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• Posted April 12, 2024

Blood Loss Drives Higher Death Rate for Women During Bypass Surgeries

It's long been documented that women have a slimmer chance of surviving heart bypass surgery compared to men, and researchers believe that they now know why.

Women tend to be more vulnerable to blood loss during surgery -- red blood cells, specifically -- than men are, concluded a team from Weill Cornell Medicine in New York City.

They published their findings recently in the Journal of the American College of Cardiology.

Knowing that surgery-linked anemia raises risks for female patients should spur safeguards that can boost their survival during coronary artery bypass grafting (CABG) surgeries, the research team said.

Minimizing blood loss is "an actionable target to improve operative mortality in women after CABG and reduce the sex gap," wrote a team led by Dr. Mario Gaudino. He's a professor of cardiothoracic surgery at Weill Cornell.

The new study is based on data from over a million bypass patients, compiled by the Society of Thoracic Surgeons.

Those numbers confirmed the "sex gap": While 1.7% of men died during their bypass procedures, 2.8% of women did -- a nearly 50% difference, the researchers noted.

They next looked at a wide range of possible factors that could drive this disparity. They included age, ethnicity, heart disease severity, history of prior heart attack and the presence of other illnesses.

The team also looked at factors involved in the surgery itself, such as the length of time patients needed to be placed on a heart-lung bypass machine, or the volume and type of blood loss.

Only one factor stood out: Crunching the numbers, Gaudino's group found that 38% of the excess risk seen among female patients could be blamed on the impact of red blood cell loss during the surgery. It's a condition known as intraoperative anemia.

As the research team explained, some anemia is inevitable, because the heart-lung bypass machine that keeps patients alive during these surgeries relies on blood-diluting fluids.

However, women's average smaller body size, and the fact that they tend to arrive for bypass surgery with a lower red blood cell count than men, makes them more vulnerable to intraoperative anemia, Gaudino's group believes.

The study was not designed to conclusively prove that intraoperative anemia was the major cause of women's poorer survival. However, the Weill Cornell team believe more could be done to level the playing field for female patients.

"Using heart-lung bypass machines with shorter circuits, for example, would limit the volume of blood-diluting solution needed to run the pump," they explained in a Weill Cornell news release.

Clinical trials aimed at proving the effectiveness of such interventions are also "urgently needed," said Gaudino, who is also a cardiovascular surgeon at NewYork-Presbyterian/Weill Cornell Medical Center.

More information

Find out more about bypass surgeries at the American Heart Association.

SOURCE: Weill Cornell Medicine, news release, April 11, 2024