Experimental studies of moderate temperature burns.

The pathology and characteristics of moderate temperature burns have been investigated in rats with a heating apparatus capable of applying thermal doses varying in temperature and exposure time, to which the responses have been observed both macroscopically and microscopically. The macroscopic examination showed only erythema and greyish necrosis. The microscopic changes were divided into six grades of severity from 0 to 5. From the time-temperature threshold curves made by microscopic observations, the critical temperatures for superficial and deep dermal burns, and full skin thickness burns were 37.8 degrees C, 41.9 degrees C and 47.9 degrees C, respectively. According to the data, almost all commercially available topical heaters are considered hazardous. Susceptibility to thermal injury was markedly increased by compression and ischaemia, the effects of which are thought to be due mainly to rapid heat accumulation (heat damage) and hypoxaemia (hypoxic damage).