Cryosurgery sometimes is referred to as cryotherapy or cryoablation. Cryotherapy is a commonly used in-office procedure for the treatment of a variety of benign and malignant lesions. In one report, cryotherapy was the second most common in-office procedure after skin excision. For external tumors, liquid nitrogen is applied directly to the cancer cells with a cotton swab or spraying device. The mechanism of destruction in cryotherapy is necrosis, which results from the freezing and thawing of cells. Adverse effects of cryotherapy are usually minor and short-lived.
What is the Mechanism of Cryosurgery?
Cryogenic agents: A cryogen is a substance (generally a gas or a liquid) which has the ability to remove the heat from a given target area. The most commonly used cryogens are liquid nitrogen, nitrous oxide and carbon dioxide.
The mechanism of action in cryotherapy can be divided into 3 phases:
The mechanism by which cryotherapy destroys the targeted cells is the quick transfer of heat from the skin to a heat sink. The most commonly used cryogen is liquid nitrogen, which has a boiling point of -196°C. The rate of heat transfer is dependent on the temperature difference between the skin and the liquid nitrogen.
When using the spray cryotherapy 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.
When using a cryoprobe for cryotherapy, conduction heat transfer occurs where the heat is transferred via the copper-metal probe.
Cell injury occurs during the thaw, after the cell is frozen. Because of the hyperosmotic intracellular conditions, ice crystals do not form until -5°C to -10°C. The transformation of water to ice concentrates the extracellular solutes and results in an osmotic gradient across the cell membrane, causing further damage. Rapid freezing & slow thaw maximize tissue damage to epithelial cells and is most suitable for the treatment of malignancies. Fibroblasts produce less collagen after a rapid thaw. Therefore, a rapid thaw may be more suitable for the treatment of keloids or benign lesions in areas prone to scarring.
Keratinocytes need to be frozen to -50°C for optimum destruction. Melanocytes are more delicate and only require a temperature of -5°C for destruction. This fact is the reason for the resulting hypopigmentation following cryotherapy on darker-skinned individuals. Malignant skin cancers usually need a temperature of -50°C, while benign lesions only require a temperature of -20°C to -25°C.
The last response to cryotherapy is inflammation, which is usually observed as erythema and edema. Inflammation is the response to cell death and helps in local cell destruction. A thorough cryotherapy treatment causes basement membrane separation, which may result in blister formation.
What are pros and cons of cryotherapy:
A dermatologist can better suggest you the type of ablation procedure that can give the best results on the basis of your skin condition. To choose among the best dermatologists/skin care clinics near your location, visit our portal and avail discount on every consultation & treatment procedures.
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