Effect of epidural analgesia on muscle amino acid pattern after surgery

Free amino acids in muscle were studied before and 96 hours after skin incision in 14 patients undergoing elective hip replacement and allocated to general anesthesia or epidural analgesia (T10-S5) effective before incision and maintained with intermittent 0.5% bupivacaine during the first 24 postoperative hours. The general anesthesia group (n = 8) showed the characteristic changes in muscle amino acids, with increase of branched chain amino acids and phenylalanine and decreased glutamine, arginine and lysine, as well as raised plasma levels of cortisol and glucose. The epidural group (n = 6), contrastingly, showed no significant changes in plasma cortisol and glucose and an attenuated postoperative response in all amino acids, without significant difference from the preoperative values. Differences in postoperative muscle amino acid concentrations between the epidural and the general anesthesia group were significant as regards glutamine, valine and asparagine. These results suggest that post-trauma changes in muscle amino acids are predominantly mediated by afferent neurogenic stimuli and the secondary increase in catabolic hormones.