Ketamine block of bronchospasm in experimental canine asthma

Experimental asthma was induced in dogs previously sensitized to ascaris antigen by ventilation with ascaris antigen, in an aerosol, for 10 min. Before the administration of antigen, there was no significant difference in pulmonary airways resistance (RL) during thiopentone and ketamine anaesthesia. In dogs anaesthetized with thiopentone, RL increased significantly from a pre-antigen control of 0.36 +/- 0.13 (mean +/- SEM) kPa litre-1 s to 1.56 +/- 0.38 at 5 min after administration of antigen. In dogs anaesthetized with ketamine, RL before (0.30 +/- 0.10) and 5 min after antigen (0.47 +/- 0.18) was not significantly different. Beta adrenergic blockade with propranolol abolished the protective effect of ketamine so that there was no significant difference in the maximal increase (5 min after antigen) in RL in dogs anaesthetized with ketamine (2.92 +/- 0.74) or thiopentone (3.28 +/- 1.16). Beta adrenergic blockade also increased pre-antigen RL in both groups (ketamine 0.87 +/- 0.24; thiopentone 0.77 +/- 0.32).