Overview of Wound Healing
Wound healing is the complex biological process by which skin, muscle, blood vessels, and other tissues repair themselves after injury. There are four main phases of wound healing: hemostasis, inflammation, proliferation, and remodeling. Proper wound healing is essential to prevent infection, scarring, and other complications.
The hemostasis phase begins immediately after injury, when blood vessels constrict and a clot forms to stop bleeding. The inflammatory phase follows, where white blood cells rush to the area to fight infection and remove debris. After inflammation comes the proliferation phase, involving the growth of new tissue. Finally, the remodeling phase reorganizes the new tissue and strengthens the wound over time.
Wounds can heal by first, second, or third intention. First intention healing is the ideal process where clean surgical incisions are sutured together. Second intention healing involves leaving a wound open to heal from the inside out. Third intention healing is a delayed primary closure where wounds are left open for several days before being sutured. Proper wound management techniques are necessary throughout the healing process.
Second Intention Healing
Second intention healing refers to the process where wounds are left open to heal and granulate from the base upward 1. This is in contrast to first intention healing, where the wound edges are sutured together. Second intention healing typically occurs in wounds where primary closure is not possible or recommended, such as large/deep wounds, contaminated wounds, or wounds on high motion areas of the body.
The process of second intention healing involves several stages. First, inflammation occurs as the body initiates the healing cascade. Next, granulation tissue composed of new blood vessels, collagen, and fibroblasts forms to fill the open wound. The wound then contracts over time as collagen crosslinking takes place. Finally, the open area is covered with epithelialization as keratinocytes migrate across the wound bed from the edges and divide to provide wound coverage 2.
Veterinarians may deliberately create second intention healing for some wounds by leaving them open after surgery rather than suturing them closed. This is typically done for wounds that are contaminated or at high risk of infection, in areas where bandages can’t be applied, or when tension on the incision would cause complications with primary closure 3.
When Second Intention Occurs
Veterinarians may choose second intention healing for wounds that are too large, traumatized, or contaminated to close with sutures or staples. According to a study published in the journal Veterinary Clinics of North America: Small Animal Practice, second intention healing is often used for “wounds that cannot be closed primarily without excessive tension on the wound edges” (source). This includes large open wounds, degloving injuries, deep puncture wounds, and wounds with substantial tissue loss.
Some common reasons vets use second intention healing include (source):
- Wounds that are already infected or contaminated
- Wounds that have delayed treatment
- Wounds with substantial tissue loss where suturing the skin closed would create tension
- Large traumatic wounds or degloving injuries
- Deep puncture wounds
- Wounds over joints or other areas of motion that would disrupt sutures
Allowing these types of complex wounds to heal by second intention reduces complication risks and supports the best possible outcome for the cat.
The Process
Second intention healing involves three main overlapping phases: granulation, contraction, and epithelization ([1]).
During the granulation phase, new blood vessels and connective tissue form in the wound. This results in the production of granulation tissue, which has a bumpy, red appearance ([2]).
Contraction occurs as myofibroblasts in the granulation tissue contract and pull the edges of the wound together. This decreases the size of the open wound.
Finally, epithelization involves the migration of epithelial cells across the wound bed to cover it with new skin. The new epithelium is initially thin and fragile but over time develops into stronger scar tissue ([3]).
Creating Second Intention
Second intention healing is a process where the wound is left open to heal from the inside out. This type of healing may be necessary if there is substantial tissue loss, contamination, or if the wound is already infected or inflamed. There are several techniques vets can use to help manage second intention healing in cats:
Bandages
Vets may apply sterile bandages over the open wound to help protect it. Bandages absorb drainage, keep the wound moist, and prevent contamination. The bandages need to be changed frequently to avoid damaging new tissue growth (1).
Sutures
In some cases, vets may place a few strategic sutures around the wound edges. These help reduce tension on the skin and encourage contraction of the wound. However sutures are only used sparingly, as the goal is to allow the wound to heal from the inside out (2).
Dressings
Specialized wound dressings may be applied, such as hydrogels, hydrocolloids or alginates. These maintain moisture balance and facilitate granulation tissue formation. Silver dressings may also be used for their antimicrobial properties. The dressings require regular changing as part of the wound management protocol (3).
Whatever techniques are used, the goal is to protect the open wound while allowing healing to occur gradually from the inside out. This is the essence of second intention healing.
Pros and Cons of Second Intention Healing
Second intention healing has both advantages and disadvantages compared to other wound closure methods. Some of the key pros and cons include:
Pros:
- Faster healing time – Allowing the wound to heal on its own avoids additional trauma from suturing and allows quicker closure.
- Less tension on wound edges – Without sutures pulling the skin together, there is reduced tension which improves blood flow.
Cons:
- Higher infection risk – Open wounds are more prone to bacteria and contaminants entering the wound.
- Increased scarring – Scars may be larger without surgical closure.
Veterinarians balance these factors when deciding between second intention healing and other closure methods like sutures or surgery. The size and location of the wound are key considerations. Ultimately, allowing second intention healing when appropriate can lead to faster recovery.
Aftercare
Aftercare is crucial for proper second intention healing. The main aspects of aftercare include:
- Monitoring the wound – Check the wound at least once a day. Look for signs of infection like pus, foul odor, heat, and redness. Make sure the wound is contracting and filling in with new tissue.
- Changing dressings – Bandages or dressings may be needed to protect the wound. Change them regularly according to your veterinarian’s instructions, usually daily or every few days. Be gentle and avoid disturbing any new granulation tissue.
- Preventing infection – Keep the wound clean to prevent bacterial contamination. Your vet may prescribe antibiotics or antiseptics. Restrict your cat’s activity to prevent dirt entering the wound. Good nutrition supports healing and immunity.
Follow your veterinarian’s recommendations for proper aftercare. Monitor the wound closely and alert your vet to any concerns about infection or lack of healing progress.
Healing Time
Several factors affect how long second intention healing takes in cats:
Wound size – Larger wounds take longer to heal. Deep wounds that expose deeper tissue layers or bone also require more time.
Wound location – Wounds on the limbs, face, or body may heal faster than wounds on the feet or areas prone to motion or tension.
Pre-existing health conditions – Conditions like diabetes or hyperthyroidism can delay wound healing.
Medications – Corticosteroids like prednisone may impede the healing process.
For less severe second intention wounds on the body, healing may take 2-4 weeks. More extensive wounds on the limbs or paws may take 4-8 weeks or longer to completely close. Check with your veterinarian for an estimate based on your cat’s specific wound.
Cost
Allowing a wound to heal by second intention can help avoid some surgical costs, but it’s not always the cheapest option. The main costs associated with second intention healing include:
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Surgical fee – If the wound required any initial trimming or debridement by a veterinarian, there will likely be a surgical fee. However, avoiding primary closure helps avoid anesthesia and standard surgery costs.
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Aftercare costs – Second intention wounds require regular cleaning, bandage changes, medication, and rechecks by a veterinarian during the prolonged healing process. These costs can add up over time.
Overall, second intention healing avoids major surgery but requires intensive aftercare and monitoring. Pet owners should weigh the projected costs compared to primary closure or reconstruction when choosing the best wound healing approach.
When to See the Vet
While second intention healing is a natural process, complications can arise that require veterinary attention. Signs that a wound is not healing properly include:
- Increased swelling, redness, pain, or heat around the wound
- Pus or foul-smelling discharge coming from the wound
- Bleeding that doesn’t stop
- Loss of healthy granulation tissue
- No progress towards closing after 2 weeks
Reasons to follow up with your veterinarian include:
- Having the vet evaluate healing progress
- Changing bandages and cleaning the wound
- Monitoring for signs of infection
- Ensuring proper second intention techniques are being followed
- Discussing options if healing seems delayed
With proper aftercare and monitoring, second intention healing can successfully close wounds. But it’s important to watch for complications and seek veterinary help if the wound doesn’t seem to be improving.
