to the editor: I enjoyed Dr. Andrews’ article, “Cryosurgery for Common Skin Conditions,”1 in American Family Physician. However, I was disappointed that he only mentioned liquid nitrogen as the refrigerant of choice. For the past five years, I have been using an aerosolized mixture of rapidly evaporating hydrocarbons (Verruca-Freeze, by CryoSurgery Inc., Nashville, Tenn.; another similar product is Histofreezer, by Delasco, Council Bluffs, Iowa), with results similar to those that I have achieved in the past with the use of liquid nitrogen. The technique uses a mixture of three compressed gases (trifluoroethane, pentafluoroethane, and tetrafluoroethane), which are sprayed as a liquid into a limiting cone held over flat lesions, or onto a cotton swab (such as a Q-tip) device for lesions in delicate areas or on curved surfaces such as fingers. The cone is held in place over the lesion for 20 to 30 seconds while the liquid evaporates, producing (according to the manufacturer) local temperatures down to −70°C (−94°F).
The major advantage to the physician in a small or solo practice is that the shelf life of the aerosol is five years; thus, one does not have to pay regularly to replace liquid nitrogen, which boils off whether you use it or not. Also, the aerosol is easily portable. The drawbacks are the initial cost of the 355-mL canister kit at $295, and the replacement canisters at $215. However, you can freeze around 50 to 70 average-size lesions with a can this size, and the cost is quickly recouped after the first few procedures. Also, it may take a little longer to freeze a lesion while you wait for the liquid to evaporate. However, patients and I have been pleased with the results when used for the usual range of cryosurgery–amenable lesions.