centuries, workers occasionally realised that air was composed of more than one component. The behaviour of oxygen and nitrogen as components of air led to the advancement of the phlogiston theory of combustion. Oxygen was prepared by several workers, including Bayen and Borch, but they did not recognise it as an element. Its discovery is generally credited to J. Priestley in 1774, in Leeds, and independently to C.W. Scheele in Uppsala, Sweden.
Oxygen is a colourless, odourless, tasteless gas. Oxygen, as a gaseous element, forms 21% of the atmosphere by volume from which it can be obtained by liquefaction and fractional distillation. The element and its compounds make up 49.2%, by mass, of the Earth's crust. About two-thirds of the human body and nine-tenths of water is oxygen.
Oxygen is very reactive and capable of combining with most other elements. It is a component of thousands of organic compounds, and is essential for the respiration of all plants and animals and for almost all combustion. Oxygen is the basis of all life as part of the DNA molecule. It is breathed in by animals and restored to the air by the photosynthesis mechanism of plants.
Compressed medical gas (for medicinal use only). Modern anaesthetic practice is almost totally dependent on oxygen which provides a dimension of safety that makes possible some of the complicated medical manoeuvres required by modern surgery, and without which the risks would be too great to justify the method. Of equal value is the use of oxygen in intensive care units where it provides the main life-saving support, particularly for patients whose lungs need to be artificially ventilated
if they are to survive. Although the immediate management of cardiac arrest does not depend on an oxygen supply other than in the ambient air, continued treatment almost invariably depends on artificial ventilation with supplementary oxygen. The use of oxygen in chronic respiratory and cardiac conditions is very often essential and it is needed for the relief of all forms of hypoxia other than histotoxic- (Histotoxic hypoxia is the inability of cells to take up or utilize oxygen from the bloodstream, despite physiologically normal delivery of oxygen to such cells and tissues).In short, modern medicine could not be practiced without the support that oxygen provides.
Oxygen is widely used:
• in clinical practice to provide a basis for virtually all modern anaesthetic techniques as
well as pre and post-operative management.
• to restore the tissue oxygen tension towards normal by improving oxygen availability
in a wide range of conditions, Such as:
• cyanosis of recent origin as a result of cardio-pulmonary disease
• surgical trauma, chest wounds and rib fractures
• shock, severe haemorrhage and coronary occlusion
• carbon monoxide poisoning
• hyperpyrexia-( an excessive and unusual elevation of set body temperature ).
• major trauma, eg. road traffic accidents and gunshot wounds.
• in the management of sudden cardiac and respiratory arrest, whether drug induced
• in the resuscitation of the critically ill when the circulation is impaired.
• in neo-natal resuscitation.