The purpose of this study is to examine if morphine administered by bolus before initiating Remifentanil by infusion decreases the incidence of acute post-operative opioid tolerance as demonstrated by decreased post - operative morphine consumption in children undergoing scoliosis surgery.

At our institution, a study has recently demonstrated that intraoperative infusion of remifentanil is associated with development of clinically relevant acute opioid tolerance in adolescents undergoing scoliosis surgery. This results in increased morphine consumption which in turn is associated with increased incidence of side effects such as respiratory depression, nausea and vomiting, pruritus, ileus and urinary retention. All of these side effects can result in increased consumption of rescue medications with the additional potential for increased duration of patient stay. Any measures that can be introduced to decrease the development of acute opioid tolerance in this patient population would have significant impact on patient morbidity, patient comfort and possibly duration of patient stay.

Inclusion Criteria:

• Unpremedicated
• ASA physical status 1 or 2
• Aged 11 - 18
• Scheduled to undergo posterior instrumentation for correction of idiopathic scoliosis

Exclusion Criteria:

• Chronic opioid use within three months prior to surgery
• Inability to self-administer morphine using a patient-controlled analgesia (PCA) device
• Elective postoperative ventilation
• Obesity (> 130% ideal body weight)
• Known sensitivity to morphine, remifentanil or any other agent within the standardized protocol
• Failure to obtain written consent or assent