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Infection, Death Rates Higher in Women After Bypass Surgery

Breaking News - March 2006 - Week 1

(Mar 1, 2006)

Healthcare in  the News

-- An increased incidence of infection may explain why women are more likely than men to die days or weeks after having heart bypass surgery.

A picture of a female physician at work

Heart bypass surgery is performed to treat a blockage or narrowing of one or more of the coronary arteries, restoring the blood supply to the heart muscle.

Anew University of Michigan study suggests that the answer to the gender deathmystery may lie with infections, regardless of their location in the body.

U-M researchers report in the medical journal Archives of Internal Medicine that 96 percent of the gender difference in death risk within 100 days of coronary artery bypass surgery may be explained by differences in infection rates.

The researchers used hospital and post-hospital data from 9,218 Michigan residents who had bypass surgery in a 15-month period. All were Medicare beneficiaries age 65 years or older.

Infection May Cause Higher Death Rate in Women

“Overall, we found that women’s increased risk of [death] after coronary artery bypass surgery may be due to differences in infection,” says lead author Mary A. M. Rogers, Ph.D., research director of the Patient Safety Enhancement Program of the U-M Health System and the Veterans Affairs Ann Arbor Healthcare Center.

“We found that 16 percent of women patients had an infection, compared with 10 percent of men," Dr. Rogers adds.

This difference persisted even when factors such as age, race, urgency of the operation, length of hospital stay, co-existing medical conditions, and the number of bypass operations performed at each hospital or by each surgeon were taken into account.

According to the study, coronary artery bypass surgery, or CABG, is one of the most common surgeries in the US, with more than half a million procedures performed every year.

While it is well known that women are more likely to die after the procedure, explanations for this gender gap remain controversial.

Possible explanations include females' smaller arteries, along with a greater likelihood for other preexisting conditions.

Infection's Role

“We suspect that there may be a systemic, or body-wide, response to infection, making infection at any site a concern in elderly patients,” Dr. Rogers says.

She notes that women in the study were more likely than men to have infections of the urinary, respiratory, and digestive tracts. Women were also more likely than men to have skin and post-operative infections.

But this was not the study’s only finding. Although women who had heart surgery were much more likely to have an infection than their male counterparts, women with an infection were less likely to die than men who had an infection.

“This finding was a surprise since, overall, women had greater mortality,” says Dr. Rogers. “But when we looked closer, we found that there were two underlying relationships here: a greater prevalence of infection in women, and a higher mortality once infected for men.”

In all, about 12 percent of patients in the study who had infections during their hospital stay died before leaving the hospital, compared with 4 percent of those without infections.

And when the researchers looked at who had died in the first 30 and 100 days after their operation, those who had had an infection in the hospital were still far more likely to die.

Why Do Women Have More Infections?

As to why women have an higher incidence of infection, the authors can only speculate.

Women are more likely than men to have diabetes, which is a risk factor for infection. Good control of blood sugar after surgery, in particular, has been shown to reduce the chance of infection.

Women are also more likely to have immune-related disorders such as lupus and arthritis, and the use of immunosuppressant therapy or corticosteroids increases the risk of infection.

Perhaps the more pertinent point is that hospitals already have guidelines in place, which, if followed, should reduce this burden.

"We have recommendations for infection control," Dr. Rogers says. "It's a problem of putting into practice these procedures on a daily basis."

Infection control guidelines include administering antibiotics one hour prior to incision, yet one recent study showed that this actually occurred only about 55 percent of the time, Dr. Rogers says.

There are also things women (and men) can do to minimize the risk of infection.

Elderly people should get annual flu vaccines and, every five years, vaccines for bacterial pneumonia (pneumococcal vaccine).

According to Dr. Rogers, only two-thirds of elderly people actually get their influenza vaccination and only about half receive their pneumococcal vaccine on schedule.

Healthcare workers who take care of these patients are also undervaccinated.

In the hospital, patients should start to walk as soon as possible after the operation and should also wash their hands frequently, to cut down on infection risk.

Always consult your physician for more information.

For more information on health and wellness, please visit health information modules on this Web site.


About Bypass Surgery

Coronary artery bypass graft surgery (CABG) is a procedure used to treat coronary artery disease in certain circumstances.

Coronary artery disease (CAD) is the narrowing of the coronary arteries (the blood vessels that supply oxygen and nutrients to the heart muscle), caused by a buildup of fatty material within the walls of the arteries.

This buildup causes the inside of the arteries to become rough and narrowed, limiting the supply of oxygen-rich blood to the heart muscle.

One way to treat the blocked or narrowed arteries is to bypass the blocked portion of the coronary artery with another piece of blood vessel.

Blood vessels, or grafts, used for the bypass procedure may be pieces of a vein taken from the legs or an artery in the chest.

One end of the graft is attached above the blockage and the other end is attached below the blockage. Thus, the blood is rerouted around, or bypasses, the blockage through the new graft to reach the heart muscle.

This bypass of the blocked coronary artery can be done by performing coronary artery bypass surgery.

Traditionally, in order to bypassa blocked coronary artery in this manner, the chest is openedby cuttingthe breastbone (sternum) in half and spreading it apart.

Once the heart is exposed, tubes are inserted into the heart so that the blood can be pumped through the body during the surgery by a cardiopulmonary bypass machine (heart-lung machine). The bypass machine is necessary to pump blood while the heart is stopped and kept still in order for the surgeon to perform the bypass operation.

While the traditional “open heart” procedure is still performed and often preferred in many situations, newer, less invasive techniques have been developed to bypass blocked coronary arteries.

“Off-pump” procedures, in which the heart does not have to be stopped, were developed in the 1990’s. Other minimally-invasive procedures, such as key-hole surgery (performed through very small incisions) and robotic procedures (performed with the aid of a moving mechanical device), have been developed.

Always consult your physician for more information.


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