Relationship between cardiac toxicity of K and acute alterations of blood pH and pCO₂

¹ Department of Medicine, University of North Carolina School of Medicine, Chapel Hill, North Carolina

Dog heart-lung preparations were studied to determine the relationship between the toxicity of elevated potassium and the blood pH and pCO₂. During hyperkalemia, a) a change from hypercapneic acidosis to hypocapneic alkalosis produced electrocardiographic deterioration after a delay of 3–5 minutes; cardiac function improved during alkalosis until ECG deterioration occurred; b) increase of pH produced by hypertonic bicarbonate infusion during hypercapnia improved mechanical performance; ECG also improved, even when pCO₂ was later decreased; c) infusion of hypertonic NaCl during hypercapnia partially prevented ECG deterioration after reduction of pCO₂. These experiments indicate that potassium toxicity is aggravated by acute reduction of pCO². This may not be due solely to the change in pH, since similar pH increase from bicarbonate infusion did not make the ECG worse. Reduction of [Ca⁺⁺] by pH increase is not the cause of ECG deterioration; if it were, ECG should be more affected in bicarbonate and NaCl infusion experiments than in the others. The cause of ECG deterioration with reduction of pCO₂ remains unknown.