Effects of Cooling After Scald Injury to a Dorsal Skin Fold of Mouse

Abstract

Shaved trunk skin folds of hairy mice were scalded for 20 s by water immersion. In one set of experiments the effect of increasing burn temperature (51d`C-60d`C) was studied, in another the folds were first scalded at 51d`C-54d`C and then immediately cooled for 30 min in 8d`C water. Animals were killed 2 h and 4 days postburn. Before sacrifice, Evans blue was injected i.v. to some animals to visualize preserved vascular perfusion and areas of increased permeability. Macroscopic observations (and photographic documentation) were made of the outside and inside of the injured skin and biopsies for light microscopy were obtained centrally in the burns. The injured area was measured by planimetry on photographs and expressed in percent of the whole burned area. At 4 days, brownish, oval areas appeared on the skin being progressively larger with increasing burn temperature. The 51d`C burn only resulted in a very small, spotlike, tissue injury, while the ≥52d`C produced a macroscopic necrosis amounting to 40%-94% of the burned area. Postburn cooling did not reduce the damaged area as recorded 4 days postburn. Histologically, the tissues seemed well preserved at 2 h after 51d`C scalds, whereas cell damage was obvious and increasingly pronounced after ≥53d`C burns. After 52d`C burns a mixed picture emerged. A similar microscopic pattern was seen at 4 days; 51d`C specimens were undamaged, some 52d`C and all ≥53d`C were necrotic. Reparative phenomena had begun with phagocyte infiltration and probable capillary growth. There were no obvious histologic differences between cooled and uncooled skin. An intense Evans blue staining of the burned tissue area at 2 h was replaced by absence of perfusion in necrotic areas at 4 days. The study confirms earlier observations on scalded mouse ears that there is a threshold temperature at ∼52d`C, above which mouse skin is irreversibly injured, irrespective of postburn cooling.