Effect of Two Anesthetic Regimes with Dexmedetomidine as Adjuvant on Transcranial Electrical Motor Evoked Potentials during Spine Surgery

Abstract

Abstract Background Transcranial motor evoked potential (TcMEP) recording during spinal cord/spinal column surgery is a reliable and valid diagnostic adjunct to assess spinal cord integrity and is recommended if utilized for this purpose. Electrophysiologic monitoring in terms of TcMEP has been proven to be a useful tool in detecting spinal cord dysfunction at the earliest and allows corrective action to be taken before permanent neuronal dysfunction sets in. The quality of intraoperative neuromonitoring is influenced by various factors. Most anesthetics used in clinical practice suppress the evoked potentials. Thus, selecting an appropriate technique is always a challenging task. Materials and Methods Thirty ASA I and II patients scheduled for elective dorsolumbar spine surgery with TcMEP monitoring were recruited in the study. Patients were randomized into three groups: (1) Propofol (group P) 100 to 150 µg/kg/min with dexmedetomidine 0.6 µg/kg/hr and fentanyl 1 µg/kg/hr, (2) desflurane (group D) (<0.5 MAC) with dexmedetomidine 0.6 µg/kg/hr and fentanyl 1 µg/kg/hr, and (3)standard group (group S) patients received propofol 100 to 150 µg/kg/min, fentanyl 1 µg/kg/hr along with equal volume of saline (placebo). TcMEP amplitudes were recorded bilaterally from electrodes placed at least in one set of muscles with motor origin rostral and one set of muscle caudal to the spinal level of lesion at different time points. Results Three patients were excluded after allocation; 27 out of 30 patients were analyzed. The demographic and surgical characteristics of patients were comparable. The stimulation voltage needed to elicit the responses in all the three groups was comparable. No difference was observed in brachioradialis muscle amplitudes between the groups at different time points. However, in the right brachioradialis muscle, we found reduced amplitudes at baseline in group D and at 120 minutes in group P. We noticed reduced amplitudes of bilateral brachioradialis muscle in group P at 60 minutes and 90 minutes with respect to the baseline. For lower extremity, we measured amplitudes of TcMEP in tibialis anterior (TA) and did not find any difference in amplitudes between the groups at different time points. Conclusion We observed that the desflurane–dexmedetomidine combination did not hinder TcMEP as compared with both standard and propofol–dexmedetomidine groups. Thus, this combined regime could be used in surgeries requiring motor evoked potential monitoring.