We tested the hypothesis that continuous intraopera-tive infusion of remifentanil is associated with the development of clinically relevant acute opioid tolerance in adolescents undergoing scoliosis surgery. Thirty adolescents were randomly assigned to receive an intra-operative analgesic regimen consisting of continuous remifentanil infusion or intermittent morphine alone. Postoperative analgesic consumption was assessed with a patient-controlled analgesia device that was used to self-administer morphine. Cumulative postop-erative morphine consumption, pain scores, and sedation scores were recorded by a blinded investigator every hour for the first 4 h postoperatively and then every 4 h for a total of 24 h. Cumulative morphine consumption in the remifentanil group was significantly more than that in the morphine group at each time point in the initial 24 h after surgery (P 0.0001). At 24 h after surgery, cumulative morphine consumption was 30% greater in the remifentanil group (1.65 0.41 mg/kg) than in the morphine group (1.27 0.32 mg/ kg) (95% confidence interval for the difference, 0.11 to 0.65 mg/kg). Differences in pain and sedation scores were not statistically significant. These data suggest that intraoperative infusion of remifentanil is associated with the development of clinically relevant acute opioid tolerance in adolescents undergoing scoliosis surgery.

Moderate hypercapnia with respiratory acidosis improved arterial oxygenation and reduced oxygen consumption and arterial lactate levels, thus improving overall oxygen transport in children after bidirectional superior cavopulmonary anastomosis.