Cardiovascular function in dogs with acute hypokalemia.

The effects of acute hypokalemia on plasma electrolytes, cardiovascular function, osmolality, and hematocrit were investigated in anesthetized dogs for 2 hours. There was progressive increase in the total systemic vascular resistance, but no change in the osmolality and blood hematocrit. All of the hemodynamic parameters decreased except the preferred index of myocardial contractility, [dp/dt]/IIP, which increased during hypokalemia. The changes in this index of myocardial contractility were associated with changes in the plasma potassium but not the plasma sodium. The results suggest that hypokalemia-induced increases in myocardial contractility might be associated with an increased influx of Ca++ as a result of hypokalemia-induced inhibition of sarcolemmal Mg++ -dependent, Na+-K+-ATPase.