TREATMENT OF BUSHFIRE-AFFECTED WILDLIFE

4.1 Treatment

The successful treatment of any bushfire-affected wildlife patient not only relies on specific treatment relevant to the burn injury but also general principals of emergency and hospital care.

Before you start and at each subsequent procedure when treating a burn patient, the following are important recommendations.

• The animal should be anaesthetised for each bandage change. Appropriate analgesia must be administered before and during procedures (see section 4.1.4 and Appendices 3 and 4)

• Establish a burns team with each member having specific responsibilities: a veterinarian (anaesthesia, clinical examination, diagnostic and therapeutic decision making, treatments); veterinary nurse (anaes­thesia monitoring, note taking, managing fluid and medication administration); and assistants (soaking, cleaning, treatment of burns). This will reduce the duration of the procedure, minimising the risk of hypothermia, hypotension and other complications

• Weigh, condition score and thoroughly examine the animal at each treatment. Document progress and any deterioration or adverse findings and adjust therapy, husbandry or feeding accordingly. Photograph wounds at each procedure

• Ensure all cleaning fluids, antiseptic, dressings, other treatments and instruments are prepared and accessi­ble before each procedure

• Always wear disposable gloves to minimise further contamination of the burns

• Cooling of burn wounds, fluids, low ambient tempera­tures, topical wound treatments and prolonged proce­dures all contribute to hypothermia.

4.1.1 Immediate treatment

Bushfire-affected wildlife may require emergency treat­ment (Vaughn et al. 2012) before a full evaluation can be made. This will usually be animals that have been rescued during or immediately after a fire event (see section 3.3 on patient evaluation and triage).

• Administer appropriate analgesia and anaesthetise the patient even if unstable.

• Establish an airway via intubation if necessary.

• Supplemental oxygen therapy (essential for patients with suspected exposure to smoke and carbon monoxide): delivered via endotracheal tube, face mask, nasal cannula or oxygen cage.

• Cooling burns within 30 min of thermal injury is ben­eficial. It prevents ongoing tissue damage, reduces oedema, improves wound healing and contributes to multimodal analgesia. Use continuous running cool (15°C) tap water for 20 min (Vaughn et al. 2012). This is preferable to cold wet towels and ice should not be used. Prevent and manage hypothermia and monitor the patient’s temperature regularly. Cooling burns beyond 30 min after thermal injury is less beneficial.

4.1.2 Fluid therapy

Fluid resuscitation is critical for patients suffering SBI (Vaughn et al. 2012), although most wildlife patients with SBI are likely to be euthanased. Most burn patients with a good prognosis and for which treatment is elected are likely to be dehydrated and fluids (oral, SC or IV) should be given. It is recommended that fluids are provided during bandage changes under anaesthesia, particularly if the procedure is prolonged. Isotonic colloids are generally used and standard principles of fluid therapy for domestic mammals are applicable to most mammalian wildlife patients (see Chapter 33 for fluid therapy for koalas).

4.1.3 Wound management

The treatment of superficial and partial thickness burns primarily involves decontamination, debridement, topi­cal treatment and protective dressings (Vaughn et al.

Decontamination and debridement

a. Flush and soak burns with copious, tepid sterile

saline to remove soot and other debris. Use gauze swabs to assist removing debris and dead tissue (Fig. 27.7).

b. Trim singed fur from around the wound with scissors

or clippers to create a clear narrow margin of unburnt skin exposed around the wound.

Fig. 27.7. Feet of a common brush-tailed possum (Trichosurus vulpecula) being a) soaked in tepid sterile saline to remove soot and debris; b) cleaned and lightly debrided using saline-soaked gauze swabs.

c. If there is significant contamination (particularly

faecal) or evidence of infection, a 1:40 dilution of chlorhexidine or 1:9 dilution of povidone iodine solution can be used to clean the wound. Avoid prolonged use of these solutions and they should not be used on clean wounds during the healing phase.

d. While soaking and flushing the burn, debride all

necrotic skin leaving a clear bed of healthy tissue.

e. Once clean, gently pat the wound dry with sterile

gauze swabs.

Topical treatment and dressings

Topical antimicrobial agents are initially required (up to ~72 h) to prevent bacterial colonisation of the wound. Once the wound is fully debrided and clean with no evidence of infection, dressings that reduce biofilm and support wound healing should be used. Choice of topical treatments and dressings is dependent on individual clinician preference and experience, availability and affordability.

Consistency in approach, thoroughness and compliance with standard principles of burn management by clinicians and between clinicians is likely more important than the choice of specific products used.

Several topical products and dressings are available for use on burns.

• Silver sulfadiazine (Flamazine® (Smith & Nephew Australia, North Ryde, NSW)) was once considered the gold standard for topical burns treatment. It has broad-spectrum antimicrobial efficacy, fair to good penetration of the wound and maintains a moist envi­ronment. Recent studies, however, have shown that this formulation of topical silver has cytotoxic effects and delays healing (Heyneman et al. 2016; Aziz and Hassan 2017; Khansa et al. 2019). If used, it should not be for more than 48-72 h. A layer is applied evenly over all burnt surfaces, including the nails and sides of the digits.

• Sustained silver-releasing dressings (e.g. Acticote product range (Smith & Nephew), Mediplex Ag (Moln- lycke, Gothenburg, Sweden)) only require changing every 3-7 days, eliminating the need for frequent anaesthetics and frequent painful dressing changes. Dressings containing nanocrystalline silver have been found to be superior to silver sulfadiazine and to silver- free dressings for burns, in terms of epithelialisation, infection, pain and cost. Silver-containing dressings, especially nanocrystalline silver, are most useful in infected wounds, but do not provide added benefit in clean, uninfected wounds, and may slow the healing of those wounds (Khansa et al. 2019).

• Medical-grade Manuka honey (e.g. Medihoney products (Comvita, Paengaroa, New Zealand)) aids wound healing through its broad-spectrum antimi­crobial efficacy; antioxidant and anti-inflammatory properties; creation of an osmotic gradient and a viscous barrier; stimulation of leukocytes to enhance tissue repair; provision of a physical barrier to micro­organisms; acting as a non-adherent dressing; and provision of a moist environment for wound healing. Honey results in more rapid healing rate, less contrac­ture, reduced hypergranulation, better wound strength and a more sterile wound environment than silver sulfadiazine (Vaughn et al. 2012). Several formulations are available, including Manuka honey-impregnated adhesive dressings.

• A range of flushing and cleaning solutions can be used for cleaning, lightly debriding, moistening and rinsing burns. Some also have antibacterial properties and are useful for managing biofilm. All solutions must be warmed before use. Examples include sterile isotonic saline; Granudacyn irrigation solution and gel (Moln- lycke); Prontosan wound irrigation solution and gel (B. Braun, Bethlehem, PA, USA); Ocentilin wound irrigation solution and gel (Schulke, Norderstedt, Germany). The gel formulation of these products can be applied directly to the burn for cleaning. Dressings soaked in gel can be used to maintain wound moisture between dressing changes.

• When the burn has been cleaned, debrided and a topical product applied, a non-adhesive dressing is then applied. Dressings protect the burn, maintain a moist healing environment and provide pain relief. Melolin (Smith & Nephew) is commonly used (apply with the shiny side on the burn). Soft paraffin gauze dressings, without antiseptic (Jelonet (Smith & Nephew)) or with chlorhexidine (Bactigras (Smith & Nephew)) may also be used, the latter without the need for another antimi­crobial agent and only on contaminated wounds for no longer than 48-74 h. Bandage feet in flat bandages (do not use mittens or ‘ball’ bandages) using a self-adhesive bandage such as Vetrap (3M, North Ryde, NSW) or Co-Plus (BSN Medical, Mulgrave, Vic.). For koalas and possums, bandage digit one of the hind feet separately to the other digits and if possible, leave the nails of other digits out of the bandage so the animal can self-

Fig. 27.8. a) Koala (Phascolarctos cinereous) with bandages applied to the digits of a hind foot. Digit one is bandaged separately to the other digits and the nails of the other digits are left out of the bandage. b) Bandages applied to the digits of a fore foot. The tips of the nails are left exposed so the animal can climb and grasp browse.

Fig. 27.9. Koala (Phascolarctos cinereous) with burns to the nasal planum and ears to which Flamazine® has been applied.

feed (Fig. 27.8). However, if the nail bed is burnt, it needs to be covered by the bandage.

• A wide range of hydroactive wound dressings are available that can be used once there is no longer a need for antimicrobial dressings (e.g. Duoderm (ConvaTec, Mulgrave, Vic.), Allevyn, Solosite, Algisite (Smith & Nephew)). These come as adhesive dressings, pads or gels. Careful clinical assessment of wounds is required to ensure appropriate use of these products. Each product is designed for different types, depths and stages of healing of wounds and the correct product must be used for a given situation.

Depending on the depth of the wound and stage of healing, dressing changes may be required daily (particu­larly in the early stages) to up to every 4-7 d (depending on the type of dressing being used). The sooner the fre­quency can be reduced the better for the patient.

Once the burns on limbs and tail are addressed, burns in other locations such as ears, muzzle and face are addressed in a similar fashion, although they cannot be bandaged (Fig. 27.9).

4.1.4 Pain management

Managing pain is a critical component of effective treat­ment of a burn patient. Burns are severely painful due to nerve damage and regeneration and there is also pain associated with procedures, background pain during rest and normal activity or breakthrough pain associated with movement after long periods of immobility. Acute pain at the burn site is associated with decontamination, tissue debridement and dressing changes and must be managed each time procedures are performed. Background pain may be mild to moderate and relatively constant and management requires ongoing analgesia. Breakthrough pain can occur despite analgesia and is unpredictable, intense and generally of short duration (Vaughn et al. 2012). Assessing pain in wildlife patients can be challeng­ing. Close observation of behaviour, activity, demeanour, appetite, urination and defaecation by experienced per­sonnel is important. Patients must be continually reas­sessed and analgesia adjusted accordingly. Commonly used anaesthetic agents such as isoflurane and alfaxalone have poor analgesic properties. A multimodal analgesic regimen, tailored to each patient should be used and should include systemic and local analgesics. Lignocaine or bupivacaine-soaked gauze swabs can be applied topi­cally to burns for 5-10 min at a dose rate not exceeding 2 mg/kg before debridement. Diluting 50:50 with sterile saline or water may be useful to expand the volume but may reduce onset of activity and duration of effect. Refer to Appendix 4 for analgesic and anti-inflammatory drugs used in Australian mammals.

Gabapentin is being used with increasing frequency for analgesia in Australian wildlife, with anecdotal evi­dence of efficacy. It is an affordable drug that targets neuropathic pain and pruritus. Specifically, it reduces nerve injury-induced hypersensitivity and has a synergis­tic effect when combined with other classes of analgesics. Non-steroidal anti-inflammatory drugs should be used judiciously in burn patients and their limited benefits should be weighed against risks, especially in dehydrated patients. A mild to moderate amount of inflammation recruits immune cells for healing, but excessive or pro­longed inflammation can cause scarring and pain and can impair healing (Butkus et al. 2021).

4.1.5 Other treatments

• Flush eyes and conjunctiva with saline to remove soot. Clean soot from the nostrils using a cotton tip. Apply antimicrobial, anti-inflammatory or lubricating eye preparations as indicated by clinical evaluation

• Systemic antibiotics are generally NOT necessary and are usually ineffective as they do not penetrate burn wounds in high enough concentrations due to micro­thrombosis of vessels and oedema causing compres­sion of vessels that supply the area (Vaughn et al. 2012). Systemic prophylactic antibiosis is not indicated in management of burn injuries. Topical antimicrobial agents adequately prevent and treat local infections. Systemic antibiotics may be indicated in cases of sig­nificant wound infection or where bronchopneumonia or sepsis are suspected or confirmed. Antibiotics should be prescribed with consideration of antimicro­bial stewardship (see Chapter 17). The risk of antibiotic resistance should promote prioritising the use of methods other than systemic antibiotics to reduce infection in burn patients. Antibiotics must not be used in Australian wildlife unless prescribed by a reg­istered veterinarian. Antimicrobials rated as ‘high importance’ in the Importance Ratings and Summary of Antibacterial Uses in Human and Animal Health in Australia (ASTAG 2018) are essential antibacterial drugs for the treatment or prevention of infections in humans and other animals where there are few or no treatment alternatives for infections. These com­pounds should only be used where culture and suscep­tibility testing indicate no suitable alternative or where no alternative is recommended for the species. The fluoroquinolone, enrofloxacin, is in this ‘high impor­tance’ category and has been commonly prescribed in the treatment of burnt wildlife. Although enrofloxacin is not used in humans, it is metabolised in other animals to ciprofloxacin (also rated as ‘high impor­tance’ and used exclusively in humans as a major agent to treat resistant gram-negative infections). Resistance to one fluoroquinolone (such as enrofloxacin) can confer resistance to other fluoroquinolones. There are alternative antibiotics that can be used in Australian wildlife where there is a clear indication to do so (see Appendix 4)

• Vitamin C reduces post-burn lipid peroxidation, oedema of burnt and non-burnt tissue, and vascular permeability. Although the use of high doses of vitamin C has not been evaluated in the treatment of bushfire-affected Australian wildlife, it may be worth considering in some cases

• The judicious use of sedatives and tranquillisers (see Appendix 3) is important in some burn patients, most notably macropods, during confinement and trans­port. Neuroleptic drugs such as azaperone, haloperidol or Zuclopenthixol do have a place but they mostly calm the animal without necessarily reducing anxiety. Seda­tives such as diazepam or midazolam are anxiolytic. Trazodone, alone or in combination with gabapentin, is being used with increasing frequency in Australian mammals, with anecdotal evidence of a calming/ anxiolytic efficacy in macropods (see Appendix 4).

5.