Experience with the use of frozen blood.

The long-term preservation of blood by conventional methods, i.e. beyond five to six weeks, has not progressed significantly since World War I. In the past 10 years, freezing techniques have opened new avenues in this field; it is now possible to store blood for periods of five years or more. Several techniques have been developed, either using liquid nitrogen and the rapid-freezing principle or using "cryophylactic agents" such as glycerol, where the rate of freezing is unimportant and the blood is kept at -85 degrees C. The latter methods require washing of the blood before transfusion to remove the intracellular glycerol and thus avoid post-transfusion osmotic hemolysis. At the National Defence Medical Centre in Ottawa, the Huggins' technique of freeze-preservation of blood has been adopted. This novel method of deglycerolization is based on the "reversible agglomeration" of erythrocytes in electrolyte-free sugar solutions. The in vitro and in vivo studies have yielded satisfactory results, and certain applications of the method are discussed.