Effects of sevoflurane,isoflurane and desflurane on transcranial electrical motor evoked potentials in patients undergoing neurosurgery

Objective To compare the effects of sevoflurane,isoflurane and desflurane on transcranial electrical motor evoked potentials(MEPs)in patients undergoing neurosurgery.Methods Sixty ASA Ⅰ or Ⅱ patients aged 18-64 yr undergoing neurosurgery were randomly divided into 3 groups(n = 20 each): sevoflurane group,isoflurane group and desflurane group.BIS value and MEPs were monitored.The end-tidal concentrations of sevoflurane,isoflurane and desflurane were adjusted and maintained at 0.50,0.75,1.00 and 1.30 MAC respectively for at least 15 min during 6 stimuli delivered at 1000 Hz and 300 V lasting for 75 μs.The amplitudes and latency of MEPs and BIS value were recorded before administration(baseline)and the each stable state (T1-4).The failure rate of MEPs was also recorded.Results The amplitude of MEPs and BIS value were significantly decreased at T1.2 and the latency of MEPs was prolonged at T1-4 in desflurane group compared with sevoflurane and isoflurane groups(P＜0.05).There was no significant difference in the amplitudes and latency of MEPs and BIS value between group sevoflurane and isoflurane(P＞0.05).The failure rates of MEPs were 0 at baseline,T1 and T2,0,5% and 20% at T3 ,and 5%,20% and 45% at T4 in sevoflurane,isoflurane and desflurane groups respectively.The failure rate of MEPs was significantly higher in desflurane group than in sevoflurane and isoflurane groups(P＜0.05).Conclusion Desflurane has greater suppressive effect on MEPs than sevoflurane and isoflurane.1.00 MAC of sevoflurane and isoflurane,while 0.75-1.00 MAC of desflurane may be the suitable end-tidal concentration for MEP monitoring. Key words: Anesthetics,inhalation; Isoflurane; Evoked potentials,motor; Electric stimulation