Hypoxemia During Extreme Hyperleukocytosis: How Spurious?

Area of Science:

• Hematology
• Critical Care Medicine
• Clinical Pathology

Background:

• Spurious hypoxemia is a known complication in extreme hyperleukocytosis, prompting immediate cooling and arterial blood gas (ABG) analysis.
• Current recommendations aim to mitigate this artifact, but its magnitude in processed samples remains unclear.

Purpose of the Study:

• To quantify the extent of spurious hypoxemia in acute leukemia patients with hyperleukocytosis.
• To assess the agreement between pulse oximetry (SpO2) and arterial oxygen saturation (SaO2) in these patients.

Main Methods:

• Retrospective chart review of acute leukemia patients with white blood cell (WBC) count > 50 × 10(9) cells/L from 2003-2014.
• Collected PaO2, SaO2, simultaneous WBC count, and SpO2 for ABG samples.
• Utilized Bland and Altman analysis to evaluate SpO2 and SaO2 agreement.

Main Results:

• Analysis included 146 samples; 57 were suitable for Bland and Altman analysis.
• Mean (SpO2 - SaO2) was 2.5%, with wide 95% limits of agreement (-10.1, 15.1)%.
• Poor correlation (r²=0.19) between SpO2 and SaO2; difference correlated with WBC count (r²=0.44).
• Significant spurious hypoxemia (PaO2 < 55 mm Hg with SpO2 > 94%) occurred in 11/19 samples with WBC > 150 × 10(9)/L (P < .001).
• Three patients showed >10-20% SpO2-SaO2 difference pre-leukapheresis, resolving post-treatment.

Conclusions:

• Despite sample cooling and rapid analysis, poor SpO2-SaO2 correlation and agreement were observed in acute leukemia with hyperleukocytosis.
• Agreement was unacceptably low for WBC counts > 100 × 10(9)/L.
• Current guidelines may not entirely prevent the misdiagnosis of spurious hypoxemia in these critical cases.