Hyperkalemia

54-year-old man with childhood-onset type I diabetes mellitus who had preserved renal function but blindness secondary to his diabetes mellitus presented with a 5-day his-tory of malaise and diarrhea.On admission, he was dehydrated, hypotensive, and hypo-thermic (96.1oF/35.6oC). Initial laboratory values showed a potassium level of 9.2 (N, 3.6–5.0) mmol/L, and a sodium level of 122 (N, 137–145) mmol/L. The potassium level was confirmed on arterial samples.The initial ECG showed a regular idioventricular rhythm with bizarre, broad QRS complexes, and a frequency of 32 beats per minute (Figure A). Over a 5-hour period, on correc-tion of the hyperkalemia, he converted to sinus rhythm (Figure B and C) initially with a first-degree atrioventricular block (Figure B). Furthermore, the characteristic peaking of the T waves related to the hyperkalemia normalized (Figure C).On follow-up, an increased level of adrenocorticotropic hormone, the absence of response to synthetic adrenocorti-cotropic hormone, and strongly positive adrenal antibodies revealed that the patient had developed autoimmune adrenal insufficiency (Addison disease).Thomas Addison recognized the potential effects of adrenal insufficiency on the heart, and he described one of the marked features of the condition as “a remarkable feebleness of the hearts action” in his original monograph from 1855.