Blood substitute

Blood substitute (also called blood surrogate) is the name for a number of substances that can perform some functions of blood. Blood substitutes are often used in blood transfusions where real blood is not available. Losing a lot of blood can mean there is not enough blood left to keep up the oxygen transfer to certain organs, or the brain. This state is a medical emergency, as it can lead to organ failure and death. Blood substitutes can help in these situations.
Types.
There are two basic types of blood substitutes:
An oxygen-carrying blood substitute, or artificial haemoglobin, is an artificially made red substitute whose main function is to carry oxygen, as does natural haemoglobin.
The first goal of oxygen carrying blood substitutes is just to mimic blood's oxygen transport capacity. Unfortunately, oxygen transport, one function that distinguishes real blood from other "volume expanders", has been very difficult to reproduce.
Reasons for use.
There are some good reasons why the world needs blood substitutes:
Since oxygen therapeutics are not yet widely available, the United States Army is experimenting with varieties of dried blood, which take up less room, weigh less and can be used much longer than blood plasma. Saline has to be added before use. Dried blood is better for first aid during combat than whole blood or packed red cells.