Effects Of Neuromuscular Blockade On Transcranial Electric Motor Evoked Potentials During Surgery For Idiopathic Scoliosis

Objective To evaluate the effects of varying levels of neuromuscular blockade for the transcranial electric motor evoked potentials(TCcMEPs)during surgery for idiopathic scoliosis under total intravenous anesthesia.Methods Fifty ASA ? or ? patients with idiopathic scoliosis of both sexes,aged 11-27 yr,scheduled for posterior spinal fusion surgery,were included in the analysis.All patients were maintained with total intravenous anesthesia.The neuromuscular blockade was measured by train of four twitch test(TOF).The intraoperative partial neuromuscular blockade(pNMB)levels were classified into 5 states by TOF counts or ratio of T4/T1(TOFR):one or two TOF counts(TOF1),three TOF counts-TOFR at 15%(TOF2),TOFR at 16%-25%(TOF3),TOFR at 26%-50%(TOF4),TOFR at 51%-75%(TOF5).No neuromuscular blockade(nNMB)was achieved when TOFR>75%.All of the partial neuromuscular blockade states were maintained for 10 minutes.The latency,amplitude and area under curve(AUC)of TCeMEPs were recorded at nNMB and pNMB.The failure rate,false-positive rate,unexpected movement rate and satisfaction rate were also calculated.Results There was no significant difference among six phases during TCeMEPs monitoring with regarding to the measured temperature,BIS and mean arterial pressure(P>0.05).No significant difference was found between left side and right side regarding to the absolute latency,amplitude and AUC for both abductor halluces muscles TCeMEPs monitoring(AH-TCeMEPs)and tibialis anterior muscles TCeMEPs monitoring(TA-TCeMEPs)(P>0.05).Compared with nNMB,there was no significant difference at TOF4 and TOF5 for AH-TCeMEPs and at TOF3,TOF4 and TOF5 for TA-TCeMEPs with regards to relative parameters,failure rate and false-positive rate,respectively(P>0.05).Compared with TOF4,the failure rate and false-positive rate increased significantly at TOF1,TOF2 and TOF3 for AH-TCeMEPs(P<0.05).Compared with TOF3,statistically significant increase occurred in the failure rate and false-positive rate at TOF1 and TOF2 for TA-TCeMEPs(P<0.05).Compared with nNMB,the unexpected movement rate was significantly decreased at TOF1,TOF2,TOF3 and TOF4 while the satisfaction rate was significantly increased at TOF1,TOF2,TOF3,TOF4 and TOF5(P<0.05).Compared with TOF4,the unexpected movement rate was significantly increased while the satisfaction rate was significantly decreased at TOF5(P<0.05).Conclusion Partial neuromuscular blockade is suitable for TCeMEPs monitoring during posterior spinal fusion surgery for idiopathic scoliosis.The results demonstrate that,the application of a stable level of pNMB with TOFR aimed at 26%-50%for AH-TCeMEPs modality or 16%-50%for TA-TCeMEPs modality seems to be an appropriate regimen for TCeMEPs monitoring during surgery for idiopathic scoliosis under total intravenous anesthesia.