Effect of Dexmedetomidine Combined Anesthesia on Motor evoked Potentials During Brain Tumor Surgery.

BACKGROUND: Dexmedetomidine (DEX) is used as an adjunct to total intravenous anesthesia. However, its effect on intraoperative neurophysiologic monitoring (IOM) during brain tumor surgery remains controversial. The aim of this study was to explore the effect of DEX on IOM during brain tumor surgery.

METHODS: Seventy-eight consecutive patients (DEX group, n = 40; control group, n = 38), who underwent brain tumor surgery with IOM, were retrospectively reviewed. The outcomes included the predictability, laterality of alterations, and stimulation parameters of transcranial motor evoked potentials (tcMEPs) and somatosensory evoked potentials (SSEPs).

RESULTS: The predictability of tcMEPs for postoperative motor outcomes showed a higher false-positive rate in the DEX group than in the control group (27.5% vs. 5.3%, P = 0.047). Bilateral alterations were observed only in the DEX group (31.3%; P = 0.053). Compared with the control group, the DEX group required significantly higher intensity (377.5 ± 48.0 vs. 347.1 ± 30.0 mV; P = 0.001) and repetition rate (6.0 ± 0.2 vs. 5.7 ± 0.5 pulse/train; P = 0.001) of transcranial electric stimulation to evoke adequate tcMEPs. The SSEP results were comparable between both groups. In the DEX group, false-positive tcMEPs changes occurred 222.2 ± 70.5 minutes (range, 95-342 minutes) after the induction of anesthesia. In addition, the patients who were administered DEX under bispectral index monitoring (n = 12) showed a significantly higher false-positive rate than shown by the control group (50.5% vs. 5.3%; P = 0.003).

CONCLUSIONS: This study showed that DEX had significant effects on tcMEPs during IOM in brain tumor surgery. Because the high false-positive rate could decrease the accuracy of IOM, outcomes after using DEX should be cautiously interpreted.