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

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.