Vasopressin release following operation upon the vagina performed under general anesthesia or epidural analgesis

Plasma vasopressin concentrations were determined in 27 patients undergoing vaginal operations for pelvic relaxation. Thirteen of the 27 patients were operated upon under lumbar epidural analgesia and 14, under general anesthesia. The blood samples for plasma vasopressin determinations were taken before, during and after the operation. The blood pressure and plasma osmolality were measured each time a blood sample was taken. In patients receiving a general anesthetic, the plasma vasopressin concentration was significantly higher 30 minutes after the beginning of the operation and at the end of the operation than immediately before premedication, p less than 0.05. In patients given lumbar analgesia, there were no significant differences among the plasma vasopressin values. Neither in the anesthesia nor in the epidural group was there a significant difference in blood pressure or plasma osmolality. It is concluded that the main cause of vasopressin release after vaginal operations lies in nerve impulses originating at the operative site.