Cation Interdependency in Acute Stressor States

Abstract Acute stressor states are inextricably linked to neurohormonal activation which includes the adrenergic nervous system. Consequent elevations in circulating epinephrine and norepinephrine unmask an interdependency that exists between K + , Mg 2+ and Ca 2+ . Catecholamines, for example, regulate the large number of Mg 2+ -dependent Na/K ATPase pumps present in skeletal muscle. A hyperadrenergic state accounts for a sudden translocation of K + into muscle and rapid appearance of hypokalemia. In the myocardium, catecholamines promote Mg 2+ efflux from cardiomyocytes, whereas intracellular Ca 2+ influx and overloading account for the induction of oxidative stress and necrosis of these cells with leakage of their contents, including troponins. Accordingly, acute stressor states can be accompanied by nonischemic elevations in serum troponins, together with the concordant appearance of hypokalemia, hypomagnesemia and ionized hypocalcemia, causing a delay in myocardial repolarization and electrocardiographic QTc prolongation raising the propensity for arrhythmias, including atrial fibrillation and polymorphic ventricular tachycardia. In this review, we focus on the interdependency between K + , Mg 2+ and Ca 2+ which are clinically relevant to acute stressor states.