In vivo analysis of concentration-dependent effects of halothane or isoflurane inhalation on the electrocardiographic and hemodynamic variables in dogs

We assessed concentration-dependent effects of halothane or isoflurane inhalation on the electrocardiographic and hemodynamic variables using a cross-over design in intact beagle dogs (n = 4). Elevation of inhaled halothane from 1.0% to 2.0% or isoflurane from 1.5% to 2.5% decreased the mean blood pressure and prolonged the QRS width without significantly altering the heart rate, PR interval or QT interval. However, the observed changes disappeared after regressions of both anesthetic conditions to their initial settings. These results indicate that hypotension-induced, reflex-mediated increase of sympathetic tone may have counterbalanced the direct negative chronotropic, dromotropic and repolarization slowing effects of the anesthetics. (C) 2020 The Authors. Production and hosting by Elsevier B.V. on behalf of Japanese Pharmacological Society.

Automated summary

In intact beagle dogs, increasing the concentration of inhaled halothane or isoflurane decreased mean blood pressure and prolonged QRS width without significant effects on heart rate, PR interval, or QT interval. These effects were reversible upon cessation of anesthesia, suggesting a counterbalancing mechanism involving reflex-mediated increase in sympathetic tone.