a special program of the National Emergency Medicine Association (NEMA)
Transcripts: 503-1 to 503-5
Week: 503.1 Guest: Robert E. Wenk, MD.. Topic: Human Blood and the Blood Supply - Part One Host: Richard Roeder Producer: Ed Graham
NEMA: This is a five part series on human blood and how it works and the safety of the blood supply. My guest is the Director of the blood bank at Sinai Hospital in Baltimore, Maryland, Dr. Robert E. Wenk.
NEMA: Dr. Wenk, the dangers of receiving a blood transfusion have been given far more attention since the arrival of AIDS but is the blood supply really more dangerous to a transfusion recipient in 1995 than it was in 1965 or is there just more awareness?
WENK: No, it's actually less dangerous in 1995 than it was in 1965.
NEMA: Can you explain?
WENK: Yes. The reason is primarily that the blood supply is screened much more extensively and carefully now than it was back in '65. In '65, we had very ill-defined concepts of what diseases could be transmitted through blood. Essentially there were fewer blood products available. The process of controlling the manufacture of those processes was less rigorous than what it is now and I think it's fair to say and it has been said repeatedly in the medical literature that the blood supply in the United States is safer now than it has ever been.
NEMA: Certainly I know you understand based on the coverage that the AIDS epidemic has received that to the average person, that would come as a big surprise.
WENK: The problems primarily related to diseases transmissible such as hepatitis and although AIDS/HIV virus did not exist as a disease in the population at that time, what's caused the public to consider that blood became less safe was the fact HIV is universally regarded as a lethal disease and relatively few people are known to die of hepatitis acquired through blood transfusions so although the problem then as well as now is primarily relatively high frequency of transmission of hepatitis viruses, in fact the HIV's lethality is what caused the panic.
NEMA: Talk a little bit about the safeguards that are employed now for protecting the blood supply.
WENK: Well, in the first place there is extensive questioning of donors, something that did not go on in the era that you asked me to compare the current supply with so if there are risks either because of where a person was born or what diseases that person might have picked up as a world traveler or if the person has risk behaviors that might cause higher frequency of disease in the particular population at risk, then those donors are eliminated from donating to the blood supply. For example, people traveling to certain parts of the world may pick up malaria. Well, people don't regard malaria as a high risk but in fact you can transmit malaria through blood transfusion. A common example now is that in the United States along the southern border and in the southwest, there's a disease known as Chagas' disease which is prevalent in Central America and South America so immigrants from those regions or travelers from those regions in fact may transmit Chagas' disease, a kind of sleeping sickness, through transfusion.
NEMA: Join me for part two on human blood and the blood supply with Dr. Robert E. Wenk.
Week: 503.2 Guest: Robert E. Wenk, MD.. Topic: Human Blood and the Blood Supply - Part Two Host: Richard Roeder Producer: Ed Graham
NEMA: This is part two in a five part series on human blood and the blood supply. My guest is the Director of the blood bank at Sinai Hospital in Baltimore, Maryland, Dr. Robert E. Wenk. I asked Dr. Wenk why he says the blood supply is actually safer in 1995 than it was in 1965.
WENK: The fact is that just questioning the donor as to what their life's habits are, where they've lived, where they've traveled to, all makes a difference in proving the quality and the safety of the blood. Those questions and the discipline with which the questions were asked is much better now than what it had been. Aside from the questioning, what we refer to in medicine as history taking, there are a number of tests, half a dozen added in the last ten years or so which were not available before that time and of course we now test not just for hepatitis B but we now know of ways to test for hepatitis C virus which is the most commonly transmitted hepatitis virus in blood and of course HIV, the virus that most people are afraid of acquiring in a transfusion, is now tested extensively too.
NEMA: Does anyone in this country still do what was done very commonly decades ago which is pay for blood? In other words, I don't mean a patient but I mean there used to be clinics where a person could walk in and make a few bucks.
WENK: There are still places in which one can donate blood or plasma and be paid for it but in general the material collected, the blood collected, is not only tested but almost always pasteurized. In other words, it's possible to obtain materials from blood in a safe manner even if the blood originally might have been contaminated with virus. And so for example, if you pasteurize the product, if you heat it in such a way that it rids the blood of viruses or bacteria that are present, it's still okay to use that material. The voluntary blood supply, of course nobody is paid, the definition of a volunteer is you're not paid for the blood - you donate out of altruistic motives - and that material which is potentially risky is what's used in transfusing people in hospitals and for medical purposes but to acquire things like albumen in blood, it is possible to donate it to have the material pasteurized, made safe, and the albumen is put on the market as a pasteurized safe product.
NEMA: As you're just referring to, blood is used for a lot of things other than just transfusions of whole blood. Can you briefly just name some of the different components that it's broken down into?
WENK: Yes. Blood products are generally broken down into at least three components initially. There are red cells, there is plasma and there are platelets. Platelets are used to stop bleeding in people who lack platelets or who are deficient in the number of platelets or who have poorly functioning platelets. Plasma is used for other coagulation or clotting disorders and red cells are used to carry oxygen for people who are extremely anemic.
NEMA: Join me for part three on human blood and the blood supply with Dr. Robert E. Wenk.
Week: 503.3 Guest: Robert E. Wenk, MD.. Topic: Human Blood and the Blood Supply - Part Three Host: Richard Roeder Producer: Ed Graham
NEMA: This is part three in a five part series on human blood and the blood supply. My guest is the Director of the blood bank at Sinai Hospital in Baltimore, Maryland, Dr. Robert E. Wenk. I asked Dr. Wenk about products derived from whole blood in addition to red cells, plasma, and platelets.
WENK: There are additional products, mostly derivatives of plasma and you can extract specific proteins from the plasma for diseases in which only those proteins are deficient so there are a host of other specific protein components that are available to selected patients.
NEMA: How is blood stored?
WENK: Generally speaking, blood is stored at four degrees in a refrigerator and the refrigerators are monitored and controlled for temperatures so that the blood is not allowed to be warmed to any temperature where bacteria might grow.
NEMA: And if stored properly, how long will blood remain usable?
WENK: Six weeks. It really depends on the kind of preservative in the blood but in general we've extended the storage from, I think it originally was something like three weeks to where we can now store it for seven weeks but it's even possible to go beyond the usual storage time if you freeze blood and freezing is a possibility.
NEMA: Explain the procedure of blood donation for listeners who have never donated blood.
WENK: It's a relatively simple process. The donor arrives at a donor center, is questioned, is asked to fill out some forms and the process has been recently shortened from about two hours down to something like 30 minutes. After the questionnaire, a sample of blood is obtained to make sure that the donor is not anemic and then the blood is collected generally with the patient or donor lying flat on a table and a sample of blood in addition to the one used to transfuse a patient is collected and that sample is used for all of the testing. Essentially a pint of blood is given at each donation.
NEMA: Now many people have not given blood because they are fearful of the many blood-borne diseases they've heard about. Is there any danger under any circumstances to a blood donor?
WENK: There is no chance of transmission of disease to the blood donor. No. There are risks. There are people who will faint. There are people who have had problems donating but in general they are a rather rare event.
NEMA: But in terms of them having something transmitted to them that they're afraid of in the blood supply, that has nothing to do with the donor?
WENK: That is not possible.
NEMA: And about a pint of blood is taken. Is there any difference in the amount of blood that can be donated by men as opposed to women in general on the average?
WENK: Fundamentally, if you meet a minimum weight requirement, I think it's 110 pounds, you can give a standard unit of blood. Remember, we're collecting this blood as a unit dose for a patient so we try to fix the dose at a given amount of blood. A small person theoretically should give less than a large person but the amount given is small enough in volume that it really has little effect on a small donor.
NEMA: Join me for part four on human blood and the blood supply with Dr. Robert E. Wenk.
Week: 503.4 Guest: Robert E. Wenk, MD.. Topic: Human Blood and the Blood Supply - Part Four Host: Richard Roeder Producer: Ed Graham
NEMA: This is part four in a five part series on human blood and the blood supply. My guest is the Director of the blood bank at Sinai Hospital in Baltimore, Maryland, Dr. Robert E. Wenk.
NEMA: What is an autologous transfusion?
WENK: An autologous transfusion is the deposit by a patient of his or her own blood prior to an elective surgical procedure in which blood might be used.
NEMA: Now one recent study questioned the value of autologous transfusions. I think it was a cost benefit evaluation. Are you familiar with the study and do you think they are of great value or is it really more a peace of mind perception issue?
WENK: Currently my belief is it's more a piece of mind issue. To be sure, I collect autologous units. I believe that units are clearly the safest blood to be transfused when transfusion is necessary and there are certainly surgical procedures in which a surgeon or anesthesiologist could predict that blood would be used in that procedure and therefore autologous blood is very beneficial. On the other hand, there is a concern in the general public about the fear of transmission of disease such that autologous donation is used far more frequently than it really needs to be.
NEMA: I see. Would you explain what the term "blood type" means and how is a person's blood type determined?
WENK: Generally speaking, there are two major blood groups in which it's important to know a person's blood type. There is the ABO group. You've heard people who are group A or group B or group O or group AB. There are four major groups that way. There's a second major grouping called the RH system in which case you're called RH positive or RH negative so when you hear somebody who is group A positive it means that he is blood group A in the ABO system and he is RH positive in the RH system. They are independent systems such that there are people who will be A positive, A negative, B positive, B negative, O positive, O negative and so on. Generally speaking, a group O donor is considered a universal donor because his red cells are compatible with any recipient of any of the blood groups A, B, O or AB. An AB person is considered a universal recipient because they can receive blood from any of the A, B, O or AB donors. Now the RH factor is important because you don't want to give an RH negative person an RH positive unit of blood because a good proportion of the people who receive such blood would then develop antibodies and be unable to receive the same kind of blood a second time.
NEMA: And the danger being if a person is transfused with the wrong type of blood that essentially the body views it as an invasion and therefore attacks it as if it was some sort of an infecting agent, correct?
WENK: Yes. The person would develop antibodies to an incompatible unit. If it's an ABO incompatible unit, you need not have even been exposed previously the way it would work for the RH system. There are risks of death, decreased blood pressure, a shock in people receiving the wrong kind of blood.
NEMA: Join me for part five on human blood and the blood supply with Dr. Robert E. Wenk.
Week: 503.5 Guest: Robert E. Wenk, MD.. Topic: Human Blood and the Blood Supply - Part Five Host: Richard Roeder Producer: Ed Graham
NEMA: This is part five in a five part series on human blood and the blood supply. My guest is the Director of the blood bank at Sinai Hospital in Baltimore, Maryland, Dr. Robert E. Wenk. I asked Dr. Wenk about the importance of matching the blood types of donors to recipients.
WENK: It's very critical that each unit of blood is not only tested for ABO and RH but that the labeling is correct and that the blood bank transfusing it issues it to the appropriate kind of patient.
NEMA: Scientists have been working on an artificial blood for a long time and I think they now have it carrying oxygen but blood does a lot more than that. What makes it so difficult to produce an artificial blood and do you think there will ever be such a product developed in the foreseeable future?
WENK: Well, there are a number of products available now that do carry oxygen but there are technical problems associated with them. One of the products put on the market several years ago by the Japanese required that the material be emulsified or mixed before it was used. It also didn't unload oxygen as effectively as red cells so it fell into disuse and is not generally available. I believe that there will be eventually an artificial oxygen carrying material and it may be a derivative of human hemoglobin raised in animals or cultures so that it would be viral free and conceivably it would work in the same way that hemoglobin works in our own blood streams. Now beyond this, the red material that carries the oxygen - blood is needed for coagulation or clotting and there are becoming available a great number of recombinant clotting factors. For example, already on the market is a recombinant factor aid for people with hemophilia. It used to be that these people almost all acquired viruses transmitted in blood if they had to be transfused frequently. That's a thing of the past with the use of recombinant products because they don't carry viruses. In the future there will be people with many unusual or rare diseases which the offending or lacking protein will be grown in artificial media and transfused to patients.
NEMA: Are the current numbers of people who donate blood supplying enough blood to meet the needs of medicine or are you frequently struggling with a blood shortage?
WENK: The problem of shortage seems to be getting worse. There used to be communities in which there was actually an abundance or an excess in the amount of blood and that blood could be distributed to communities where there was need. But I guess with the economy and the concern that people have with the lack of time, fewer people are going to blood centers to donate. I have to also consider that the process of donation has become more tedious. Although it's a faster process, you can expect that someone at the blood center will have to ask you about your lifestyle and life habits and so you have to offer personal information that was not a problem in the old days.