• Francesca Holt, Samuel Strantzas, Christian Zaarour, Racha Chamlati, Ian Vreugdenhil, Igor Luginbuehl, Cengiz Karsli, and David Faraoni.
• Department of Anesthesia and Pain Medicine, The Hospital for Sick Children, University of Toronto, 555 University Avenue, Toronto, ON, M5G 1X8, Canada.
• Can J Anaesth. 2020 Oct 1; 67 (10): 1341-1348.

PurposeMotor-evoked potentials (MEPs) are frequently used in pediatric posterior spinal fusion surgery (PSFS) to detect spinal cord ischemia. Dexmedetomidine is increasingly being used as an adjunct to total intravenous anesthesia, but its effect on MEP amplitude has been variably reported. The purpose of this study was to evaluate the effect of an infusion of dexmedetomidine on the amplitude of MEPs.MethodsWe performed a retrospective case-control study of 30 pediatric patients who received a 0.5 µg·kg-1·hr-1 infusion of dexmedetomidine, ten patients who received 0.3 µg·kg-1·hr-1 dexmedetomidine, and 30 control patients who did not receive dexmedetomidine during PSFS. Two neurophysiologists reviewed the MEP amplitudes in six muscle groups at three time points: when the patient was turned prone (baseline; T1), one hour after incision (T2), and after exposure of the spine but before insertion of the first screw (T3).ResultsIn all muscles tested, the mean MEP amplitude was reduced by T3 when dexmedetomidine was infused at 0.5 µg·kg-1·hr-1. The greatest reduction from baseline MEP amplitude was 829 µV (95% confidence interval, 352 to 1230; P < 0.001) seen in first right dorsus interosseous. When dexmedetomidine was infused at 0.3 µg·kg-1·hr-1, there was a significant reduction in MEP amplitude in four of the six muscles tested at T3 compared with the control group.ConclusionsDexmedetomidine at commonly used infusion rates of 0.3 µg·kg-1·hr-1 or 0.5 µg·kg-1·hr-1 causes a significant decrease in MEP amplitude during pediatric PSFS. We suggest that dexmedetomidine should be avoided in children undergoing PSFS so as not to confuse the interpretation of this important neurophysiological monitor.

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