During the operation, the blood count drops. Medics transfuse the patient with the substitute, which is good for two or three days. Meanwhile, the body regenerates its own red cells. The product comes in durable bags that resemble the IV solution containers field medics carry. Brooke Army Medical Center only recently began testing Biopure.
Medical officials get patients' voluntary approval to use the blood products.
The trials are expected to last two to four years.