Local Edema and Pain
Definition
The development of serious local swelling due to excessive oedema formation at the site of cryosurgery
Risk factors
Tumoral masses with a (very) large base
Dependant antomical locations (ventral abdomen, chest, prepuce, etc.)
Pathogenesis
Local edema develops almost immediately after thawing (Figures 11.2a, b) and results from the vascular damage in the frozen tissue. It augments in the next 24–48 hours with subsequent gradual resolution over the following days (up to 1 week) [13]. This is more obvious in dependant anatomical locations more prone to develop edema such as ventral abdomen, ventral chest, prepuce or distal limbs. Cryosurgery of limbal squamous cell carcinomas also results in some corneal edema and corneo‐conjunctival inflammation [5]. This is considered to be normal.
When treating very large tumors, the amount of tissue necrosis after freezing can be very extensive, resulting in excessive local swelling and associated pain. In some cases, local infections or lymfangitis may develop [13, 14].
Ocular pain evident as blepharospasm and/or miosis has been observed in 4 out of 10 horses treated with cryosurgery for limbal squamous cell carcinomas [5].
Diagnosis and monitoring
Obvious oedematous swelling at the site of cryosurgery
Figure 11.2 Equine sarcoid on the medial aspect of the right elbow of a horse before (a) and after (b) cryosurgery using a liquid nitrogen circulation probe. The tumor has been debulked at the base and 1 freeze‐thaw cycle has already been applied resulting in pronounced edema, which will even increase after the second freeze‐thaw cycle. This is not a complication but a normal biological response after cryosurgery. Note the thermocouple needles inserted at the periphery of the lesion to ensure a sufficiently low temperature.
Source: Ann Martens.
Prevention
Application of a compressive bandage immediately after cryosurgery will limit the development of oedema. This is recommended for cryosurgery of large masses at the level of the distal limbs but is technically challenging or impossible at other locations (e.g. axilla, prepuce, inguinal region, chest, etc.).
Treatment
Excessive local swelling and pain can be managed by strong analgesic and anti‐inflammatory medication and the application of bandages at the distal limbs.
Management of excessive ocular pain includes non‐steroidal anti‐inflammatory medication and topical application of 1% atropine [5].
Expected outcome
The oedema commonly resolves in 1 to 2 weeks.
Excessive Tissue Necrosis
Definition
Formation of too much tissue necrosis resulting in undesired damage of underlying or surrounding tissue and resulting in functional impairment
Risk factors
Cryosurgery without temperature control
Tumors located over joints and tendons sheahs, or close to the coronary band [14, 15]
Cryosurgery of ocular lesions [14, 15]
Pathogenesis
Necrosis and sloughing of the frozen tissue start from 7–10 days after cryosurgery and are commonly accompanied by a yellowish exudate and a malodourous smell which disappears once all necrotic tissue has been fully rejected (Figure 11.3). This is a normal evolution after cryosurgery. However, overly aggressive freezing results in necrosis of too much healthy tissue and may damage vital structures surrounding the tumor. This results in unwanted tissue necrosis and sloughing of neighboring tissue, which is one of the most serious complications after cryosurgery.
Prevention
Tumors for which cryosurgery is feasible should be carefully selected by determining the risk of damaging important surrounding or underlying structures. Thermocouple needles should be aplied into the tissues to be preserved around the lesion [13] and these tissues should not be cooled below 0 to –5°C. The risk of inadvertent freezing of vessels at the edge of the lesion is relatively low as the circulating blood is a source of heat, thus delaying the development of very low temperatures.
Figure 11.3 Sloughing of the cryonecrotic eschar 3 weeks after cryosurgery of a sarcoid at the inner aspect of the right thigh, with the normal accompanying mucopurulent discharge.
Source: Ann Martens.
The use of cryosurgery has been discouraged for periocular sarcoids as they are commonly located on or very close to the eyelids, resulting in a high risk of excessive scarring of the eyelids and/or damage to the globe [23]. However, cryosurgery for ocular squamous cell carcinoma’s can be performed safely if appropriate equipment and expertise are available [5]. Over‐freezing at that location is less likely to occur with N2O (–89°C) compared to liquid nitrogen [8].
When using contact circulation probes for limbal squamous cell carcinomas, freezing occurs very fast and should be stopped when the frozen area exceeds 2–3 mm beyond the visible tumor margins. Detachment of the probe is then needed to stop further cooling down of the tissues. This can be achieved by applying 10–20 ml of saline solution at body temperature to the eye [5] . Once the probe is detached, the tumor is further allowed to thaw slowly.
Diagnosis
Diagnosis can commonly not be made within the first days after cryosurgery and the presence of oedema in the tissues to be preserved does not mean that they will become necrotic. It takes several days (at least 7–10) before demarcation of the necrotic tissue becomes evident and before a correct diagnosis of the extent of undesired tissue damage can be made.
Treatment
The necrotic tissue should be removed once it is demarcated (2–4 weeks after cryosurgery) to support
