Heparin-associated thrombocytopenia has been reported most commonly with bovine lung preparations. We prospectively evaluated the incidence of thrombocytopenia in 43 patients receiving intravenous continuous infusions of either bovine lung heparin, manufactured by a new process, or a standard porcine intestinal mucosa heparin for a minimum of five days in a double-blind, randomized fashion. The decision to continue heparin therapy beyond five days was made by the patient's primary physician. All patients had documented acute thromboembolic disease, pretherapy platelet counts greater than 150 000/mm3, and no evidence of prior coagulation disturbance. No patients had undergone cardiopulmonary bypass or hemodialysis within seven days previous to the initiation of heparin therapy. Thrombocytopenia was defined as a decline in platelet count from the normal range of 150 000-350 000/mm3 to less than 100 000/mm3. Thrombocytopenia occurred in one patient (4.6 percent) receiving bovine lung heparin on day nine of therapy and in no patients (0 percent) receiving porcine intestinal mucosa heparin. Adverse reactions occurred in nine patients (42.9 percent) receiving porcine intestinal heparin and five patients (22.7 percent) receiving bovine lung heparin. This difference was not statistically significant. The results of this study indicate that the incidence of thrombocytopenia is low (less than five percent) with both bovine lung heparin, manufactured by a new process, and porcine intestinal mucosa heparin when therapy is limited to short therapeutic courses (less than 1 week).

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