Pulse oximetry is accurate in acute anemia from hemorrhage.
OBJECTIVE
Pulse oximetry is an accurate, noninvasive assay of oxygen saturation percentage (SaO2) in acutely severe anemia (less than 5 g/dL).


METHODS
A paired comparison of SaO2 by pulse oximetry (SpO2) and arterial blood gas analysis (SaO2) in patients with either acute gastrointestinal bleeding or blunt trauma with hematocrit of less than 20%.


METHODS
An academic emergency department in a tertiary referral hospital with a Level I trauma center.


METHODS
Seventeen nonhypoxic patients were identified with initial hematocrit of less than 20% over a 9-month period.


RESULTS
Determination of SaO2 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 was 0.53 +/- 0.23% (mean +/- SEM; n = 17). The 95% confidence interval associated with this difference score ranged from 0.044 to 1.014.


CONCLUSIONS
Despite reports that pulse oximetry is inaccurate below a hemoglobin concentration of 5 g/dL, our study suggested that this technology is accurate and reliable at 2.3 g/dL for nonhypoxic SaO2 values (SaO2 of more than 93%). The anemic endpoint where pulse oximetry either becomes inaccurate or simply fails to work has not been determined. Pulse oximetry overestimates SaO2 on average by 0.53% over a range of hemoglobin concentrations from 2.3 to 8.7 g/dL.
Jay
G D
GD
Department of Emergency Medicine, Brown University School of Medicine, Rhode Island Hospital, Providence.
Hughes
L
L
Renzi
F P
FP
D000208:Acute Disease; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000740:Anemia / Q000097:blood* / Q000209:etiology; D005260:Female; D006400:Hematocrit; D006454:Hemoglobins / Q000032:analysis; D006470:Hemorrhage / Q000097:blood / Q000150:complications*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010092:Oximetry; D010100:Oxygen / Q000097:blood*
D006454:Hemoglobins; D010100:Oxygen