The influence of neutralizing heparin after carotid endarterectomy on postoperative stroke and wound hematoma. The influence of neutralizing or not neutralizing heparin after carotid endarterectomy on postoperative stroke and wound hematoma is unknown. During the past 6 years some of the authors frequently gave protamine sulfate to neutralize heparin, whereas others did not unless a patch was used or wound hemostasis was not readily obtained. To determine the influence of protamine sulfate on stroke and wound hematoma the records of 697 patients having a carotid endarterectomy from January 1984 to September 1989 were reviewed. Protamine sulfate was given to 328 patients, and 369 did not receive protamine sulfate. The incidence of stroke in the two groups was 1.8% (n = 6) and 2.7% (n = 10), respectively, and the difference was not significant (p = 0.6019). Excluding three strokes that could not be related to neutralizing or not neutralizing heparin, the difference remained insignificant (1.5% vs 2.2%, p = 0.7290). The incidence of wound hematoma was 1.8% (n = 6) in patients given protamine sulfate and 6.5% (n = 24) in patients not given protamine sulfate, and this difference was significant (p = 0.0044). The difference remained significant when three hematomas not related to protamine sulfate were excluded (1.2% vs 6.2%, p = 0.0013). In patients not given protamine sulfate draining the wound lessened the incidence of wound hematoma (4.4% vs 8.6%), but this difference was not statistically significant (p = 0.1475). In patients given protamine sulfate the dose of protamine sulfate (15 to 45 mg vs 50 to 75 mg) had no statistically significant effect on the incidence of stroke (0.8% vs 2.0%, p = 0.6530) or wound hematoma (1.6% vs 1.0%, p = 1.000). 