Opioid-Related Adverse Effects in Children Undergoing Surgery: Unequal Burden on Younger Girls with Higher Doses of Opioids

Objective: Unpredictable interindividual variability in response to opioids results in inadequate analgesia and opioid-related adverse effects. The effects of the child's sex on opioid response have not been well studied. The aim of this study is to determine the effects of sex on opioid-related adverse effects in children undergoing tonsillectomy. Design: Prospective observational clinical study. Setting: Outpatient pediatric surgery. Subjects: Two hundred and seventy five children between 6 and 15 years of age undergoing outpatient tonsillectomy. Methods: All children received standard perioperative care with a standard intraoperative dose of morphine. Opioid-related analgesia and safety outcomes included incidences of respiratory depression (RD), postoperative nausea and vomiting (PONV) and incidence of prolonged stay in the, post-anesthesia recovery unit (PACU) due to opioid related adverse effects. Results: Given the small sample of minority population, we focused our study on 219 white children. Significant morphine effect was observed in girls but not boys for PONV (P = 0.001) and prolonged PACU stay due to PONV (P = 0.010). Although the overall incidence of RD is not statistically different between boys and girls, the incidence of RD (52% vs 32%) and PONV (43% vs 4%) tended to be more in white girls than boys as the total perioperative morphine dose increased to 0.3 mg/kg or more. Conclusions: This study demonstrates that child's sex influences morphine's dose response and adverse effects. White girls have an unequal burden with higher incidences of PONV, RD, and prolonged PACU stays following tonsillectomy from PONV and RD as total morphine doses are increased.