Monitoring End-tidal Sevoflurane Concentration For Preventing Awareness During Anesthesia, A Prospective Clinical Trial

Objective To investigate the incidence of awareness of patients undergoing generalanaesthesia who were monitored with end-tidal sevoflurane(ETS) during endoscopicsurgery. In this trial, we also sought to determine whether the use of ETS-basedprotocol could increase the time of tracheal extubation and the incidences ofpostoperative complications.Methods2500ASAⅠ-Ⅲ patients aged18-80undergoing general anaesthesia wererandomly divided into2groups (n=1250): routine care group (R) and end-tidalsevoflurane concentration group (E). Anaesthesia was induced with venous Anesthesia.Patients in group E were monitored with end-tidal sevoflurane concentration andmaintained with0.7-1.3minimum alveolar concentration （MAC） sevoflurane, andpatients in group R were monitored with routine care and maintained with sevoflurane.The protocol of intravenous injection were similar in both groups.Awareness of patientsduring surgery were assessed by questionnaire for explicit memory at24–48h aftersurgery and at least two anesthetists, blinded to group identity, assessed every report ofawareness.Meanwhile the concentration of ETS, total dosage of sevoflurane andintravenous anesthetics and other parameters were recorded.Results A total of2532patients were selected and eighty-six patients were ruledout.1219patients were assigned to the E group and1227patients to the routine care group.There were two reports of awareness in group E and fourteen reports in groupR.Compared with group R, the incidence of awareness in group E were significantlylower (P=0.003), the time-averaged ETS concentration and the dosage of Sevfluranewere lower in the group E（P＜0.05）,while no significant change was found in the time totracheal extubation,the dosage of intravenous general anesthetic and the incidences ofpostoperative complications in the two group（sP＞0.05）.we also found that the incidenceof awareness of female was higher than that of male in group R (P<0.05).Conclusion Using ETS-guided anaesthesia and maintaining the concentration of sevoflurane (0.7-1.3MAC) can decrease the incidence of awareness of patients duringendoscopic surgery.