Dermatology Challenge: Resolution of a necrotizing wound in a debilitated cat

Dermatology Challenge: Resolution of a necrotizing wound in a debilitated cat

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Jun 01, 2004

A 6-year-old, 11.2-lb (5.1-kg), neutered male domestic shorthaired cat was presented to South Athens Animal Clinic for evaluation of a large cutaneous wound. The cat had been absent from its residence for nine days. Before its disappearance, the cat had been in good health, and its vaccination status, including rabies, was current.

Physical examination and diagnostic procedures

At presentation, the cat was listless with a subnormal body temperature of 100 F (37.7 C). The cat was determined to be about 10% dehydrated based on prolonged skin tenting and delayed capillary refill time. A 3-x-4-in cutaneous wound in the left axilla extended over most of the scapula, including the lateral and ventral thorax and upper forelimb.

Initial evaluation revealed a necrotizing, subcutaneous lesion involving the fascia and superficial musculature of the lateral shoulder, thorax, and triceps area. The thoracic cavity and deeper musculature exhibited no penetrating wounds or tears, but portions of the dorsal and lateral tendons attaching muscle groups to the olecranon were exposed. The elbow joint capsule and tendon sheaths of the triceps, anconeus, and ulnaris lateralis muscles were visible but not compromised. The skin on the medial side of the left forelimb was intact. In addition to the primary wound site, two superficial puncture wounds were detected on the cat's right lumbar area and thorax, leading to a presumptive diagnosis of a chronic, infected bite wound. Results of feline leukemia virus and feline immunodeficiency virus ELISA tests were negative. Additional blood work was not done because of the cat's debilitated state. A decision about continuing treatment would be made after wound débridement.

Treatment

After the physical examination, the cat was anesthetized by intravenous administration of tiletamine hydrochloride and zolazepam hydrochloride (3 mg/kg) in combination with 0.06 mg/kg acepromazine maleate. Débridement consisted of first gently flushing the wound with lactated Ringer's solution. The skin over the left chest wall, forelimb, axilla, and shoulder was also shaved. Obviously devitalized tissue was surgically excised. Because of the wound size, we were conservative with tissue removal.

The resulting open wound was flushed several times with lactated Ringer's solution, and wet-to-dry bandages were applied to the left side of the thorax and left forelimb. The area surrounding the two superficial puncture wounds on the right side was shaved, and the wounds were treated with a topical antibiotic ointment. Lactated Ringer's solution was administered slowly intravenously (240 ml/day), and liquefied food (Prescription Diet a/d—Hill's, mixed with water) was given orally by syringe. Amoxicillin (10 mg/kg orally b.i.d.) was initiated.


Figure 1: The appearance of the wound after the second débridement (Day 2).
The cat was anesthetized again the next day to remove residual necrotic tissue, and the wound was débrided a second time, resulting in a larger area (8 x 8 in) of exposed subcutaneous fascia and superficial musculature (Figure 1). The area was copiously flushed with lactated Ringer's solution, and wet-to-dry bandages were applied. The cat's prognosis was guarded because of the extent of the wound and the cat's debilitated condition.

On Day 3, 1 L of an aqueous solution of EDTA-tris (8 mmol USP disodium ethylenediamine-tetraacetate dihydrate and 20 mmol USP 2-amino-2-hydroxymethyl-1,3-propanediol; Tricide—Molecular Therapeutics, Athens, Ga.) was mixed with 125 mg ampicillin; the mixture was used to flush and cleanse the tissues. Gauze bandages, soaked in the Tricide–ampicillin solution, were placed over the wound. To prevent the bandages from drying out and sticking to the wound, the gauze covering the chest wall and left forelimb was covered with food-grade plastic wrap, which was held in place with loosely applied Vetrap (3M). Additional gauze and light bandaging were applied to hold the wet bandages and plastic wrap in place.

On Day 4, the cat's body temperature had increased to 104 F (40 C), and we noted peripheral edema in the left forepaw. The bandages were repositioned to relieve the pressure on the distal forelimb. The cat remained depressed but was able to sit up and move around in its cage and was eating small quantities of liquefied food. Because of this increased activity and the frequent bandage changes, hydration was maintained by subcutaneous administration of lactated Ringer's solution (120 ml b.i.d.). We performed a radiographic examination of the thorax (to rule out pneumonia) and abdomen (to rule out fecal impaction). The thoracic radiographs were normal. The abdominal radiographs revealed a diffuse, intraluminal soft tissue opacity causing colonic distention. The cat received two soap-and-water enemas that day, which resulted in the passage of a large quantity of feces. The cat was also given lactulose syrup (0.67 g [1 ml] orally b.i.d. for 21 days), orbifloxacin (4.5 mg/kg orally q.i.d. for 10 days), metronidazole (22 mg/kg orally b.i.d. for seven days), and butorphanol tartrate (0.2 mg/kg orally b.i.d.).


Figure 2: Marked granulation is present over most of the exposed tissue (Day 8).
The cat remained hospitalized for the next five days and was given liquefied food orally and lactated Ringer's solution subcutaneously (120 ml b.i.d.). Wound treatment consisted of flushing the site daily with 100 to 200 ml Tricide-ampicillin solution and applying wet bandages covered with plastic wrap and Vetrap as described above. Cage rest and supportive care continued, and the cat's body temperature returned to normal by Day 9.


Figure 3: Surgical closure of the thoracic and scapular area (Day 9). Suture tension required subsequent removal of four sutures, which partially opened the wound to allow forelimb movement. The arrows indicate the site of the drain exit.
On Day 8, the wound had sufficient granulation tissue to support surgical closure of the thoracic and scapular regions of the wound (Figure 2), which was performed the next day. Anesthesia was induced with tiletamine and zolazepam and maintained with 2% isoflurane. To close the wound, the skin margins were freshened, and the skin on the ventral thorax and lateral shoulder was extensively undermined. These two sections were pulled together over the olecranon. The dorsal and ventral margins were apposed and sutured with 3-0 polydioxanone in a simple interrupted pattern (Figure 3). A Penrose drain was placed along the left lateral thoracic wall, which exited at the ventral margin of the surgical site. The cat recovered from anesthesia without complications.

Postoperatively, excessive skin tension at the suture line over the elbow was noted. This finding required that the cat be anesthetized again later that day. The suture line was opened by removing four sutures from the point of the elbow dorsally to the intersection of the shoulder and lateral chest wall. This left about 10% of the surgical site open and exposed portions of the tendons, fascia, and granulation bed over the elbow. Postoperatively, hot packs were placed on the surgical site two or three times a day to enhance skin attachment to the granulation bed as well as to improve local circulation. The exposed tissues were rinsed with the Tricide–ampicillin solution, and the wound was left open to heal by second intention.

The cat was quite active, so the drain was lightly covered with gauze and one layer of Vetrap. The drain fluid remained clear, and there was little exudate (1 to 2 ml per bandage change). On Day 11, a complete blood count and serum chemistry profile were done because the cat was not gaining weight; it weighed 10.6 lb (4.8 kg). The only abnormalities were a moderate neutrophilia (27.7 × 103 neutrophils/μl; normal = 2.5 to 12.5 × 103/μl) and a mild hypoproteinemia (total protein 5.4 g/dl; normal = 6 to 7.77 g/dl) with hypoalbuminemia (albumin 2 g/dl; normal = 3 to 4.3 g/dl). These results indicated inflammation and protein loss from the wound without sufficient protein replacement by oral feeding. Although the cat did not object to syringe feeding, it was not consuming enough food to maintain its weight, so it was discharged and allowed to recover at home. The cat was given a third enema before discharge.