Eighty-three infants received i.v. morphine following surgery as a continuo
us infusion to a targeted morphine concentration of 20 ng ml (-1) (n = 56)
or as intermittent bolus doses as needed (n = 27). Ventilation was compared
in the two groups by continuous pulse oximetry, by venous blood gases on p
ostoperative day 1 (POD1) and by CO2 response curves. Infant pain scores we
re done to assess analgesia every 4 h. Both groups achieved pain scores con
sistent with analgesia but the bolus group showed a higher percentage of pa
in scores indicating distress (32 vs. 13%, P < 0.001). Room air saturations
of <90% were seen for 2.3% of POD1 in infusion-treated infants and for 2.5
% of POD1 in bolus-treated infants. Mean venous PCO(2)s were normal in the
two groups. Four infants showed ventilatory effects in the infusion group (
4/ 56 = 7%); venous hypercarbia in two (2 days, 36 days), oximetry desatura
tion in one (240 days), both effects in one (6 days). Ventilatory effects w
ere not statistically different between the intermittent bolus-treated and
infusion-treated infants but may be clinically important. Monitoring with c
ontinuous oximetry is necessary. Morphine clearance increased with age. Inf
ants with detectable morphine also had measurable morphine-6-glucuronide in
both groups. Oral intake began at 16 h in both groups and other side effec
ts were infrequent. (C) 2000 International Association for the Study of Pai
n. Published by Elsevier Science B.V. All rights reserved.