Clinical question: To what extent does diagnostic phlebotomy contribute to hospital-acquired anemia (HAA) during acute myocardial infarction (AMI)?
Background: During AMI, hospital-acquired HAA is associated with higher mortality and poorer health status. Moderate to severe HAA (nadir hemoglobin level <11 g/dL) has been shown to be prognostically important. The contribution of diagnostic phlebotomy blood loss on HAA is unknown and is a potentially modifiable factor.
Study design: Retrospective observational cohort study.
Setting: Fifty-seven U.S. hospitals.
Synopsis: Using Cerner Corp.'s Health Facts database, information was collected on 17,676 patients with AMI. Moderate to severe HAA developed in 3,551 (20%) patients who were not anemic upon admission. The diagnostic blood loss was estimated by assuming minimal blood volume per adult tube required to perform the lab work obtained. The mean phlebotomy volume was higher in patients with HAA compared with patients without HAA (173.8 mL vs. 83.5 mL; P<0.001). There was significant variation of diagnostic blood loss between hospitals. The risk of HAA increased by 18% (RR 1.18; 95% CI, 1.13-1.22) for every 50 mL of diagnostic blood loss.
Patients with HAA were noted to have greater disease severity and comorbidities. No causal inference can be made given the observational nature of the study. Randomized trials are needed to evaluate if strategies to reduce diagnostic blood loss can reduce HAA and improve clinical outcomes for patients with AMI.
Bottom line: Diagnostic blood loss is associated with development of hospital-acquired anemia in patients with acute myocardial infarction.
Citation: Salisbury AC, Reid KJ, Alexander KP, et al. Diagnostic blood loss from phlebotomy and hospital-acquired anemia during acute myocardial infarction. Arch Intern Med. 2011;171:1646-1653.
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