Background: Dexmedetomidine may be a useful agent as an adjunct to an opioid-propofol total intravenous anesthesia (TIVA) technique during posterior spinal fusion (PSF) surgery. There are limited data regarding its effects on somatosensory (SSEPs) and motor evoked potentials (MEPs).
Methods: The data presented represent a retrospective review of prospectively collected quality assurance data. When the decision was made to incorporate dexmedetomidine into the anesthetic regimen for intraoperative care of patients undergoing PSF, a prospective evaluation of its effects on SSEPs and MEPs was undertaken. SSEPs and MEPs were measured before and after the administration of dexmedetomidine in a cohort of pediatric patients undergoing PSF. Dexmedetomidine (1 microg x kg(-1) over 20 min followed by an infusion of 0.5 microg x kg(-1) x h(-1)) was administered at the completion of the surgical procedure, but prior to wound closure as an adjunct to TIVA which included propofol and remifentanil, adjusted to maintain a constant depth of anesthesia as measured by a BIS of 45-60.
Results: The cohort for the study included nine patients, ranging in age from 12 to 17 years, anesthetized with remifentanil and propofol. In the first patient, dexmedetomidine was administered in conjunction with propofol at 110 microg x kg(-1) x min(-1) which resulted in a decrease in the bispectral index from 58 to 31. Although no significant effect was noted on the SSEPs (amplitude or latency) or the MEP duration, there was a decrease in the MEP amplitude. The protocol was modified so that the propofol infusion was incrementally decreased during the dexmedetomidine infusion to achieve the same depth of anesthesia. In the remaining eight patients, the bispectral index was 52 +/- 6 at the start of the dexmedetomidine loading dose and 49 +/- 4 at its completion (P = NS). There was no statistically significant difference in the MEPs and SSEPs obtained before and at completion of the dexmedetomidine loading dose.
Conclusion: Using the above-mentioned protocol, dexmedetomidine can be used as a component of TIVA during PSF without affecting neurophysiological monitoring.