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Published on: September 15, 2023
Perioperative Anemia and Transfusions and Late Mortality in Coronary Artery Bypass Patients
Thomas A Schwann1, Andrew M Vekstein2, Milo Engoren3
1Department of Surgery, University of Massachusetts-Baystate, Springfield, Massachusetts.
Insights
Red blood cell transfusions after coronary artery bypass graft surgery increase long-term mortality risk. Lower intraoperative anemia tolerance may be better than transfusions for patient survival.
Area of Science:
- Cardiovascular Surgery
- Anesthesiology
- Critical Care Medicine
Background:
- Perioperative anemia and red blood cell (RBC) transfusions are linked to adverse outcomes in coronary artery bypass graft (CABG) surgery.
- The independent impact of intraoperative anemia and RBC transfusions on long-term survival after CABG remains unclear.
Purpose of the Study:
- To investigate the association of intraoperative anemia and RBC transfusions with long-term mortality in elderly patients undergoing CABG.
- To determine if RBC transfusions improve survival outcomes across different levels of intraoperative anemia.
Main Methods:
- Analysis of a large cohort (n=504,596) of patients aged 65+ undergoing CABG from 2011-2018, linked to Medicare data.
- Assessment of intraoperative nadir hematocrit (nHct) and RBC transfusion rates.
- Utilized Kaplan-Meier estimates and multivariable Cox regression to evaluate associations with long-term mortality.
Main Results:
- 41% of patients had preoperative anemia; mean intraoperative nHct was 24%; RBC transfusion rate was 43.7%.
- RBC transfusions were significantly associated with increased adjusted mortality regardless of timing or nHct level.
- Lower intraoperative nHct showed only a marginal association with increased mortality risk.
Conclusions:
- RBC transfusions are linked to higher long-term mortality in CABG patients, even with adequate hematocrit levels.
- Intraoperative anemia has a less significant impact on long-term mortality compared to RBC transfusions.
- Consideration of tolerating lower intraoperative nHct may be a preferable strategy to RBC transfusions.
Background:
Perioperative anemia and transfusions are associated with adverse operative outcomes after coronary artery bypass graft surgery (CABG). Their individual association with long-term outcomes is unclear.
Methods:
Patients aged 65 years and older who had undergone CABG and were in The Society of Thoracic Surgeons (STS) Adult Cardiac Surgery Database (n = 504,596) from 2011 to 2018 were linked to Centers for Medicare and Medicaid Service data to assess long-term survival. The association of intraoperative anemia defined by intraoperative nadir hematocrit (nHct) and red blood cell (RBC) transfusions, and their interactions, on long-term mortality were assessed with Kaplan-Meier estimates and multivariable Cox regression. Restricted cubic splines were used to explore the association between nHct as a continuous variable and long-term mortality.
Results:
258,398 on-pump CABG STS Adult Cardiac Surgery Database patients surviving the perioperative period were linked to Centers for Medicare and Medicaid Service claims files. Per World Health Organization criteria, 41% had preoperative anemia. Mean intraoperative nHct was 24%; RBC transfusion rate was 43.7%. Univariable analysis associated both RBC transfusion and lower nHct with worse survival. Lower nHct was only marginally associated with risk-adjusted mortality: adjusted hazard ratio (AHR) 1.04 (95% CI, 1.01-1.06) and 1.07 (95% CI, 1.00-1.14) at nHct 20% and at nHct 14%, respectively. RBC transfusion was associated with significantly higher adjusted mortality irrespective of timing of transfusion: AHR intraoperative 1.21 (95% CI, 1.18-1.27); AHR postoperative 1.26 (95% CI, 1.22-1.30); AHR both 1.46 (95% CI, 1.40-1.52) and across all levels of nHct. RBC transfusion was not associated with improved survival at any level of nHct.
Conclusions:
Among Medicare CABG patients, RBC transfusions were associated with increased risk-adjusted late mortality across all levels of nHct whereas intraoperative anemia was only marginally so. Tolerance of lower intraoperative nHct than currently accepted may be preferable to transfusions.
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