Brief Summary:

Significant pain may occur following posterior spinal fusion despite the use of conventionally accepted techniques including patient controlled analgesia. If detected, a significant reduction in opioid requirements may lead to improved patient satisfaction and decreased opiate side effects.

The current study would use a prospective, randomized trial investigating the efficacy of one of 2 regimens as adjuncts to intraoperative anesthesia and postoperative analgesia, along with a third control group. The patients would be randomized to receive remifentanil plus a single intraoperative dose of methadone; remifentanil plus a bolus followed by an infusion of magnesium; or remifentanil alone. In addition, the two medications being studied might make it easier to determine the efficacy of neurophysiologic monitoring including somatosensory evoked potential (SSEP) (amplitude and latency) and motor evoked potential (MEP) (mA) required to elicit the response.

The purpose of this study would be to explore the effects of intraoperative methadone vs magnesium on intraoperative anesthetic requirements, postoperative opioid requirements, the efficacy of neurophysiologic monitoring including SSEP and MEP, inspired concentration of desflurane, remifentanil, and the need for intraoperative supplemental agents to control blood pressure.