The effect of propofol-based anesthesia versus low dose propofol with less than half MAC sevoflurane on intraoperative trans-cranial motor evoked potential during spine surgeries: Ratios rather than values

Abstract

ABSTRACT Background Transcranial motor evoked potentials (TcMEP) were proved to be useful during complicated spinal surgeries to prevent iatrogenic complications. The effect of anesthetic agents was comprehensively discussed in literature. We investigated a new balanced anesthetic protocol using propofol and sevoflurane in addition to continuous fentanyl infusion in which we compared values and ratios of amplitudes and latencies of TcMEP waves at different time point. Materials and Methods A total of 60 patients underwent spinal surgeries were randomly allocated into two groups who received either 75–100 µg/kg/min propofol ( P group) or 25 ug/kg/min propofol and 0.2% below corrected-to-age- half MAC of sevoflurane ( BA group). TcMEP was recorded before positioning (R1), after positioning (R2), and after skin incision (R3). R2/R1 and R3/R2 ratios were calculated. Modified Aldrete Score was recorded on discharge from PACU. Results Fluids infused and urine output were significantly increased in P group (p˂0.001). HR and MAP were significantly lower in P group (p˂0.001), but CVP was lower in P group at R1 and R2 (p = 0.019, 0.037). TcMEP was recorded from Vastus lateralis (VL) and Deltoid(D) muscles, which showed a significant lower amplitude in P group at different time points (p˂0.05) without significance in latencies. While when ratios were compared (L2/L1 and L3/L2), it showed significant differences (P˂0.001 and 0.041, respectively). Aldrete score was significantly higher in BA group. Conclusion Balanced regimen using propofol and sevoflurane resulted in a comparable TcMEP recording, hemodynamic stability and a better recovery from anesthesia during spinal surgeries.