LONDONDERRY, NORTHERN IRELAND. Cardiologists at a Londonderry hospital report the case of a 55-year-old woman who was admitted due to a spell of dizziness whilst out walking. Prior to admission her GP had done an ECG (electrocardiogram) and noticed an abnormal heart rhythm (markedly widened QRS complexes). The patient had hypertension and had suffered one previous episode of atrial fibrillation. Her medications included a beta-blocker, amiodarone, amlodipine (a dihydropyridine prescribed for angina and hypertension), warfarin, and recently prescribed cephalexin (a cephalosporin antibiotic) for a urinary tract infection.

At admission the patient's creatinine level was 114 micromol/L or 1.3 mg/dL, which is well outside the normal range of 0.5 to 1.0 mg/dL and thus would indicate impaired kidney function. Her serum potassium level was 9.6 mmol/L, which is well outside the reference range of 3.5 – 5.0 mmol/L. Questioning by the attending physician revealed that the patient had been prescribed potassium citrate for painful urination 6 months earlier. She had continued to take it every day ever since in a dose of 200 mmol/day which corresponds to 7800 mg/day. The patient was treated with calcium gluconate, insulin and dextrose after which her heart rhythm (ECG) returned to normal.

Lyons, KS and McGlinchey, P. Hyperkalaemic cardiac arrhythmia due to prolonged ingestion of potassium citrate. International Journal of Cardiology, Vol. 131, 2009, pp. e134-e136

Editor's comment: This case illustrates the danger of supplementing with excessive amounts of potassium when kidney function is impaired. The patient's total potassium intake, including the amount obtained from the diet, would likely approach 10 grams/day, which is more than twice the recommended intake of 4.7 grams/day. The case also underscores the importance of having kidney function checked before embarking on any potassium supplementation protocol at all. Most afibbers, who have found potassium supplementation beneficial, use about 1.5 grams/day and maintain their serum level in the 4.1- to 4.5-mmol/L range.