Potassium loss from the heart during the immediate posthypercapnic period

¹ Department of Physiology, University of Minnesota, Minneapolis, Minnesota

Experiments have been carried out on mongrel dogs in which plasma potassium concentrations in blood samples simultaneously drawn from the aorta and coronary sinus have been determined before, during and following 4 hours of high CO₂ breathing. No significant difference between potassium concentration in aorta and coronary sinus blood was evident before or during breathing of high CO₂ mixtures. Five minutes after returning to air breathing however, coronary sinus plasma potassium concentration was significantly elevated above that of the aorta. This loss of potassium from the heart is accompanied by severe cardiac irregularities, premature systoles, ventricular tachycardia and, sometimes, ventricular fibrillation. Coronary blood oxygen concentration differences decrease significantly during hypercapnia, and estimates by the N₂O technique indicate that this decrease is the result of an increase in coronary flow.