Our objective was to determine the effect of perioperative epidural anaesthesia and analgesia on the increase in energy expenditure which accompanies major elective abdominal surgery in a prospective, randomized study. Eight patients undergoing elective resections of the colon and/or rectum received general anaesthesia alone (nitrous oxide, oxygen, and isoflurane, supplemented with intravenous fentanyl to a maximum of 10 micrograms.kg-1), and 12 patients received perioperative epidural anaesthesia and analgesia using lidocaine (carbonated lidocaine 2% with epinephrine 1:200,000, 20 ml over 30 min) and morphine (preservative-free morphine 0.10 mg.kg-1 after catheter insertion and 0.05 to 0.10 mg.kg-1 every 12 hr as needed until the morning following surgery) via a lower lumbar catheter in addition to general anaesthesia. Respiratory gas exchange was measured using a metabolic cart and canopy system early on the morning of surgery, six hours postoperatively, and on the first and second postoperative mornings. Parenteral analgesic administration (P < 0.001) and visual analogue pain scores (P < 0.05) were lower in the patients receiving epidural anaesthesia and time to first parenteral analgesia was longer (P < 0.005). Oxygen consumption, carbon dioxide production, and energy expenditure increased after surgery (all P < 0.001) but were very similar in the two groups (all P > or = 0.8) before and after surgery. Despite substantial effects on postoperative pain, we conclude that oxygen consumption and energy expenditure following major abdominal surgery are not diminished by perioperative epidural anaesthesia and analgesia.