Doctors in UPMC Presbyterian Hospital in Pittsburgh, Pennsylvania are now waiting for a patient to show up with a gaping chest wound, who’s lost around 50% of his / her blood so they can replace the entire blood supply with a cold saline solution, which rapidly cools the body and stops almost all cellular activity. This reduces the amount of oxygen required by the heart and other vital organs. They hope to fix the structural issues whilst the patient is in a cooled state, then return the blood and warm it up slowly.
This has been demonstrated in pigs in 2002.

Gunshot victims to be suspended between life and death – health – 26 March 2014 – New Scientist.