FIBRILLATION AND DEFIBRILLATION IN DOGS AFTER CHLOROFORM AND EPINEPHRINE

¹ Department of Pharmacology, University of Toronto, Canada

Defibrillation by electric shock through the unopened thorax was found to be feasible for resuscitation from ventricular fibrillation induced by chloroform and epinephrine. This procedure permits many more repeated observations than is practical even with aseptic thoracic surgery.

In 90 trials on five dogs the incidence of ventricular fibrillation was the same (83 to 86 per cent) at the three doses of epinephrine HCl which were used (0.01, 0.02, and 0.04 mgm./kgm.). The incidence was not affected by previous treatment when the interval between trials was kept at 30 minutes.

Electroshocks (60 cycle A.C., 255 volts, 3.0 to 5.2 amps.) lasting 0.5 second invariably converted ventricular fibrillation to multifocal tachycardia. This in turn sometimes changed to a sinus rhythm without further interference but often reverted to ventricular fibrillation requiring the application of additional shocks. The total number of shocks necessary to restore a sinus rhythm increased with the dose of epinephrine used.

As a striking incidental observation it was noted that electroshock administration through the chest produced marked hyperventilation regardless of the success of defibrillation.