Effect of epidural anesthesia on airway constrioction induced with methacholine or vagal nerve stimulation

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Purpose. To know the usefulness of local anesthetics to the airway hyperresponsiveness during epidural anesthesia or intravenous administration, we investigated the effect of lidocaine to the bronchoconstriction elicited by methacholine with or without airway hyperresponsiveness.Methods. All rabbits, separate in the three groups, were and anesthetized and mechanically ventilated. Group 1 : A single dose of 1% lidocaine 0.5 mL or saline was injected through the epidural catheter. Group 2 : We administered lidocaine or saline bolus 3 mg ・kg^<-1> followed by 200 mu ・kg^<-1> ・min^<-1>. Group 3 : For hyperresponsiveness, we nebulized bovine 0.25% albumin for 2 mm and PAF for 1 hour and stay for 6 hour. The effects of intravenous lidocaine or saline were experienced as group 2. Respiratory resistance, arterial blood gas, lidocaine plasma concentration were measured before ad 8 min after epidural injection of lidocaine or saline ad 3 min after each methacholine administration. Each inhalation … More period last 5 min with stepwise increase in the concentrations, 0.02%, 0.2% and 2%, of methacholine.Results. The spread level of methylene blue was T1.3*0.5 (SD) - T10.8*1.6 in lidocaine group and T1.0*0-T11.3*2.3 in saline group. Though epidural anesthesia decreased blood pressure in epidural group, there were no differences on respiratory resistance and PaO2 between saline and lidocaine administration. Intravenous lidocaine, 95*10 (cmH20 ・ 1^<-1> ・sec^<-1>*SD) and 73*15, attenuated the respiratory resistance compare to the saline group, 71*9 and 50*9 at 2% methacholine inhalation with or without hyperresponsiveness, respectively. There were no difference in BP and PaO2 between the lidocaine and salinegroups. Plasma lidocaine concentrations were below 1mu ・mL^<-1> in group 1, and about 5 mu ・mL^<-1> in group 2 and 3.Conclusion. Lidocaine at non-toxic blood concentrations significantly reduce the respiratory resistance with or without airway hyperresponsiveness. Intravenous infusion of lidocaine or continuous epidural anesthesia could some extent useful against bronchoconstriction. Less