THE EFFECTS OF PENTOBARBITAL-INDUCED MYOCARDIAL DEPRESSION ON CARDIAC ELECTROLYTE DISTRIBUTION

¹ University of British Columbia, Vancouver, B. C., Canada

A species difference in resistance to the cardiovascular depressant effects of continuous PB infusions has been found. The cardiac lethal dose for dogs was 171, for cats 326, and for rabbits 404 mgm./kgm. of NaPB.

Myocardial ischemia resulting from the hypotensive effects of PB is not the cause of cardiac failure in PB-intoxicated cats and dogs.

Electrolyte studies indicate a selective action of PB on the control of intracellular Na and water concentrations in cat auricle.

Failure of cat and dog ventricular muscle occurred without important alterations in electrolyte distribution in this tissue. The evidence thus confirmed the hypothesis that changes in cardiac contractility occur independently of changes in Na and K distribution.

The distribution of electrolytes in different cardiac tissues suggests that tissues with greater automaticity, such as the atria, may contain more intracellular Cl.