Anesthesia with sevoflurane, but not isoflurane, prolongs bleeding time in humans

Purpose. Halothane has been shown to suppress platelet aggregation in vitro and ex vivo and to prolong bleeding time. In a previous in vitro study, we demonstrated that sevoflurane had a stronger suppressive effect on platelet aggregation than halothane. The present study investigated whether clinical use of sevoflurane affects bleeding time in vivo. Methods. Thirty-four patients undergoing minor elective surgery were randomly assigned to sevoflurane or isoflurane. Anesthesia was induced with intravenous thiopental and maintained with sevoflurane or isoflurane with nitrous oxide. Bleeding time was measured by the Duke method. An initial (control) measurement was obtained in the operating room before the induction of anesthesia, and a second was obtained 5-10 min after endotracheal intubation but before starting the operation, when the end-expiratory concentration of sevoflurane or isoflurane had been stabilized at 1-1.5 times the minimum alveolar concentration (MAC), and the mean arterial pressures were between 80% and 120% of the preanesthetic values. Results. Bleeding time was increased from the preanesthetic value of 2.07 ± 0.82 min to 2.83 ± 0.93 min (n = 15) in the sevoflurane group (P < 0.01) but was not significantly altered in the isoflurane group. Conclusion. Sevoflurane alters bleeding time in the clinical situation.