Effects of different levels of neuromuscular blockade on transcranial electric motor-evoked potentials during idiopathic scoliosis

Abstract

Objective To evaluate the effects of different levels of neuromuscular blockade(NMB)on transcranial electric motor-evoked potentials(TCeMEPs)during idiopathic scoliosis. Methods Thirty American Society of Anesthesiologists physical status Ⅰ or Ⅱ patients of both sexes, aged 11-23 yr, weighing 31-62 kg, scheduled for elective idiopathic scoliosis under general anesthesia, were enrolled in the study.NMB was monitored with train of four(TOF)-Watch SX.The levels of partial NMB were classified into 5 states according to TOF ratio(TOFR)and TOF counts: 1 or 2 TOF counts(TOF1), 3 TOF counts and TOFR≤15%(TOF2), TOFR 16%-25%(TOF3), TOFR 26%-50%(TOF4), TOFR 51%-75%(TOF5) and TOFR>75%(no NMB). Each state was maintained for 10 min.Failure and false-positive findings in TCeMEP monitoring, development of unexpected body movement and satisfaction with NMB were recorded. Results Compared with no NMB, the failure and false-positive rates of TCeMEP monitoring were significantly increased, the incidence of unexpected body movement was decreased, and the rate of satisfactory NMB was increased at TOF1, TOF2 and TOF3(P 0.05), and the incidence of unexpected body movement was decreased and the rate of satisfactory NMB was increased at TOF4, the rate of satisfactory NMB was increased at TOF5(P 0.05). Compared with those at TOF4, no significant change was found in the failure or false-positive rates of TCeMEP monitoring(P>0.05), the incidence of unexpected body movement was significantly increased, and the rate of satisfactory NMB was decreased at TOF5(P<0.05). Conclusion Maintaining TOFR at 26%-50% the partial NMB during surgery does not affect TCeMEP monitoring during idiopathic scoliosis and meets the intra-operative NMB requirements simultaneously, and it is the optimum NMB for this type of surgery. Key words: Neuromuscular blockade; Evoked potentials, motor; Scoliosis