Effects of total intravenous anesthesia without muscle relaxants on motor evoked potential monitoring during scoliosis surgery

Abstract

Objective To evaluate the effects of total intravenous anesthesia without muscle relaxants on motor evoked potential (MEP) monitoring during scoliosis surgery.Methods Fifty ASA Ⅰ or Ⅱ patients of both sexes,aged 18-25 yr,scheduled for posterior spinal fusion surgery,were randomly divided into 2 groups with 25 patients in each group: muscle relaxants combined with total intravenous anesthesia group (group Ⅰ) and total intravenous anesthesia without muscle relaxant group (group Ⅱ).In both groups,a loading dose of dexmedetomidine 1 μg/kg was infused over 20 min,followed by infusion at 0.2 μg· kg-1 · h-1.After the loading dose of dexmedetomidine was given,anesthesia was induced,the patients were tracheal intubated and mechanically ventilated.Anesthesia was maintained with remifentanil 0.2μg· kg-1 · min-1 and propofol 80-120 μg· kg-1 · min-1.The bispectral index value was maintained at 40-60.Train of four stimulation of ulnar nerve was used to monitor the neuro-muscu-lar block.Cisatracurium was infused at 0.5-1.5 μg·kg-1 ·min-1,T1 was maintained at 45％-55％,and the infusion was stopped 30 min before the isolation of paraspinal muscles was completed in group Ⅱ.MEP were monitored and recorded during the period when the administration of the muscle relaxation was stopped,and the degree of muscle relaxation was assessed by the surgeon.The successful wake-up test was recorded.Results The incidence of successful MEP monitoring was significantly higher in group Ⅱ than in group Ⅰ (P ＜ 0.05).There was no significant difference in the degree of muscle relaxation between the two groups (P ＞ 0.05).All the patients were successfully woken up.Conclusion Total intravenous anesthesia without muscle relaxants can provide satisfactory muscle relaxation for scoliosis surgery and increase the probability of successful MEP monitoring simultaneously. Key words: Neuromuscular blocking agents; Evoked potentials,motor; Monitoring,intraoperative; Anesthesia,general; Scoliosis