The Modifying Effect of General and Regional Anesthesia on the Endocrine-metabolic Response to Surgery

The modifying effect of anesthetic procedures on the endocrine-metabolic response to surgery is reviewed. Administration of intravenous or volatile agents in normal “low” doses has no major effect on endocrine-metabolic parameters in themselves or on the surgically induced metabolic changes. In contrast, “high-dose” opiate anesthesia or administration of volatile agents at high minimum alveolar concentration (MAC) values suppress the intraoperative endocrine-metabolic response to surgery but without a persistent effect on postoperative responses or on nitrogen balance. Regional anesthesia prevents a predominant part of the endocrine-metabolic response to surgery, and postoperative nitrogen balance is improved. This inhibitory effect of neurogenic blockade (combined afferent blockade of stimuli from the surgical area and blockade of efferent pathways to the adrenal medulla) on the surgically induced endocrine-metabolic changes is most consistent during lower abdominal surgery and operations on the lower extremities. During upper abdominal surgery, regional anesthesia has a lesser modifying influence on the stress response, probably because of insufficient afferent blockade. Epidural administration of opiates has no influence on the intraoperative stress response, but partially inhibits the normal postoperative increase in plasma cortisol and glucose. Posttraumatic application of regional anesthesia prevents further amplification of the stress response. Future studies should consider the influence of regional anesthesia on the stress response during major abdominal surgery, the relative importance of sensory analgesia versus blockade of sympathetic afferent and efferent pathways. Existing data should lead to randomized clinical studies on the effect of regional anesthesia on postoperative morbidity, based upon the hypothesis that inhibition of the surgically induced endocrine-metabolic response will reduce postoperative morbidity.