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Abstract: FR-PO703

A Case of Spurious Hyponatremia in Hyperleukocytosis

Session Information

Category: Trainee Case Report

  • 902 Fluid and Electrolytes: Clinical

Authors

  • Leisring, Joshua, Ohio State University Medical Center, Columbus, Ohio, United States
  • Gutkoski, Tyler, Ohio State University Medical Center, Columbus, Ohio, United States
  • Prosek, Jason, Ohio State University Medical Center, Columbus, Ohio, United States
  • Parikh, Samir V., Ohio State University Medical Center, Columbus, Ohio, United States
Introduction

Hyponatremia is commonly seen in the oncology population. Here we report a case of discordance between serum sodium and whole blood sodium measurements in the setting of severe leukocytosis.

Case Description

A 72-year-old male with blastoid variant mantle cell lymphoma presented with fatigue and nausea. He appeared hypovolemic on exam. Laboratory evaluation revealed a WBC count of 476 K/uL. Serum sodium (SNa) was 117 mmol/L, potassium > 10 mmol/L, BUN 27 mg/dL and creatinine 1.36 mg/dL. Whole blood potassium was 3.73 mmol/L. Glucose was 96 mg/dL and total protein was 5.2 g/dL. Urine chemistry showed sodium < 10 mmol/L, chloride < 15 mmol/L, potassium 66.0 mmol/L, osmolality 722 mosm/kg.

SNa initially improved with normal saline hydration to 121, but did not improve further over the next 24 hours. No alternative causes for hyponatremia were identified. SNa at our institution is measured by the direct ion-specific electrode method which makes pseudohyponatremia from lipids or proteins unlikely.

Whole blood sodium (WBNa) checked on day two was 131.7 mmol/L while concurrent SNa remained 121. With leukopheresis and R-CHOP the WBC count improved from 476 to 31.5 K/uL. Serial WBNa measurements remained stable (129.6 – 135) during treatment while SNa gradually increased from 117 to normal levels (Fig. 1). The gap between WBNa and SNa diminished as WBC burden was reduced and these measurements correlated well when WBC count decreased below 150 K/uL.

Discussion

This case identifies a disparity between SNa and WBNa measurements in the setting of severe leukocytosis. Psuedohyperkalemia has been previously described in this population and is thought to be due to leukocyte membrane fragility and mechanical stress during blood tube handling leading to cell lysis and leakage of intracellular contents into plasma. This case suggests that SNa measurements are also distorted by this mechanism. Whole blood sodium measurements may be more reliable than serum measurements in the setting of severe leukocytosis.