Transfusion practice and outcomes in non–ST-segment elevation acute coronary syndromes

Objectives

To describe the association between transfusion and outcomes as a function of nadir hematocrit (HCT) in patients with non–ST-segment elevation acute coronary syndromes (NSTE ACS).

Background

The adverse outcomes associated with transfusion in NSTE ACS is uncertain and may vary by nadir HCT of the transfused.

Methods

Using data from 44242 patients with NSTE ACS in 400 US hospitals in the CRUSADE initiative (January 2004-December 2005), we describe blood transfusion as a function of nadir HCT and associated outcomes across nadir HCT groups (≤24%, 24.1%-27%, 27.1%-30%, >30%). We further explore patient and process variation across hospital quartiles defined by transfusion use.

Results

Overall, 22.2% of patients with NSTE ACS are anemic and 10.4% receive a blood transfusion during their care. Likelihood of transfusion rose from 1% when nadir HCT was >30% to 70% when nadir HCT was ≤24%. The threshold for transfusion is a median nadir HCT of 25.7% (interquartile range 23.8%-27.5%). Although nadir HCT of transfused remains constant across quartiles of transfusion use, occurrence of bleeding increases. Inhospital mortality is higher in lower nadir HCT groups. In those with a nadir HCT of ≤24%, transfusion tended to have a beneficial impact on mortality (HCT ≤24% adjusted odds ratio [OR] 0.68 [0.45-1.02]). In the median range where transfusion occurs, transfusion had a neutral impact on mortality (HCT 24%-27% adjusted OR 1.01 [0.79-1.30]). Although rare, those transfused with nadir HCT of 27% to 30% (adjusted OR 1.18 [0.92-1.50]) or HCT of >30% (adjusted OR 3.47 [2.30-5.23]) had higher mortality.

Conclusion

Anemia and transfusion are common in the care of NSTE ACS. The observed association between transfusion and adverse outcomes is neutral in the nadir HCT range where transfusions are most often given and trends strongly to benefit when nadir HCT is ≤24%. Although reassuring, randomized trials are needed to confirm the safety of transfusion in NSTE ACS. In the meantime, avoiding the need for transfusion is the best approach.

Abbreviations: ACS, acute coronary syndromes, CABG, coronary artery bypass grafting, CHF, congestive heart failure, CRUSADE, Can Rapid risk stratification of Unstable angina patients Suppress ADverse outcomes with Early implementation of the American College of Cardiology/American Heart Association Guidelines, HCT, hematocrit, NSTE ACS, non–ST-segment elevation acute coronary syndromes, PCI, percutaneous coronary intervention, PRBC, packed red blood cell