A Single Dose of Morphine Sulfate Increases the Incidence of Vomiting after Outpatient Inguinal Surgery in Children

BACKGROUND: In children, opioids are valuable both for their analgesic properties and for their salutary effect on emergence delirium. Although intraoperative administration of opioids is often cited as the cause of postoperative emesis, few data quantitating the magnitude of this effect exist. METHODS: Patients undergoing inguinal surgery as outpatients were randomly assigned to one of two groups. One group received a single intravenous dose of morphine 0.1 mg/kg (morphine group), and the other (control) group had the identical anesthetic but instead received saline. Intravenous ketorolac was administered in response to verbal complaints of pain or a Children's Hospital of Eastern Ontario Pain Score greater than 9 on two successive evaluations performed at 5-min intervals. The authors compared the incidence of postoperative emesis and emergence, behavior, and pain scores between the two groups. RESULTS: Patients in the morphine group (n = 48) were 5.6 +/- 2.8 yr old and weighed 20.8 +/- 7.8 kg, and those in the control group (n = 49) were 4.5 +/- 2.9 yr old and weighed 18.9 +/- 9.2 kg. More patients in the morphine group were cooperative and deeply asleep both on arrival and through the first 30 min of their stay in the postanesthesia care unit (PACU) (P < 0.05). Sixty-three percent of the children in the control group received ketorolac in the PACU compared with 20% of the morphine group (P < 0.01). The incidence of emesis for the 24 h after arrival in the PACU was 56% for those who received morphine compared with 25% in the control group (P < 0.01). CONCLUSIONS: For children undergoing inguinal surgery, the administration of a single dose of intravenous morphine after the induction of anesthesia smooths emergence from anesthesia as assessed by improved cooperation and sedation in the PACU, decreases the need for postoperative analgesics, but increases the incidence of vomiting in the first 24 h after surgery.