From the 2024 HVPA National Conference
Rohini Kaku MD (Texas Tech University Health Sciences Center), Prithvi Nikesh K MBBS (Madras Medical College), Barath Rangaswamy MD, Priya Velumani MD
Overtreatment not only increases cost of health care but also causes iatrogenic harm. Treatment of spurious electrolyte abnormalities is a common example. Several electrolytes such as sodium, potassium, phosphate, bicarbonates can be artifactually increased or decreased in patients with malignancy. We describe Pseudohyperkalemia and Reverse Pseudohyperkalemia in the context of CLL (Chronic Lymphocytic Leukemia) which can present with spuriously elevated potassium levels leading to overuse of laboratory tests and treatments.
CASE DESCRIPTION:
A 66-year-old female patient with a history of chronic lymphocytic leukemia (CLL) was referred to ER for elevated potassium levels warranting an urgent evaluation for potential tumor lysis syndrome.
Initial labs showed white blood cells of 338 thousand/mm<sup>3</sup>, K 6.2 mmol/L. Phosphorus, calcium, magnesium, bicarbonate, uric acid, renal function tests were unremarkable. Lactate dehydrogenase was normal. EKG revealed normal sinus rhythm without T-wave changes. Patient was treated with hyperkalemia protocol with Calcium gluconate IV, D50, insulin and sodium zirconium cyclosilicate. K decreased to 5.4 mmol/L. Patient was then admitted to internal medicine wards. Subsequent labs showed K at 6.9 mmol/L, leading to further interventions such as IV bumetanide, scheduled oral sodium zirconium cyclosilicate. K was corrected to 3.6 mmol/L. Nonetheless, a persistent fluctuation was observed, with a rebound to 5.6 mmol/L, the same interventions were repeated, with potassium levels decreasing to 3.0 mmol/L at one point. Though patient was asymptomatic, she had a frustrating five days of hospital stay with multiple blood draws and medication administrations daily. She was discharged home with normalized potassium of 4.8meq/L for outpatient follow up.
DISCUSSION
Pseudohyperkalemia can result from several causes such as traumatic venipuncture, prolonged tourniquet use, issues with sample transportation such as usage of pneumatic tubes, cell damage, intravascular hemolysis, metabolic changes, leukocytosis, or thrombocytosis. Pseudohyperkalemia is an invitro increase in serum potassium while plasma potassium is normal. In case of reverse pseudohyperkalemia, the opposite occurs, plasma potassium is noted to be higher than serum potassium. This has been reported in patients with CLL. Though the mechanism is unclear, several theories such as heparin mediated cell membrane damage, increased fragility and lysis during centrifugation, high metabolic fuel demand causing impaired Na/K-ATPase have been postulated. In this patient, causes of true hyperkalemia such as tumor lysis syndrome, acidosis and acute kidney injury were effectively ruled out with normal labs, however pseudohyperkalemia or reverse pseudohyperkalemia was not taken into consideration. Differentiating true hyperkalemia from pseudohyperkalemia is important to prevent inappropriate treatment leading to potentially dangerous hypokalemia. If pseudohyperkalemia is suspected, ABG potassium can be used to confirm the suspicion as the ABG analyzer does not require centrifugation. Alternatively, blood samples can be drawn in a non-heparinized tube, allowing it to clot, thus stabilizing the leukemic cells with fibrin.
CONCLUSION :
This case highlights the importance of identifying spurious electrolyte disorders in malignancy. Awareness of pseudo hyperkalemia and reverse pseudo hyperkalemia and methods to differentiate them from true hyperkalemia helps high value care avoiding potentially detrimental treatment strategies.
CLINICAL IMPLICATIONS:
Clinicians should have a high index of suspicion of spurious disorders especially when the laboratory values are not concordant with the clinical picture. We recommend that high potassium levels should be flagged by clinical laboratories in the context of severe leukocytosis and consider testing serum potassium if plasma potassium is elevated.