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Definition

When the cryogen runs down from the site that should be frozen

Risk factors

 Use of a cryosurgical device that sprays liquid nitrogen

 Fast freezing by pouring liquid nitrogen onto the tissues

Pathogenesis

Application of cryogen by spray is less precise than by probes and some technical experience is required to apply cryogen safely [21]. When the sprayed liquid nitrogen comes into contact with the tissue, it evaporates. However, when too much liquid nitrogen is applied at any one time, it does not evaporate immediately and runs off the skin causing inadvertent frost lesions. This complication is more likely to occur when treating large lesions that require the application of more cryogen in order to obtain rapid freezing of the entire lesion.

When liquid nitrogen is poured onto the tissues without a device to keep it in place, run‐off is unavoidable.

The size and depth of the frostbite injury that occurs following run‐off depends on the amount that has been spilled. However, full thickness skin lesions are unlikely to occur.

Diagnosis

Evident during the procedure as the cryogen runs away from the desired area

Prevention

For spraying instruments, “cups” can be used to confine the cryogen to the lesion and prevent run‐off. The use of cups is essential when pouring liquid nitrogen directly onto the lesion. Cups are commercially available [20] or can be custom‐made from PVC‐tubing or any other material (Figure 11.1). Different sizes should be used, depending on the lesion to be treated. The use of a contact gel is advised to ensure that the entire cup fits well on the surrounding skin and sticks to the skin as soon as the liquid nitrogen is applied.

An alternative to the use of cups for spraying instruments is to pack the surrounding area with vaseline‐impregnated sponges or styrofoam to prevent run‐off [16]. This is more difficult compared to the use of cups as they often do not seal perfectly to the surrounding normal tissue [14]. Open cell foams and gauze swabs should be avoided as they soak up the cryogen and become themselves a cold sink producing damage which it was intended to prevent [13].

Figure 11.1 A self‐made PVC cup is used to confine the sprayed liquid nitrogen to the lesion. Thermocouple needles (arrowheads) are placed in the tissue to be frozen and the underlying healthy tissue and a gel is used to ensure good sealing between the cup and the surrounding healthy skin.

Source: Ann Martens.

Treatment

When run‐off of cryogen is identified during surgery, the frozen skin should be warmed up as quickly as possible (e.g. with a sponge soaked in warm water). Rubbing is contraindicated as this worsens the skin damage. Topical aloe vera cream or gel (antithromboxane) applied immediately after injury and in the follow‐up period can help prevent local thrombosis and ischemia [22].

Expected outcome

Most injuries are superficial and will heal uneventfully. In case of deep injury, hypo‐ or leukotrichia can result.