Synthetic blood platelets injected into patients at the scene of a traumatic injury can speed up blood clotting and stem internal bleeding, U.S. researchers reported on Wednesday.

The researchers say the synthetic platelets, made from polymers already approved by the U.S. Food and Drug Administration, bind with natural platelets that become activated at a wound and help blood clots form more rapidly, the researchers reported in Science Translational Medicine.

Blood loss is a major case of death in traumatic injury. Blood clotting, which helps wounds heal, works well with normal cuts and scrapes but can be overwhelmed by serious injury.

The faster the bleeding is stopped the better in most trauma situations, said research leader Erin Lavik of Case Western University.

There's a lot of great technology for stopping external wounds ... but there aren't a lot of technologies that can be used to stop internal wounds and there are even fewer that can be used in the field, Lavik, a bioengineering professor, said in a telephone interview.

She said the small nanoparticles developed by her team bond very well with activated platelets, can be injected intravenously and reduce bleeding time.

In tests, rats injected with the synthetic platelets before injuries stopped bleeding in half the time of untreated rats, the researchers said.

Rats injected 20 seconds after being injured stopped bleeding in 23 percent less time than rats that did not get the treatment.

Lavik said she did not know how long the window of opportunity would be for treating people.

The artificial platelets worked 25 percent faster than recombinant factor VIIa, a drug now used in surgery and emergency rooms to stop uncontrolled bleeding, the researchers reported.

Livik says the they have a patent for the synthetic platelets but have not joined forces with a company that might produce them.

There are still a huge number of studies that have to be conducted to look at safety and efficacy before it could potentially go into clinical trials, Livik said.

Several companies are working on artificial blood products but the field is littered with failures.

Northfield Laboratories began bankruptcy proceedings in June after its product PolyHeme failed to win FDA approval.

Biopure Corp, which developed the blood substitute Hemopure, filed for bankruptcy relief under Chapter 11 in July.

Biotechnology firm ZymoGenetics Inc is working on building the market for its synthetic blood-clotting enzyme Recothrom.