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Pseudohyperkalemia in Chronic Lymphocytic Leukemia

Department of Medical Oncology, Dana-Farber Cancer Institute; Department of Medicine, Harvard Medical School, Boston, MA

David Wu

Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA

Jennifer R. Brown

Department of Medical Oncology, Dana-Farber Cancer Institute; Department of Medicine, Harvard Medical School, Boston, MA

A 61-year-old man diagnosed with chronic lymphocytic leukemia (CLL) in 2001 was initially observed expectantly for more than 3 years, until progressive lymphadenopathy and splenomegaly led to treatment with intermittent fludarabine and rituximab. Cyclophosphamide, vincristine, prednisone, and rituximab were begun 1 year later, due to inadequate response. Neither treatment resulted in remission, so he was enrolled onto a clinical trial of rituximab and alemtuzumab. The initial 2 weeks of trial therapy included alemtuzumab 30 mg subcutaneously on days 1, 3, and 5 each week, and rituximab 375 mg/m² on day 1 of each week. The patient came to clinic on day 1 of week 2 of the therapy, and routine chemistries in the outpatient clinic revealed a venous plasma potassium of 6.0 mmol/L (normal 3.5 to 5.0 mmol/L) at 10:06 AM. His potassium value 3 days prior had been normal. His home medications included acyclovir 400 mg three times per day, allopurinol 300 mg daily, sulfamethoxazole and trimethoprim double-strength three times per week, multivitamin, and dexamethasone 20 mg the night before each rituximab dose. His review of systems was significant for increasing fatigue and edema. At the time of the initial elevated potassium value, his vital signs were within normal limits other than a heart rate of 108 beats per minute. ECG revealed sinus tachycardia with a left axis deviation but no T-wave changes. His examination was significant for multiple ecchymoses, lower extremity edema, enlarged spleen (12 cm below the costal margin) and numerous 2-cm nodes in the anterior and posterior cervical chains as well as the supraclavicular, inguinal, and axillary regions. Other laboratory analyses revealed a lactate dehydrogenase of 485 U/L (normal 107 to 231 U/L), uric acid of 2.5 mg/dL (normal 3.5 to 8.5 mg/dL), glucose of 201 mg/dL, calcium of 8.3 mg/dL (normal 8.8 to 10.5 mg/dL), albumin 3.9 g/dL (normal 3.7 to 5.4 g/dL), alkaline phosphatase 155 U/L (normal 36 to 118 U/L). His WBC count was found to be 283.5 K/µL (normal 3.8 to 9.2 K/µL), hematocrit 28.0% (normal 38.4% to 48.2%), and platelets 20 K/µL (normal 155 to 410 K/µL). Peripheral smear (Wright-Giemsa stain; Fig 1) showed marked lymphocytosis with abundant small, round, mature-appearing lympocytes and "smudge" cells. Low-power image was taken at x40 magnification, whereas the inset was taken at x400. Before starting the study drugs, his WBC count had been even higher, 307.7 K/µL, at which time his potassium had been 5.1 to 5.8 mmol/L. On a repeat venous blood draw at 12:17 PM, the potassium level had risen to 6.9 mmol/L. He was treated with sodium bicarbonate, insulin, glucose, calcium gluconate, normal saline, and furosemide. The patient was sent from the clinic to the emergency department, where repeat venous potassium level at 4:31 PM was 7.2 mmol/L. Still no ECG changes were evident. Three hours later, at 7:38 PM, an arterial potassium level was found to be 3.8 mmol/L, but a venous level drawn within minutes and received by the laboratory at 8:09 PM showed potassium 6.2 mmol/L. Four hours later, at 12:20 AM, venous potassium was 6.3 mmol/L, so a dose of kayexalate was given, and at 1:34 AM venous potassium was 5.8 mmol/L. At 6:15 AM the venous potassium was 5.2 mmol/L. At 8:46 AM the arterial potassium sent superstat was 4.4 mmol/L.

View larger version (150K): [in this window] [in a new window] [PowerPoint Slide for Teaching]   Fig 1.

AUTHORS’ DISCLOSURES OF POTENTIAL CONFLICTS OF INTEREST

The author(s) indicated no potential conflicts of interest.

REFERENCES

1. Bellevue R, Dosik H, Spergel G, et al: Pseudohyperkalemia and extreme leukocytosis. J Lab Clin Med 85:660-664, 1975[Medline]

2. Colussi G, Cipriani D: Pseudohyperkalemia in extreme leukocytosis. Am J Nephrol 15:450-452, 1995[Medline]

3. Colussi G: Pseudohyperkalemia in leukemias. Am J Kidney Dis 47:373, 2006[CrossRef][Medline]

4. Kellerman PS, Thornbery JM: Pseudohyperkalemia due to pneumatic tube transport in a leukemic patient. Am J Kidney Dis 46:746-748, 2005[CrossRef][Medline]

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This Article Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Email this article to a colleague Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Save to my personal folders Download to citation manager Rights & Permissions Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Ruddy, K. J. Articles by Brown, J. R. Search for Related Content PubMed PubMed Citation Articles by Ruddy, K. J. Articles by Brown, J. R. Social Bookmarking                            What's this?