Argon plasma coagulation Health Dictionary

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Argon Plasma Coagulation: From 1 Different Sources

an endoscopic procedure used predominantly to control bleeding in the gastrointestinal tract. secondary to angiodysplasia and bleeding following polypectomy. Occasionally it is used in the debulking of tumours not amenable to surgery. An intermittent stream of argon gas is delivered through a catheter in the endoscope and ionized by a monopolar electrical current producing a controlled release of thermal energy. This causes coagulation in the adjacent tissues.
Health Source: Oxford | Concise Colour Medical Dictionary
Author: Jonathan Law, Elizabeth Martin

Plasma

The name applied to the straw-coloured ?uid portion of the BLOOD composed of a solution of various inorganic salts of sodium, potassium, calcium, etc., as well as SERUM and ?brinogen, the material which produces clotting (see COAGULATION). When the plasma is clotted, the thinner ?uid separating from the clot is the serum.... plasma

Coagulation

Coagulation of the blood is the process whereby bleeding (or haemorrhage) is normally arrested in the body. Blood starts to clot as soon as the skin (or other tissue) has been cut. Coagulation is part of the process of HAEMOSTASIS which is the arrest of bleeding from an injured or diseased blood vessel. Haemostasis depends on the combined activities of vascular, platelet (see PLATELETS) and PLASMA elements which are o?set by processes to restrict the accumulation of platelets and FIBRIN to the damaged area.

The three-stage process of coagulation is complex, involving many di?erent substances. There are two cascading pathways of biochemical reactions for activating coagulation of blood. The extrinsic pathway is the main physiological mechanism, which is triggered when blood vessels are damaged, usually by trauma or surgery. The intrinsic pathway is activated by internal disruption of the wall of a blood vessel. The basic pattern is broadly the same for both and is summarised simply as follows:

prothrombin + calcium + thromboplastin

thrombin + ?brinogen

?brin

Prothrombin and calcium are normally present in the blood. Thromboplastin is an enzyme which is normally found in the blood platelets and in tissue cells. When bleeding occurs from a blood vessel, there is always some damage to tissue cells and to the blood platelets. As a result of this damage, thromboplastin is released and comes into contact with the prothrombin and calcium in the blood. In the presence of thromboplastin and calcium, prothrombin is converted into thrombin, which in turn interacts with ?brinogen – a protein always present in the blood – to form ?brin. Fibrin consists of needle-shaped crystals which, with the assistance of the blood platelets, form a ?ne network in which the blood corpuscles become enmeshed. This meshwork, or CLOT as it is known, gradually retracts until it forms a tight mass which, unless the tissue injury is very severe or a major artery has been damaged, prevents any further bleeding. It will thus be seen that clotting, or coagulation, does not occur in the healthy blood vessel because there is no thromboplastin present. There is now evidence suggesting that there is an anti-thrombin substance present in the blood in small amounts, and that this substance antagonises any small amounts of thrombin that may be formed as a result of small amounts of thromboplastin being released.

The clotting or coagulation time is the time taken for blood to clot and can be measured under controlled conditions to ensure that it is normal (3–8 minutes). In certain diseases – HAEMOPHILIA, for example – clotting time is greatly extended and the danger of serious haemorrhage enhanced.... coagulation

Plasma Cells

These are cells that produce ANTIBODIES and occur in bone-forming tissue as well as the lining of the gastrointestinal tract and the lungs. The cells develop in LYMPH NODES, SPLEEN and BONE MARROW when T-lymphocytes (see IMMUNITY) are stimulated by antigens (see ANTIGEN) to produce the precursor cells from which plasma cells originate.... plasma cells

Disseminated Intravascular Coagulation

(DIC) A type of bleeding disorder in which abnormal clotting leads to depletion of coagulation factors in the blood; the consequence may be severe spontaneous bleeding.... disseminated intravascular coagulation

Plasma Exchange

Also known as plasmapheresis. The removal of the circulating PLASMA from the patient. It is done by removing blood from a patient and returning the red cells with a plasma expander. The plasma exchange is carried out through an in-dwelling CANNULA in the femoral vein, and the red cells and plasma are separated by a hemonetics separator. Usually a sequence of three or four sessions is undertaken, at each of which 2–3 litres of plasma are removed. The lost plasma can either be replaced by human serum albumin (see ALBUMINS) or a plasma expander.

In autoimmune disorders, disease is due to damage wrought by circulating ANTIBODIES or sensitised lymphocytes (see LYMPHOCYTE). If the disease is due to circulating humoral antibodies, removal of these antibodies from the body should theoretically relieve the disorder. This is the principle on which plasma exchange was used in the management of autoimmune diseases due to circulating antibodies. Such disorders include Goodpasture’s syndrome, SYSTEMIC LUPUS ERYTHEMATOSUS (SLE) and MYASTHENIA GRAVIS. One of the problems in the use of plasma exchange in the treatment of such diseases is that the body responds to the removal of an antibody from the circulation by enhanced production of that antibody by the immune system. It is therefore necessary to suppress this homeostatic response with cytotoxic drugs such as AZATHIOPRINE. Nevertheless, remissions can be achieved in autoimmune diseases due to circulating antibodies by the process of plasma exchange.... plasma exchange

Plasma Transfusion

This procedure is sometimes used instead of blood TRANSFUSION. PLASMA – the ?uid part of blood from which the cells have been separated

– may be dried and in powder form kept almost inde?nitely; when wanted it is reconstituted by adding sterile distilled water. In powder form it can be transported easily and over long distances. Transfusion of plasma is especially useful in the treatment of SHOCK. One advantage of plasma transfusion is that it is not necessary to carry out testing of blood groups before using it.... plasma transfusion

Coagulation, Blood

The main mechanism by which blood clots are formed, involving a complex series of reactions in the blood plasma (see blood clotting).... coagulation, blood

Plasma Proteins

Proteins present in blood plasma, including albumin, blood clotting proteins, and immunoglobulins.... plasma proteins

Argon Laser

a type of *laser that utilizes argon gas to produce a beam of intense light, used especially in eye surgery to treat disease of the retina (e.g. diabetic retinopathy) or glaucoma (as in argon laser *trabeculoplasty). See also photocoagulation.... argon laser

Blood Plasma See Plasma.

... blood plasma see plasma.

Blood Coagulation

(blood clotting) the process whereby blood is converted from a liquid to a solid state. The process may be initiated by contact of blood with a foreign surface (intrinsic system) or with damaged tissue (extrinsic system). These systems involve the interaction of a variety of substances (*coagulation factors) and lead to the production of the enzyme thrombin, which converts the soluble blood protein *fibrinogen to the insoluble protein *fibrin, forming the blood clot. Finally, fibrin is broken down by the action of *plasmin. Anticoagulants and tissue plasminogen activators act by inhibiting or activating various pathways in this cascade (see illustration). Blood coagulation is an essential mechanism for the arrest of bleeding (*haemostasis). See also platelet activation.... blood coagulation

Coagulation Factors

(clotting factors) a group of substances present in blood plasma that, under certain circumstances, undergo a series of chemical reactions leading to the conversion of blood from a liquid to a solid state (see blood coagulation). Although they have specific names, most coagulation factors are referred to by an agreed set of Roman numerals (e.g. *Factor VIII, *Factor IX). Lack of any of these factors in the blood results in the inability of the blood to clot. See also haemophilia.... coagulation factors

Coagulation Time

(clotting time) the time taken for blood or blood plasma to coagulate (see blood coagulation). When measured under controlled conditions and using appropriate techniques, coagulation times may be used to test the function of the various stages of the blood coagulation process.... coagulation time

Cold Coagulation

see cervical intraepithelial neoplasia.... cold coagulation

Plasma Coagulation

a type of *electrocoagulation used to arrest haemorrhage or destroy abnormal tissue. A stream of inert gas, such as argon or helium, is ionized, thereby carrying electrical energy to adjacent tissue; there is no physical contact between the plasma coagulation apparatus and the tissue.... plasma coagulation

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