Application Of Sevoflurane Combined With Remifentanil And Changes Of Bis And Aai During General Anesthesia Induction In The Elderly

Objective To investigate the reasonable application of sevoflurane combined with remifentanil during general anesthesia induction in the elderly and the effect on the depth of anesthesia;to investigate the effect of different end-tidal sevoflurane concentration on electroencephalogram bispectral index (BIS), auditory evoked potential index (AAI) and hemodynamics parameters, and evaluation the accuracy of BIS,AAI for monitoring the depth of sevoflurane anesthesia in the elderly.Methods①Experient 1: Sixty ASAⅠ-Ⅱelderly patients who undergoing elective surgery under endotracheal anesthesia were randomly divided into four groups (n=20 each). sevoflurane groups(S1,S2,S3): anesthesia was induced with inhalation of sevoflurane 4﹪,6﹪,8﹪respectively;propofol group ( P ): anesthesia was induced with target plasma concentration of propofol (3μg/ml). Duration from the start of induction to loss of consciousness and eyelash reflex,duration from the start of induction to Alertness/Sedation Scale (OAA/S)=1,BIS and AAI at corresponding points were recorded. Arterial pressure (MAP),heart rate(HR),BIS,AAI value at time of before induction,before administration of remifentanil, before intubation, tracheal intubation, 1, 2, 3 minutes after intubation were recorded and compared among the 4 groups. Adverse events during induction of anesthesia were observed.②Experient 2: Thirty ASAⅠ-Ⅱelderly patients who undergoing elective surgery under endotracheal anesthesia were selected, including fifteen patients in the S3 group of experient 1 (inhalation of sevoflurane 8﹪). All patients were induced and tracheal intubation according the method of in the S3 group of experient 1. Patients were ventilated mechanically after endotracheal intubation, end-tidal concentration of sevoflurane were maintained 15 minutes at 0.6 mininum alveolar concentration (MAC), 1.0MAC, 1.3MAC after remifentanil stopped infusion for 6 minutes. The BIS, AAI, MAP, HR values were recorded at each time point of different sevoflurane concentrations.Results Time to loss of consciousness, loss of eyelash reflex, sedation alert score (OAA / S) = 1 in group S3 were significantly shorter than in group S1 and S2(P<0.01), time in group S2 at corresponding points were significantly shorter than in group P(P<0.01), time in group P at corresponding points were significantly longer than in group S1, S2, S3(P<0.01). There were no significant difference in BIS and AAI at all time points among the 4 groups(P >0.05). MAP in all groups reduced to the lowest value after induction, group P was more lower than other 3 groups(P<0.01). MAP in all groups after tracheal intubation were higher than before tracheal intubation ,and group S1 were higher than other 3 groups at 1,2minute after tracheal intubation (P<0.05). There were no significant difference in HR after induction in all groups, HR in all groups at immediately and 1 minute after intubation were significantly increased than before(P<0.01或P<0.05), There were no significant difference among the 4 groups.②Experient 2: With the end-tidal concentration of sevoflurane increasing, the BIS, AAI, MAP, HR values decreased significantly compared with those before anesthesia (P<0.01) at the concentration of 0.6MAC, 1.0 MAC, 1.3 MAC of sevoflurane, the BIS, AAI were decreased significantly at the concentration of 1.0 MAC, 1.3 MAC of sevoflurane compared with that of 0.6MAC (P<0.01), but there was no differents at the concentration of 1.0 MAC, 1.3 MAC of sevoflurane(P>0.05). BIS, AAI and MAP increased with the decrease of sevoflurane concentration in the range of 0.6-1.3MAC, and there was a significant rank correlation, but there was no correlation between HR and the concentration of sevoflurane.Conclusion Inhaled 6﹪, 8﹪sevoflurane with remifentanil in elderly patients can provide rapid and stable induction of anesthesia, fewer side effects, but should pay attention to the usage of remifentanil, and strengthening monitoring to avoid the excessive inhibition of circulation. There were good correlations between BIS, AAI value and end-tidal concentration of sevoflurane in elderly patients during sevoflurane anesthesia.