For medics in the field, getting replacement blood into patients as soon as possible can make the difference between life or death.
But scientists working to develop artificial blood cells could bring life-saving transfusions to more trauma patients within the next 10 years.
The hope is that the artificial blood could be freeze dried and stored in powder form, ready for use by paramedics and combat medics on the battlefield.
At the heart of the breakthrough are tiny synthetic cells which mimic red blood cells, holding onto oxygen and slowly releasing it as they circulate around the body.
Developed by a team at Washington University in St Louis, the artificial cells carry oxygen to tissues and have already been shown to be effective in animals.
At around 2 per cent the size of a human red blood cell, the synthetic blood cells can be stored at room temperature and mixed with water, ready for use.
Dr Allan Doctor, who is leading the research, told CBS News: ‘It’s a dried powder that looks like paprika, basically.