Thrombin time compares a patient's rate of clot formation to that of a sample of normal pooled plasma. Thrombin is added to the samples of plasma. If the plasma does not clot immediately, a fibrinogen deficiency is present. If a patient is receiving heparin, a substance derived from snake venom called reptilase is used instead of thrombin. Reptilase has a similar action to thrombin but unlike thrombin it is not inhibited by heparin.
The thrombin time is used to diagnose bleeding disorders and to assess the effectiveness of fibrinolytic therapy. Reference values for thrombin time are 10 to 15 seconds or within 5 seconds of the control. If reptilase is used, the reptilase time should be between 15 and 20 seconds. Thrombin time can be prolonged by: heparin, fibrin degradation products, lupus anticoagulant.
Click here to study details of coagulation tests, such as thrombin and reptilase time. This WorldWide Anaesthetist also discusses clinical applications of coaguation tests in postop and ICU
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