Effects of patient's tolerance to laryngeal mask airway and tracheal tube on the appropriate level of sevoflurane anesthesia

Objective To compare the effects of patient's tolerance to laryngeal mask airway (LMA) and tracheal tube (TT) on the appropriate level of sevoflurane anesthesia.Methods Eighty ASA Ⅰ or Ⅱ patients aged 30-60 yr weighing 50-70 kg undergoing elective thyroid or breast surgery were randomly divided into 2 groups (n=40 each):LMA group and TT group.Anesthesia wag induced with propofol 1.6mg/kg,fentanyl 3μg/kg and recuronium 0.6mg/kg.LMA or tracheal tube was inserted,and the patients were mechanically ventilated.Anesthesia was maintained with inhalation of 1.5%-3.0% sevoflurane and 50% N2O in O2 in group LMA,and with 2.5%-5.0% sevoflurane and 50% N2O in O2 in group TT.The flow of O2 and N2O was 0.7-1.0L/min,and the concentration of sevofluranee was adjusted to maintain AAI at 15-25.ECG,HR,MAP,SpO2,PETCO2,AEP and end-tidal sevoflurane concentration were continuonsly monitored.The end-tidal sevoflurane concentration was recorded at 1,5 and 10 min after LMA/TT was placed (T1-3),at 1h after skin incision (T4) and at the end of operation before removal of LMA or extubation (T5).The recovery time of consciousness,adverse cardiovascular events and adverse reactions were recorded.Results The end-tidal sevoflurane concentration was significantly lower,the recovery time of consciousness and removal of LMA or extubation time were shorter,and the incidence of adverse cardiovascular events and adverse reactions was lower in LMA group than in TT group.Conclusion At the same depth of anesthesia (AAI 15-25),sevoflurane concentration is significantly lower in LMA group than in TT group,with fewer complications and smaller cardiovascular reaction. Key words: Laryngeal masks; Intubation,intratracheal; Sevoflurane