Effects of the extradural administration of local anaesthetic agents and morphine on the urinary excretion of cortisol, catecholamines and nitrogen following abdominal surgery.

Twenty patients undergoing major abdominal surgery were allocated randomly to receive either general anaesthesia with low-dose fentanyl plus intermittent systemic morphine for postoperative pain or the same general anaesthetic plus extradural analgesia during and following surgery (local anaesthetics from before skin incision until 24 h after skin incision plus extradural morphine 4 mg every 12 h from 3 h to 72 h after skin incision). Postoperative pain scores were lower (P less than 0.05) in the group receiving extradural analgesia, but this regimen failed to prevent the increase in the urinary excretion of cortisol, adrenaline, noradrenaline and nitrogen both on separate days and on cumulative measurements over 4 days. Pain scores did not correlate to urinary excretion of the various endocrine-metabolic indices either on separate days or over the cumulative 4-day period. It is concluded that the relief of pain per se has no major influence on the catabolic response to abdominal surgery.