What if you need a transfusion?
It's only common sense to think ahead about how you might want to deal with the need for blood replacement in the event of surgery. Between 15 and 18 million units of donated blood are administered every year to patients in American hospitals (a unit is about a pint; your body contains about 10 units, or 9.5 pints). But doubts about the presence of contaminants in this banked blood continue to nag at many people. What are the real risks?
Dr. Joseph Bove of Yale University School of Medicine states the problem bluntly: "Patients and physicians need to understand that an absolutely safe blood supply is an unattainable goal." But he also notes that "current approaches to donor selection and testing are highly effective in minimizing the risk of transfusion-transmitted infection." Nonetheless, a National Institutes of Health Consensus Development Conference has proposed a reevaluation of the criteria surgeons use to judge the need for transfusions after blood loss. These experts want transfusions kept to a minimum because the more units of blood patients receive, the more likely they will be exposed to viral hepatitis and other infections.
The risk that makes the headlines is AIDS, and people tend to worry about it most. But recent government estimates put the chances of transfusion-related AIDS infection (actually HIV, or human immunodeficiency virus) at only one case per million units of blood in low-risk areas, like the Midwest, and one per 40,000 units in high-risk cities like New York or San Francisco.
Why, if donated blood is screened for HIV, does some contaminated blood slip through? Because there is a period--the so-called antibody-negative window--when an infected donor can transmit the HIV virus but hasn't yet developed enough antibodies to be detected by standard screening tests. A second problem arises from the possibility that the virus may hide in immune-system cells (macrophages) in a small number of people for several years before detectable antibodies make their appearance. There is a new diagnostic test that amplifies the least trace of genetic material from the virus in any given blood sample as much as a million times, making detection much easier, but it is not yet practical for routine screening by blood banks.
The risk of being infected with AIDS from a transfusion is very small when contrasted with the risk of viral hepatitis, a disease that can vary greatly in severity, from an asymptomatic condition to a potentially fatal disease. There are three main types of viral hepatitis:
Hepatitis A is spread mostly by contaminated food or water. It is rarely transmitted via transfusion.
Hepatitis B is spread by direct blood contact, contaminated needles, sexual intercourse, and transfusions, much like HIV. Though a screening test was developed for hepatitis B in 1972, and mandatory testing of all donated blood was instituted in 1987, this virus still accounts for about 10% of all cases of transfusion-related hepatitis in the U.S.
Non-A, non-B hepatitis (so named because it is a so-far-unidentifiable virus) spreads the same way as hepatitis B. No screening test is currently available for this virus, which accounts for about 90% of all cases of transfusion-related hepatitis. But recent discoveries offer hope for the eventual development of a screening test.
It's hard to estimate the incidence of transfusion-related hepatitis. Highly sensitive blood tests that reflect minor changes in liver function indicate that as many as 5% to 10% of all people who receive transfusions develop some degree of hepatitis--but the great majority of these cases are asymptomatic and clear up result in clinical symptoms of hepatitis, such as liver tenderness and mild jaundice. However, when research is restricted to people who develop full-blown hepatitis, the incidence drops substantially--one study found only 4 to 7 cases per 10,000 transfusion recipients.
What to do
When you know in advance that you'll need blood, you can donate autologously--that is, for your own use. The surest way to avoid infection from donated blood lies in storing your own blood for delivery to the operating room on the day you need it. It will remain usable for a maximum of 42 days, so at the donation rate of one unit a week you could safely build up a supply of six units. (The average amount of blood needed for a transfusion is two to three units. Exceptions include heart and blood vessel surgery and some plastic, orthopedic, and gynecologic procedures.) To allow your body to replace lost fluid, you will be asked not to give blood during the three days preceding surgery.
What about emergencies? Planning ahead this way really works only for people facing elective surgery. But a surgeon can resort to "intraoperative salvage"--a variation on the autologous-transfusion technique. The surgeon simply recycles blood lost during an operation. It is filtered, cleaned, and fed back into the patient's circulatory system on the spot. It helps solve the problem of the need--as in open-heart surgery--for many more units of blood than can safely be donated ahead of time. Another advantage: the apparatus used to do the job can recycle three units in nine minutes, and that's less time than it takes in emergency situations to identify the type of donated blood and cross-match it to the recipient.
A word of caution
There are two alternatives to traditional blood banks and autologous transfusions that may at first sound like good choices. But on closer examination, they prove not so smart after all.
The first is called "directed" donations. You ask friends and relatives to donate blood. But is their blood safer than anonymous donations from a blood bank? Not necessarily. A friend or family member will find it hard to turn down a request to give blood--but might find it harder to admit to a high-risk life-style.
The second alternative is having your own blood frozen and stored for future use. As we've said before (December 1986), there are two serious drawbacks: expense, for one. It costs a lot to store frozen blood that you may never need, and it must be thrown out after three years, anyway. Time is the other disadvantage. If your stored blood is in a San Francisco deep freeze, and you face emergency surgery in New Orleans, considerable time (and more expense) is involved in rushing it to the surgeon--who must then wait another 90 minutes while it thaws. Don't be bamboozled. Chances are that in an emergency, even with a large supply of your own blood in cold storage somewhere, you'll have to rely on the public blood supply anyway.
This may all sound discouraging, but remember that blood transfusions are lifesaving measures. Compared to the risks of not receiving blood, the risks from transfusions are negligible.
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|Publication:||The University of California, Berkeley Wellness Letter|
|Date:||Mar 1, 1989|
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