Morphine not first choice after neonatal surgery

By Piriya Mahendra, medwireNews Reporter

Neonates and infants undergoing major surgery should be treated with postoperative intermittent intravenous acetaminophen (paracetamol) as opposed to continuous morphine, research suggests.

Saskia de Wildt (Erasmus MC-Sophia Children's Hospital, Rotterdam, the Netherlands) and team report that intermittent intravenous acetaminophen resulted in a reduced cumulative morphine dose over 48 hours in a group of 71 neonates undergoing major surgery.

"These results suggest that intravenous paracetamol may be an interesting alternative as primary analgesic in neonates and infants," the team writes in JAMA.

Their analysis involved infants under 1 year undergoing major thoracic (noncardiac) or abdominal surgery between March 2008 and July 2010, with a follow-up period of 48 hours. All patients received a loading dose of morphine 30 minutes before the end of surgery, followed by continuous morphine or intermittent intravenous acetaminophen for up to 48 hours postsurgery.

Infants in both study groups received morphine (boluses and/or continuous infusion) as rescue medication on the guidance of the validated pain assessment instruments, the Numeric Rating Scale-11 and COMFORT-Behavior Scale.

The cumulative median morphine dose in the first 48 hours postoperatively was 121 µg/kg in infants who received acetaminophen (n=33) and 357 µg/kg in those who only received morphine (n=38) after surgery.

The between-group difference in cumulative morphine dose was 66%, favoring the acetaminophen group, the authors note. They originally defined a significant difference in outcomes between the groups as greater than 30%.

Pain scores and adverse effects were not significantly different between groups. The amount or number of morphine rescue doses, and the number of patients requiring rescue doses did not differ between the groups either.

"This randomized controlled trial shows that infants who receive intravenous paracetamol as primary analgesic after major surgery require significantly less morphine than those who receive a continuous morphine infusion," write the authors. "Judging from the rescue morphine doses, a similar level of analgesia was obtained in either group."

Editorialist Kanwaljeet Anand (University of Tennessee Health Science Center, Memphis, USA) writes in a related commentary: "These findings merit consideration because of the careful study design, well-matched study groups, and the magnitude of effects observed."

However, he adds that the findings should be interpreted in light of the brief exposure to morphine, potential synergism between acetaminophen and morphine, and the possibility of age-related susceptibility to opioid adverse effects. The reduced susceptibility of infants to hepatic toxicity from oral or rectal acetaminophen should also be considered, he says.

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