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Clot-forming bandages standard issue now in medics' kits on the battlefield

Monday, March 24, 2003

By Anita Srikameswaran, Post-Gazette Staff Writer

Along with tanks and tents, the Army is taking one very sophisticated medical item onto the battlefields of Iraq: clot-forming bandages.

Scientists have transformed the standard, 4-by-4-inch gauze pads found in every hospital and drugstore into life-saving dressings that rapidly stanch even the most severe bleeding.

In addition to the antibiotics, splints, painkillers and other supplies in their kits, Army medics may have fibrin bandages, which are coated with human clotting factors that were bioengineered to be produced in the milk of pigs. They also carry the chitosan bandage, which is made with shrimp shells and vinegar.

With them, "you get an instant scab," said Col. Bob Vandre of the U.S. Army Medical Research and Materiel Command.

Both products faced tough tests. In pig experiments, researchers punctured the thumb-sized aorta close to where the artery exits the heart. Blood gushes out of such wounds, which can quickly kill. But press either bandage against the hole and a strong, stable clot rapidly forms to stem the blood flow.

The American Red Cross says half of all military deaths are the result of excessive blood loss.

The U.S. Food and Drug Administration hasn't approved the fibrin bandage yet, but is allowing the Army to use it under a humanitarian exemption. Consent forms were obtained from soldiers in the units that have the bandages, Vandre said.

Created by Army researchers and the American Red Cross, the fibrin bandage is absorbable and should be safe to leave in the body.

In the animal experiments, "you can close [sew] the animal up and a half-hour later these pigs are eating at the trough," Vandre said.

A sequence of chemical reactions between special proteins in the blood causes clotting. The bandage contains layers of the dried factors fibrinogen and thrombin, which upon contact with a bloody wound combine to make a fibrin seal. The bandage can make a clot that is 10 to 20 times stronger that one made naturally by human blood.

Large amounts of the clotting factors are needed, so pigs were bred to produce the human clotting factors in their milk.

The clotting factors also could be obtained from blood donations. "But the amount of blood given in the whole United States in a year isn't enough to fulfill the military need," Vandre said. "And this will probably be in every ambulance in the future."

Federal officials approved the chitosan bandage in November. It is already in medics' packs, said Dr. Bill Wiesmann, who helped develop the product with his colleagues at Portland, Ore.-based HemCon Inc. He was once head of combat casualty care for the Army.

Chitosan is derived from the chitin in the hard coatings of shrimp and other shellfish. It is freeze-dried into a bandage that looks like a cracker, not gauze.

Chitosan, a polysaccharide, doesn't contain the proteins that can trigger an allergic reaction. The molecule has a strong positive electrical charge that draws negatively charged red blood cells to create a plug, rather than by overstimulating the clotting cascade.

"It also forms an adhesive so when it binds to the wet, bloody surface, it sticks strongly," Wiesmann explained. "It forms a kind of hardened matrix over the wound and [later] you can pull it off."

In animal models, the bandage can stop bleeding from liver wounds similar to those caused by an AK-47, he added.

The fibrin and chitosan bandages have many civilian applications, especially after they are developed and approved for internal use so that they can be used in surgery.

In addition to the wound dressings, Army medics are carrying tourniquets that can be tied with one hand,

Vandre said. Eventually every soldier will carry one, instead of learning to use a stick to tighten a bandage around a bleeding extremity.

"Over in the desert, there aren't a lot of sticks," he noted wryly. "The [old] tourniquets were like what Boy Scouts do. That was the sophistication level of the U.S. Army."

At the other end of the technology spectrum, the military has been funding development of a gas-exchanging catheter at the University of Pittsburgh that can aid damaged lungs for up to two weeks, buying time for the organs to heal themselves after a severe injury. It could rescue people who have inhaled lung-damaging gases or anthrax spores.

Dr. Brack Hattler, a cardiothoracic surgeon, said that clinical trials in civilians could begin in Europe in a year.

"We have a big project right now where we're going to be studying this catheter in simulated models of battle injury that the Army has available," he said. "It'll allow us to really determine how many lives this catheter can save."

Vandre, in Pittsburgh last week to attend the Engineering Tissue Growth International Conference and Exhibition, is eagerly awaiting the conclusion of final clinical trials and FDA approval of two artificial blood products.

"As soon as it's approved for civilians, we'll have it in the military, too," he said.

Back in the days of the Civil War, soldiers stood shoulder to shoulder, in part because they couldn't hit anything otherwise with their inaccurate weapons, Vandre said. Today's weapons allow soldiers to spread out on the battlefield, and they will likely get farther apart in the future, probably on fast-moving vehicles, and still be linked through digital communication technology.

"Medically, that's a real big complication because that means the medics are far away from everybody," he said.

Anticipating that problem, Army researchers are beginning to design a combat suit that is air-conditioned and monitors pulse, blood pressure and parameters.

"That suit will automatically inflate tourniquets and inject life-saving drugs into the soldier while he's waiting for the medic to show up," Vandre said.

He predicted that a prototype with at least the tourniquet feature could be ready by 2010.

Anita Srikameswaran can be reached at anitas@post-gazette.com or 412-263-3858.

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