MECHANISM OF CARDIAC ARRHYTHMIAS DURING CYCLOPROPANE ANESTHESIA

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Abstract
Cat hearts are more sensitive to cyclopropane than dogs'' hearts. Anesthetic concns. will produce ventricular arrhythmias in cat. In dog, although the reflex irritability of the heart is increased, epineph-rine has to be administered to produce arrythmias. Thirty-four cats were anesthetized with 30% cyclopropane and 70% O2 using an endotracheal tube. Ecg''s. were recorded every 2 min. for 30 min.; arrhythmias were noted for an avg. of 22 min. of the 30-mon. observation period. On a subsequent day 7 cats were similarly anesthetized and splenectomy with removal of the gastrointestinal tract from cardia to rectum was done; this abolished the arrhythmia in 5. In 7 of 10 cats partial abdominal denervation abolished arrhythmias; injected epinephrine produced in 1 cat a few premature contractions lasting 4 sec. Bilateral adrenalectomy reverted ventricular tachycardia to normal rhythm within 2 min. in 15 of 17 cats. Parenteral epinephrine (2.5-10 [mu]g./ kg.) reproduced tachycardia lasting 40-70 sec. in all of 6 cats injected. It is concluded that cyclopropane stimulates some un-localized mesenteric receptors producing afferent impulses which pass to the cord via the splanchnics. Efferent impulses from a hypothalimic reflex center pass to the heart in the cardiac sympathetics, increasing myocardial irritability. In cyclopropane-sensitized cats, endogenous epinephrine is necessary.

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