Pneumatic Tube-Induced Reverse Pseudohyperkalemia in a Patient With Chronic Lymphocytic Leukemia
Conclusion
In the hospital setting, pseudohyperkalemia is a potentially dangerous situation. Because the patient discussed here initially presented with potassium values as high as 8.2 mEq/L, treatment was warranted. However, given the presence of CLL with extreme leukocytosis and otherwise
normal clinical findings, suspicion for pseudohyperkalemia was high. Initial treatment of the elevated potassium levels, which were revealed to be borderline low later in his clinical course, may have had detrimental effects on his cardiac function if hypokalemia had been inadvertently exacerbated to a significant level. The authors bring this case to the attention of health care providers of patients with CLL because this patient had been chronically managed for hyperkalemia with a lowpotassium diet.
Further, this case confirms the importance of avoiding the use of pneumatic tubes to prevent WBC lysis in patients with significant malignant leukocytosis. Importantly, the authors were able to differentiate between postulated heparin-mediated lysis and pneumatictube usage. As the literature has suggested, the authors speculated that mechanical stress on chronic lymphocytic leukemia cells is the primary cause of pseudo-hyperkalemia.
Pneumatic tube use or mechanical manipulation seemed to cause unwanted WBC lysis in this case, as values in the standard 81 IU heparin tubes used in this case study could be corrected by manually transporting the tube to the lab. This suggests that the process is heparin-independent, although initial investigations on that effect focused on the use of low-heparin vials. The potassium correction also was supported by the correction of likely falsely elevated LDH, which normalized when samples were manually transported. This supports the mechanism of WBC lysis. The authors’ observations are in line with several recent reports where pneumatic tube use was suspected as the cause of reverse pseudohyperkalemia.4,5,7,8
During the authors’ monitoring of the patient for TLS, comparison of repeat values for potassium showed a significant difference of about 2.7 mEq/L between samples transported manually and samples sent via pneumatic tube (Figure). Similar elevations of values have been described in other case reports.1
Reverse pseudohyperkalemia is a phenomenon that should not be overlooked in the medical management of patients with CLL with leukocytosis, especially in asymptomatic chronic patients. Although initially the differences can be benign, as the tumor burden increases, the degree of falsely elevated potassium can increase to thresholds that lead to inappropriate management in an acute setting. To prevent mismanagement, the authors recommend placing precautionary flags with hospital laboratories so that if a patient with CLL has a high potassium draw, lab values are rechecked with hand-delivered samples. The authors hope that this case will highlight the importance of suspecting this diagnosis in patients with CLL and provide guidance on obtaining accurate labs to better manage these patients.
Author disclosures
The authors report no actual or potential conflicts of interest with regard to this article.
Disclaimer
The opinions expressed herein are those of the authors and do not necessarily reflect those of Federal Practitioner, Frontline Medical Communications Inc., the U.S. Government, or any of its agencies. This article may discuss unlabeled or investigational use of certain drugs. Please review complete prescribing information for specific drugs or drug combinations—including indications, contraindications, warnings, and adverse effects—before administering pharmacologic therapy to patients.
