cryogens like Nitrous oxide (-750C), Carbon- dioxide snow (-790C) and liquid Nitrogen (-1960C). The cryogens produce Cryosurgery involves local freezing of tissues for the controlled destruction or removal, by using various their action through heat transfer, cell injury, and inflammation. The clinical applications of the technique include treatment of equine sarcoids, prostate, angiomas, bovine eye squamous cell carcinoma, oopherectomy in bitches, feline cutaneous squamous cell carcinoma, disbudding in calves. Cryosurgery is also used to treat a number of skin conditions like warts, moles, skin tags, solar keratoses, and small skin cancers. The technique requires minimal post operative care. Conditions such as skin discomfort, burning sensation of skin and hypopigmentation are some the complications of the technique. Cryosurgery is contraindicated in animals with history of conditions such as melanoma, compromised circulation, cold intolerance and cold utricaria. Advantages of cryotherapy are ease of use, low cost, good cosmetic results and minimal surgical complications.
Cryotherapy and hypothermia are terms for the therapeutic application of cold. Cold is the thermal agent of the choice for managing the acute phase of tissues injury because it minimizes inflammatory process and provides analgesia. Lowering the temperature of the skin and underlying tissues causes vasoconstriction, reduces blood flow and decreases sensory and motor nerve conduction velocity. Cryosurgery is the deliberate destruction, in a controlled manner, of diseased tissue by cold (Colver, 2005). Cryosurgery comes from the Greek cryo meaning icy cold and the word surgery meaning literally hand. Different synonyms are used for the word cryosurgery like cryotherapy, cryoablation or targeted cryoablation. Although cryotherapy and cryoablation are used interchangeably, the term “cryosurgery” is reserved best for cryotherapy performed using an open, surgical approach. Cryosurgery is used to treat a number of diseases and disorders, especially skin conditions like warts, moles, skin tags, solar keratoses, and small skin cancers. Some internal disorders including liver cancer, prostate cancer and cervical disorders are also treated with cryosurgery. In the past cryosurgery was more commonly used to treat hemorrhoids. Cryotherapy may be a better description of the procedure since surgery is usually associated with cutting and in most cases, the treatment (therapy) does not involve actual cutting. Cryotherapy is commonly used to treat post operative inflammation, musculo skeletal trauma, and muscle spasms and to minimize secondary inflammation following therapeutic exercise. It induces a temperature change in the affected tissue of between 1 and 4 intramuscularly and 12-13 at skin surface as heat is removed from the body. The general advantages of cryotherapy are its ease of use, low cost, and its good cosmetic results.
Advantages of Modern Cryosurgery in Comparison to Conventional Surgical Methods
Mechanism of Action
The mechanism of action of cryosurgery can be divided into 3 phases, heat transfer, cell injury, and inflammation.
Heat transfer: 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 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, conduction heat transfer occurs where the heat is transferred via the copper-metal probe.
Cell injury: Cellular injury following freezing may be brought about by both intra- and extracellular ice formation, disruption of cell membranes and changes in cutaneous circulation during freezing. Within 30 minutes of freezing, the capillary endothelial cells swell and micro thrombi form. Hypoxia develops as the circulation is impaired. Much cellular injury occurs during thawing. The critical determinants of the extent of this injury are the rate of freezing, the lowest temperature reached, the duration of the freeze and the rate of thawing. Repetition of the freeze thaw cycle produces greater tissue destruction than a single freeze-thaw cycle .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 and 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 (Guan et al., 2007) Therefore, a rapid thaw may be more suitable for the treatment of keloids or benign lesions in areas prone to scarring. Low temperature also ensures maximum damage by further concentrating electrolytes intracellularly. 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 is the reason for hypopigmentation following cryotherapy on darker-skin. Malignant skin cancers usually need a temperature of -50°C, while benign lesions require only a temperature of -20°C to -25°C (Colver, 2005; Kuwahara, 2007).
Inflammation: 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. When a liquid nitrogen spray or probe is applied to the skin surface the temperature drops quickly. Warm air temperature reduces the effect directly and produces vasodilatation. The temperature drop is less in the deeper tissues and laterally. Accurate temperature mapping shows the isotherms and the shape of the ice ball. The ice ball looks like hemisphere, but in deeper parts, the shape is more pointed (Colver, 2005).
Equipment and Technique
Freezing source: The commonly used freezing sources, called cryogens, are liquid Nitrogen, Freon, Carbon dioxide and Nitrous oxide. Because of low boiling point liquid nitrogen is most extensively used. Continuous source of liquid nitrogen & storage apparatus called Cryocan are mandatory items required.
Spray technique: The spray technique is probably the most commonly used method. This method is suitable for most benign and some superficial neoplastic lesions. The basic unit of the cryospray is a vacuum flask with an attached treatment arm. To the treatment arm is attached either spray nozzle or probes of varying dimensions The rate of delivery of cryogen depends on the nozzle size A – D. B and C are most frquently used. The Spray tips bent at right angles and helpful spraying various sites. The nitrogen can be concentrated onto a small area by a plastic shield with apertures of different sizes. The nozzle tip of the spray gun is held about 1 cm from the treatment site, and liquid nitrogen is sprayed on the lesion until an ice ball is formed. The operator then palpates the lesion to determine the size of the ice ball created. This process is repeated until an ice ball of the desired size is created. The time for which the lesion is frozen is the freeze time. This freeze-thaw cycle can be repeated, depending on the type of lesion being treated
Dipstick applicator method: In this technique a cotton-tipped applicator is dipped into liquid nitrogen from a polystyrene cup. The dipstick applicator is then firmly pressed against the lesion for the desired duration. Low temperatures are not achieved in the dipstick applicator method unlike spray technique; therefore, this method is suitable only for benign lesions (Orengo et al.,
1994). Since Adenovirus is capable of survival in liquid nitrogen; therefore, same source of liquid nitrogen should not be used in different patients. The unused liquid nitrogen after every patient should be discarded promptly.
Cryoprobe: In this technique heat conducting probes like copper is used for conduction of a thin film of white petrolatum for application on the treatment site, and the cold probe is firmly pressed against the lesion. Many practitioners do not use the probe techniques because it is cumbersome and time consuming (Kuwahara, 2007).
Thermo-couple device: To treat malignant lesions, a temperature probe coupled to a digital thermometer that can read to -75°C can be used. Local anesthetic is injected into the lesion, and a temperature probe is inserted into the estimated depth of the lesion. Usually, a metal or styrene cone is used to concentrate the freeze. The liquid nitrogen is sprayed into the cone until the desired temperature -50°C to -60°C is reached, usually. This process can be repeated until the desired destruction is achieved (Kuwahara, 2007).
Sarcoids in horses
Sarcoids are the benign skin growths composed mainly of connective tissue. They are small and innocuous or grossly disabling, as tiny as toenail or as large as a grapefruit, Caused by equine papilloma virus and are related to bovine papillomavirus (BPV). In such cases local anesthetic is applied after sedation of the patient, liquid nitrogen is then sprayed on the growth and freezing done at -20oC. The day after treatment, the tumor is seen swollen, and the sarcoid sloughs off within three to seven days. Healing of the wound takes several weeks, and white hair growth over the site is visible in about two months (Meszoly, 1999).
Bovine eye squamous cell carcinomas
These are nodular and cauliflower-like growth on limbus, the third eyelid, and on the upper and lower eyelid margins. There are four common stages in the development of these ocular tumors. These stages include plaques, keratomas, papillomas, and eventually carcinoma. Plaques appear as small, circular, white elevation on the surface of the eye. Keratoma is a hard raised growth on the eyelids. Papilloma will appear as a wart-like growth. The carcinoma will appear nodular and cauliflower-like. Etiology usually includes prolonged exposure to sunlight of non-pigmented eyelids and conjunctiva, and viral infection. These carcinomas are effectively treated with cryosurgery. The success rate has been reported to be 90% except for for eyelid tumors 60%. The major disadvantage includes scar formation that interfes with future vision (Aiello, 1999).
Periocular squamous cell carcinoma in the horse
Cryotherapy is effective in treating squamous cell carcinoma in horses as well. In one study squamous cell carcinoma around the eyes of 3 horses was treated with liquid nitrogen, using cryotherapy probes as the method of application. In 2 cases, there was complete regression of the tumor; in the 3rd case, remission and relief of discomfort were temporary (Hilbert et al., 1977).
Prophylactic for prevention of laminitis secondary to colitis in horses
In one study, 7 horses suffering from colitis characterized by pyrexia, diarrhoea, endotoxaemia were placed in plastic tub containing water with ice at temperature of -5o C. They were also given fluids, antibiotics, NSAIDS, hay & water. Horses were removed after rectal temperature reached 38.5oC. All horses were observed for 10 days. No horse developed laminitis, thus indicating that cryotherapy can be used as a prophylactic measure for controlling laminitis (Andrew et al., 2004).
Feline cutaneous squamous cell carcinoma
Liquid nitrogen cryosurgery was used to treat 50 cats with 100 squamous cell carcinoma lesions located in the unpigmented areas of the ears (n = 32), eyelids (n = 12), nose (n = 40) and other areas (n = 16). In a study conducted by Lucas et al. (2004) there was remission of 80% of the lesions following a single treatment. Complications of cryotherapy were observed in 13 cats (26%). It was concluded that cryosurgery is a practical, safe and effective method of treating feline cutaneous squamous cell carcinoma (Lucas and Larson, 2004).
Prostate may be safely frozen by application of a cryoprobe. In one study six normal mongrel dogs received cryotherapy to their entire prostate. They were observed for selected periods of 1 day to 12 weeks. The ultrasonographic and pathologic results in this canine model showed that prostate was completely necrotic in three of six dogs, (Littrup et al, 1994).
Cryotherapy has been used successfully for haemostasis in a canine bleeding ulcer model via a flexible catheter passed through an upper endoscope. These results, although preliminary, demonstrate the feasibility of endoscopic cryotherapy (Pasrichasp et al, 1999)
Cryotherapy for ocular parasitic granuloma
Cryosurgery is well suited for treatment of the ocular surgical affections especially parasitic granulomas and tumourous growths. A Mithun with a growth at the lateral aspect of cornea, which was increasing in size, was treated successfully with cryosurgery for two minutes each of 3 freeze thaw cycles (Nath et al., 2002).
Cryosurgical sterilization in bitches
Cryosurgical oophorectomy is preferred in bitches as it is quicker and safer than that of conventional method. In one study cryosurgical approach took only 32 minutes as compared to 35 minutes taken by the conventional surgical oophorectomy for performing sterilization in bitches (Mankad et al., 2008).
Cryonecrosis of trachea and bronchus
A study conducted on mongrel dogs revealed that trachea and bronchi may be safely frozen by application of a cryoprobe either to the external surface or to the mucosal surface (Bryan et al., 1973)
Cryosurgical disbudding in calves
Cryosurgical disbudding is more successful in younger calves below 4 weeks of age. In one clinical study seven crossbred cattle and six buffalo calves were subjected to cryosurgical disbudding. Results were excellent only in calves below the age of 4 weeks. (Paithanpagare et al., 2009).
For melasma, a light, uniform freeze with feathering every 4-6 weeks has been used, (Kuawahara, 2007).
For tattoos 30 sec freeze thaw cycles are used every 4weeks, (Kuawahara, 2007).
Two 30 second freeze thaw cycles are used every 4weeks. Angiomas are treated with one 10- second freeze-thaw cycle. Capillary hemangioma can be treated with two 30-second freeze-thaw cycles, (Kuawahara, 2007).
Cysts and tumors: One 10-second freeze-thaw cycle, (Kuawahara, 2007).
Skin tags: can be treated with one 10-second freeze-thaw cycle, (Kuawahara, 2007).
Seborrheic keratosis: can be treated with one 10-second freeze-thaw cycle, (Kuawahara, 2007).
Other lesions: One 15- to 30-second freeze-thaw cycle, (Kuwahara, 2007) .
An antiseptic dressing is advisable for those lesions treated with longer freeze times. Some degree of exudation may be expected during the first few days and an antiseptic dressing such as povidone-iodine helps prevent secondary infection. Wounds can be washed and it is important that crust and exudate is removed regularly. Adequate analgesics should also be prescribed.
Cryosurgery is also inherited with many complications and side effects. Skin discomfort, generally a burning sensation, occurs with cryosurgery, but intensity is variable. The most sensitive areas are the fingertips, ears, and temples. Freezing of lesions on the forehead or temple may produce headaches. Treatment in hair-bearing areas can result in permanent hair loss. A care should be taken when applying cryotherapy in animals with decreased or absent sensation and those with metal implants. Hypopigmentation is common, especially with longer freeze times, but is less noticeable in light- skinned patients and improves within several months. Hypopigmentation is caused by the greater sensitivity of melanocytes to freezing, a situation that can be used to advantage in the treatment of dermatofibromas, which frequently have some mild overlying hyperpigmentation. Feathering of the freeze margin (lighter freeze area) often results in a better transition of pigmentary change. Andrews, (2004) classified the complications for the sake of comprehension as,
Contraindications can be divided into 2 groups: relative contraindications and absolute contraindications. Relative contraindications include cold intolerance, cold urticaria, cryoglobulinemia, history of pyoderma gangrenosum, and contraindications include the use of cryotherapy near the eye margins.
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