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Preoperative predicted risk does not fully explain the association between red blood cell transfusion and mortality
Gaetano Paone1, Robert Brewer, Patricia F Theurer
1Division of Cardiac Surgery, Henry Ford Hospital, Detroit, Mich 48202, USA. gpaone1@hfhs.org
Insights
Red blood cell transfusion after coronary artery bypass grafting (CABG) is linked to higher mortality. This association remains significant even after accounting for patient risk factors, suggesting transfusion itself may contribute to adverse outcomes.
Area of Science:
- Cardiovascular Surgery
- Transfusion Medicine
- Critical Care Medicine
Background:
- Perioperative red blood cell transfusion is a common practice following coronary artery bypass grafting (CABG).
- Existing data suggest an association between transfusion and increased morbidity and mortality in CABG patients.
- The precise nature of this association, whether causal or indicative of patient risk, remains debated.
Purpose of the Study:
- To investigate the relationship between red blood cell transfusion and operative mortality in isolated CABG procedures.
- To determine if the preoperative risk profile of transfused patients explains the observed association with mortality.
- To test the hypothesis that transfusion is an independent risk factor for mortality after CABG.
Main Methods:
- Retrospective analysis of 31,818 patients undergoing isolated CABG from a statewide collaborative database (2006-2010).
- Patients stratified into four groups based on predicted risk of mortality (PROM) using the Society of Thoracic Surgeons risk calculator.
- Statistical analysis included chi-squared tests, Breslow-Day tests for homogeneity, and Cochran-Mantel-Haenszel tests to assess transfusion-mortality association across risk strata.
Main Results:
- 55.7% of patients received red blood cell transfusions during hospitalization, with higher rates in higher-risk groups (93.3% in PROM >10%).
- Operative mortality was significantly higher in transfused patients (3.3%) compared to non-transfused patients (0.6%), with an overall odds ratio of 6.19.
- The association between transfusion and mortality remained statistically significant across all PROM strata and persisted even after controlling for preoperative risk (adjusted OR, 2.99).
Conclusions:
- The association between red blood cell transfusion and mortality after CABG is robust and statistically significant.
- This correlation is independent of the patient's preoperative risk status.
- The findings suggest that red blood cell transfusion may be an independent risk factor contributing to adverse outcomes post-CABG.
Objective:
Perioperative red blood cell transfusion is associated with increased morbidity and mortality after coronary artery bypass grafting (CABG). Whether transfusion is a cause of these outcomes or serves as a surrogate for a high-risk patient population remains uncertain. This retrospective study tested the hypothesis that increased preoperative risk profile of patients receiving transfusion would explain the relationship between red blood cell transfusion and operative mortality in isolated CABG.
Methods:
A total of 31,818 patients undergoing isolated CABG were entered into a statewide collaborative database between January 2006 and June 2010. With the Society of Thoracic Surgeons risk calculator, patient cohorts were stratified into 4 groups by predicted risk of mortality (PROM) of less than 2%, 2% to 5%, more than 5% to 10% and more than 10%. The association between blood transfusion and mortality was tested at each stratum with a χ(2) test. A Breslow-Day test for homogeneity of odds ratios was used to test whether the 4 odds ratios of the strata were similar, and a Cochran-Mantel-Haenszel test was used to test the association between blood transfusion and mortality while controlling for predicted risk mortality strata.
Results:
In all, 17,720 (55.7%) of all patients were transfused during the hospitalization. Incidence of transfusion increased stepwise with risk level; 93.3% of patients with PROM greater than 10% received blood. Operative mortality was 2.1% overall, 0.6% among the 44.3% of patients who were not transfused, and 3.3% in the transfused group (odds ratio, 6.19; P < .0001). The association between blood transfusion and mortality was significant within each predicted risk stratum. Increased mortality associated with transfusion was statistically equivalent across all predicted risk strata (P = .1778). The association between blood transfusion and mortality for all patients lessened somewhat when controlling for PROM (odds ratio, 2.99 vs 6.19), yet remained highly significant (P < .0001).
Conclusions:
The association between red blood cell transfusion and mortality after CABG is highly significant and independent of increased preoperative risk status. The correlation persists after controlling for increased PROM.
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