The incidence of heparin-induced antibodies in patients undergoing vascular surgery: a prospective study.

PURPOSE

This study prospectively assessed the incidence of heparin-induced antibodies in patients undergoing peripheral vascular surgery and determined whether the incidence is influenced by previous heparin exposure.

METHODS

Fifty-four hospitalized patients (36 men and 18 women) undergoing peripheral vascular surgery and receiving intraoperative heparin anticoagulation were studied. Unfractionated porcine heparin was given for intraoperative anticoagulation and was not continued postoperatively. Carotid endarterectomy was performed in 36 patients, aortic reconstruction in 11 patients, and infrainguinal bypass in 7 patients. Plasma was tested before and after (14 +/- 7.5 [SD] days) surgery for IgG antibodies to the complex of heparin/platelet factor 4, using a standardized, validated enzyme-linked immunosorbent assay (ELISA). Results are expressed as an optical density ratio (ODR) of patient plasma to normal plasma, with the threshold for a positive result of > or = 1.8. Platelet counts and clinical outcomes were also assessed.

RESULTS

The mean patient age was 67.2 +/- 9.7 years. A prior exposure to heparin was documented in 41% of patients. The mean intraoperative heparin dose was 9089 +/- 3607 units. Only 1 patient converted from a negative antibody status to a positive status (1.9%, 95% CI = 0.10%-11.18%). The change in the ELISA ODR after surgery was not significantly different for patients with (+0.042 +/- 0.272) and without (-0.022 +/- 0.299, P = 0.57) prior heparin exposure. Postoperatively, the platelet counts dropped from 227,620 +/- 78,308 microL, to 185,706 +/- 80,842 microL (P < .001). The decrease in platelet count was the same in patients with prior heparin exposure (-23.0 +/- 18.0%) and without (-18.0 +/- 14.0%, P = .46). One thrombotic complication occurred, a femorotibial bypass graft occlusion in a patient who tested negative for antibodies.

CONCLUSION

Heparin-induced antibodies occur infrequently after peripheral vascular surgery. The commonly observed, mild degree of postoperative thrombocytopenia does not appear to be caused by heparin-induced antibodies. These results indicate that a standard dose of heparin for intraoperative anticoagulation during vascular surgery is not associated with a significant risk of heparin-induced thrombocytopenia and thrombosis.