THE ROLE OF ARTERIAL PRESSURE IN THE INDUCTION OF IDIOVENTRICULAR RHYTHMS UNDER CYCLOPROPANE ANESTHESIA

¹ Department of Pharmacology, Univeisity of Michigan, Ann Arbor

1. Dibenamine and -naphthylmethylethyl--bromoethylamine reverse the pressor action of epinephrine in dogs and protect against the induction of idioventricular rhythms under cyclopropane.

2. Idioventricular rhythms (but possibly not ventricular fibrillation) can still be induced by epinephrine after Dibenamine if arterial pressure is mechanically elevated.

3. Prevention of a pressor response to epinephrine by means of a pressure regulator also protects markedly, but not completely, against the appearance of idioventricular activity.

4. There is a quantitative relationship between the level of arterial pressure and the threshold dose of epinephrine required to induce ventricular ectopic rhythms.

5. Atropine and tetraethylammonium offer no significant protection, although ergotamine does.

6. Sudden elevation of pressure in the denervated heart-lung preparation may cause ventricular premature contractions (bigeminal rhythm).

7. Epinephrine (in the absence of cyclopropane) prevents the bigeminal rhythm induced by pressure elevation in the heart-lung preparation.

8. Epinephrine plus a sufficient rise of pressure will induce multifocal ventricular discharges, but possibly not fibrillation, in the heart-lung preparation exposed to cyclopropane.