Potassium of 8? It May Be Okay to Wait

Introduction: Tumor Lysis Syndrome (TLS) can cause renal failure and life-threatening hyperkalemia due to the release of intracellular potassium. We report an unusual cause of severe hyperkalemia, resistant to therapy, in a patient with suspected tumor lysis syndrome. Case Description: A 69-year old man undergoing chemotherapy with Bendamustine and Rituximab for Chronic Lymphocytic Leukemia (CLL) was admitted for possible tumor lysis syndrome. On admission, his labs were significant for WBC 364,000/uL, Hb 9.1 gm/dL, K 6.9 mmol/L, Cr 1.77 mg/dL (baseline ~1.4-1.6), BUN 22 mg/dL, Phos 3.4 mg/dL, uric acid 9.7 mg/dL, and Ca 7.8 mg/dL. He was started on IV fluids and allopurinol for TLS and given calcium gluconate, albuterol, Lasix, and insulin for hyperkalemia. His renal function improved to a Cr of 1.5 mg/dL and BUN of 18 mg/dL; however, his hyperkalemia persisted, ranging from 5.5 to 6.5 mmol/L, for which he was repeatedly shifted and started on sodium zirconium cyclosilicate TID. On hospital day 3, patient’s hyperkalemia acutely worsened to 7.6 mmol/L and nephrology service was consulted. EKG did not show characteristic changes of hyperkalemia. A venous blood gas with electrolytes was performed, which showed a K of 3.8 mmol/L, confirming the diagnosis of pseudo-hyperkalemia. Discussion: TLS often complicates hematological malignancies and can result in acute renal failure and hyperkalemia. Although TLS was initially suspected because of hyperkalemia and hyperuricemia in this patient with CLL, the stable or worsening WBC counts and lack of hyperphosphatemia or hypocalcemia all raised questions about TLS. The absence of symptoms, EKG changes, response to therapy, and stable renal function pointed to pseudo-hyperkalemia. Hyperkalemia in CLL is thought to be due to lysis of white cells during the centrifugation step necessary for measuring plasma or serum K. Blood gas analyzers use capillary or venous whole blood samples and do not require centrifugation. Timely recognition of pseudo-hyperkalemia is required to avoid unnecessary and potentially hazardous therapy.