Influence of thoracic epidural anaesthesia on the metabolic stress response

Surgery leads to a stress response characterized by sympathetic arousal, altered balance of catabolic and anabolic hormones, hypermetabolism, negative protein economy, altered carbohydrate metabolism and immune function. These responses have been developed as natural mechanisms to maintain homeostasis after trauma and illness. Long-lasting and inadequate perioperative stress, however, may contribute to postoperative morbidity and mortality. By interrupting nociceptive input from the injured area and related sympathetic outflow, epidural anaesthesia with local anaesthetics has favourable effects upon afferent and efferent branches of the ancient defence mechanism, which may restore metabolic activities and reduce postoperative morbidity. Epidural local anaesthetics inhibit the increase of oxygen consumption that has been observed after major surgery. Intra- and postoperative alterations of glucose metabolism are reduced, the postoperative decline of tissue protein synthesis is arrested, and the postoperative decrease of natural killer cells is attenuated. To obtain these positive effects, and to interrupt nociceptive reflexes without the major side effects of epidural local anaesthetics, catheters should be placed at the spinal segments which are involved in the transmission from peripheral to spinal neurons. Therefore, patients undergoing abdominal or thoracic procedures need a thoracic epidural local analgesic application.