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Hyperkalemia is a common and potentially dangerous condition in elderly patients. These subjects are more likely to have a disease or be taking medications that may induce this disorder. We describe three such cases where the increased concentration of potassium in plasma resulted from decreased renal excretion of this ion, and suggest a simple approach to the etiological diagnosis of hyperkalemia.

One hundred patients with chest pain of cardiac origin were evaluated on the basis of clinical findings, electrocardiograph results, and total creatine kinase (CK) and creatine kinase B-subunit (CK-B) activity (as determined by immunoinhibition with the Boehringer CK-MB kit) in serum. All patients diagnosed as having had an acute myocardial infarction had increased values for both CK-B and total CK. In no case was normal total CK activity associated with an increased CK-B, nor was normal CK-B associated with an increased total CK. During collection of data for reference ranges, we found 10 patients who had no evidence of cardiac disease but had various other diseases, who exhibited high values for CK-B in serum; four of these had normal values for total CK. We conclude that estimations of CK-B in serum by this method added no more diagnostic information than did data on total CK in the evaluation of chest pain.