Evaluation of the Effect of Continuous Infusion of Dexmedetomidine or a Subanesthetic Dose Ketamine on Transcranial Electrical Motor Evoked Potentials in Adult Patients Undergoing Elective Spine Surgery under Total Intravenous Anesthesia: A Randomized Controlled Exploratory Study

Abstract

Purpose: To compare effects of dexmedetomidine or a subanesthetic dose of ketamine on the amplitude and latency of transcranial electrically generated motor evoked potentials. Overview of Literature: Total intravenous anesthesia (TIVA) is a standard anesthesia technique for transcranial electrical motor evoked potential monitoring in spine surgery. We aimed to determine whether the use of dexmedetomidine and ketamine as a component of TIVA exerted any beneficial effect on the quality of monitoring. Methods: A total of 90 American Society of Anesthesiologist grade I-III patients, aged 18-65 years, with a motor power of ≥4/5 grade as per the Medical Research Council Scale in all four limbs who were scheduled for elective spine surgery under transcranial electrical motor evoked potential monitoring were enrolled. The subjects were randomly allocated into the following three groups: group PD who received 0.5 µg/kg/hr dexmedetomidine infusion, group PK who received 0.5 mg/kg/hr ketamine infusion, and group PS who received normal saline infusion, along with standard propofol-fentanyl based TIVA regime. Amplitude and latency of bilateral motor evoked potentials of the tibialis anterior and abductor halluces muscle were recorded at Ti (at train-of-four ratio >90%), T30 (30 minutes post-Ti), T60 (60 minutes post-Ti), and Tf (at the end of spine manipulation). Results: Baseline median amplitudes were comparable among the study groups. In group PK, we noted a gradually enhanced response by 24%-100% from the baseline amplitude. The median amplitudes of all the muscles were higher in group PK than those in groups PS and PD at time points T60 and Tf (p<0.05). Conclusions:The present study demonstrated that compared with dexmedetomidine and control treatment, a subanesthetic dose of ketamine caused gradual improvement in amplitudes without affecting the latency.

Comparison of Dexmedetomidine Versus Fentanyl-Based Anesthetic Protocols Under Patient State Index Guidance in Patients Undergoing Elective Neurosurgical Procedures with Intraoperative Neurophysiological Monitoring

“…Chakrabarti et al [ 33 ] reported similar findings in patients undergoing cerebellopontine angle surgeries with TIVA when dexmedetomidine was used as an adjuvant. Andleeb et al [ 16 ] compared various adjuvants (ketamine, dexmedetomidine, normal saline) in patients requiring TIVA with IONM and found a significant reduction in propofol consumption in the dexmedetomidine group.…”

“…They found no significant changes in amplitude and latency in intergroup and intragroup analysis. Andleeb et al [ 16 ] demonstrated that the baseline median amplitude was comparable in three groups receiving dexmedetomidine, ketamine, and saline. At 60 minutes and at the end of the surgery, there was an increase in the amplitude of MEP in the ketamine group and dexmedetomidine group (significantly higher in the ketamine group) with no changes in the latencies.…”

“…The requirement for additional intraoperative fentanyl boluses was comparable between the two groups in our study (Table 2 ). The majority of the studies on TIVA employ a propofol-opioid combination as the standard regimen [ 16 , 35 ]. Our study differs from those studies, as the opioid (fentanyl) is not a part of the standard TIVA regime in either of the groups.…”

“…Fentanyl was used in both groups, and this is probably why the additional fentanyl requirement was lower in the dexmedetomidine group in their study. Andleeb et al [ 16 ] reported that fentanyl consumption in dexmedetomidine and ketamine groups was lower than in the saline group, though the difference was not statistically significant. In their respective studies, Wu et al [ 28 ] and Ngwenyama et al [ 23 ] found conflicting results to our study.…”

“…Dexmedetomidine is a sought-after choice in anesthetic practice as an adjuvant for its sympatholytic, sedative, anesthetic-sparing, and hemodynamic stabilizing properties without causing significant respiratory depression. The pharmacodynamic interaction between dexmedetomidine and propofol has been shown to decrease the requirement for propofol [11][12][13][14][15], but its effect on evoked potentials remains unclear [16][17][18][19][20]. Dexmedetomidine as an adjuvant has also been shown in studies to reduce opioid requirements due to its α-2 agonist property [21][22][23][24][25][26][27].…”