Effect of epidural anesthesia on airway constriction induced with methacholine or capsaicin in cats

The choice of epidural anesthesia for patients with bronchial asthma is controversial. We studied the effect of epidural anesthesia on airway constriction induced by methacholine or capsaicin in cats. Cats were anesthetized with pentobarbital and mechanically ventilated. Peak airway pressure and compliance, as well as cardiac sympathetic and vagal nerve activity were recorded. We sprayed 0.2% methacholine of 0.2% capsaicin into the trachea to produce airway constriction, and 15 min after drug spray we injected 2% lidocaine 1.0 ml into the epidural space. Methacholine increased peak airway pressure by 25% and decreased compliance by 26%. Capsaicin increased peak airway pressure 20% and decreased compliance 22%. After epidural anesthesia, cardiac sympathetic nerve activity decreased to 40% and 44%, vagal nerve activity decreased to 92% and 61% of control values in methacholine and capsaicin groups, respectively. However, here were no changes in the peak airway pressure and compliance in the two groups. These results suggest that epidural anesthesia, even if epidural anesthesia decrease sympathetic nerve activity, has no effect on the airway constriction induced with methacholine or capsaicin.