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.

Keywords: dexmedetomidine; intraoperative neuromonitoring; motor evoked potential (MEP); somatosensory evoked potential (SSEP); thoracic spinal decompression surgery.

FIGURE 1

CONSORT flow diagram of patients’ inclusion. MEP, motor evoked potential. SSEP, somatosensory evoked potential. T group: propofol- and remifentanil-based total intravenous anesthesia (TIVA) group; D₁ group: TIVA combined with dexmedetomidine at a constant infusion rate; D₂ group: TIVA combined with dexmedetomidine delivered by a loading dose and then by a constant infusion rate.

FIGURE 2

Time course of SSEP and MEP amplitude variability, as well as SSEP latency variability in the three groups. ^△Compared with baseline value (after muscle incision, but before dexmedetomidine or placebo infusion) at corresponding time points, p<0.05; compared with the D₁ group at corresponding time points, p<0.05; * compared with the T group at corresponding time points, p<0.05. DEX: dexmedetomidine; the T group: propofol- and remifentanil-based total intravenous anesthesia group; the D₁ group: TIVA combined with dexmedetomidine at a constant infusion rate; the D₂ group: TIVA combined with dexmedetomidine delivered by a loading dose and then by a constant infusion rate.

FIGURE 3

Time course of intraoperative mean arterial pressure (MAP) (as depicted in 3A) and heart rate (HR) (as depicted in 3B) in the three groups. ^△ Compared with baseline value (after muscle incision, but before dexmedetomidine or placebo infusion) at corresponding time points, p<0.05; * compared with the T group at corresponding time points, p<0.05. DEX: dexmedetomidine; the T group: propofol- and remifentanil-based total intravenous anesthesia group; the D₁ group: TIVA combined with dexmedetomidine at a constant infusion rate; the D₂ group: TIVA combined with dexmedetomidine delivered by a loading dose and then by a constant infusion rate.