Hemoglobin Determination Using Pulse Co-Oximetry and Reduced-Volume Blood Gas Analysis in the Critically Ill: A Prospective Cohort Study

Abstract

Hospital-acquired anemia is common in patients hospitalized in the intensive care unit (ICU). A major source of iatrogenic blood loss in the ICU is the withdrawal of blood for laboratory testing. The aim of our study was to analyze the feasibility and accuracy of non-invasive spot-check pulse co-oximetry (SpHb), and a reduced-volume blood gas analysis (ABG Hb) for the determination of Hb concentration in critically ill patients. Comparisons between Hb determined with test devices and the gold standard—complete blood count (CBC)—were performed using Bland–Altman analysis and concordance correlation coefficient (CCC). The limits of agreement between SpHb and CBC Hb were –2.0 [95%CI −2.3–(−1.7)] to 3.6 (95%CI 3.3–3.9) g/dL. The limits of agreement between ABG Hb and CBC Hb were −0.6 [95%CI −0.7–(−0.4)] to 2.0 (95%CI 1.9–2.2) g/dL. Spearman’s coefficient and CCC between ABG Hb and CBC Hb were 0.96 (95%CI 0.95–0.97, p < 0.001) and 0.91 (95%CI 0.88–0.92), respectively. Non-invasive spot-check Hb co-oximetry is not sufficiently accurate for the monitoring of hemoglobin concentration in critically ill patients. Reduced volume arterial blood gas analysis has acceptable accuracy and could replace complete blood count for the monitoring of Hb concentration in critically ill patients, leading to a significant reduction in blood volume lost for anemia diagnostics.