An injectable fluid may buy doctors an extra 30 minutes to save the lives of people who are bleeding heavily

Trauma patients could be saved from bleeding to death using an injection of a fluid that becomes more viscous when a magnet is applied.

Scientists have designed a “magnetically activated fluidic valve” that uses tiny particles to slow bleeding.

The particles are designed to be injected into the bloodstream above a wound. They flow normally in the blood until a magnetic field is applied, for instance at the site of a wound, when they become far more sluggish.

It is hoped that the technique, which has not yet been tested in humans, could be used to buy doctors more time as they try to save critical patients.

“Our hope is to extend patients’ survival time by at least 30 minutes by conserving blood, so that