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Care in a cold climate: the practice of cryosurgery

Alexander J Chamberlain
MB BS
Clinical Research Fellow

Rodney PR Dawber
FRCP
Consultant Dermatologist
Department of Dermatology
Churchill Hospital
Oxford
E:alex_chamberlain@hotmail.com

Although the therapeutic application of cold dates as far back as ancient Egyptian times, it is Dr James Arnott of London who is considered the father of modern cryosurgery.(3) In the mid-1800s he pioneered the use of a solution of ice and saline for the purpose of local analgesia and treatment of tumours.(4) By the late 19th and early 20th century a number of clinicians had begun to use liquefied air at low temperatures for the treatment of benign and precancerous skin lesions. Up until 1945, both liquid air and carbon dioxide snow were the principal cryogens used in cryosurgery; however, after this time, liquid nitrogen gained increasing popularity. The major advantage of liquid nitrogen was its availability as well as its potential for far greater reductions in skin surface temperature - as low as -196°C. It was Irving Cooper in the early 1960s who was responsible for the introduction of pressurised spray devices.(5) At the beginning of the 21st century, liquid nitrogen cryosurgery is now practised widely by dermatologists, GPs and nurse practitioners on a day-to-day basis.

Mechanism of action
Following a substantial freeze, one observes the development of a white icefield. This thaws within minutes and the area takes on a mauve colour, which also subsides. A haemorrhagic blister frequently develops, and this crusts over and generally takes a few weeks to resolve. A degree of contraction of the skin may also be seen following cryosurgery.
 
Freezing induces an iceball beneath the skin that has a rounded margin to a depth of 6mm and triangular beyond that. The lateral spread of ice is equal to the depth of freezing, which helps to give an idea of depth of penetration. Different cells within the skin show varying sensitivity to the effects of cryosurgery. Melanocytes or pigment cells show the greatest sensitivity, while fibroblasts (which are responsible for laying down collagen) are more resistant. The significance of this is that pigment loss in dark-skinned persons occurs frequently after cryosurgery, while the regenerative potential of connective tissue is usually maintained. Cryosurgery results in target cell death by a combination of mechanisms, including alterations in osmolarity (solute concentration) and blood flow, and then ultimately inflammation.

Equipment and techniques
Liquid nitrogen is the principal cryogen used today. It may be delivered directly with a cotton-tipped applicator, with a cryoprobe (a metal attachment), or with a spray device, which is the principal method employed at the present time. A variety of brass spray tips are available with openings of diminishing diameters (down to 0.375mm). Liquid nitrogen is widely available and for regular use must be stored in metallic vacuum vessels that allow a small degree of evaporation/leakage. A 50-litre vessel, for example, will not completely evaporate for over four months.
 
A variety of spray techniques can be employed with equivalent ice distribution and effects. The spray tip is generally held 1cm away from the skin surface and applied in a spot-freeze, paint-spray, spiral or rotatory manner. Once an icefield of desirable size has formed (1-2mm margin for benign lesions and 5-10mm margin for premalignant or malignant lesions), the area should be palpated to ensure an adequate iceball has formed. Feathering (frequent gentle sprays) may be necessary to maintain the icefield for a period of time appropriate to the lesion being treated. Overly hyperkeratotic lesions may be best treated following debulking with curettage or shaving. While adults generally tolerate cryosurgery well, most young children will need some form of local anaesthesia such as EMLA cream (AstraZeneca).
 
Indications and contraindications
Worldwide experience has shown that a vast number of benign epidermal and dermal lesions (not to mention premalignant and malignant neoplasms) may be responsive to cryosurgery. In the setting of a nurse-led cryosurgery clinic the more important indications are listed in Table 1. Young children (under the age of around seven) traditionally tolerate cryosurgery poorly, so for them it should be avoided. Pigmented skin is more prone to permanent hypopigmentation following cryosurgery, so for that too it is best avoided. The leg is often slow to heal after all forms of destructive therapy, and ulceration that takes months to heal may occur; hence this is not a desirable site for cryosurgery in the elderly. Equally, treating periungual skin requires caution due to the risk of damaging tendons or the nail matrix permanently. Cold intolerance, cold urticaria, cryoglobulinaemia, pyoderma gangrenosum, Raynaud's disease and blood dyscrasias are also relative contraindications to consider before cryosurgery.

[[NIP09_table1_24]]

Caveats and complications
A confident diagnosis is absolutely mandatory before treatment with cryosurgery. A biopsy for histology should be performed if the clinician is unable to come to a diagnosis on clinical grounds. This is even more important for pigmented lesions or painful, ulcerated hyperkeratotic lesions.
 
The response to cryosurgery varies widely, so a wise approach is to perform a test treatment on the first occasion with only a 5-second freeze-thaw cycle. In some patients blistering will be seen after only a light freeze, and this effect cannot be reliably predicted. The common side-effects and complications of cryosurgery are listed in Table 2.

[[NIP09_table2_26]]
 
Sensory impairment is not uncommon after cryosurgery but its rarely permanent (caution should always be taken in the vicinity of superficial nerves, though).
 
A very important risk to warn patients of is that of pigmentary change (hyper- or hypopigmentation). For this reason, cryosurgery is not usually appropriate in persons with dark skin.

Aftercare
It is good practice to provide patients with an information leaflet in preparation for cryosurgery. This should outline the nature of the treatment, the degree of discomfort that they can expect, and the usual range of sequelae. It is particularly important to warn patients that a blister may occur and that a large blister should be lanced and treated with antiseptic cream. Redness and inflammation usually occur in the days following cryosurgery but swiftly subside. Postcryosurgery analgesia will be required by a minority of patients, and all patients should be able to contact the nurse or clinician easily should an unexpected adverse effect occur.

Nurse-led cryosurgery(1)
With the ever-increasing pressure on health services, nurses are beginning to take on extended roles within healthcare across the community. For some years now nurses in certain settings have been involved in cryosurgery both in primary and secondary care. Now that warts are primarily dealt with in primary care, and that many dermatology departments have long waiting lists for patients with skin cancer, it is entirely appropriate that nurses with an interest develop this skill. It is essential that any nurse wishing to undertake cryosurgery receives adequate training from a clinician with experience in the field, and that a period of direct supervision occurs before independent practice. Nurse-led cryosurgery should always occur in close proximity to a doctor, who will have ultimate responsibility for the patient. The doctor will generally be responsible for making the diagnosis and will also be required if a prescription for a local anaesthetic or topical corticosteroid is required.

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References

  1. Dawber RPR, Colver G, Jackson A. Cutaneous cryosurgery. Principles and clinical practice. 2nd ed. London: Martin Dunitz; 1997.
  2. Hanke CW, Bailin PL. Current trends in the practice of dermatologic surgery. J Dermatol Oncol 1990;16:130-1.
  3. Cooper SM, Dawber RPR. The history of cryosurgery. J R Soc Med 2001;94:196-201.
  4. Arnott J. On the treatment of cancer by the regulated application of an anaesthetic temperature. London: J Churchill; 1851.
  5. Cooper IS. A new method of destruction or expiration of benign or malignant tumours. N Engl J Med 1963;268:743-9.

Further reading
Dawber RPR, Colver G, Jackson A. Cutaneous cryosurgery. Principles and clinical practice. 2nd ed. London: Martin Dunitz; 1998.
Extensively illustrated handbook covering basic information for the management of a cryosurgery clinic
 
Thai KE, Sinclair RD. Cryosurgery of benign skin lesions. Aust J Dermatol 1999;40:175-84. Recent review of cryosurgery of benign lesions

Cryosurgery. In: Burge S, Colver G, Lester R, editors. Simple skin surgery. 2nd ed. Oxford: Blackwell Science; 1996. ch. 7.
Practical guide suitable for nurses embarking on cryosurgery

Cryosurgery chapter in online textbook of medicine
W:www.emedicine.com/derm/topic553.htm