You grab the first-aid kit you keep in your trunk and pull out a vial of liquid that looks like ordinary water. You pour it on the wound, and the blood stops flowing.

That's the promise of a new biodegradable liquid that has halted bleeding in surgical wounds in laboratory rats in less than 15 seconds.

Scientists at the Massachusetts Institute of Technology and Hong Kong University announced the liquid's development last week.

Rutledge Ellis-Behnke, the neuroscientist who led the study, says the substance may revolutionize bleeding control and dramatically reduce time in surgery. It could also eventually be used in battlefield medicine.

But the most immediate benefits would be seen in surgery. As much as 50 per cent of a surgeon's time is spent packing wounds to reduce bleeding. When the biodegradable liquid, made up of bits of proteins called peptides, is poured on a surgical wound in a rat, it self-assembles — like two magnets that click together but don't bond permanently — into a nanofibre gel that seals the wound and stops bleeding, says Ellis-Behnke.

"Surgeons are very good at seeing big bleeders and can clamp them off, but the little capillary bleeding is very difficult, especially when doing neurosurgery," says Ellis-Behnke. "Visibility of the brain is the most important thing when you are doing any cutting, so it's very important to control bleeding."

The liquid doesn't expand when it is applied, meaning that it doesn't bring additional pressure to surrounding tissue or constrict blood flow in nearby areas.

The wound also remains sealed after excess gel is removed. The gel breaks down into amino acids, which can be used by the body as tissue-building blocks to repair the cut.

Researchers have used the liquid on 300 rodents — on livers, spinal cords and in skin wounds — over the past 2 1/2 years, and plan to begin trials on larger mammals and, within five years, on humans. If it works on humans, it could be in public use, in first-aid kits for example, within 10 years, Ellis-Behnke says.

He adds that the solution does not degrade over time. He has kept a bottle on his desk for more than two years. "You can keep it at room temperature, with no funny storage."

The research by Ellis-Behnke and his associates focuses on reconnecting parts of the brain that have been disconnected because of stroke or spinal-cord injury.

It was in the course of other research — attempting to restore vision in hamsters — that scientists discovered the unexpected capability of the peptides to stop bleeding.

"When bleeding stops during neurosurgery, it usually means the heart has stopped, but the animals were still breathing normally and weren't in any distress," Ellis-Behnke says. "We were really quite shocked."

It's still not clear how the solution works, he adds, though it cannot be explained by clotting, which takes considerably longer — one to two minutes.

"If you think about it, the simplest things to keep you alive are the most cloaked in mystery," says Dr. Edward Buchel, head of plastic and reconstructive surgery at the University of Manitoba, who reviewed the procedure on video. "We have not figured out how to micro-manage keeping the blood flow going."

There are many other way of controlling bleeding — clamping, sponges, cauterizing with lasers, heat or electrodes, or chemical vasoconstrictors — but this new method offers two things the others do not: immediacy and clarity, Buchel says

"The liquid fills the entire area (of a bleeding wound) and stops the bleeding. It's clear, it's biocompatible — you can put it in and it sits there and isn't rejected and doesn't cause any problems — and it's localized. It stops bleeding exactly where you want."

This method also offers surgeons a clear view during surgery, unlike clotting agents. "The material we use for clotting can be like a big black barrier," says Buchel, "like I'm operating behind a curtain."

But while he is intrigued by the procedure, Buchel remains cautious. "It's at the rat stage now...

"It's an interesting concept and makes good sense, but the complications of playing with someone's blood system are huge. History says these things fail. Just because it works in a rat doesn't mean it will work in a primate or a pig."

This is not the first agent to control bleeding, but it does seem to be a new solution to a challenging medical problem, and one that drug companies have been spent years looking for, says Buchel.

"It's a multimillion dollar, if not multibillion dollar, endeavour."

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