Blood Substitute

¶ … Blood Shortage and Potential Life-Supporting Alternatives When the AIDS pandemic began to take its toll in many countries in the mid-1980s, it led to countless fears among people and institutions around the world. One of those fears was that the supply of life-saving blood could somehow become contaminated by the HIV virus. (HIV, of course, is the human immunodeficiency virus, which leads to AIDS.) In fact, informed people had good cause to be anxious about the possible contamination of blood.

That is because some doctors in France, while assuring the public that blood was safe there, covered up the fact that some blood supplies in France were indeed contaminated. The international media frenzy from that incident stirred even more fears about the safety of blood supplies. There is a fear, which continues today, regarding safe blood and HIV - albeit, the "odds" of contracting HIV are from 1-in-450,000 to 1-in-a-million. But beyond contamination, there is another serious blood issue, and that is blood shortages.

In the U.S., for example, about 12 million units of blood are needed annually - yet health officials say that by the year 2030 there will be an "annual shortfall" of four million units in America. This prediction of shortages is partially due to the fact that America's population is becoming an older population, and older people need blood transfusions the most. In addition, at the time the article was written, about 5% of Americans donate blood, and yet, every three seconds another person in the U.S. requires a transfusion.

What function does blood actually provide within - and for - the body? According to the assigned article in Scientific American, blood "transports nutrients, hormones and waste products"; blood also fights infections and has the ability to "clot" - preventing or at least slowing down serious hemorrhaging. The part of human blood which helps fight disease is the white blood cells.

But the most "familiar" function of blood in the body of mammals is the "capture and release of oxygen and carbon dioxide." The protein most commonly found in blood, hemoglobin, is also a critically important protein. Hemoglobin picks up oxygen in the lungs, and distributes it throughout the body. The red blood cells pick up carbon dioxide, which is a waste product given off through the respiration of cells, and humans exhale the carbon dioxide out through the lungs.

What happens when a person is in an accident and loses up to 40% of his or her blood? The body quickly begins producing more red blood cells; it also moves blood away from organs which are not crucial to survival. There are an estimated 4.5 to 5.5 million red blood cells in a typical cubic centimeter of blood. There are about 7,000 to 12,000 white blood cells in that same amount of human blood, plus 150,000 to 400,000 platelets. Platelets assist in the clotting of blood following a wound.

Blood is made up of about one-half cells, and one-half plasma. Blood transfusions must be carefully planned. A person with type "O" blood can donate to anyone else, but those type "O" individuals can only receive "O" type blood. Persons with type "A" blood can donate to "A" or "AB" blood types; and those with "B" can be shared with "B" or "AB." But a person with type "AB" may receive any type of blood from another (that's called being a "universal acceptor").

The scientist believed most responsible for discovering these facts about blood types and transfusions was a pathologist named Karl Landsteiner, an Austrian-American. His work in the early 1900s paved the way for safe treatment of people who need a fresh infusion of blood.

In the 1940s, medical researchers discovered that besides the "type" of blood given, there is an "Rh" factor; people with "Rh+" can only receive "Rh+" blood from others, albeit those who are "Rh-" can receive blood from either "Rh+" or "Rh-." How safe is most blood that is transfused in America? Of the approximately 23 million units of blood transfused annually in the U.S., there chances for anyone receiving blood to die from it are 1-in-100,000.

And what would be in the blood that would cause death? Besides the HIV virus, and blood-typing errors by medical technicians, a person could possibly get hepatitis from a blood transfusion. Becoming infected with hepatitis from a blood transfusion is possible, but unlikely: there is a 1-in-63,000 chance of getting hepatitis B, and a 1-in-103,000 chance of contracting hepatitis C, the New England Journal of Medicine reports. To duplicate all the functions that blood performs in the human body would seem to be an impossible challenge.

Any artificial blood product must pass several tests: It must be nontoxic, disease-free, and be "easily transportable." Also, it "cannot elicit an immune response" from the body and it must be adaptable to all blood types. Further, any substitute blood must stay in the body until the body can reproduce enough of its own blood to help the person survive.

And lastly, synthetic blood ideally must have a "long shelf life" - even real human blood (as of the date the article was published, nearly six years ago) only stays fresh for up to 42 days. Given all the above-mentioned criteria for imitation blood, researchers are approaching synthetic blood production from two distinct directions: one is based on chemicals, and the other is based on hemoglobin. The first, the chemical-based blood replacement solution, is being developed using "perfluorocarbons" (PFCs), which will be able, reportedly, to carry oxygen throughout the body.

While "floating in the plasma," PFCs will collect oxygen from the lungs, and then travel throughout the rest of the body, where they then "diffuse out in the capillaries," and exchange the oxygen for carbon dioxide. The second scenario for artificial blood, based on hemoglobin, is the subject of study by "far more" researchers than those working with PFCs. In order to function in the body, hemoglobin must contain 2,3-diphosphoglycerate (2-3-DPG) - present only in red blood cells.

Scientists in Illinois are developing "PolyHeme," and "HemAssist," two potential solutions based on the reshaping of the hemoglobin molecule. In Colorado, a synthetic blood called "Optro" is under research, and "Biopure" - produced with cow's blood - is being developed in Massachusetts. And the fifth research effort based on hemoglobin is the work of the authors of the.