Intraoperative heparin flushes and subsequent acute heparin-induced thrombocytopenia.

HEPARIN-INDUCED thrombocytopenia is one of the most important immune-mediated adverse reactions in clinical medicine because of its paradoxical strong association with thromboembolic complications Although most cases of heparin-induced thrombocytopenia occur in patients receiving therapeutic- or prophylactic-dose heparin, 4 a few cases have been reported in patients receiving ongoing intermittent heparin flushes to maintain patency of indwelling intravascular catheters, particularly in intensive care unit patients receiving such heparin for several days. 5-8 However, it is unknown whether a very brief, low-dose heparin exposure, such as occurs during intermittent heparin flushing restricted to the intraoperative use of a single intraarterial catheter, could trigger clinically significant immune sensitization to heparin. Potentially, such an event could be important, because if a large dose of heparin was necessary a few days or weeks later, unexpected, life-threatening, acute thrombocytopenia with risk for thrombosis or bleeding could result. We describe two patients in whom such a trivial intraoperative exposure to heparin proved to be the cause for immune sensitization to heparin, resulting in subsequent acute heparin-induced thrombocytopenia, with a fatal outcome in one patient.