Severe hyperkalemia in critically ill patients treated with prophylactic doses of enoxaparin

Dear Editor, Low-molecular-weight heparin (LMWH) is extensively used in intensive care unit (ICU) patients for prevention of thrombosis, with few adverse effects [1]. We report three cases of severe hyperkalemia induced by prophylactic doses of enoxaparin. A 71-year-old diabetic man was admitted for sepsis, with creatinine and serum potassium concentrations of 1.5 mg/dL and 2.0 mEq/L. Potassium increased to 4.7 mEq/L with 60 mEq/day supplement. On day 4, potassium supplement was stopped and enoxaparin started [40 mg subcutaneously (SC) once daily (o.d.)]. By day 6, potassium had increased to 6.1 mEq/L and was resistant to insulin/dextrose and sodium polystyrene sulfonate (SPS) treatments. Enoxaparin was discontinued, and potassium decreased in 4 days. A few days later, enoxaparin (20 mg o.d.) was reintroduced and potassium increased to 5.2 mEq/L. The patient was treated with SPS and discharged without thrombosis prophylaxis (Fig. 1a). A 63-year-old diabetic woman was admitted with cardiogenic shock. Creatinine was 0.7 mg/dL. Enoxaparin 20 mg o.d. was started and increased to 40 mg o.d. after 4 days. Serum potassium increased to 6.1 mEq/L within 3 days. The hyperkalemia was resistant to SPS treatment, and enoxaparin was withdrawn, following which there was a decrease in the potassium level. A few days later, enoxaparin was reintroduced and potassium increased again to 5.3 mEq/L rapidly. Enoxaparin was switched to fondaparinux (2.5 mg o.d.), and the potassium returned to normal values (Fig. 1b). A 71-year-old woman, treated for arterial hypertension, was admitted for spinal cord injury. Her creatinine concentration was 0.4 mg/dL. Five days after surgery, enoxaparin (40 mg o.d.) was started. Potassium rapidly increased, needing treatment with SPS. Enoxaparin was switched to fondaparinux (2.5 mg o.d.), resulting in a decrease in potassium to 4.6 mEq/L. A few days later