Effect of Intrathecal Opioids on Somatosensory-Evoked Potentials During Spinal Fusion in Children

STUDY DESIGN: Intraoperative recording of somatosensory-evoked potentials is useful for monitoring spinal cord tolerance during spinal fusion with instrumentation. Volatile anesthetic agents are known to have prominent suppressive effects on somatosensory-evoked potentials. This study evaluates the effect of intrathecal administration of opioid, consisting of morphine sulfate and sufentanil, on somatosensory-evoked potential monitoring. OBJECTIVES: To study the effect of different anesthesia techniques on somatosensory-evoked potentials during spinal fusion. SUMMARY OF BACKGROUND DATA: The effect of intravenous narcotic administration on somatosensory-evoked potentials has been well studied and reported. This study shows the effect of intrathecal opioids on somatosensory-evoked potentials. METHODS: Ten patients scheduled for spinal fusion with Cotrel-Dubousset instrumentation were induced with thiopental and maintained with intrathecal morphine sulfate (20 micrograms/kg) and sufentanil 50 micrograms, supplemented with isoflurane 0.5% air and oxygen. Routine monitoring was done, including arterial line and continuous somatosensory-evoked potentials. Anesthesia was maintained constant, with a mean blood pressure of 55 mm Hg. Normocarbia and normothermia were maintained. Baseline somatosensory-evoked potentials were recorded using bilateral posterior tibial nerve stimulation, with constant somatosensory-evoked potential monitoring after the induction of anesthesia. RESULTS: There were no significant changes in either latencies or amplitudes in cortical somatosensory-evoked potentials after opioid injection at any time during the surgical procedures. CONCLUSIONS: Somatosensory-evoked potential monitoring was possible in all patients undergoing extensive spinal surgery. Intrathecal opioid anesthesia with low concentrations of isoflurane in air and oxygen seems to have no effects on somatosensory-evoked potentials.