[color=66ff00]The whole point of this is to prolong the life of a patient as long as possible thus increasing the survivability.
As Bob has stated once you drop the core body temperature below a certain level the body's functions tend to slow down. The brain accounts for a rather large chunk of the oxygen requirement of the body (hence it's got it's own pulmonary sub system) the brain also regulates most of the body's functions; if you try to put the brain into a 'standby' mode the rest of the body shuts down first in order to maximise the O2 and nutrients going to the brain. Blood vessels in the extremities narrow their diameter, as a result the blood and everything in it is redirected and a person loses their colour. When the brain enters this standby mode all of the higher brain functions are diminished or shut down entirely reducing the brain's energy and oxygen needs.
The body is a self regulating mechanism, it requires a certain temprature and chemical balance to be maintained. Temperature effects a number of chemical systems, notably enzymes which facilitate a vast array of chemical processes including respiration; reduce the body temp. and you reduce respiration. Respiaton in this case is not 'breathing' (a common misconception for some reason) it's the breakdown and conversion of nutrient sources (sugars, fats and protien) to form adenosine triose phosphate (ATP).
So on to the main reasoning behind the experiment; you've just had some kind of life threatening accident and you're not in a position to recieve treatment. In the time that's required to get you to a place where an operation can take place a medic will have to regulate your breathing, control blood leakage from wounds and constantly monitor your condition including temperature. Now as you may all be aware no workable, mass producable (i.e. cheap) substitute for blood has yet been discovered so the medic may require a significant volume of plasma to keep you alive between the scene of the accident and the operating theatre. This blood will have to have been screened and chemically altered to inhibit clotting, it will also have to be of the same type as your blood otherwise your immune system will see the new blood cells as foreign bodies and will attack (read up on antigens if you wish to know why).
Saline by comparison is cheap, plentiful and readily available, it can be quickly and cheaply sterilised, is compatible will everyone (no antigens) and does not require donors. You could build a relatively small, mobile unit that would cool and pump the saline. If you've got twenty guys stuck in the middle of a battlefield and you've got two medics and a limited blood supply you can imagine how this kind of process wold be useful.
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