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Transfusion and heart surgery: Only when needed

Unnecessary blood transfusion can do more harm than good.

Blood transfusion deserves a prominent place in the pantheon of medical advances. It has saved countless lives on the battlefield and in hospital emergency departments. It is a life-prolonging treatment for people with conditions that prevent the body from making blood or blood components, from kidney disease and cancer to disorders such as hemophilia and sickle cell anemia. But whether blood should be routinely transfused during or after heart surgery is a question that more and more people are asking. The answer is tilting toward “no.”

Questioning 30/10

The theory behind transfusing blood during and after coronary artery bypass grafting, heart valve repair or replacement, aortic aneurysm repair, or other cardiovascular surgery makes perfect sense. Loss of blood during an operation depletes the number of oxygen-delivering red blood cells in circulation. That could mean less oxygen available to tissues throughout the body, especially to surgically traumatized heart muscle.

Doctors measure the blood’s ability to deliver oxygen in two ways:

Hematocrit. Blood is made up of red blood cells, white blood cells, platelets, and plasma (the liquid component). Hematocrit measures how much of the volume of whole blood is made up of red blood cells. A normal hematocrit is typically set at 36% or higher for women and 40% or higher for men.

Hemoglobin. Hemoglobin is an oxygen-carrying protein found in red blood cells. In women, a normal hemoglobin level is 12 grams per deciliter of blood (g/dL) or higher; in men, it is14 g/dL or higher.

For years, doctors relied on a “30/10” rule of thumb, ordering a transfusion if the hematocrit fell below 30% or the hemoglobin below 10 g/dL. A growing body of evidence is challenging the wisdom of this arbitrary rule and suggesting that liberal use of transfusions may do more harm than good.

In an eye-opening British study published in 2007, people who received a transfusion during or after heart surgery were six times more likely to have developed a complication related to ischemia (insufficient oxygen delivery to the tissues), such as heart attack, stroke, kidney trouble, and even death, when compared with those who did not get a transfusion. In another clinical trial, individuals undergoing cardiac surgery were randomly allocated to one of two groups. Those in the liberal transfusion group were given blood if their hematocrit dropped below 30%, while those in the restrictive group were given blood only when the hematocrit fell below 24%. The restrictive strategy was just as effective as the liberal strategy, and led to fewer deaths and complications such as shock, breathing problems, or kidney failure (JAMA, Oct. 13, 2010).

Your blood is best

Blood banks across the country collect, store, and deliver more than 14 million units of blood each year. They are used by the five million or so Americans who require transfusions. Blood banks rigorously check blood to make sure it isn’t carrying hepatitis C, HIV, or other infectious agents. What they can’t do is provide blood that is as good as your blood.

Stored blood isn’t nearly as effective as fresh blood at delivering oxygen to tissues. Chemical changes that occur during storage increase the likelihood that transfused blood will cause inflammation or make blood vessels constrict. Stored red blood cells lose their flexibility and can get stuck in capillaries, the tiny blood vessels that connect arteries and veins. A European study showed that mixing stored blood with fresh blood activates platelets, making them stick together (European Heart Journal, Nov. 22, 2010). Sticky platelets can form the kind of blood clots that cause heart attacks and strokes. In addition, blood from another person can trigger an immune reaction and inflammation. These aren’t the kinds of stresses you want to add when the heart is more fragile than usual.

Talking about transfusion

In some hospitals in the United States, more than 90% of people undergoing coronary artery bypass grafting receive a transfusion of red blood cells; in other hospitals, under 10% get one (JAMA, Oct. 13, 2010). This huge variation indicates that the transfusion decision is as much about a doctor’s training and preferences as it is about medical necessity.

Minimizing the need for transfusion is not only possible, but safe and effective. Working with Jehovah’s Witnesses, whose religion does not allow transfusion, surgeons have developed so-called bloodless surgery programs. These aim to improve a person’s hematocrit and hemoglobin level before surgery, and then minimize blood loss and maximize blood recovery during surgery. These strategies are being used at hospitals across the country to reduce the need for transfusions among people who are not Jehovah’s Witnesses who need heart surgery.

There isn’t much you can do about whether you get a transfusion during or after surgery — if your doctors think you need one, you’ll get it. What you can do is have a conversation about transfusion beforehand, say doctors at Harvard’s three main teaching hospitals who have given a lot of thought to transfusions: Dr. Adam B. Lerner, director of cardiac anesthesia at Beth Israel Deaconess Medical Center; Dr. Thomas E. MacGillivray, surgical director of the adult congenital heart disease program at Massachusetts General Hospital; and Dr. James D. Rawn, director of the cardiac surgery intensive care unit at Brigham and Women’s Hospital. In this conversation, ask your surgeon how his or her team decides who needs a transfusion, or if there is a hospital policy.

All three experts stressed that there are definitely times when the benefits of transfusion during or after heart surgery far outweigh the risks. They also agreed that transfusion should be done only when medically necessary.

If your doctor thinks you are likely to need a transfusion, ask if there is anything you can do beforehand to minimize the need for one. Also ask what transfusion-sparing steps the surgical team will take during the operation.

One possibility is to capture lost blood and return it to the bloodstream. Another possibility is a technique known as acute normovolemic hemodilution. It involves taking one to three units of your blood right before surgery and replacing it with fluids called volume expanders. The blood is held at your bedside and then given back to you during or after surgery to replace any blood lost during the operation. This self-transfusion avoids the chance of acquiring an infection from a donor, developing an immune response, or facing the potential hazards of stored blood.

“In many parts of the world, blood is a precious resource,” says Dr. Deepak Bhatt, associate professor of medicine at Harvard Medical School and chief of cardiology for the VA Boston Healthcare System. “It is time we begin to view it the same way here, and be far more thoughtful about who should get a transfusion.”

Posted by: Dr.Health

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