Thrombolytic

6 c. apTT is the activated partial thromboplastin time test which is used to determine the most effective dosage of some medication such as heparin that prevent blood clots. When activators are used the test is called apTT. The test is termed partial due to the absence of the tissue factors from the reaction mixture. Mixing studies are performed in which a patient’s plasma is initially mixed at 50:50 dilution with normal plasma. The apTT also measures how well the coagulation sequences of the intrinsic pathway( factors Xll, Xl, lX,Vlll ) and the common pathway ( factors X, V, ll, and fibrinogen ) are functioning. An elevated apTT could indicate disorders of any coagulation factors except Vll and Xlll. Clinical condition associated with an elevated apTT include DIC, von Willebrand’s disease, and liver disease. Drugs that may affect apTT include chlorpromazine, codeine, phenothiazine, salicylate, and warfarin. But it is used to monitor the patient’s response to heparin therapy.

The target apTT values for a patient with a pulmonary embolism ( PE ) depends on the amount of heparin given. For example, for subcutenaneous treatment with unfractioned heparin, 250 U/kg is given every 12 hours to obtain an apTT with the therapeutic range at 6to8 hours. The heparin dosage should prolong the apTT to range that corresponds to a plasma heparin level of