SESSION TITLE: Critical Care Posters II
SESSION TYPE: Original Investigation Poster
PRESENTED ON: Wednesday, October 28, 2015 at 01:30 PM - 02:30 PM
PURPOSE: Spurious hypoxia, ascribed to oxygen larceny by leukocytes, has been described in case reports during extreme hyperleukocytosis, and led to recommendations for immediate cooling and analysis of samples with high white blood cell count (WBC). We sought to determine, in samples processed as recommended, the magnitude of spurious hypoxia in acute leukemia patients with hyperleukocytosis.
METHODS: Retrospective chart review of all patients admitted between 2003 and 2013 for newly diagnosed acute leukemia, who presented with a WBC > 50.109/L and had arterial blood gas (ABG) performed during admission. ABG samples were stored in ice after collection and analyzed without delay. For each ABG, we collected PaO2, SaO2, as well as simultaneous WBC, and SpO2 when available. Bland and Altman analysis was used to assess the agreement between SpO2 and SaO2.
RESULTS: One hundred and forty six samples (45 patients) were included, among which 57 samples (18 patients) had data available for Bland and Altman analysis. Mean (SpO2 - SaO2) was 2.5% and 95% limits of agreement between SpO2 and SaO2 were (-10.1%; 15.1%). The mean (SpO2 - SaO2) was significantly higher for WBC > 100.109/L as compared to WBC < 100.109/L (3.8% versus 0.4%, p=0.04) and the 95% limits of agreement were (-10.3%; 18.0%) versus (-7.9%; 8.6%). SpO2 and SaO2 were poorly correlated (R2 = 0.19) while the difference (SpO2 - SaO2) was fairly correlated with WBC (R2 = 0.44). Overall, eleven out of 19 samples with WBC > 150.109/L had PaO2 < 55 mm Hg while SpO2 was higher than 94%, the proportion being 5 out of 62 samples for WBC < 150.109/L (p=0.0001). Six patients who underwent leukapheresis had ABG performed before and after the procedure: (SpO2 - SaO2) was 9.4 ± 9.2% before leukapheresis versus 0.5 ± 3.8% afterwards (p= 0.055). Three of these patients, with WBC > 150.109/L, exhibited large SpO2 to SaO2 differences (10-20%) prior to leukopheresis, which decreased to below 5% afterwards.
CONCLUSIONS: In acute leukemia patients with hyperleukocytosis, despite cooling and quickly analyzing the samples, we observed poor correlation and agreement between SpO2 and SaO2, unacceptably low for WBC > 100.109/L. Spurious hypoxia seems related to WBC, improves after leukapheresis, and may lead to significant misinterpretation of patient`s oxygenation.
CLINICAL IMPLICATIONS: Our results reinforce the guidelines for immediate cooling and analysis of ABG especially for WBC > 100.109/L, but suggest that these recommendations are not sufficient to totally prevent spurious hypoxia.
DISCLOSURE: The following authors have nothing to disclose: Ruchi Desai, Coursen Schneider, David Claxton, Andry Van de Louw
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