We studied 40 children younger than 4 yr having elective abdominal surgery under general anaesthesia supplemented with either systemic opioids or extradural bupivacaine. Venous blood samples were obtained before tracheal intubation to measure baseline concentrations of adrenaline, noradrenaline, glucose, ACTH and cortisol. Additional samples were obtained 45 min after the start of surgery, at the end of surgery, 1 h and 24 h after the end of surgery. Plasma concentrations of bupivacaine were measured also in the extradural group at each sampling time. Both techniques provided acceptable analgesia, but the perioperative increases in adrenaline, glucose and ACTH were significantly greater in the opioid group. Noradrenaline concentrations decreased to less than baseline values in the extradural group and were significantly less than in the opioid group. The perioperative increase in cortisol was similar in the two groups, despite the differences in ACTH responses. Most responses returned to the baseline values within 24 h. Plasma bupivacaine concentrations remained within safe limits during the study, but systemic concentrations increased in some of the patients during postoperative infusion with 0.125% bupivacaine.

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