The modifying effect of spinal anaesthesia on intra- and postoperative adrenocortical and hyperglycaemic response to surgery.

Plasma cortisol and glucose were measured in 24 patients undergoing abdominal hysterectomy during spinal anaesthesia with 0.5% hyperbaric tetracaine or neurolept anaesthesia. The sensory level of analgesia to pinprick extended to at least T4 before skin incision in the spinal group. The mean sensory analgesic level regressed almost linearly, reaching the fourth lumbar segment 4 h after incision. Plasma cortisol and glucose measurements from before to 9 h after skin incision showed significant increases in both parameters during and after surgery. Plasma cortisol and glucose levels were significantly lower during and immediately after surgery in the spinal group, but later postoperatively the mean levels were similar in the two groups. The increase in plasma cortisol 1 h after skin incision in the spinal group correlated to the segmental level of analgesia at that time (r = 0.77, P less than 0.01) and a similar correlation was found with regard to plasma glucose changes (r = 0.60, P less than 0.05). The regression lines showed that maintenance of a sensory analgesic level about the fourth thoracic segment prevented the adrenocortical and hyperglycaemic response to surgery. These findings are in accordance with the anatomical assumption that the upper segmental level of visceral afferent input to the spinal cord is about the fourth thoracic segment. Our results further demonstrate that the inhibitory effect of spinal anaesthesia on the stress response to surgery is transient, and correlates to the regression of sensory analgesia.