The story is all too familiar to us, whether from the evening news, morning paper, or film: an injured victim lies helpless on the ground while attempts to stop the deadly blood loss turn futile. On the battlefield and in our streets, homes, and workplaces, violent or traumatic injury claims tens of thousands of lives each year. In war, an estimated 95% of deaths occur on the battlefield, and approximately 50% of these are due to excessive blood loss. Here in the United States, 50,000 people bleed to death each year: 30,000 in hospitals and 20,000 in the streets. Unfortunately, modern first aid techniques to staunch the loss of blood before life-saving surgery can be performed are identical to those used in the battle of Troy...using cloth bandages, pressure, and tourniquets.
The tide is turning against this lack of progress for staunching blood loss at the scene of injury. A novel application of biochemistry has yielded a new type of bandage that forms an instant scab on even extremely bad wounds that previously could only be stopped in an operating room. This bandage, developed by U.S. Army, Virginia Tech, and Red Cross researchers, incorporates purified human clotting factors to mimic the body's normal scabbing process for stopping blood loss, yet to a much greater degree. Animal tests have shown that the bandage can reduce bleeding by 65-85% over the previous standard gauze dressing, and decreases the loss of arterial pressure that leads to shock. A new liquid foam based on the same clotting technology as the bandage and similar in delivery to injectable foam insulation is also being developed for treating deep, invasive wounds.
After upcoming human trials, these new bandages are anticipated to be stocked in ambulances and other emergency vehicles, as well as standard issue for wartime field medics. Eventually, the bandages could even be placed in home and car first aid kits.
How it works
The concept for the new bandage is based upon how the body seals blood vessels through a sequential process called hemostasis. Upon injury, blood cells called platelets adhere to damaged blood vessels and each other, releasing chemicals that stimulate vasoconstriction to reduce the blood flow at the site of injury. At this point, the platelets and damaged tissue act to initiate blood clotting by activating a protease (protein-cutting protein) called thrombin. The protease thrombin then digests a common blood (serum) protein called fibrinogen, making a blood clot (a thrombus in medical terms). This new bandage is a synthetic mesh coated with these two proteins in an inactive freeze-dried state. The dried protein mix is activated to coagulate on contact with water, so once the bandage is applied to a bleeding wound, a scab forms in seconds.
Blood clotting is a physiological process involving a cascade of biochemical events. The cascade is a series of steps by which an activated protease cleaves a portion of another inactivated protease, thereby activating it so it can cleave and activate another protease, and so on. At the end of this enzymatic cascade is the proteolytic cleavage of prothrombin into thrombin. Thrombin then cuts fibrinogen to form fibrin, which is the protein that readily polymerizes (joins together) into a fibrous network that makes up a blood clot.
Because fibrin seals wounds as it is formed from fibrinogen, for a bandage to take advantage of these proteins both fibrinogen and thrombin have to be brought together at the site of the wound to work effectively as an instant bandage. Early attempts to make a fibrin sealant were problematic because thrombin prematurely digested the fibrinogen into fibrin when the two were mixed. The new bandage works around this issue by first freeze-drying the proteins into a fine powder in a process called lyophilization, for thrombin is inactive unless in solution. This protein powder is coated on the mesh of the bandage, and upon being placed on a wound the proteins are dissolved in the escaping blood and clotting begins immediately, stopping the bleeding. The bandages must be sealed in watertight packages to keep moisture from activating the thrombin and clotting the bandage in the package before use.
Recent advances in cloning and mass production of human proteins have opened the door for this type of product. Human blood-clotting proteins can now be cloned and the gene can be placed in bacteria, yeast, or even in cows for expressing large quantities of the proteins. Cows can produce hundreds of grams of these proteins in their milk a day--a large amount compared to the approximate 1 gram of blood-clotting proteins found in human plasma.
Blood Clotting Bandage Web Site Links
Army Link News - News brief from the U.S. Army on potential uses of the bandage.
The Red Cross - Information from the American Red Cross Organization for preventing and mitigating human suffering.
The Red Cross Biomedical Services News Release - Brief announcing the fibrin sealant bandage.
The University of Virginia Tissue Adhesive Center - Describes clinical use of the fibrin sealant.
The THCME Medical Biochemistry Page: Blood Coagulation - Description of the process of blood clotting.
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