Assessment of tissue viability by thermography after experimentally produced frostbite of the rabbit ear.

Since it is difficult and time-consuming to monitor the formation of a demarcation line in frostbite by visual inspection only, thermography was used to study experimental freezing injuries of the rabbit ear. In 8 rabbits, anesthetized with ketamine hydrochloride and xylazine hydrochloride, frostbite was induced by pressing the bottom of a glass bottle 2 cm in diameter, filled with liquid nitrogen against the shaved ear skin. Thermography was performed on both ears after 2, 24, and 48 hours, and one and 3 weeks. At 2 to 48 hours the frost-bitten area was clearly warmer than the surroundings, after one week there were ill-defined diffuse cold spots in the injured area, and after 3 weeks a cold area had become clearly demarcated with a warm zone between the cold area and the surroundings. Thermography is an easy, noninvasive method for monitoring thermal changes after experimental frostbite, but its clinical value is as yet unresolved.