Hormonal and metabolic stress responses after major surgery in children aged 0-3 years: a double-blind, randomized trial comparing the effects of continuous versus intermittent morphine

Children aged 0-3 yr were stratified for age and randomized to receive eith er continuous morphine (CM, 10 rhog kg(-1) h(-1)) with three-hourly placebo boluses or intermittent morphine (IM, 30 mug kg(-1) every 3 h) with a plac ebo infusion for postoperative analgesia. Plasma concentrations of epinephr ine, norepinephrine, insulin, glucose and lactate were measured before and at the end of surgery and 6, 12 and 24 h after surgery. Pain was assessed w ith validated pain scales [the COMFORT scale and a visual analogue scale (V AS)] with the availability of additional morphine doses. Minor differences occurred between the randomized treatment groups, the oldest IM group (aged 1-3 yr) having a higher blood glucose concentration (P=0.003), mean arteri al pressure (P=0.02) and COMFORT score (P=0.02) than the CM group. In the n eonates, preoperative plasma concentrations of norepinephrine (P=0.01) and lactate (P<0.001) were significantly higher, while the postoperative plasma concentrations of epinephrine were significantly lower (P<0.001) and plasm a concentrations of insulin significantly higher (P<0.005) than in the olde r age groups. Postoperative pain scores (P<0.003) and morphine consumption (P<0.001) were significantly lower in the neonates than in the older age gr oups. Our results show that continuous infusion of morphine does not provid e any major advantages over intermittent morphine boluses for postoperative analgesia in neonates and infants.