The effect of dexmedetomidine on motor-evoked potentials during pediatric posterior spinal fusion surgery: a retrospective case-control study.

PURPOSE: Motor-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. METHODS: We 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). RESULTS: In 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. CONCLUSIONS: Dexmedetomidine 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.

RéSUMé: OBJECTIF: Les potentiels évoqués moteurs (PEM) sont fréquemment utilisés lors de chirurgies de fusion spinale postérieure chez l'enfant afin de détecter une ischémie de la moelle épinière. La dexmédétomidine est de plus en plus utilisée comme adjuvant à l'anesthésie intraveineuse totale, mais son effet sur l'amplitude des PEM n'a été rapporté que de façon variable. L'objectif de cette étude était d'évaluer l'effet d'une perfusion de dexmédétomidine sur l'amplitude des PEM. MéTHODE: Pendant une chirurgie de fusion spinale postérieure, nous avons réalisé une étude cas témoins rétrospective auprès de 30 patients pédiatriques ayant reçu une perfusion 0,5 µg·kg−1·h−1 de dexmédétomidine, 10 patients ayant reçu 0,3 µg·kg−1·h−1 de dexmédétomidine, et 30 patients témoins n'ayant pas reçu de dexmédétomidine. Deux neurophysiologistes ont passé en revue les amplitudes des PEM dans six groupes musculaires à trois moments de la chirurgie : lorsque le patient a été tourné sur le ventre (valeur de base; T1), une heure après l'incision (T2), et après l'exposition de la colonne mais avant l'insertion de la première vis (T3). RéSULTATS: Dans tous les muscles testés, l'amplitude moyenne des PEM était réduite à T3 lorsque la dexmédétomidine était perfusée à 0,5 µg·kg−1·h−1. La plus grande réduction par rapport à l'amplitude de base des PEM était de 829 µV (intervalle de confiance 95 %, 352 à 1230; P < 0,001) et a été observée au niveau du premier interosseux dorsal. Lorsque la dexmédétomidine était perfusée à 0,3 µg·kg−1·h−1, une réduction significative de l'amplitude des PEM a été observée dans quatre des six muscles testés à T3 par rapport au groupe témoin. CONCLUSION: La dexmédétomidine, administrée à des taux de perfusion fréquemment utilisés de 0,3 µg·kg−1·h−1 ou 0,5 µg·kg−1·h−1, a entraîné une réduction significative de l'amplitude des PEM pendant une chirurgie de fusion spinale postérieure chez l'enfant. Nous proposons d'éviter l'administration de dexmédétomidine chez les enfants devant subir une chirurgie de fusion spinale postérieure afin de ne pas brouiller l'interprétation de ce moniteur neurophysiologique important.

Responding to Intraoperative Neuromonitoring Changes During Pediatric Coronal Spinal Deformity Surgery.

STUDY DESIGN: Retrospective case study on prospectively collected data. OBJECTIVES: The purpose of this explorative study was: 1) to determine if patterns of spinal cord injury could be detected through intra-operative neuromonitoring (IONM) changes in pediatric patients undergoing spinal deformity corrections, 2) to identify if perfusion based or direct trauma causes of IONM changes could be distinguished, 3) to observe the effects of the interventions performed in response to these events, and 4) to attempt to identify different treatment algorithms for the different causes of IONM alerts. METHODS: Prospectively collected neuromonitoring data in pre-established forms on consecutive pediatric patients undergoing coronal spinal deformity surgery at a single center was reviewed. Real-time data was collected on IONM alerts with >50% loss in signal. Patients with alerts were divided into 2 groups: unilateral changes (direct cord trauma), and bilateral MEP changes (cord perfusion deficits). RESULTS: A total of 97 pediatric patients involving 71 females and 26 males with a mean age of 14.9 (11-18) years were included in this study. There were 39 alerts in 27 patients (27.8% overall incidence). All bilateral changes responded to a combination of transfusion, increasing blood pressure, and rod removal. Unilateral changes as a result of direct trauma, mainly during laminotomies for osteotomies, improved with removal of the causative agent. Following corrective actions in response to the alerts, all cases were completed as planned. Signal returned to near baseline in 20/27 patients at closure, with no new neurological deficits in this series. CONCLUSION: A high incidence of alerts occurred in this series of cases. Dividing IONM changes into perfusion-based vs direct trauma directed treatment to the offending cause, allowing for safe corrections of the deformities. Patients did not need to recover IONM signal to baseline to have a normal neurological examination.