Unique Therapies for Difficult Wounds

Jennifer L. Wardlaw, DVM, MS, Diplomate ACVS and Kristen O’Connell

Traumatic wounds are frequently encountered by the small animal practitioner The inciting cause and severity of the wound dictate the duration of treatment, required materials/equipment, and labor intensity. Despite the availability of cutting-edge antibiotics, age and underlying disease or concurrent illness may contraindicate administration.

Many “old-school” remedies are re-emerging and have shown to be beneficial in wound treatment, including wounds that are complicated, nonhealing, and/or infected. These topical treatments kill bacteria using pH and osmolarity, avoiding induction of bacterial resistance.

Since each wound and patient is unique, there is no one set of rules regarding therapy. In addition, wounds change during the healing process, so a therapy used in the initial stages may delay healing if used too long. Proper research and knowledge of topical therapies is vital to correct usage and successful treatment.

INDICATIONS

All of the topical therapies discussed in this article are indicated for full thickness wounds without granulation tissue or those with superficial infections. Many of the therapies are bacteriocidal and promote granulation. See the Table for indications for specific therapies.

Seven to 8 psi of lavage pressure can diminish wound bacteria by greater than 75%.¹

SUGAR

For centuries granulated sugar has been used to treat wounds, such as mechanical injuries, ulcers, and burns. Sugar is a desirable treatment because it:²

• Has antibacterial effects against organisms, such as Escherichia coli, Pseudomonas aeruginosa, and Streptococcus canis
• Improves superficial debridement
• Enhances tissue growth and epithelialization
• Promotes rapid wound healing
• May decrease malodor from the wound
• Is inexpensive and easy to obtain.

Mechanism of Action

Sugar has high osmolality, which draws water and nutrient-rich lymph into the wound, nourishing the regenerating tissues. In addition, the high osmotic stress caused by sugar on bacteria interferes with cell signaling and cell wall permeability, leading to bacterial death. Bacterial cells are affected by osmostic stress because they rapidly divide, which makes them more susceptible to metabolic attacks. Sugar also attracts macrophages and forms a protective layer of protein by accelerating sloughing of devitalized tissue and allowing a granulation bed to form. This protein layer is created from inflammatory cells and sloughing dead cells.

Application

1. Lavage & Debridement: See Wound Preparation. Due to sugar’s debriding properties, grossly contaminated wounds may not need superficial debridement. The wound represented in the figures below typically receives 1 liter of lavage at initial cleaning and 500 to 1000 mL of lavage at each bandage change.
2. Application: A copious layer (at least 1–2 cm thick) of sugar should be applied to the entire wound, including undermined areas (Figures 1 through 3). It is important that the entire wound be filled with sugar because the wound’s osmolarity must remain high to effectively kill bacteria.²
3. Bandaging: The primary bandage layer should consist of an adherent contact layer (large amount of sterile absorbent gauze or lap sponges) (Figure 4). A second layer should be used to hold the primary absorbent layer in place (Figure 5). This should be followed by a protective tertiary layer (Figure 6).
4. Bandage Changes:
   • Bandages need to be changed (following Wound Preparation steps 1 through 3) once to twice daily depending on the amount of exudate produced or if strikethrough is found in the tertiary layer.
   • If the sugar layer is saturated, bandage changes need to take place more frequently. This is evident when there is (1) a granular sanguinous layer and no sugar covering the wound or (2) a naked wound and complete absence of sugar. If either condition is present, perform bandage changes more frequently until the wound exudate diminishes.
   • Large and infected wounds are edematous; therefore, bandages for these wounds should be changed at least twice daily. These frequent bandage changes will help keep the osmolarity high within the wound. Severely infected wounds may take 5 or more days to become “clean.”²
   • As granulation tissue forms, the frequency of bandage changes may be decreased to once daily and eventually every other day. A general rule of thumb to follow is when white, dry, granulated sugar is still present, bandage changes can be less frequent.
5. Length of Treatment: Treatment with sugar should continue until pockets and undermined tissue are closed and debridement is complete. Presence of a granulation bed and epithelialization are also indicators that sugar treatment may be stopped (Figure 7).² Once healthy granulation tissue is present, superficial infections are much less likely and a simple, nonadherent primary bandage layer can be used.

Disadvantages

Potential disadvantages of sugar bandages include:

• Difficulty in applying the primary and secondary bandage layers to assure a 1-inch layer of sugar covers the entire wound.
• The frequent bandage changes required for this modality. In our experience sugar bandages need to be changed more frequently than wet-to-dry bandages due to the exudative nature of the wounds and quickly saturating sugar layer.
• Sugar bandages lose their osmotic pull once the sugar starts dissolving, while wet-to-dry bandages wick away moisture and facilitate mechanical debridement.

Figure 1. Initial presentation of a degloving and crushing injury of the dorsal metatarsus infected with Pseudomonas.

Figure 2. After cleaning the wound, a thick layer of granulated sugar was poured over the entire wound.

Figure 3. Large sterile cotton gauze was used to hold the sugar on the distal wound.¹

Figure 4. The wound was wrapped to ensure the sugar stayed in place and covered the entire wound. The primary layer must be sterile and very absorptive.

Figure 5. The secondary layer should bulk the bandage to prevent strikethrough. An aluminum rod was incorporated in this layer to support the hock, which was unstable.

Figure 6. A tertiary layer was applied to hold and protect the bandage. This layer must not be too tight.

Figure 7. Preoperative picture of the metatarsal injury illustrating granulation, epithelialization, and lack of infection. This wound was successfully closed with a mesh graft.

HONEY

Historical documentation suggests Egyptians used honey as a topical wound treatment for over 4000 years. Not until the past decade has interest in honey as an adjunct to wound therapy accelerated in medical practice. Honey has antibacterial activity and enhances both granulation and epithelialization of wounds.

Mechanism of Action

The antibacterial effects of honey can be attributed to its high osmolarity, acidity, and peroxide activity.^3,4,5

• Increased osmolarity draws fluid and lymph from the underlying tissues and this fluid provides nourishment to the healing wound
• Honey’s pH (3.6–3.7) creates the desired acidic environment that has been shown to decrease bacterial growth, increase fibroblast activity, and increase oxygen release, all of which further promote wound healing.
• Glucose oxidase produces hydrogen peroxide and gluconic acid, which provide the main antibacterial qualities of honey. The well-tolerated, low levels of hydrogen peroxide promote angiogenesis and fibroblast activity, enhancing oxygen delivery to tissue.³

Research suggests that honey’s ability to enhance wound healing is related to release of inflammatory cytokines from surrounding tissue and attraction of macrophages to further cleanse the wound.^6,7 Honey also appears to:

• Accelarate sloughing of devitalized tissue
• Provide local nutrition
• Decrease inflammatory response with a protective layer of protein from wound turnover
• Improve epithelialization.⁴

Application

1. Lavage & Debridement: See Wound Preparation.
2. Application: The amount of honey applied to the wound depends on the size of the wound. For ease of application, presoak gauze or absorbent pads in honey prior to application instead of pouring honey directly onto the wound.
3. Bandaging: Since honey does not interfere with bandage absorbency, wound exudate will stay contained within the bandage. However, to prevent honey from oozing from the dressing, a secondary occlusive or absorbent dressings may be warranted.
4. Bandage Changes: Frequency of bandage changes depends on how rapidly the honey is diluted by the wound exudate or whether strikethrough occurs.

Disadvantages

Disadvantages of using honey on topical wounds include:

• Honey’s sticky consistency, which makes it difficult to use.
• Its cost and limited availability (see Selecting Honey for Healing), which may delay initiation of treatment (it typically takes 7 to 10 days for honey to arrive and it costs approximately $20 for 10 to 12 ounces).
• The pain it appears to cause when applied to full-thickness wounds; however, discomfort has not been noted when applied to partial-thickness wounds.³

VINEGAR

Vinegar (acetic acid) has been used to fight infections since 300 BC.10 Despite its antimicrobial properties, its use in wound treatment is controversial.

Nontoxic concentrations (< 0.0025%) are slightly effective as an antibacterial agent against gram positive and negative bacteria, such as S aureus and P aeruginosa.10,11 At this concentration, vinegar has no detrimental effects on fibroblasts and keratinocytes; however, it’s ineffective against E coli, Bacteroides fragilis, and Enterococcus. Studies have shown that diluted vinegar (2% acetic acid) is effective for treating ear infections, but the low pH may irritate inflamed skin.¹⁰

Application

1. Lavage & Debridement: See Wound Preparation.
2. Application: Acetic acid is applied directly onto the wound or soaked into the primary bandage layer prior to application.
3. Bandaging: After acetic acid has been applied to the wound, gauze or a nonadherent dressing is added. By using an absorptive secondary layer, the acetic acid becomes the base of a wet-to-dry bandage and provides antibacterial effects topically. Alternatively, using a nonadherent or occlusive secondary layer helps keep the acetic acid on the wound for prolongation of antibacterial effects but does not mechanically debride it. The remainder of the dressing continues as it would for a standard modified Robert Jones bandage.

Disadvantages

Common canine and feline ear cleansers containing acetic acid are frequently used. However, their concentrations may vary, which affects efficacy. They also lack broad-spectrum efficacy and have a narrow safety margin compared to commonly used solutions, such as chlorhexidine and povidone iodine.⁸ However, chlorhexidine can be irritating and povidone iodine is inactive in organic material and can cause sensitivity/allergy issues in some patients, providing a place for both acetic acid and Dakin’s solution (see below) in wound therapy.

DILUTED SODIUM HYPOCHLORITE SOLUTION 0.5%

When initially discovered, sodium hypochlorite’s composition was unknown, but its bleaching and disinfecting properties were noted. A diluted sodium hypochlorite solution (Dakin’s solution) at 0.5% concentration has:

• High germicidal activity
• No irritating contaminants.

At this concentration, it may be applied continuously for > 7 days without irritation.¹² Studies have shown that a modified Dakin’s solution, 0.025%, is therapeutically as efficacious as a fluid dressing. At this concentration, the solution preserves its bactericidal properties and is not detrimental to wound healing.¹³ At a 0.25% concentration, the solution is effective against gram positive and negative bacteria, fungi, and viruses.⁸

Application

1.  Lavage & Debridement: See Wound Preparation.
2. Application: Similar to vinegar, Dakin’s solution may be applied directly onto the wound or soaked into the primary bandage layer.
3. Bandaging: The remainder of the dressing is applied as you would to create a wet-to-dry bandage.
4. Length of Application: Application of Dakin’s solution is recommended for 7 days or less. It is efficacious against bacteria, but will not debride the wound, encourage macrophages, relieve edema, or provide anti-inflammatory properties.

Disadvantages

Similar to vinegar, disadvantages of Dakin’s solution are its limited spectrum of efficacy and narrow safety margin when compared to chlorhexidine and povidone iodine.8

MAGGOT THERAPY

In the early 1800s, it was accidentally discovered that maggots prevented infection and accelerated wound healing in soldiers with battle injuries. They were intentionally introduced into wound management shortly after; however, it wasn’t until recent years that their popularity increased in human medicine due to increasing antimicrobial resistance.^11,15

Maggot therapy refers to the application of disinfected fly larvae to a wound; specifically, the common green bottle fly, Lucilia sericata. Common applications include:^11,16,17

• Debridement of necrotic tissue
• Infection control (microbial killing & antifungal activity)
•  Stimulation of granulation tissue.

Although little is known about specific advantages and disadvantages of maggots in veterinary wound management, information is extrapolated from human reports/research. In addition, experienced practitioners report that maggot therapy is beneficial and safe.¹⁶

Application

1. Obtaining maggots: Medical maggots are easily accessible and can be obtained from distributers in the U.S., such as Monarch Labs (monarchlabs.com).
2. Application: The number of maggots needed for treatment varies based on wound size and amount of necrotic tissue.
3. Bandaging: A porous bandage should be placed to prevent escape of maggots while allowing them to breathe. The bandage should remain in place for approximately 3 days, at which time the maggots are removed or replaced.¹⁵

Cost of treatment varies based on the individual wound. In a human study of necrotic venous ulcers, the average cost of maggot therapy was approximately half the cost of conventional treatment and required fewer applications to achieve the same end result.¹⁵

Disadvantages

According to practitioners, the most common disadvantage of maggot therapy is that it may take 24 to 48 hours to receive maggots. In addition, application takes longer because the dressing must withstand any efforts the patient may make to remove it.15 Human patients undergoing maggot wound debridement frequently complain about discomfort or pain associated with movement of maggots within the wound.¹⁵

CONCLUSION

Using unique, and what may be considered “old school,” remedies for treating wounds that are infected or nonhealing may be the ideal option for companion animal patients. As long as current research supports a modality, clinicians should not be afraid to use it when indicated. Topical old-school agents are not susceptible to bacterial resistance and offer practical, low-cost alternatives to more expensive and potentially toxic antibiotics. ⁿ

Kristen O’Connell is a third-year veterinary student at Mississippi State University. After receiving her DVM, she plans to specialize in small animal surgery.

Jennifer L. Wardlaw, DVM, MS, Diplomate ACVS, is an assistant professor of small animal surgery in the Department of Clinical Sciences at the Mississippi State University College of Veterinary Medicine. Her interests include arthritis, reconstructive surgery, wounds, nutraceuticals, and developmental orthopedic diseases. Dr. Wardlaw has spoken at numerous national meetings as well as published various research articles and book chapters. She received her DVM from University of Missouri and completed her internship, residency, and MS at Mississippi State University.