coagulation time

coagulation time.

See clotting time.

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time [tīm]

a measure of duration. See under adjectives for specific times, such as bleeding time.

activated partial thromboplastin time (APTT, aPTT) the period required for clot formation in recalcified blood plasma after contact activation and the addition of platelet substitutes such as brain cephalins or similar phospholipids; used to assess the coagulation pathways. A prolonged aPTT can indicate a deficiency of any of various coagulation factors, including factors XII, XI, IX, VIII, X, V, and II, and fibrinogen.

AEC minimal response time the shortest duration at which x-ray exposure can be terminated by automatic exposure control.

atrioventricular sequential time a fixed nonprogrammable interval that extends from the atrial stimulus to the ventricular stimulus.

bleeding time the time required for a standardized wound to stop bleeding; used as a test for platelet disorders; see also bleeding time.

circulation time the time required for blood to flow between two given points; see also circulation time.

clotting time (coagulation time) the time required for blood to clot in a glass tube; see also clotting.

cold ischemia time the time between the placement of a traumatically amputated body part in ice and the time of surgical replantation.

inertia time the time required to overcome the inertia of a muscle after reception of a stimulus.

ischemia time the total time between traumatic amputation of a limb or portion of a limb and its surgical reimplantation; it is the sum of warm and cold ischemia times.

minimal response time in radiology, the shortest possible exposure time for an x-ray film to be exposed automatically.

one-stage prothrombin time prothrombin time.

prothrombin time see prothrombin time.

real time a term used to describe a recording device that shows events simultaneously to their occurrence.

R peak time intrinsicoid deflection.

thrombin time the time required for plasma fibrinogen to form thrombin; see also thrombin time.

warm ischemia time the time interval between traumatic amputation of a limb or part and its placement on ice.

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time,

n a measure of duration.

time, clot retraction,

n the time required for a given quantity of blood to separate in the tube in which it has been placed. For 3 ml of blood at room temperature, 1 hour is normal. It is very slow in thrombocytopenia.

time, coagulation,

n the time required for blood clotting to begin in a capillary tube, normally 2 to 8 minutes. A coagulation time three times normal is a definite danger sign.

time, gel,

n (gelation time), the interval of time required for a colloidal solution to become a solid or semisolid jelly or gel. Usually refers to the working time of a hydrocolloid or alginate impression material.

time, gelation,

n See time, gel.

time limits,

n.pl the periods within which a notice of claim must be filed.

time, median lethal,

n (LD₅₀ time, MLT), the time required for 50% of a large group of animals or organisms to die after administration of a specified dose of radiation.

time, prothrombin

n (one-stage test), a gross but useful screening test of the completeness of the second and third stages of blood coagulation. Normal prothrombin time by the Quick method is 12 to 15 seconds. The time is affected by deficiencies of factor V or VII as well as of prothrombin. See also test, prothrombin consumption.

time, serum prothrombin,

n See test, prothrombin consumption.

time, setting,

n the length of time for a mixed preparation of materials to reach a state of hardness, measured from the start of the mixing. The end point for dental materials is usually determined by a penetration test.

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coagulation

1. formation of a clot.

2. in surgery, the disruption of tissue by physical means to form an amorphous residuum, as in electrocoagulation and photocoagulation.

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activated coagulation time (ACT)

a test of the intrinsic or common pathway of coagulation, using diatomaceous earth as an activating agent to hasten coagulation of whole blood, the time being measured. More sensitive than Lee-White or capillary tube tests. See also clotting time.

biterminal coagulation

see monopolar electrocoagulation.

coagulation cascade

the sequence of enzymatic reactions leading to the formation of a blood clot. Each is initiated by the preceding and, in turn, produces the enzyme that catalyzes the next with an amplification of the process as it progresses.

cerebrospinal coagulation

normal CSF does not coagulate. Inflammation of the meninges or contamination of the fluid by blood, possibly during collection, can cause coagulation in a sample.

coagulation defects

see coagulopathy.

disseminated intravascular coagulation (DIC)

widespread formation of thromboses in the microcirculation, mainly within the capillaries. It is a secondary complication of a wide variety of disorders all of which activate in some way the intrinsic coagulation sequence. Paradoxically, the intravascular clotting ultimately produces hemorrhage because of rapid consumption of fibrinogen, platelets, prothrombin, and clotting factors V, VIII and X. Because of this pathology, DIC is sometimes called defibrination syndrome or consumption coagulopathy. Called also diffuse intravascular coagulation. Called also consumption coagulopathy, defibrination syndrome, defibrinogenation syndrome.

coagulation factors

see clotting factors. platelet factors also play a role in coagulation. They are designated by Arabic numerals from 1 to 4.

coagulation inhibitors

these systems prevent widescale intravascular coagulation as a result of minor injury. The important systems are c₁-inactivator, antithrombin III, alpha1-antitrypsin, α2-macroglobulin, factor XIa inhibitor, lipoprotein factor Xa inhibitor.

coagulation necrosis

see coagulative necrosis.

coagulation pathways

the coagulation cascade can follow alternative routes depending on the initiating factor. The extrinsic pathway is initiated by tissue thromboplastin (factor III) and involves calcium ions and factor VII. In the intrinsic pathway, factors XII, XI, IX and VIII are activated by exposure to subendothelial collagen or foreign surfaces. Both pathways lead to the activation of factor X and proceed along the common pathway, involving factors V, II, I and XIII, to the formation of a fibrin clot.

coagulation proteins

see clotting factors.

synovial coagulation

normal synovial fluid does not clot, but gels on standing (thixotropism). It contains no fibrinogen, nor any of the coagulation factors. Clotting is an indication of damage to the synovial membrane.

coagulation tests

are used to determine the integrity of the coagulation pathways, and platelet function. In general, the common tests for the intrinsic or common pathways are the activated partial thromboplastin time (APTT) and activated coagulation time (ACT). One-stage prothrombin time (OSPT) is usually used to evaluate the extrinsic or common pathways, and platelet count, clot retraction, bleeding time and activated coagulation time reflect platelet numbers and function.

coagulation time

see clotting time.

unipolar coagulation

see bipolar electrocoagulation.