Histologically demonstrable vital reactions to frostbite in guinea pigs dying of hypothermia.

Vital reactions in the paw skin of guinea pigs dying of hypothermia were examined using a variety of histochemical methods to find ways of distinguishing between ante-mortem and post-mortem frostbites. Some animals were treated with ethanol or diazepam. Edema, hyperemia, and incipient accumulation of granulocytes were seen to develop within the 2-6 h for which the animals had survived in the cold (-20 degrees C). The granulocytes were first seen in the capillaries beneath the epithelial papillae and thereafter deeper in the dermis. They mostly accumulated inside the venules in the endothelium, but there were cases in which emigration had started. The best method for demonstrating the reaction appeared to be the alkaline phosphatase reaction, which is strong in guinea pig granulocytes and highlighted the latter well against a negative background. The conclusion is that it is possible to detect a positive vital reaction, but methodologic investigations are needed before similar changes can be visualized in cases of acute hypothermia in human beings.