PULSE OXIMETRY IS ACCURATE IN ACUTE ANEMIA FROM HEMORRHAGE

Hypothesis: Pulse oximetry is an accurate, noninvasive assay of oxygen saturation percentage (SaO2) in acutely severe anemia (less than 5 g/ dL). Design: A paired comparison of SaO2 by pulse oximetry (SpO2) and arterial blood gas analysis (SaO2) in patients with either acute gastr ointestinal bleeding or blunt trauma with hematocrit of less than 20%. Setting: An academic emergency department in a tertiary referral hosp ital with a Level I trauma center. Participants: Seventeen nonhypoxic patients were identified with initial hematocrit of less than 20% over a 9-month period. Measurements and main results: Determination of SaO 2 by pulse oximetry and arterial blood analysis was not statistically significantly different (P<.05) over a range of hemoglobin levels from 2.3 to 8.7 g/dL. The observed mean difference between SpO2 and SaO2 w as 0.53 +/- 0.23% (mean +/- SEM; n = 17). The 95% confidence interval associated with this difference score ranged from 0.044 to 1.014. Conc lusion: Despite reports that pulse oximetry is inaccurate below a hemo globin concentration of 5 g/dL, our study suggested that this technolo gy is accurate and reliable at 2.3 g/dL for nonhypoxic SaO2 values (Sa O2 of more than 93%). The anemic endpoint where pulse oximetry either becomes inaccurate or simply fails to work has not been determined. Pu lse oximetry overestimates SaO2 on average by 0.53% over a range of he moglobin concentrations from 2.3 to 8.7 g/dL.