Weightman and colleagues have conducted a longitudinal analysis of 1,841 consecutive patients undergoing primary coronary artery surgery followed for a mean of just over 8 years. Their analysis revealed no association between moderate blood transfusion requirements and long-term mortality for those patients that survived greater than 60 days. An exhaustive analysis controlling for important perioperative risk factors, including anemia, was conducted. While no negative or positive association was found, I believe the study was underpowered to detect small but clinically important differences. Furthermore, focusing on long-term mortality and not including patients that died within 60 days ignores the complete impact of blood transfusion. Finally, any prior or subsequent transfusions between the time of their primary cardiac surgery and time of follow-up were not recorded or incorporated into the analysis. This too, would raise the potential for biased results.
– Dean A. Fergusson