1. For post-cardiac surgery patients, a restrictive transfusion threshold was not superior to a liberal transfusion threshold in terms of major infection and ischemic events at 3 months.

2. More deaths occurred in the restrictive threshold group than the liberal threshold group.

3. No significant differences in total cost was found between the two treatment groups.

Evidence Rating Level: 1 (Excellent)

Study Rundown: Current transfusion thresholds are based on past trials of patients in an intensive care setting or in the setting of gastrointestinal bleeding. Previous studies examining transfusion thresholds in the cardiac surgery population have demonstrated mixed results with many lacking statistical power.

This multicenter, randomized control trial from the United Kingdom (TITRe2) randomized cardiac surgery patients post-operatively to a transfusion threshold of either less than 9 g/L (liberal) or less than 7.5 g/L (restrictive). At three months follow up, there was no statistical difference between the two groups in terms of the primary outcome of combined major infection (sepsis, wound infections) and ischemic events (strokes, myocardial infarction, ischemic gut, and specific acute kidney injury). However, more deaths occurred in the restrictive threshold group than the liberal threshold group. Overall, mean cost was similar in both groups at 3 months post operation.

Even with a paucity of evidence, restrictive thresholds are often favored in most patients for reasons of decreased health utilization and the belief that it does not improve survival. However, this large randomized trial in post-cardiac surgery patients may create a shift towards slightly more aggressive transfusion thresholds for this patient population. While baseline characteristics in both groups were well matched pre-operatively, the suspected underlying cause for anemia was not documented in this study. These results would also be mostly generalizable to only cardiac surgery patients. Future studies will likely further examine wider transfusion thresholds for similar and other patient populations.

Click to read the study, published today in NEJM

Click to read an accompanying editorial in NEJM

Relevant Reading: A blast from the past – Trial of Transfusion Requirements in Critical Care (NEJM 1999)

In-Depth [randomized controlled trial]: This study enrolled 2004 patients from 17 major centers in the United Kingdom and randomized post-cardiac surgery patients to either a restrictive (<7.5g/L) or liberal (<9.0g/L) transfusion threshold. Pre- and intra-operative baseline characteristics were well-matched between the groups including age, gender, CCS angina class, type of cardiac surgery, hemoglobin and use of intra-operative blood-recovery devices. At 3 months follow up, the primary endpoint of combined major infection and ischemic events occurred in 35.1% and 33.0% (p=0.35) in the restrictive versus liberal groups, respectively. There was also no difference in total costs and duration of patient stay in ICU between groups. However, patients randomized to a restrictive threshold had a higher risk of death (hazard ratio 1.64, p=0.045) and acute kidney injury (odds ratio 1.20, p=0.04).

Image: PD

©2015 2 Minute Medicine, Inc. All rights reserved. No works may be reproduced without expressed written consent from 2 Minute Medicine, Inc. Inquire about licensing here. No article should be construed as medical advice and is not intended as such by the authors or by 2 Minute Medicine, Inc.