[The effect of ketamine on epinephrine-induced arrhythmias in dogs anesthetized with halothane-nitrous oxide].

The effect of ketamine on the arrhythmogenic dose of epinephrine (ADE) was studied in dogs anesthetized with halothane-nitrous oxide. Groups K (ketamine 2, 4, 6, 10, 20 mg.kg-1.hr-1) were compared with group C (only halothane-nitrous oxide), and the ADE in group K2, 10 was significantly lower than that in group C. The arrhythmogenicity of ketamine was not found in group K20. There was a significant correlation between % ADE (ADE in group K/ADE in group C X 100) and plasma ketamine levels. However, antiarrhythmic action of ketamine was found following intravenous injection of ketamine 6 mg.kg-1, when plasma ketamine level was 14.3 +/- 1.9 micrograms.ml-1. Ketamine was cardiovascular depressant at high concentration, and this effect could account in part for the antiarrhythmic action of ketamine in this condition. The ketamine inhibited adrenal catecholamine secretion, but plasma epinephrine level in group K4 was higher than that in group C when the same dose of epinephrine was infused. Therefore the inhibition of neuronal and extraneuronal catecholamine uptake by ketamine would offer an explanation for the augmentation of response to epinephrine. Then, this augmentation would cause the arrhythmogenic action of ketamine.