Therapeutic principles and techniques

Abstract

Cryosurgery is based on removing heat from a tissue by applying cold and this is accomplished by using a cryogen with a probe, spray or cotton swab. The selection depends on the depth of freeze needed to accomplish removing a lesion and a cotton swab may be used for a wart but is inadequate for a skin cancer. The size of the target is also important as lesions over 2 cm may be treated in stages or referred for excision or MOHS surgery. Alterations following freezing are dependent on (1) temperature fall (2) the rate of re- warming (3) solute concentration (4) length of time cells are exposed to below freezing temperatures (0 to -50 °C) and (5) coldest temperature reached in the target tissue (generally minus 50 °C). While benign lesions require brief freezing of 5-10 s, malignant lesions generally require 1 min of freezing and the use of a double freeze thaw cycle.