A Loading Dose of Dexmedetomidine With Constant Infusion Inhibits Intraoperative Neuromonitoring During Thoracic Spinal Decompression Surgery: A Randomized Prospective Study

Abstract

Background: The effect of a bolus dose of dexmedetomidine on intraoperative neuromonitoring (IONM) parameters during spinal surgeries has been variably reported and remains a debated topic.Methods: A randomized, double-blinded, placebo-controlled study was performed to assess the effect of dexmedetomidine (1 μg/kg in 10 min) followed by a constant infusion rate on IONM during thoracic spinal decompression surgery (TSDS). A total of 165 patients were enrolled and randomized into three groups. One group received propofol- and remifentanil-based total intravenous anesthesia (TIVA) (T group), one group received TIVA combined with dexmedetomidine at a constant infusion rate (0.5 μg kg−1 h−1) (D1 group), and one group received TIVA combined with dexmedetomidine delivered in a loading dose (1 μg kg−1 in 10 min) followed by a constant infusion rate (0.5 μg kg−1 h−1) (D2 group). The IONM data recorded before test drug administration was defined as the baseline value. We aimed at comparing the parameters of IONM.Results: In the D2 group, within-group analysis showed suppressive effects on IONM parameters compared with baseline value after a bolus dose of dexmedetomidine. Furthermore, the D2 group also showed inhibitory effects on IONM recordings compared with both the D1 group and the T group, including a statistically significant decrease in SSEP amplitude and MEP amplitude, and an increase in SSEP latency. No significance was found in IONM parameters between the T group and the D1 group.Conclusion: Dexmedetomidine delivered in a loading dose can significantly inhibit IONM parameters in TSDS. Special attention should be paid to the timing of a bolus dose of dexmedetomidine under IONM. However, dexmedetomidine delivered at a constant speed does not exert inhibitory effects on IONM data.

Multimodal Analgesia and Intraoperative Neuromonitoring

“…[12][13][14][15][16][17][18][19] Theoretically, dexmedetomidine could inhibit evoked potentials by increasing inhibitory synaptic transmission through activation of the descending noradrenergic system. 20 In a retrospective, observational study of 78 patients undergoing intracranial tumor resections, patients who received dexmedetomidine 0.5 mcg/kg bolus followed by 0.5 mcg/kg/h infusion had significantly higher TcMEP stimulation thresholds as compared with a control group, while SSEP stimulation thresholds were not significantly different between the 2 groups; 21 TcMEP amplitudes in both upper and lower extremities were also significantly lower among those who received dexmedetomidine. In a retrospective case-controlled study of 70 pediatric patients undergoing posterior spine surgery, dexmedetomidine infusion at 0.3 to 0.5 mcg/kg/h without bolus was associated with a statistically and clinically significant reduction in TcMEP amplitude from baseline.…”

“…In a double-blinded RCT involving 160 patients undergoing thoracic spine surgery, participants were randomized to receive either dexmedetomidine 1 mcg/kg bolus followed by 0.5 mcg/kg/h infusion, dexmedetomidine 0.5 mcg/kg/h infusion without bolus, or placebo infusion. 20 The authors reported, through within-group analysis, a significant decrease in TcMEP and SSEP amplitudes and a significant increase in SSEP latencies for up to 25 minutes following the administration of dexmedetomidine bolus and infusion; this phenomenon was not observed in the placebo group or in the dexmedetomidine infusion only group. Taken together, dexmedetomidine, while apparently compatible with IONM at low-doses, may elicit a dose-dependent suppression of SSEP and TcMEP amplitudes at higher doses.…”

“…Earlier literature has reported conflicting results regarding the compatibility of dexmedetomidine with IONM, though such pharmacological interaction appeared to be, to a certain extent, dose-dependent 12–19. Theoretically, dexmedetomidine could inhibit evoked potentials by increasing inhibitory synaptic transmission through activation of the descending noradrenergic system 20. In a retrospective, observational study of 78 patients undergoing intracranial tumor resections, patients who received dexmedetomidine 0.5 mcg/kg bolus followed by 0.5 mcg/kg/h infusion had significantly higher TcMEP stimulation thresholds as compared with a control group, while SSEP stimulation thresholds were not significantly different between the 2 groups;21 TcMEP amplitudes in both upper and lower extremities were also significantly lower among those who received dexmedetomidine.…”

Anesthesia management of neonates and infants requiring intraoperative neurophysiological monitoring: A concise review

“…The reported effects on MEPs in adults are variable. However, a loading dose of 1 mcg/kg of dexmedetomidine inhibited the MEP amplitude, for up to 25 min, suggesting a Ce–response relationship 34 . Use of dexmedetomidine at a TCI of 0.3–0.6 ng/mL combined with propofol/remifentanil to a target BIS 40–60, allows measurable MEPs.…”

“…However, a loading dose of 1 mcg/kg of dexmedetomidine inhibited the MEP amplitude, for up to 25 min, suggesting a Ce-response relationship. 34 Use of dexmedetomidine at a TCI of 0.3-0.6 ng/mL combined with propofol/remifentanil to a target BIS 40-60, allows measurable MEPs. However, dissenting study in children and adolescents demonstrated dexmedetomidine 0.3 and 0.5 mcg/kg/h (expected Ce 0.33-0.4 and 0.55-0.6 ng/mL) reduced MEPs by more than 50% in most measured muscle groups during spinal surgery.…”