http://www.medscape.com/viewarticle/490583 (registration required)
Blood Transfusion May Be Associated With Higher Mortality in ACS Patients
Yael Waknine
Oct. 5, 2004 — Blood transfusion in patients with acute coronary syndrome (ACS) is associated with an increased risk of 30-day mortality, according to the results of a post-hoc analysis of data from three large trials published in the Oct. 6 issue of
JAMA. The investigators suggest caution in using transfusions to maintain arbitrary hematocrit levels in stable patients.
"Patients hospitalized for an [ACS] are at risk of developing anemia acutely as a consequence of bleeding," write Sunil V. Rao, MD, from the Duke Clinical Research Institute in Durham, North Carolina, and colleagues. "[A]lthough transfusing blood to anemic patients with ischemic heart disease may theoretically increase oxygen delivery and improve outcomes, there is no definitive evidence to support such a practice."
To determine whether transfusions are associated with improved outcomes in ACS patients, the investigators analyzed clinical data from the Global Use of Strategies to Open Occluded Coronary Arteries (GUSTO) IIb, Platelet Glycoprotein IIb/IIIa in Unstable Angina: Receptor Suppression Using Integrilin Therapy (PURSUIT), and Platelet IIb/IIIa Antagonism for the Reduction of Acute Coronary Syndrome Events in a Global Organization Network (PARAGON) B trials.
Of 24,112 patients, 2,401 (10%) received at least one blood transfusion during their hospital stay. The patients in this group were older (mean, 68.9 vs. 64.0 years;
P < .001) and presented with a greater number of comorbid conditions including diabetes, hypertension, and hyperlipidemia (
P < .001 for all) compared with those who did not receive any transfusions.
Data analysis showed that patients receiving transfusions had significantly greater unadjusted 30-day rates of mortality (8.00% vs 3.08%;
P < .001), myocardial infarction ([MI] 25.16% vs. 8.16%;
P < .001), and combined death/MI (29.24% vs. 10.02%;
P < .001) compared with those who did not receive any transfusions.
Transfusion was associated with an almost fourfold increase in the risk of mortality (hazard ratio [HR], 3.94; 95% confidence interval [CI], 3.26 - 4.75), and an almost threefold increase in risk of combined mortality/MI (HR, 2.92; 95% CI, 2.55 - 3.35) within 30 days, after adjustments for baseline characteristics, bleeding and transfusion propensity, and nadir hematocrit in a model that included transfusion as a time-dependent covariate.
Landmark analysis with additional adjustment for invasive procedures such as catheterization, percutaneous coronary intervention, and/or coronary artery bypass graft surgery (CABG) showed a trend between blood transfusion in the first seven days of hospitalization and increased 30-day mortality.
Transfusion at a nadir hematocrit greater than 25% was associated with a significantly greater risk of 30-day mortality, both before and after excluding patients who died within the first five days of the study or who underwent CABG.
"This suggests that a hematocrit as low as 25% may be tolerated without blood transfusion in otherwise stable patients with ischemic heart disease," the authors comment. "[These] results...run counter to conventional clinical thinking about cardiac function and anemia.
"In our study, blood transfusion in the setting of ACS was associated with an increased risk of short-term mortality," the authors write. "This risk persisted despite adjustment for patient characteristics, including baseline and nadir hematocrit, bleeding, and in-hospital procedures.
"Given the disparity in results between our study and other observational studies of transfusion and outcome, a randomized trial of transfusion strategies in anemic patients with ACS is warranted to guide clinical practice," the authors conclude. "Until then, we caution against the routine use of blood transfusion to maintain arbitrary hematocrit levels in stable patients with ischemic heart disease."
The study was funded by the Duke Clinical Research Institute.
Two prior observational studies have yielded contradictory results, note Paul C. Hébert, MD, MHSc, and Dean A. Fergusson, PhD, from the Ottawa Health Research Institute in Ontario, in an accompanying editorial. One study recommended transfusions below a hematocrit level of 33% in elderly patients after acute MI, while the other concluded that transfusions were not associated with improved survival when nadir hematocrit values were in the 20% to 25% range and were associated with worsened outcomes at values greater than 30%.
"Rather than primarily focusing on transfusions in [ACS], physicians should first administer all therapies that have been shown to be effective to reduce mortality and limit infarct size, such as aggressive revascularization and newer antiplatelet agents," the editorialists suggest.
"In the absence of clinical trial evidence related to transfusion triggers, it appears that red blood cells may potentially be beneficial when hemoglobin concentration falls below 8.0g/dL," Drs. Hébert and Fergusson write, recommending that physicians measure hematocrit levels after administration of each individual unit and accept a concentration in the range of 9.0 g/dL.
JAMA. 2004;292:1555-1562, 1610-1612
Reviewed by Gary D. Vogin, MD
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