Gelatin solution has been used as a blood plasma substitute (man made blood plasma) for blood volume expander in severe trauma since 1915. However, the high viscosity and its tendency to gelation at low temperature limit its use as a blood plasma substitute.
After the Second World War modified medical gelatin was gradually used in artificial blood. When it is heated to hydrolyzed, chemical agents are used to modify their amino groups. The eliminated amino group reduces the number of positively charged groups to make it less likely to form hydrogen bonds and networks. Its gelling point is usually close to 0℃. The molecular weight of these modified pharmaceutical gelatin becomes smaller and the long chain-like molecules become closer to spherical structure. This reduces viscosity and prevents it from aggregating in the body. It is usually mixed with various electrolytes, which makes the osmotic pressure, pH and other physicochemical properties more similar to those of human blood plasma.
When it is injected into the body, it expands blood volume and maintains blood pressure; it promotes blood circulation to improve oxygen delivery. Compared to polysaccharide blood plasma substitute, it has better compatibility with body and rarely causes allergy and rejection. It rarely interferes with blood clotting even in high doses. Because of its small molecular weight and low viscosity, gelatin blood plasma substitute is easily excreted in urine, and the portion left in the body will be broken down into amino acids to be absorbed. It has a half-life of about 4 hours and disappears completely in the body after two days.
Compared to human blood, the use of gelatin blood plasma substitute does not require to match blood types, which increases the survival of patients with acute blood loss; it also prevents HIV, hepatitis and other blood-borne diseases infection during transfusion. In emergency, it can be transfused directly into the body in large quantities to replace the lost blood until the patient recovers or sufficient suitable blood is found.
Pharmaceutical gelatin has been produced for hundreds of years, with mature technology, high output and affordable price.