Tens of thousands of people bleed to death every year in the United States before they can reach a hospital. That’s because ambulances, medical helicopters, and military doctors can’t routinely carry blood, which spoils too quickly without proper refrigeration.
So, scientists have been seeking to develop artificial blood that can be stored as a powder and reconstituted by doctors on-site to save lives.
At the University of Maryland School of Medicine in Baltimore, where part of this research is being conducted, a white rabbit is lying on the floor of a cage. It is in a “special intensive care unit that we created for resuscitating our rabbits,” says Dr. Allan Doctor, a scientist at the school.
Dr. Doctor’s team has just drained blood from the animal to simulate what happens to a person who is hemorrhaging due to an injury, like from a car accident or a battlefield wound.
“This rabbit is still in shock. You can see it’s lying very still. It’s like it’s at the scene of an accident,” Doctor says. “If we did nothing, it would die.”
But Dr. Doctor and his team will save this rabbit today. They will fill its veins with something they hope will finally allow them to achieve a goal that has frustrated researchers for decades: developing safe and effective artificial blood.
“Good bunny,” says Danielle Waters, a technician on Dr. Doctor’s team, as she carefully lifts it and begins infusing it with three large syringes of artificial blood.
Dr. Doctor’s team manufactures synthetic blood from hemoglobin, the protein that nourishes the body with oxygen. The researchers extract hemoglobin from expired blood and encase the protein in a fat bubble, essentially creating artificial red blood cells.
The protective bubble is the innovation that Dr. Doctor believes will solve the safety problems caused by other attempts to manufacture synthetic blood. Those other efforts also used hemoglobin, but exposed hemoglobin can be toxic to organs, he says.
“We have to veil the hemoglobin inside a cell. It’s an artificial cell that makes it safe and effective,” Doctor says.
The scientists then lyophilize the artificial red blood cells into a powder that can remain viable until an emergency.
“It’s designed so that, when needed, a doctor can mix it with water and in one minute you have blood,” Doctor says.
“It’s shelf-stable for years and can be easily transported. And the point is that you can do a transfusion at the scene of an accident,” Doctor says.
In addition to use in emergency medicine, military doctors could also use artificial blood to save wounded soldiers. The Department of Defense is spending more than US$ 58 million to help fund a consortium developing Dr. Doctor’s synthetic blood, along with other components that promote clotting and maintain blood pressure.
“The number one preventable cause of death on the battlefield is still hemorrhage today,” says Colonel Jeremy Pamplin, project manager at the Defense Advanced Research Projects Agency. “It’s a real problem for the military and the civilian world.”
Dr. Doctor is optimistic that his team may be on the verge of solving this problem with their artificial red blood cells, called ErythroMer. Dr. Doctor co-founded KaloCyte to develop the blood and serves on the board and as the company’s chief scientific officer.
“We have successfully recapitulated all the blood functions that are important for resuscitation in a system that can be stored for years at room temperature and used at the scene of an accident,” he says.
Promising results in animal tests
Back in the lab, Waters has finished infusing the three vials of synthetic blood into the rabbit after about 10 minutes.
“My God, bunny, you made it,” she says as she places it back in the cage. “There you go.”
Almost immediately, a monitor tracking the rabbit’s vital signs shows that its heart rate, blood pressure, and other key metrics have recovered from near death to nearly normal. It begins to resume normal behaviors, like moving on its own and drinking water.
“The really good sign is that it’s very pink,” Doctor says. “Its eyes are pink. Its ears are pink. That’s a good sign that it has plenty of oxygen in its blood and it’s being distributed effectively. It’s breathing comfortably and calmly. It’s impressive how quickly it can work.”
Dr. Doctor’s team has tested their artificial blood in hundreds of rabbits and so far it appears safe and effective.
“It would change the way we could care for people who are bleeding outside of hospitals,” Doctor says. “It would be transformative.”
Like other rabbits used in these experiments, this animal will be euthanized later so researchers can perform a necropsy and ensure the artificial blood caused no damage to tissues or organs.
Human tests still to come
Although the results so far seem reason for optimism, Dr. Doctor says he still needs to prove to the Food and Drug Administration that his artificial blood would be safe and effective for people.
But he hopes to start testing it in humans in two years. A Japanese team is already testing a similar synthetic blood in people.
“I’m very hopeful,” Doctor says.
Other experts remain cautious. Many promising attempts to create artificial blood have ultimately proven unsafe.
“I think it’s a reasonable approach,” says Tim Estep, a scientist at Chart Biotech Consulting who advises companies developing artificial blood.
“But since this field has been so challenging, the proof will be in the clinical trials,” he adds. “While I’m generally optimistic, betting on any technology right now is tough overall.”
Source: npr.org by Rob Stein