Artículos

To investigate the minimal lethal freezing temperature required to produce skin necrosis in dogs, multiple skin sites were frozen with cryosurgical equipment. Tissue temperatures were recorded from thermocouple sites placed at diverse distances, usually 5 mm from the edge of the freezing probe. In single freezing cycles of about 3 min duration, tissue temperatures in the range of 0 to −60 °C were produced. Punch biopsies of the skin at the thermocouple sites 3 days after freezing injury provided tissues for estimation of viability by histologic examination.

The histologic findings permitted classification of the biopsy tissue into three groups, that is, viable, borderline, or necrotic. When classified as borderline, the division between the necrotic and viable tissue was evident on the histologic slide. The viable specimens were scattered through the 0 to −35 °C range. All specimens frozen to −10 °C or warmer were viable. In biopsies classified as borderline, the range of viability extended from −11 ° to −50 °C. The necrotic biopsies covered a range of −14 ° to −50 °C. Cell death was certain at temperatures colder than −50 °C. The data showed cryosurgical freezing conditions produced a range of temperatures in which viability or death of tissue may occur and that the ranges of viability and necrosis overlapped to a great extent.

The wide range of temperatures at which cells were viable shows the need to achieve tissue temperatures in the range of −50 °C in the cryosurgical treatment of cancer.