Cryotherapy: Overview, Mechanism of Action, Treatment Modalities Using Cryotherapy (2024)

Various methods have been devised in the use of cryotherapy of lesions. They include the spray freeze technique, the applicator technique, the cryoprobe method, and the thermo-coupler method.

Liquid nitrogen is the best and universal freezing source because of its low boiling point and its ease of use. Other sources that are used to freeze, such as Freon, carbon dioxide, liquid helium, and nitrous oxide, do exist, but they are not as efficient in destroying lesions because of their higher boiling points.

Prior to freezing the lesion, the patient must be informed of the procedure, and verbal or written consent must be obtained. A local anesthetic, such as 1% lidocaine, or a topical anesthetic, such as ELA-Max (Ferndale Pharmaceuticals) or EMLA (Astra Pharmaceuticals), can be used. Young children almost always need some type of anesthetic prior to treatment.

Debulking keratotic material with a razor, a No. 11 blade, or a curette by shaving or by curettage facilitates the destruction.

Spray technique

The spray cryotherapy technique is probably the most commonly used method. This method is suitable for most benign and some superficial neoplastic lesions.

Pulsing each spray to avoid an overexpansion of the treatment site prevents complications.

A cone spray technique, as shown in the image below, has been suggested in the past by using an apparatus with 2 open ends; however, such accessories are not readily available and, thus, they are not often used. ^[7] The cone attachments are round; therefore, they are most suitable for round lesions. For large, irregularly shaped lesions, sequential freezing is necessary.

The use of disposable specula instead of nondisposable cone attachments offers several advantages. Disposable specula, as shown in the image below, can be cut with scissors to vary the size and the shape of the aperture. With the advent of HIV and other communicable diseases, the use of a disposable device, such as the plastic specula, is a convenient and simple solution to the problem of contamination. ^[8]

In the event that a disposable cone attachment is not available, Ashique et al recommend using a disposable paper cup with a window cut for the treatment area or making use of a disposable otoscope speculum. ^[9]

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.

Hypopigmentation is a common complication with cryotherapy. This complication is due to the temperature-sensitive melanocytes, which die at the relatively high temperature of -5°C to -10°C. ^[10] Hypopigmentation complications should be kept in mind, particularly in patients with dark skin tones.

Feathering, the process of gradually and lightly freezing the area surrounding the ice ball to prevent an abrupt edge, can provide better cosmetic results.

A spray gun is shown in the image below:

SARS-CoV-2 precautions ^[11]

Concern has been expressed over potential coronavirus disease 2019 (COVID-19) exposure to healthcare providers during cryotherapy procedures. As SARS-CoV-2 virus particles have been identified in the feces of infected patients, the British Association for Sexual Health and HIV (BASSH) published a statement in July 2020 asserting that cryotherapy of anogenital wartsis not an aerosol‐generating procedure. As such, BASSH maintained that anogenital wart cryotherapy posed no special COVID-19 risk.

However, Searle et al point out that dermatologists often carry out cryotherapy to perioral and perinasal skin and mucosae, which are high-risk sites. Therefore, the authors recommend the use of extensive personal protective equipment and air purifiers/smoke extractors when treating these areas with cryotherapy.

Dipstick applicator method ^[12]

The dipstick applicator method, as shown in the image below, is the original method used to apply liquid nitrogen to lesions. 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 as they are in the spray technique; therefore, this method is suitable only for benign lesions.

Adenovirus is capable of survival in liquid nitrogen; therefore, the same source of liquid nitrogen should not be used with different patients.

Previously unused liquid nitrogen can be placed in a polystyrene cup and then promptly discarded after use for a single patient.

Cryoprobe

Manufacturers have devised various metal attachments to serve as heat-conducting probes for cryotherapy. Copper, because of its high conductivity, is typically used.

A thin film of white petrolatum can be applied to the treatment site, and the cold probe is firmly pressed against the lesion. Many practitioners do not use the probe because it is cumbersome and time consuming.

Lim et al reported good clinical outcome with probe-delivered cryotherapy in patients with primary malignant bone tumors. ^[13]

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 is reached, usually -50°C to -60°C. This process can be repeated until the desired destruction is achieved.

Forceps technique

A forceps technique, as shown below, can also be used. ^[14]