Evidence of injury to tissues after hyperthermia

Abstract

Two criteria of injury by heat were used to ascertain whether hyperthermia produced changes that were detectable in tissues subsequently removed from the animals and incubated at 43 C. These criteria were: decrease in Qo₂ below controls and increase in production of ammonia. Pentobarbital and other anesthetics increased the production of ammonia by excised liver and it was therefore necessary to use tissues from animals heated without anesthesia. All experiments were therefore brief, acute, and terminal. Heating rats until there were marked signs of air hunger at rectal temperatures of 43.5– 44.5 C produced a significant increase in the production of ammonia by the excised liver at 43 C. Heating rabbits to a body temperature of 43 C for 1 hr produced a significant decrease in Qo₂ of liver at 43 C, compared with controls from unheated rabbits at 38 C, and significant increase in production of ammonia by cerebral cortex at 43 C.