Equipment needed for cryotherapy include a cryostat or liquid nitrogen and a styrofoam cup with a cotton-tipped applicator. Cryotherapy is used for benign lesions i.e. warts and seborrheic keratosis, premalignant lesions i.e. actinic keratosis. Liquid nitrogen is the cryogen of choice. Cellular destruction is more pronounced with rapid freezing and slow flow cycles. Regarding technique, anesthesia is usually not necessary. Considerations. Techniques include open spray with a cryogen either in a continuous fashion or a pulsed spraying or the use of a cotton-tipped applicator. The latter results in less depth of freezing. A new swab must be used with each dip into the liquid nitrogen reservoir. It is better to underfreeze than to overfreeze to prevent complications. More can be frozen at a later date. Frozen areas of the skin will turn white immediately. This is called the freeze ball or ice ball. The depth of the freeze should be roughly equal to one and one half times the radius of the freeze ball unless the lesion is superficial in which the depth is less. For small papules or thin flat lesions, freeze three seconds, leaving a rim of white one to three millimeters around the lesions. For thick lesions, freeze for five seconds. For multiple freezes, wait until the lesion completely thaws, usually 20 to 40 seconds before refreezing. Because the freeze time between a cryostat and cotton swab varies, a general rule of thumb to remember is that the freeze ball should always be 1.5 times the size of the lesion, regardless of depth. Final recommendations for cryotherapy. For cotton tip, it is recommended to untwist it to make it less dense, then re-twist it so that it will soak up more liquid nitrogen, resulting in less frequent dipping into the liquid nitrogen and transferring that to the lesion being frozen. If using same cup for same patient, it is recommended to freeze warts last, i.e. one can freeze the AKs first prior to freezing warts. Cryostats offer no cross-contamination from one patient to the next, thus one is able to make rapid freezes more effectively than with a cotton swab.

cryotherapy equipment

liquid nitrogen

cotton-tipped applicator

lesion types

freezing times