Intraoperative blood transfusion of one or two units of packed red blood cells is associated with a fivefold risk of stroke in patients undergoing elective carotid endarterectomy

Objective: Transfused blood can disrupt the coagulation cascade. We postulated that packed red blood cell (PRBC) transfusion may be associated with thromboembolic phenomena. We used propensity matching to examine the relationship between intraoperative PRBC transfusion and stroke during carotid endarterectomy (CEA). Methods: We selected CEA procedures from the American College of Surgeons National Surgical Quality Improvement Program database from 2005-2009. We excluded bilateral, redo, and emergent procedures. We used multivariate logistic regression to identify independent risk factors for stroke. We then calculated a transfusion propensity score to match patients who received one or two units of transfused PRBC intraoperatively with patients of similar risk profiles who had not been transfused. Results: Our criteria resulted in 12,786 elective CEA patients. Of these, 82 (0.6%) received a one- to two-unit intraoperative transfusion. Thirty-day stroke rates were 1.4% (179/12,704) in the nontransfused group and 6.1% (5/82) in the transfused group (Fisher exact test, P =.007). In forward stepwise multivariable regression of risk factors, only hemiplegia, stroke history, and transient ischemic attacks were predictive of 30-day stroke. We used these same variables to calculate transfusion propensity. We matched 80 transfused patients with 160 controls, thus, creating two groups with very similar risk profiles differing only by their transfusion status. In the matched groups, there was a fivefold increase in the risk of stroke in transfused patients (Fisher exact test, P =.043) Conclusions: Intraoperative transfusion of one to two units of PRBCs is associated with a fivefold increase in stroke risk. This holds true after consideration of stroke risk variables and operative duration as a surrogate for technical difficulty. The increased risk may be related to several effects of transfused blood on the coagulation inflammation cascade.