Effect of Rapid Rewarming on Tissue Survival of Frozen Rabbits' Feet

¹ From the Naval Medical Research Institute, National Naval Medical Center, Bethesda, Maryland

The nature of the beneficial effect worked by rapid rewarming of frozen tissue on final tissue survival was investigated in rabbits' hind feet. An attempt was made to separate the effect of shortening the exposure time, which is inherent in rapid rewarming, from the effect of rapid rewarming per se. A method for producing a standard degree of cold injury was worked out based on ‘time frozen,’ the assumption being made that ice crystals are mainly responsible for damage in frozen tissue. The basic procedure was varied by changing times and/or temperatures. Results indicate that increasing the ‘time frozen’ is less harmful than increasing the thawing period, that rewarming in water at 43°C increases tissue survival while rewarming at 37°C does not. At least three independent factors apparently contribute to the final injury of frozen tissue: a) length of time frozen; b) temperature during the frozen state; and c) temperature during thawing.