The formation of the demarcation line at experimental frostbite

Experiments were carried out to gain a better understanding of the pathogenesis of frostbite and changes at the demarcation line after freezing and thawing and to determine the forming demarcation line as early as possible. These changes were investigated by histochemical techniques, by histofluorescence, by determining noradrenaline content in the tissue and nerve, by scintigraphy and thermography. The experimental animal was New Zealand white rabbit. The frostbite was produced using a small laboratory bottle filled with liquid nitrogen pressing against the shaved skin in the middle of the proximal part of the ear. Enzyme histochemistry was good in demonstrating the demarcation line between irreversibly damaged and healing frostbitten tissue. Especially the reaction to esterase was the clearest, the demarcation line was visible already after one week. The glyoxylic acid-induced fluorescence method was available for showing adrenergic nerves around the vessels and the accumulation of catecholamines in these nerves in the demarcation line. The result of quantitative measurement of catecholamines in the nerve and tissue was similar and the reaction was the most powerful during the first three days. Scintigraphy was better than thermography and necrotic areas in the middle of the frostbitten area became clearly visible after three weeks. It seems that many changes caused by frostbite happen both in tissue and cells. The role of catecholamines in vascular circumstances is important and that's why chemical or surgical sympathectomy could be useful.