Non-healing Wounds
World Small Animal Veterinary Association Congress Proceedings, 2018
P. Maguire

Wound healing is divided into the following overlapping phases:

  • Inflammation and debridement, days 0–5
  • Proliferation, days 4–12
  • Remodelling and maturation, up to 12–18 months

Identification of the stage of the wound can help to guide management. The type of support that is required for the wound will vary during wound healing and therapy should be tailored appropriately. For example, in the early inflammatory phase of wound healing management practices should revolve around supporting the wound without allowing excessive maceration from wound discharges rather than attempting to reconstruction. Inflamed tissues have poorer suture holding strength and sutures is more susceptible to pull through - primary closure at this time is not always a good idea. Attempts at premature wound closure while inflammation still predominates may result in failure of the closure and wastage of the skin utilized for reconstruction. In the proliferation phase of wound healing the wound should be adequately protected, and aggressive debridement avoided (i.e., wet to dry bandaging or other non-selective debridement techniques should not be used). Moist wound management in these circumstances will allow wound healing without constant removal of tissue healing factors and mechanical damage to the wound bed. For the remodelling period it is important to protect the wound from excessive mechanical strain or abrasion that would overcome healing.

If a wound remains in the inflammatory phase despite appropriate wound management practices the question that should be asked is - what is perpetuating the inflammation? Biopsy of the wound should take place and bacterial or fungal culture should be performed. Less common organisms such as mycobacteria or inflammatory conditions such as canine eosinophilic granuloma complex or pythiosis should remain differentials as appropriate.

If inflammation of a wound has subsided but is not adequately progressing through the remaining steps, patient factors should be considered and investigated if not already performed. Conditions that can affect wound healing include; uraemia, hepatic disease, diabetes mellitus, hyperadrenocorticism, FIV FeLV, anaemia, hypothermia, hypotension, malnutrition, local tissue hypoxia and ischemia, bacterial colonization, repetitive trauma, presence of necrotic tissue and/or tension.

The golden wound period is defined as 6 hours from injury, theoretically within this timeframe bacterial load has not proliferated to the level of 105 organisms per gram of tissue. On presentation even contaminated degloving wounds can be partially closed following surgical debridement. However, extensive flaps or reconstruction should not be attempted at this time as the risk of failure will be higher while inflammation is still severe.

If a wound is necrotic the aim of treatment will be to debride and remove as this tissue can be a host for infection and impair healing. If a wound demonstrates significant sloughing, there is often a mixture of fibrin, serous discharge, leucocytes and bacteria. The aim in this case should be to remove the sloughing tissue and infectious load to provide a clean base for granulation. If a wound is granulating, there are intact capillary loops, collagen, proteins and polysaccharides. This wound should be protected such that it can serve as a base for epithelialization. If a wound is already epithelializing, the bandaging material should aim to protect and promote maturation.

How aggressively the area is debrided is based on how accessible the region will be subsequently and the importance of the tissue. For example, if extensive muscle damage of the quadriceps is noted with in a wound that is designated for closure, aggressive debridement should take place as the muscle group is big providing some degree of redundancy. Once the wound is closed it will no longer be accessible limiting further opportunity for debridement. However, if the wound is associated with the medial aspect of the stifle a more conservative debridement could be performed to protect structures like the medial collateral ligament and joint.

The type of dressing applied to the wound and the times for bandage change remains contentious. While moist wound healing has gained significant popularity for its ability to provide selective debridement and foster a more conducive wound healing environment some still favour wet to dry or dry to dry dressings for initial management.

Wound dressing management largely revolves around the amount of wound moisture. What is the objective of the dressing? Is it t rehydrate or to absorb exudate? If a wound is too dry the bandaging should act to add moisture. If the wound is too wet moisture should be removed by absorption, retention or sequestration, or perhaps the wound should be further debrided, or an infection more comprehensively treated. Moisture retentive dressings include foams, alginates, hydrogels, and hydrocolloids. Each dressing should be utilized in response to the level of moisture within the wound. Each bandage change should serve as a means of re-assessing wound progress as the requirements will change over time as the wound progresses. The wound should also be constantly re-evaluated for options for definitive closure.

An exception to the rule of adding moisture can be in instances where there is no blood supply; (in the case of extensive eschars) it may be prudent to keep the external aspect of a wound dry. If there is suspected to be viable cutaneous tissues selective debridement and use of a moist healing technique can be employed. However, in the complete absence of viable cutaneous tissues this may not speed wound healing.


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P. Maguire