Alternatives to Regular Blood Transfusions

by Food and Drug Administration (FDA)

The second genetically engineered blood clotting factor and a new drug to stem bleeding in heart surgery last year joined other alternatives to regular "homologous" blood transfusion — blood transfused into someone other than the donor.

New steps by the Food and Drug Administration are helping to make the public blood supply as safe as possible. (See "The Real Scoop on AIDS and Shortages.") Alternatives, too, may increase safety for some patients, including those with the clotting disorder hemophilia, who all their lives depend on outside sources for clotting factors they lack.

Genetically engineered Kogenate was licensed Feb. 28, 1993, by the Food and Drug Administration as the second non-blood-derived alternative for people without clotting factor VIII. FDA licensed the first non-blood factor VIII, Recombinate, in December 1992. These products are for patients with hemophilia A. They prevent or control bleeding and prevent bleeding associated with surgery.

Previously, factor VIII could only be obtained from products derived from human plasma, the liquid part of blood. Kogenate and Recombinate are produced by hamster ovary cells into which the gene for human factor VIII has been inserted. The resulting factor is highly purified, eliminating the risk of transmission of viruses such as hepatitis or HIV, the virus that causes AIDS.

The new drug Trasylol Injection (aprotinin), approved last Dec. 29, decreases the need for transfusion in patients undergoing coronary artery bypass surgery.

In addition to drugs and biologics, several medical practices are available to lessen the already low risk of disease transmission. These alternatives include using the patient's own previously donated blood, recycling the patient's blood shed during surgery, and diluting the patient's blood before surgery.

Your Own Blood

Patients who are likely to require a transfusion during an upcoming surgery may decide to donate their own blood for possible reinfusion. FDA recommends this practice, called "autologous" transfusion, whenever possible for elective surgery.

Use of the patient's own blood may reduce the chance of infection or other adverse reaction. The practice also decreases demand on the public blood supply. In addition, autologous transfusion allows blood lost during surgery to be replaced more quickly because the process of donating blood, in itself, stimulates the bone marrow to produce new blood cells.

The disadvantages include: increased cost (about $24 more per unit), unnecessary donation if surgery doesn't require transfusion, and sometimes waste of unneeded units. Autologous blood not used by the donor-patient often cannot be used by another patient.

Some hospitals have a program for using autologous units in the public blood supply if the intended patient doesn't use them. These units must meet all FDA's safety standards for regular transfusion. In fact, the agency strongly recommends that all tests routinely performed on regular donations be performed on all autologous donations. Uniform testing is less confusing and safer, because it decreases the chance of releasing for general use an incompletely tested unit of blood. Labeling of an autologous donation must clearly indicate the intended recipient. Liquid blood can be stored refrigerated only 42 days; frozen blood, 10 years.

Autologous blood is most widely used for surgery on the bones, blood vessels, urinary tract, and heart. Nevertheless, any medically stable patient, even a child or pregnant woman, can be a candidate for autologous donation, according to Joseph Fratantoni, M.D., director of hematology at FDA's Center for Biologics Evaluation and Research.

Conditions that might prevent someone from donating blood for others don't necessarily prevent autologous blood donation. For example, people who have had hepatitis may give blood to themselves.

Autologous donation may be inadvisable for some patients, such as those with severe heart and blood vessel disease whose condition may be worsened by donating a unit or two of blood, says Fratantoni. "The decision to use autologous donation," he says, "should be made by the physician and the patient, according to the patient's condition."

For an autologous donation, the patient's doctor will make arrangements with the local blood bank, where the person can give one unit of blood a week for up to six weeks, as needed. A unit is just under a pint, about 10 percent of a person's total blood.

Although the fluid lost from donation replenishes within 24 hours, replacement of red blood cells, with their life-giving oxygen, can take as long as two months. For patients giving multiple autologous donations over several weeks, iron supplements may be prescribed to help increase the red blood cell count.

Recycling Blood During Surgery

When an operation is expected to involve a large loss of blood, the surgical team may recover the patient's blood and reinfuse it during the surgery. This practice, called intraoperative blood collection, or salvage, has been widely used in open-chest surgery, says Fratantoni, and may be done using one of two methods.

One method uses a high-speed centrifuge "specifically designed to handle blood gently," says Catherine Wentz, a biomedical engineer who reviews such instruments for FDA's Center for Devices and Radiological Health. Blood that collects in the surgical cavity is suctioned into the centrifuge, which separates it into components, Wentz says. The centrifuge concentrates the red blood cells, washes them with a saline solution, and pumps the red cell suspension into an infusion bag for return to the patient.

Despite the fact that red cell survival in salvaged blood may be as great as that of regularly transfused blood, the immune system's white cells and clotting substances such as platelets do not remain in salvaged blood in useful amounts. To protect against clotting problems, Wentz says, care must be taken to limit the amount of blood reinfused to a patient within a certain time period.

Another salvage method bypasses the centrifuge and collects the suctioned blood into a reservoir that filters the blood. After filtration, the unwashed blood is transferred into a bag for reinfusion.

"The choice of blood salvage method, washed or unwashed," Wentz says, "is usually based on the type of surgery. For example, knee and hip surgeries tend to 'taint' the suctioned blood with debris such as bone chips, so the choice may be a washed, or centrifuge, system."

Factors that make intraoperative salvage inadvisable include cancer or infection.

Scientists are investigating other blood collection practices.

About the Author

www.fda.gov
FDA is A United States government body that oversees medical devices, including contact lenses, intraocular lenses, excimer lasers and eyedrops. In the US, these products must be approved by the FDA before they can be marketed.