Cryotherapy is a controlled freeze of the skin causing local tissue damage, with the aim of destroying abnormal tissue, both by cellular damage and an immune reaction post treatment. As freeze times under 30 seconds do not damage the dermis and deeper structures, the epidermis heals well post-cryotherapy without scarring.
In this article we will discuss liquid nitrogen spray techniques using a cryogun, other methods are available (but not covered here) including the cotton-tip applicator, cryoprobe and products such as Histofreeze; however freeze-thaw times vary between these methods and most practitioners now use liquid nitrogen spray equipment – if you use these methods then please consult the product literature for further advice.
It is crucial you are confident about the diagnosis before proceeding to treatment as there will be no histology with this technique; we advise learning some dermoscopy to support your clinical diagnosis - the PCDS run excellent courses from beginners to expert
There are four lesions worth concentrating on as a GP: actinic (solar) keratosis (all grades 1-3), Bowen’s disease, ‘symptomatic’ seborrheic keratoses and finally warts/verrucae if all other treatment has failed. Table 1 summarises the treatment protocol for each of these lesions
Cryotherapy is best used on fair skin types due to melanocyte sensitivity to cryotherapy - post-treatment hypopigmentation is a real risk, although this usually improves several months after treatment. Vulnerable sites which should be avoided are the lower legs in elderly patients (leg ulcer risk), skin overlying superficial tendons (risk damage and rupture) and hair-bearing skin due to the risk of permanent hair loss. Table 2 covers the cautions to consider before performing cryotherapy
Management
Equipment required - liquid nitrogen spray equipment is easy to use and maintain. One of our sponsors, Brymill (https://www.brymilluk.com/), are very happy to advise you and are well worth contacting for friendly advice
Technique - to keep things simple, and to help reduce pitfalls, we advise the timed-spot method as this offers a very predictable and safe treatment and is easy to learn. With the cryogun filled and a suitable spray nozzle attached, the nozzle is held 1-1.5cm away from the lesion to be treated. The area is then frozen by depressing the cryogun trigger until the lesion is covered by an ice field and the desired margin is obtained, it is then necessary to keep the area frozen by pulses of cryogen until the desired freeze time has been obtained, this is one freeze-thaw cycle. Warts need two freeze-thaw cycles; you must allow the area to complete thaw before the next freezing-cycle (a few minutes may be needed). Please see the links below for an instructive video/demonstration on the technique which may be easier to understand once you have seen it in action
When recording cryotherapy treatment in the patient notes, it is best to use these standard abbreviations: LN2 (liquid nitrogen) ‘x’FTC (freeze-thaw cycle) ‘x’s (time in seconds) – for example a solar keratosis may need one freeze of 5 seconds so would be recorded as LN2 1FTC 5s. In addition to the freeze time, we suggest you clearly describe the treatment site or use a drawing tool to document this
It is best practice to gain informed consent for cryotherapy; to aid with this a bespoke consent form can be downloaded, as per links below, in word format and added to your clinical system from our website
Complications after cryotherapy include skin blistering, pain and sometimes bleeding. Following the acute inflammatory phase there is an intermediate-term risk of hypopigmentation, followed by a long-term risk of hair loss and scarring if the freeze time is prolonged
After treatment it is advisable to give the patient an advice leaflet, as per the links below
Disclaimer - the author PCDS cannot accept responsibility for any misleading or incorrect statements, and the management of individual patients remains the direct responsibility of the individual doctor. We do however hope that visitors to this site can contact us regarding comments that are considered misleading or incorrect so that we can continue to improve the site.
Image Rights - The PCDS would like to thank Dermatoweb, DermQuest (Galderma), and others who have contributed images. All named individuals and organisations maintain copyright for the relevant images.
