Researchers find that intraoperative anemia accounts for 38% of the increased risk of death in women during heart bypass surgery.

Summary: Women undergoing heart bypass surgery face higher mortality rates than men, primarily due to intraoperative anemia, which accounts for 38% of the risk disparity, according to new research. This condition, caused by significant red blood cell loss when blood-diluting fluids are used in heart-lung bypass machines, is more severe in women, partly due to generally lower pre-surgery red blood cell counts. The findings suggest that reducing intraoperative anemia could improve outcomes, with potential strategies including using shorter circuit machines to minimize blood dilution. Clinical trials are recommended to explore these interventions.

Key Takeaways:

  • Women are at a higher risk of death than men during heart bypass surgery due to intraoperative anemia, which contributes significantly to this disparity.
  • Intraoperative anemia is responsible for 38% of the increased mortality risk associated with women undergoing this surgery.
  • Suggested strategies to reduce intraoperative anemia include using heart-lung bypass machines with shorter circuits, which require less blood-diluting solution, potentially lowering the risk and improving surgical outcomes for women.

Women are at higher risk of death when undergoing heart bypass surgery than men, and now researchers have determined that this disparity is mediated, to a large extent, by intraoperative anemia—the loss of red blood cells during surgery. 

The study, published in the Journal of the American College of Cardiology, suggests that strategies for minimizing anemia that occurs during this procedure could lead to better outcomes for women with cardiovascular disease.

Study Analysis Reveals Critical Insights

This study set out to discover why women are less likely to survive coronary artery bypass grafting, a surgical procedure for restoring blood flow to the heart. The team, led by senior author Mario Gaudino, MD, the Stephen and Suzanne Weiss Professor in cardiothoracic surgery at Weill Cornell Medicine, analyzed information obtained from the Society of Thoracic Surgeons Adult Cardiac Surgery Database on more than one million patients. Lamia Harik, MD, fellow in cardiothoracic surgery research at Weill Cornell Medicine, was first author on the paper.

They examined patient demographics (such as age and ethnicity), risk factors (including disease severity, previous heart attacks, and the co-occurrence of other health conditions), and surgical data (including the time spent on the bypass machine and the volume of the components of blood, such as red blood cells).

Statistical Analysis Highlights Anemia’s Role in Mortality Rates

Crunching the numbers, Gaudino and his team previously confirmed that women had a higher mortality associated with the procedure than men: 2.8% versus 1.7%, a nearly 50% difference. 

Now, using sophisticated statistical analyses to assess all the possible variables, the researchers found that a substantial portion of this enhanced risk—38%—could be attributed to severe intraoperative anemia. 

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This depletion of red blood cells is an inevitable side effect of using blood-diluting fluids to prime the heart-lung bypass machine that takes over the job of pumping blood throughout the body during surgery. Women may be even more susceptible to the effects of intraoperative anemia because they tend to arrive in surgery with lower red blood cell counts and have smaller body size compared to their male counterparts.

Need for Interventional Studies

The study does not establish that intraoperative anemia is causing greater female mortality, but the two factors are associated. It suggests that clinicians and researchers should consider interventions to prevent or minimize severe intraoperative anemia, which can lead to dangerously reduced oxygen delivery to the body’s tissues, including the heart.

Using heart-lung bypass machines with shorter circuits, for example, would limit the volume of blood-diluting solution needed to run the pump. Randomized trials to assess whether methods for curtailing anemia could improve outcomes for women undergoing heart bypass surgery are “urgently needed,” wrote Gaudino, who is also a cardiovascular surgeon at NewYork-Presbyterian/Weill Cornell Medical Center.

This research was supported in part by the National Heart, Lung, and Blood Institute grant T32 HL160520-01A1, the National Institutes of Health, the Canadian Health and Research Institutes, and the Starr Foundation.

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