Magnesium and potassium interrelationships, experimental and clinical.

1) Coexisting Mg and K deficiency may occur with greater frequency than has been previously appreciated. 2) Profound hypokalemia, or refractoriness to K repletion or coexisting hypokalemia and hypocalcemia should suggest the possibility of concurrent Mg and K depletion. 3) The identification and treatment of concurrent K and Mg depletion is especially important in patients with congestive heart failure because of problem of digitalis toxicity. 4) We believe that the role of magnesium in optimizing cardiac function remains to be elucidated, identification and treatment of coexisting Mg and K depletion will be facilitated by making serum Mg a routine electrolyte determination together with Na, K, Cl, CO2.