Epidural analgesia reduces the release of amino acids from peripheral tissues in the ebb phase of the metabolic response to major upper abdominal surgery

The purpose of this prospective cohort study was to compare metabolic effects of epidural or patient controlled analgesia (PCA) in patients undergoing major upper abdominal surgery. Seventeen patients undergoing major upper abdominal surgery were included: 10 received perioperative epidural analgesia (Group I) and the remainder received morphine via a PCA device for postoperative analgesia (Group II). A number of measures compared between one day preoperatively (day 1) and day 2 postoperatively included femoral arterial and venous blood concentrations of glucose, lactate, pyruvate and amino acids. In addition, the relevant reflux values were measured from the products of the respective arteriovenous substrate concentration differences and calf bloodflow. The efflux of lactate from peripheral tissues was greater in Group II than in Group I (P < 0.01): glucose and pyruvate efflux did nor differ between groups. There was no difference between groups in mean individual and total flux Of amino acids on day -1. However increased efflux between day -1 and day 2 was found for alanine, valine, isoleucine, leucine, phenylalanine, lysine, arginine in both groups, and for serine, glycine, tyrosine and histidine in Group II (P < 0.05). The efflux of glycine, methionine, amino benzoic acid, alanine, and lysine was less in Group I. than Group II on day 2 (P < 0.05). There was a significant difference in the total amino acid flux on day 2 (Group I = -1.2 mu mol. (100 mi tissue)(-1).min(-1) cf Group II = -2.5 mu mol. (100 ml tissue)(-1).min(-1); P = 0.04). In conclusion, perioperative epidural analgesia was associated with a reduced postoperative amino acid efflux two days following major upper abdominal surgery.