Articles: partial-thromboplastin-time.
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Blood Coagul. Fibrinolysis · Feb 1993
The effect of aprotinin on the response of the activated partial thromboplastin time (APTT) to heparin.
Aprotinin, a broad spectrum serine proteinase inhibitor, is becoming increasingly used to control bleeding during surgery. Heparinized patients treated with aprotinin for cardiac surgery have a much longer activated clotting time (ACT) than expected for the dose of heparin used and a similar effect has been observed with the activated partial thromboplastin time (APTT). Since APTT reagents vary in their sensitivity to heparin we compared the effect of aprotinin on 25 commercially available products with respect to the APTT response to heparin. ⋯ The prolongation of the APTT by heparin was markedly increased by aprotinin. For example, APTT ratios at 0.5 IU/ml heparin increased up to eight-fold in the presence of 'therapeutic' levels of aprotinin (200 KIU/ml) and this effect was even more pronounced at higher heparin levels. The activator used did not significantly influence the effect of aprotinin on the APTT although there was a trend for kaolin-activated reagents to be less affected by the addition of aprotinin to heparinised plasma.(ABSTRACT TRUNCATED AT 250 WORDS)
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Randomized Controlled Trial Comparative Study Clinical Trial
Accuracy of drawing coagulation samples from heparinized arterial lines.
To determine the accuracy of activated partial thromboplastin time and prothrombin time studies when samples are drawn through heparinized arterial lines. ⋯ Results indicated that the minimal amount of discard volume for accurate activated partial thromboplastin time values in this population of percutaneous transluminal coronary angioplasty patients was the catheter deadspace volume plus 2 mL (total 3.6 mL).
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Comparative Study Clinical Trial
Comparison of PT and aPTT values drawn by venipuncture and arterial line using three discard volumes.
Blood samples obtained through heparinized arterial catheters are used routinely for a variety of laboratory tests. Accuracy of coagulation studies performed from samples obtained in this fashion continues to be questioned, particularly in regard to the minimum discard volume necessary to clear the catheter of heparinized solution. ⋯ We recommend that when drawing prothrombin time and activated partial thromboplastin time samples from an arterial line, a 5.3-mL discard volume be used.
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The development of a multifactorial coagulopathy after massive transfusion is a well-recognized clinical problem that is almost always accompanied by hypothermia. The purpose of this study was to investigate the isolated effect of alterations of temperature on the integrity of the coagulation cascade. Prothrombin times and partial thromboplastin times were each performed 15 times on samples of pooled normal plasma at the temperatures of 37 degrees C, 34 degrees C, 31 degrees C, and 28 degrees C, as well as 39 degrees C and 41 degrees C. ⋯ The series of enzymatic reactions of the coagulation cascade are strongly inhibited by hypothermia, as demonstrated by the dramatic prolongation of prothrombin time and partial thromboplastin time tests at hypothermic deviations from normal temperature in a situation where factor levels were all known to be normal. Clinicians who deal with critically ill massively transfused hypothermic patients all recognize the inevitable appearance of a coagulopathy that has a multifactorial origin. Unless specifically considered, the contribution of hypothermia to the hemorrhagic diathesis may be overlooked since coagulation testing is performed at 37 degrees C, rather than at the patient's actual in vivo temperature.
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Hypothermic patients commonly develop coagulopathy, but the effects of hypothermia on coagulation remain unclear because clinical laboratories routinely perform clotting tests only at 37 degrees C. Measurements of activated partial thromboplastin times (APTT), prothrombin times (PT), and thrombin times (TT) were performed on plasma from normothermic and hypothermic rats at a range of temperatures (25 degrees-37 degrees C) to assess the effects of hypothermia on apparent clotting factor levels and clotting factor activities. In general, clotting times were more severely prolonged when test temperatures were hypothermic than when body temperatures were hypothermic. ⋯ These findings reveal the observed disparity between clinically evident hypothermic coagulopathy and near-normal clotting studies. Clotting studies performed at 37 degrees C will not confirm hypothermic coagulopathy. These results indicate that the appropriate treatment for hypothermia-induced coagulopathy is rewarming rather than administration of clotting factors.