Effects of laryngeal mask airway ventilation on ventilation and stress during thyroidectomy

Objective To investigate the effects of using laryngeal mask airway(LMA) for mechanical ventilation on stress and ventilation in patients undergoing thyroidectomy.Methods Fifty ASA classⅠorⅡpatients aged 35-65 years undergoing thyroidectomy were enrolled in the study.The patients were randomized to receive either LMA ventilation(group L) or endotracheal intubation(group T).Anesthesia was induced with midazolam 0.05 mg/kg,propofol 2 mg/kg,fentanyl 3 μg/kg and norcuronium 0.10 mg/kg.HR and MAP were measured at 5 min after entering the operation-room(T0),before LMA insertion or intubation(T1),immediately after that(T2),3 min after LMA insertion or intubation(T3),immediately after LMA withdrawal or extubation(T4) and 3 min after LMA withdrawal or extubation(T5).Blood specimens were taken at T0-T5for determine of plasma concentration of epinephrine(E) and norepinephrine(NE).Peak inspiratory airway pressure(Ppeak),minute volume(MV),tidal volume(VT),SpO2,and PETCO2 were recorded at 10 min of intermittent positive pressure ventilation(IPPV)(T6),30 min(T7) and 60 min(T8).Results There was no significant difference in Ppeak,MV,VT,SpO2 at 10 min of IPPV,30 min and 60 min between the two groups.Ppeak and PETCO2 in group L were higher than those in group T at 60 min of IPPV(P0.05).The changes in MAP and HR in group L at T2,T3,T4and T5 were less than those in group T(P0.05).The concentrations of E and NE in group T at T3,T4and T5 were higher than those in group L and the concentrations of E and NE in T group at T5were still higher than those at T0(P0.05).Conclusion LMA ventilation is efficacious for mechanical ventilation with simpler operation and less cardiovascular adverse response than endotracheal intubation.