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Clinical trials are under way in the UK of new blood transfusion procedures for patients with traumatic injuries.

A study involving 22 centres in England and Wales is assessing how changing the mix of blood components given can affect outcomes.

The new trials aim to determine what is the optimal mix of red blood cells and plasma given to trauma patients.

New blood protocols have been used by US and British forces in Iraq and are credited for improved survival rates.

Modern blood transfusions involve the intravenous injection of blood components such as red blood cells, platelets and plasma, a straw-coloured blood component which acts as a clotting agent.

Until recently, plasma was given in the UK only once a blood test deemed it necessary, but this could mean valuable time was lost in stopping a patient from bleeding to death. The plasma also has to be thawed.

In recent years, military and civilian centres worldwide have been looking to use plasma early and in higher volumes with traumatic injuries. Less use of saline fluids has also been made in the immediate aftermath of an injury, for fear it will reduce clotting.

of 246 patients treated at a US combat support hospital in Iraq found a direct association between the amount of plasma given and survival rates.

The study, which involved only patients with severe injuries and massive blood loss, suggested the mortality rate fell from 65% to 19% when the ratio of plasma to red blood cells administered was increased from 1:8 to approximately 1:1.

Plasma is also being used early and aggressively in Afghanistan, as seen by ³ÉÈË¿ìÊÖ documentary maker Michael Mosley in his forthcoming ³ÉÈË¿ìÊÖ2 programme Frontline Medicine, and NHS trauma centres and trusts have adopted similar procedures.

Other clotting factors and a drug called tranexamic acid that reduces the break-up of clotting, are also being used.

But what exactly the right mix of components is for trauma patients is still to be agreed. have showed no benefits of the 1:1 ratio favoured by the military.

Prof Karim Brohi, of the Barts and The London Trauma Centre, is leading two clinical trials to investigate which blood products work best, in what ratio, and which other devices or procedures could be used to save lives.

One trial involves more than 1,000 patients from centres in London, Oxford, Copenhagen and Oslo. The second involves 600 patients at 22 medical centres in England and Wales, and will follow surviving patients for a year after injury.

suggests that a 1:2 ratio of plasma to red blood cells may be "as good as if not better" than the 1:1 ratio, said Professor Brohi.

"Around the world, 2.5 million people bleed to death each year," he told the ³ÉÈË¿ìÊÖ. "That's more than die from HIV and Malaria and a lot of those deaths are preventable.

"We're trying to work out what are the underlying problems that go along with that, so that we can treat patients better so they survive and return to full health."

The new transfusion procedures are also impacting upon the work of London's Air Ambulance, which is based during the day at the Royal London Hospital.

While they cannot yet carry blood on board, they are using a new code to instruct teams at the Royal London to ready all the products needed, including plasma. Blood units can even be brought up to the helipad.

"Code Red is a protocol we use to pre-alert the hospital to make sure that patients we pick up from the roadside who are bleeding get the blood products that they require as soon as they arrive at hospital," explains Dr Anne Weaver, lead clinician with London's Air Ambulance.

She says the new code appears to be making a difference.

"At the Royal London we've seen an improvement in the survival rates of patients with severe pelvic trauma. That's partly to do with the Code Red protocol, and partly to do with interventional radiology and packing of the pelvis."

Frontline Medicine can be seen on ³ÉÈË¿ìÊÖ Two at 21:00 on Sunday, 20 November, with part two the following week. Watch online afterwards via iPlayer at the above link