Dermatology Challenge: Resolution of a necrotizing wound in a debilitated cat - Veterinary Medicine
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Dermatology Challenge: Resolution of a necrotizing wound in a debilitated cat


VETERINARY MEDICINE


Discussion

Bite wounds are common in outdoor cats. Short-term lesions often respond favorably to minimal wound care and systemic antibiotics, but contaminated wounds such as the one described in this case report may develop secondary complications, such as necrotizing dermatitis, fasciitis, or myositis. Aerobic and anaerobic bacteria within devitalized tissue may interact synergistically to induce deep tissue cellulitis or abscessation, resulting in draining sinuses or skin sloughing.1 This report details the successful management of a chronic wound in a debilitated cat in which limb amputation, death, or euthanasia were possible sequelae. Because of the severity and chronic nature of the wound, postoperative complications were expected.


A fully recovered Oscar, the cat featured in this case report, in 2004.
Formulating a prognosis for large, necrotizing wounds in dogs or cats requires considering multiple factors, including the animal's physical condition, the severity and extent of the wound, and the client's commitment to pursuing treatment. Any treatment that facilitates regeneration of healthy tissue and improves wound healing may turn a patient presented for euthanasia into one that has a reasonable chance of recovery. Initiating systemic antibiotic treatment and supportive care and properly treating the open wound during the first few days of hospitalization allowed sufficient time for this cat to stabilize and begin showing signs of recovery.

After débridement, a primary issue was how to control infection and prepare a large area of exposed subcutaneous tissue for surgical closure. In this contaminated bite wound, we chose delayed closure because there was concern regarding tissue viability and residual areas of infection.2 We added Tricide supplemented with ampicillin to the treatment regimen to facilitate pathogen control and wound health, which allowed surgical closure eight days after presentation. Granulation tissue usually appears three to six days after injury in nondebilitated patients.3

While the wound was open, the only treatment capable of protecting such a large area of exposed tissue was wet bandaging. While the cat was hospitalized, the wound was flushed with the Tricide-ampicillin solution, and wet bandages soaked in the same solution were applied daily. Frequent bandage changes allowed the wound to be examined for signs of healing or development of additional necrotic areas. Wet bandaging protects exposed tissues while maintaining cellular hydration. A potential disadvantage of wet bandaging is nosocomial wound contamination.4 Applying bandages soaked in low concentrations of chlorhexidine (0.05%) can reduce the number of bacteria entering an open wound but may not control heavy Pseudomonas species infections.5 Higher concentrations of chlorhexidine may kill bacteria more effectively but also tend to delay the formation of granulation tissue.5

Previous in vitro testing has shown that the active ingredients in Tricide have an antibacterial effect when applied directly to wounds or bandages.6,7 These compounds in combination with various antibiotics have also been shown to reduce the minimum inhibitory concentrations of antibiotics capable of killing bacteria found in contaminated wounds (i.e. Pseudomonas species, Staphylococcus species, and Escherichia coli).8,9 The mechanism of action is thought to be increased uptake of antibiotics by the bacteria, thus enhancing the bactericidal effect.10 In this case, systemic antibiotics and repeated flushing of the open wound with Tricide resulted in excellent wound healing. A healthy granulation bed was evident within a week of initiating treatment, thereby allowing surgical closure. After surgery, topical treatments of the area included applying a mixture of lanolin, vitamin E, Tricide, and ampicillin. The decision to use Tricide in this case was based on in vitro and in vivo documentation of its ability to enhance antimicrobial agent activity.11-18

After surgical closure and opening the suture line over the elbow, wet bandaging of the proximal forelimb and olecranon was not possible because of limb movement. Since the cat was being discharged to its home environment, maintaining tissue hydration and preventing infection were important. Incorporating the Tricide–ampicillin mixture into a lanolin and vitamin E emulsion proved to be a satisfactory course of treatment. After three and a half weeks of topical treatment, the wound had contracted considerably, and a healthy granulation bed had formed over most of the wound's surface. The surrounding skin and subcutaneous tissue remained pliable, thus contributing to successful surgical closure and clinical resolution.

On presentation, the clinical assessment of this case was guarded with a poor prognosis for complete recovery. Although the degree of superficial tissue damage was extensive, the lack of penetrating wounds or fractures contributed to this patient's chances for improvement. Exposure of the tendons of the forelimb and surrounding tissue delayed closure and increased the risk of infection. We chose healing by second intention since wound closure over points of high skin tension, such as in this case, cannot be relied on because of poor underlying cutaneous blood supply.19 With wound contraction, surgical closure proved feasible three and a half weeks later.

Clinical resolution of this challenging case was possible because of a lack of complications during wound healing and postsurgical closure. Under such conditions, motivated owners capable of treating their cats at home may elect similar treatments and thereby avoid euthanasia or shorten the hospitalization of their pets.

ACKNOWLEDGMENTS

The authors would like to thank the technicians and staff of South Athens Animal Clinic for their excellent care of Oscar. They would also like to acknowledge the valuable input of Branson W. Ritchie, DVM, PhD; and Richard E. Wooley, DVM, PhD, of the University of Georgia College of Veterinary Medicine for technical advice in the use of Tricide and wound management.

The photographs and information for this case were provided by Joanne Maki, DVM, PhD, Department of Medical Microbiology, College of Veterinary Medicine, University of Georgia, Athens, GA 30602; and Mark Mosher, DVM; and Thomas Nemetz, DVM, PhD, South Athens Animal Clinic, 2040 S. Milledge Ave., Athens, GA 30606. Dr. Maki's current address is 3221 Smithonia Road, Colbert, GA 30628.


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Source: VETERINARY MEDICINE,
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