Medical use for liquid nitrogen

Dermatologists have used cryotherapy since the turn of the century. After the development of the vacuum flask to store subzero liquid elements, such as nitrogen, oxygen, and hydrogen, the use of cryotherapy dramatically increased. By the 1940s, liquid nitrogen became available and the most common method of application was by means of a cotton applicator. In 1961, Cooper introduced a closed-system apparatus to spray liquid nitrogen. By 1990, almost all dermatologists used liquid nitrogen in their cryotherapy practice. The general advantages of liquid nitrogen therapy are its ease of use, its low cost, and its good cosmetic results. Most skin cancers are treated with excision or other destructive procedures, such as electrodessication and curettage. Superficial basal cell skin cancers and Bowen disease can be treated with liquid nitrogen. When using the spray technique, the liquid nitrogen is applied directly on the skin, and evaporation (boiling heat transfer) occurs in which the heat in the skin is quickly transferred to the liquid nitrogen. This process results in the liquid nitrogen evaporating (boiling) almost immediately. Liquid nitrogen is the best and universal freezing source because of its low boiling point and its ease of use. Other sources that are used to freeze, such as Freon, carbon dioxide, and nitrous oxide, do exist, but they are not as efficient in destroying lesions. Various lesions have been treated with liquid nitrogen. Because of the histological differences in lesions, different freeze-thaw cycles are used to successfully destroy them. For most of these lesions, cryotherapy is not the only and often not the best modality for treatment. However, it does represent a valuable alternative for selected patients. For some lesions, such as actinic keratoses, warts, and seborrheic keratoses, cryotherapy is the standard first-line therapy. Although very effective, liquid nitrogen therapy may lead to complications and it is not indicated in some cases. Acute complications include headache, pain, and blister formation. Delayed complications include hemorrhage, infection, excessive granulation tissue formation. Relative contraindications include cold intolerance, cold urticaria, cryoglobulinemia and Raynaud disease. Cryotherapy is contraindicated when used near the eye margins.