Companion animal wound care – latest advances

Several outstanding texts have been produced on companion animal wound care that comprehensively examine the basic principles of management^1-3.

The mainstay treatment for traumatic wounds usually consists of initial debridement and achievement of a uniform granulation bed using a variety of techniques⁴. Thereafter, the skin can be encouraged to close by second intention or surgical closure can be attempted^1,5.

Research into human and veterinary wound care is constantly evolving. This two-part series will look at some emerging techniques.

Regardless of the treatment used, it is imperative generous, multimodal analgesia should be provided to every patient, discussion of which is outside of the scope of this article.

Importantly, clinicians should also be mindful novel treatments are not always superior treatments – evidence-based medicine should be practised wherever possible.

Negative pressure wound therapy

The most promising development in wound management is negative pressure wound therapy (NPWT), also known as vacuum-assisted closure (VAC). This involves local application of negative pressure to a wound bed via an open cell foam/gauze (Figure 1).

Provision of intermittent or continuous suction is possible via a portable suction unit and evidence exists intermittent NPWT more effectively stimulates angiogenesis and granulation tissue, compared to continuous NPWT⁶. However, intermittent suction appears to be more painful; therefore, the author uses continuous suction in clinical patients, and generally, a pressure of -125mmHg^7,8.

The benefits of NPWT may include reduced oedema and exudate accumulation, increased central wound perfusion^9-11, extremely rapid stimulation of a uniform bed of granulation tissue^12-16, increased wound fluid pO₂, interleukin-8 and vascular endothelial growth factor¹⁷ and more rapid wound contraction18. Findings in the literature are inconsistent about the ability of NPWT to reduce wound bacterial contamination^19-21.

In the author’s opinion, one of the main advantages of NPWT is the avoidance of the daily anaesthesia/sedation required for traditional debriding techniques, such as wet-to-dry dressings.

The NPWT foam should be changed every 48 to 72 hours because the granulation tissue can grow into the foam if left in place beyond this time, and the less frequent requirement for anaesthesia/sedation allows the patient to increase nutritional intake and ambulate (promoting lymphatic drainage), optimising wound healing.

Dressing strikethrough is eliminated with NPWT because all wound fluid is collected into a single use canister, which is particularly useful in highly exudative wounds.

The most common complications seen with NPWT include mild dermatitis around the wound margin and loss of vacuum; however, these complications are usually readily addressed.

NPWT is widely used in many veterinary hospitals in a variety of cases, including traumatic wounds, decubitus ulcers, degloving injuries, distal extremity wounds¹³, thoracic or abdominal wound dehiscence, septic peritonitis²², cytotoxic sloughs²³, burns²⁴, perineal wounds, osteomyelitis and traumatic wounds with exposed bone (and even shell²⁵), or overexposed orthopaedic implants²⁶.

Interesting case reports/series include:

• Successful treatment of two dogs suffering from septic shock following perforating thoracic or abdominal bite wounds. In both cases, NPWT was used in the presence of a reconstructive polypropylene mesh and multidrug-resistant Staphylococcus pseudointermedius^27,28. The latter case involved instillation of polyhexanide²⁹.
• Successful treatment of a cat with necrotising fasciitis where NPWT was used to augment a free skin graft³⁰.
• 100% survival of full thickness, meshed, free skin grafts in canine distal limbs when using NPWT³¹.
• Successful use of NPWT in combination with temporary rectal stenting to manage severe perineal wounds in dogs³².
• Treatment of a necrotic and infected cranial wound with loss of dura mater using NPWT in the human literature³³. To the author’s knowledge, reports of NPWT use in veterinary literature for treatment of wounds associated with the nervous system are still lacking.

Further studies

Several larger studies have been published, looking at the use of NPWT in dogs and cats.

In 45 clinical veterinary patients (dogs), a short time to skin reconstruction was recorded because of the rapid formation of a smooth granulation tissue bed achieved with NPWT⁷. A total of 96% of the wounds healed after 21 days, despite 11 dogs having previous unsuccessful wound treatment for a mean of 87 days⁷.

Similar findings of rapid wound healing using NPWT after unsuccessful prolonged management using other techniques have been reported in cats^19,34, which have also been reported to suffer fewer complications, less fat tissue necrosis and less sepsis compared with cats treated with a foam dressing. Although a strong effect of NPWT on the progression of infection, fever and sepsis was detected in this population of cats, this difference was not statistically significant³⁴.

NPWT is regularly used in very extensive wounds. In a study by Pitt and Stanley (2014), 50% were greater than 10cm in diameter²³.

Finally, a single study has assessed antibiotic concentrations in surgically created wounds treated with NPWT and found the use of NPWT did not statistically impact antibiotic tissue concentrations when compared with conventional non-adherent bandage therapy³⁵. Therefore, any influence of NPWT on sepsis or wound healing in the presence of infection (usually multidrug-resistant in many patients) is not due to increased antibiotic concentration; indeed, the reason for any potential enhanced bacterial clearance with NPWT remains controversial^22,21.

• In the second article of this two-part series, the author will look at advances in wound closure options and topical wound therapies.