Comparison of two combinations of anaesthetic agents with and without ketamine for motor evoked potential during spine surgeries

Background: Anesthetic agents cause a dose-dependent effect on motor-evoked potentials (MEPs). We conducted a study to find whether addition of ketamine to the combination of propofol–fentanyl–dexmedetomidine has an effect on MEP monitoring and hemodynamic parameters in patients undergoing spine surgeries. Materials and Methods: Sixty patients of American Society of Anesthesiologists Grade I–III undergoing spine surgery in general anesthesia were divided into two groups, P and K randomly. Written informed consent was obtained and all the patients were blinded to the interventions. After induction, anesthesia was maintained in Group P using propofol + dexmedetomidine + fentanyl infusion, whereas in Group K, ketamine infusion was added to the above combination. After taking baseline reading of MEP, heart rate (HR), and mean arterial pressure (MAP), mean of all the other readings was calculated and percentage fall in all factors was calculated. More than 80% fall in mean MEP and more than 20% fall in mean HR and MAP were considered significant. Statistical Analysis: Analysis was done by SPSS 20.0 statistical system. Continuous normally distributed data were analyzed using Student's independent t -test. Results: In Group P, percentage fall in MEP on the right side was 46.39 ± 24.19, whereas in Group K, it was 37.98 ± 26.17. Similar results were obtained on the left side. In Group P, percentage fall in HR in Group P was 17.68 ± 7.0, on the other hand, it was 14.02 ± 7.7 in Group K. Finally, percentage fall in MAP was found to be 14.61 ± 6.37 in Group P, whereas in Group K, it was 9.51 ± 5.02. On intergroup comparison of all factors, we found that difference in percentage fall in MEP and HR was insignificant whereas it was significant in case of MAP. Conclusion: It was found that addition of ketamine in Group K led to better hemodynamics in patients undergoing spine surgery without affecting the MEP significantly.