Aprotinin and heparin monitoring during cardiopulmonary bypass.

BACKGROUND: When high-dose aprotinin is used during cardiopulmonary bypass, there is a prolongation of the activated coagulation time (ACT), which is used to monitor heparinization. The aim of this study was to provide guidelines for monitoring heparin levels by the ACT if aprotinin is used during cardiopulmonary bypass. METHODS AND RESULTS: Heparinized blood from six healthy controls and nine patients on cardiopulmonary bypass was aliquoted and mixed with various concentrations of aprotinin. ACTs were performed on these samples. Activated partial thromboplastin times (APTT) were performed on the citrated plasma mixed with varying concentrations of heparin and aprotinin from the same control patients. Prothrombin times (PT) were performed on plasmas mixed with aprotinin. Aprotinin produced a dose-related prolongation of ACT and APTT but had no effect on PT. This effect occurred whatever the activating agent and in the absence of heparin. CONCLUSIONS: Aprotinin prolongs the ACT and APTT independently of heparin. If high-dose aprotinin is used during cardiopulmonary bypass, ACTs should be maintained at times > 750 seconds to allow for appropriate levels of heparin.