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The independent effects of anemia and transfusion on mortality after coronary artery bypass
Milo Engoren1, Thomas A Schwann2, Robert H Habib3
1Department of Anesthesiology, University of Michigan, Ann Arbor, Michigan; Department of Anesthesiology, Mercy St. Vincent Medical Center, Toledo, Ohio.
Insights
Anemia and blood transfusions after cardiac surgery significantly increase late mortality risk. The combination of anemia and transfusion poses the highest danger, emphasizing the need for careful management.
Area of Science:
- Cardiovascular Surgery
- Hematology
- Critical Care Medicine
Background:
- Anemia and blood transfusions are known risk factors for mortality post-cardiac operations.
- The independent and interactive effects of anemia and transfusion on long-term mortality remain unclear.
Purpose of the Study:
- To investigate the combined impact of anemia and blood transfusions on late mortality after isolated coronary artery bypass grafting (CABG).
Main Methods:
- Retrospective study of 922 patients undergoing isolated CABG.
- Anemia defined as hemoglobin <12 g/dL (men) or <11 g/dL (women).
- Cox analysis and propensity matching used to control for patient characteristics and compare transfusion (Tx+) versus no transfusion (Tx-) groups.
Main Results:
- Transfusion (Tx+) was associated with higher mortality (11%) compared to no transfusion (Tx-) (5.3%).
- A significant interaction between anemia and transfusion was observed, with anemic patients receiving transfusions (A+Tx+) having a threefold increased hazard of death.
- Anemic patients receiving transfusions (A+Tx+) had double the hazard of death compared to anemic patients not receiving transfusions (A+Tx-).
Conclusions:
- The interaction between anemia and blood transfusion significantly increases the hazard of late mortality after cardiac surgery.
- Managing anemia and transfusion strategies is crucial for improving long-term outcomes in cardiac surgery patients.
Background:
Both anemia and transfusions (Tx) are associated with mortality after cardiac operations. However, the relative contributions of anemia and Tx and their interaction on late mortality have not been determined.
Methods:
922 patients who underwent isolated coronary artery bypass grafting (CABG) were retrospectively studied. Anemia (A+) was defined as hemoglobin<12 g/dL for men and <11 g/dL for women. Patients who received (Tx+) and did not receive (Tx-) transfusions were compared; patient characteristics were controlled for by the use of Cox analysis and then by matching Tx+ to Tx- patients based on identical hemoglobin levels at admission and by propensity matching.
Results:
5.3% of Tx- patients died, compared with 11% of Tx+ patients (p=0.001). The interaction of anemia and Tx was associated with a greater hazard of dying. In particular, A+Tx+ (anemic, received transfusion) patients had a threefold hazard of death (2.918, 95% confidence interval=1.512-5.633, p=0.001) compared with A-Tx- (nonanemic, no transfusion) patients. A+Tx+ patients had twice the hazard of dying as did A+Tx- (anemic, no transfusion) (hazard ratio=2.087, 95% confidence interval=1.004-4.336, p=0.049). In populations matched by preoperative hemoglobin levels or by propensity scores, similar results were seen: a significant interaction between anemia and transfusion of red blood cells. A+Tx+ patients fared significantly worse than did the other three groups. Although there was no difference in mortality between A- patients who did or did not receive transfusions, A+T+ patients had triple the risk as A+T- patients, whereas A+Tx- patients had a similar risk of late mortality as A-Tx- patients.
Conclusions:
The anemia-transfusion interaction was associated with an increased hazard of late mortality.
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