Importance: Although liberal blood transfusion thresholds have not been beneficial following noncardiac surgery, it is unclear whether higher thresholds are appropriate for patients who develop postoperative myocardial infarction (MI).
Objective: To evaluate the association between postoperative blood transfusion and mortality in patients with coronary artery disease and postoperative MI following noncardiac surgery.
Design, setting, and participants: Retrospective cohort study involving Veterans Affairs facilities from January 1, 2000, to December 31, 2012. A total of 7361 patients with coronary artery disease who underwent inpatient noncardiac surgery and had a nadir postoperative hematocrit between 20% and 30%. Patients with significant bleeding, including any preoperative blood transfusion or transfusion of greater than 4 units during the intraoperative or postoperative setting, were excluded. Mortality rates were compared using both logistic regression and propensity score matching. Patients were stratified by postoperative nadir hematocrit and the presence of postoperative MI.
Exposure: Initial postoperative blood transfusion.
Main outcomes and measures: The 30-day postoperative mortality rate.
Results: Of the 7361 patients, 2027 patients (27.5%) received at least 1 postoperative blood transfusion. Postoperative mortality occurred in 267 (3.6%), and MI occurred in 271 (3.7%). Among the 5334 patients without postoperative blood transfusion, lower nadir hematocrit was associated with an increased risk for mortality (hematocrit of 20% to <24%: 7.3%; 24% to <27%: 3.7%; and 27% to 30%: 1.6%; P < .01). In patients with postoperative MI, blood transfusion was associated with lower mortality, for those with hematocrit of 20% to 24% (odds ratio, 0.28; 95% CI, 0.13-0.64). In patients without postoperative MI, transfusion was associated with significantly higher mortality for those with hematocrit of 27% to 30% (odds ratio, 3.21; 95% CI, 1.85-5.60).
Conclusions and relevance: These findings support a restrictive postoperative transfusion strategy in patients with stable coronary artery disease following noncardiac surgery. However, interventional studies are needed to evaluate the use of a more liberal transfusion strategy in patients who develop postoperative MI.