['Net loss of body protein is a prominent feature of the catabolic response to surgical tissue trauma. Epidural analgesia with hypocaloric dextrose has been demonstrated to attenuate leucine oxidation but was unable to make protein balance positive. The current study was set to determine whether an infusion of amino acids on the second day after colon surgery would revert the catabolic state and promote protein synthesis while maintaining glucose homeostasis in patients receiving epidural analgesia as compared with patient-controlled analgesia with morphine (PCA).', 'Sixteen patients undergoing colorectal surgery were randomly assigned to receive epidural blockade or PCA as analgesic techniques and underwent a 6-h stable isotope infusion study (3 h fasted, 3 h fed) on the second postoperative day. Whole body glucose kinetics and protein turnover were measured using [6,6-2H2]glucose and l-[1-13C]leucine as tracer.', 'The infusion of amino acids caused a decrease in endogenous glucose rate of appearance in both groups (P < 0.05), with greater changes in the PCA group (P < 0.05). Administration of amino acids suppressed the appearance of leucine from protein breakdown in both groups (P < 0.05), although the decrease was greater in the PCA group (P < 0.05). Leucine oxidation increased in both groups (P < 0.05), with greater change in the epidural group (P < 0.05). Protein synthesis increased to the same extent in both groups (P < 0.05). Protein balance became positive after the infusion of amino acids, and the effect was greater in the PCA group (P < 0.05).'] Does postoperative infusion of amino acids induce a positive protein balance independently of the type of analgesia used?