It sounds like something you'd use for Halloween, but artificial blood is actually receiving high R&D priority at the National Institutes of Health (NIH) and the Department of Veterans Affairs (VA). The incidence of AIDS transmission through blood transfusions in the United States (some estimates place it at > 9000 reported cases in the past 10 years) and the ongoing risk of hepatitis transmission have put an already threatened blood supply under suspicion as unsafe to use. Blood substitutes can be made by modifying outdated blood or by de novo synthesis. Those that aren't derived from human blood products and can be mass produced may be the best hope for eventually solving the problems of availability and sterility. When a patient loses a great deal of blood, fluids with high oncotic pressure (plasma volume expanders) or isotonic saline can be used to replace the lost volume, but they lack the key attribute for an effective blood substitute: provision of oxygen transport. Without that, a patient may suffocate even while breathing normally, because the oxygen has no way to get from the lungs to the tissues where it's needed.
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