********** Cryosurgery has been u...

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Cryosurgery has been used to treat skin lesions for approximately 100 years. The first cryogen were liquid air (1) and press togethered carbon dioxide snow. (2) Liquid nitrogen became available in the 1940 and popularly is the most widely used cryogen

from one side of to the other the past 50 years, greatly experience has been gained in the use of cryosurgery to treat skin lesions. (3) The cotton-tipped dipstick manner of liquid nitrogen application has been popular in the management of for the use of all benign lesions (Figure 1, left) However, this means is being supplanted by liquid nitrogen spray techniques (Figure 1 center) Liquid nitrogen spray equipment (Figure 2) is easy to use, and similar techniques can be occupyed to manage benign, premalignant, and malignant lesions.

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Mechanism of Action

Liquid nitrogen, which boils at -196[degrees]C (-3208[degrees]F) is the in the greatest degree effective cryogen for clinical use. It is particularly useful in the treatment of malignant lesions. Temperatures of -25[degrees]C to -50[degrees]C (-13[degrees]F to -58[degrees]F) can be achieved within 30 next to the firsts if a sufficient amount of liquid nitrogen is applied according to spray or probe. Generally, destruction of benign lesions requires temperatures of -20[degrees]C to -30[degrees]C (-4[degrees]F to -22[degrees]F) Effective removal of malignant tissue oftentimes requires temperatures of -40[degrees]C (-40[degrees]F) to -50[degrees]C

Irreversible damage in treated tissue happens because of intracellular ice formation. The stage of damage depends on the rate of cooling and the minimum temperature achieved. Inflammation make knowns during the 24 hours after treatment, further contributing to destruction of the lesion by the and of immunologically mediated mechanisms.

dull thaw times and repeat freeze-thaw revolution of times produce more tissue injury than a single turn to ice and thaw. Usually, several minutes are allowed between repeat freeze-thaw periods Repeat freeze-thaw cycles generally are engageed only in the treatment of malignancy.

Continuous freezing at united location for more than 30 others beyond when an adequate turn to ice ball is achieved around the target area can originate in disruption of the collagen matrix of the skin and possible scarring.

Mild freezing leads to dermoepidermal separation, which is useful in treating benign epidermal lesions. The more sensitive enclosed spaces in the epidermis are devastateed while the dermis is left intact. Treatment may be complicated by way of an element of hypopigmentation, if it were not that studies and clinical experience indicate that repigmentation many times occurs over several months because of undamaged melanocytes within hair follicles or the migration of melanocytes from the verge of the frozen zone. (4) However, the predictability of repigmentation in individual patients is uncertain.

systems of Treatment

The dose of liquid nitrogen and the choice of delivery regularity depend on the size, tissue archetype and depth of the lesion. The area of the carcass on which the lesion is located and the required deepness of freeze also should be considered. Additional patient factors to consider include the thickness of the epidermis and underlying constructions the water content of the skin, and local kin flow.

Liquid nitrogen spray rules for lesions of different sizes include the timed taint freeze or direct spray technique, the rotary or spiral pattern, and the paintbrush regularity (Figure 3).

TIMED blemish FREEZE TECHNIQUE

The timed flaw freeze technique allows greater standardization of liquid nitrogen delivery. It may be the mostly appropriate method for physicians who are learning to perform cryosurgery Use of this technique maximizes the ability to quench a lesion with minimal morbidity. The freezing time is adjusted according to variables so as skin thickness, vascularity, tissue representation and lesion characteristics.

Timed flaw freezing is performed with a small spray fire-arm that typically holds 300 to 500 mL of liquid nitrogen. Nozzle sizes range from A within F, with F representing the smallest aperture. Nozzle sizes B and C are suitable for the treatment of greatest in quantity benign and malignant lesions; they are the apertures principally frequently noted in case reports.

For the standard blemish freeze technique, the nozzle of the spray fire-arm is positioned 1 to 15 cm from the skin surface and aimed at the center of the target lesion (Figure 4) The spray fire-arm trigger is depressed, and liquid nitrogen is sprayed until an ice field (or ice ball) encompasses the lesion and the desired margin (Figure 5) The designated ice field may ne to be delineated in advance with a skin marker enclosure because freezing may blur pretreatment lesion margins.

The margin size be pendents primarily on the thickness of the lesion and whether the lesion is benign or malignant. Margins for chiefly benign lesions can extend as little as 1 to 2 mm beyond the visible pathologic border. Premalignant lesions ne margins of 2 to 3 mm while malignant lesions require margins of 5 mm of clinically normal skin to make sure adequate removal. These margin sizes allow enough extent of freeze to ensure temperatures of -50[degrees]C to a deepness of 4 to 5 mm