The ultimate blood substitute? The U.S. military is betting $46 million on it

Is mimicking the cells that carry hemoglobin the key to a blood substitute?

In 19th century New York City, Theodore Gaillard Thomas enjoyed an unusual level of fame for a gynecologist. The reason, oddly enough, was milk. Between 1873 and 1880, the daring idea of transfusing milk into the body as a substitute for blood was being tested across the United States. Thomas was the most outspoken advocate of the practice.

At the time, severe bleeding was often a death sentence. Blood transfusion was practiced, but it was something of a crapshoot. Medical science was still 3 decades removed from discovering blood types. Patients who received mismatched blood suffered discolored urine, itching, and a sometimes-fatal complication: hemolytic shock, wherein their own immune systems attacked the transfused cells.

Doctors in the U.S. were looking for something less risky to stabilize a hemorrhaging patient. 

It was not to be: Saline solutions, still used today, were introduced the next decade as a much less dangerous, if imperfect, stopgap measure for emergency bleeding.

The need for blood substitutes, however, survives. And last year in a downtown Baltimore laboratory, a white rabbit embodied the latest hope.

The bunny huddled in a black metal cage, a catheter going straight into its carotid artery. Days before, a portion of its blood had been siphoned out and replaced with an experimental blood substitute called ErythroMer. It is decidedly not milk. Developed by Allan Doctor, a bespectacled 61-year-old physician-researcher at the University of Maryland (UMD) School of Medicine, and colleagues, ErythroMer is made from “recycled” human hemoglobin—the protein in red blood cells that carries oxygen from the lungs to the rest of the body—wrapped in a membrane to mimic a tiny cell. In the rabbit, the transfusion appeared to be working. The animal’s heart rate and blood pressure, displayed on a small monitor nearby, looked just fine