Comparison of patient-controlled analgesia with and without a background infusion after lower abdominal surgery in children.

Forty children aged 6-12 yr undergoing appendicectomy were allocated randomly to receive postoperative i.v. morphine by a patient-controlled analgesia (PCA) system (bolus dose 20 micrograms kg-1 with a lockout interval of 5 min) or the same PCA with a background infusion of morphine 20 micrograms kg-1 h-1. Patients breathed air and oxygen saturation was monitored by continuous pulse oximetry. Scores for pain, sedation and nausea were recorded hourly. Patients with PCA + background infusion received significantly more morphine than those with PCA only. Both groups self-administered similar amounts of morphine using the PCA machine. There were no significant differences in the pain scores of the two groups. Patients with PCA+background infusion suffered more nausea (P < 0.01), more sedation (P < 0.05) and hypoxaemia (P < 0.001) than those with PCA only. They also had a better sleep pattern than those with PCA only.