Managing Skin Wounds

Complications leading to delays in the healing process often occur. A basic understanding of wound healing may aid in successful wound management. Nonhealing cutaneous wounds may be caused by foreign material (metal, organic debris, etc.) within the wound, periosteitis, or bone sequestrum deep to the wound. Periosteitis should be considered in the presence of chronic draining tracks, even when severing of skin was not in the history. Blunt trauma in bony areas with little soft tissue protection and crush injury, as might be the case with leg wounds, may present in this manner. Nearly all traumatic wounds in agricultural practice will be plagued with gross contamination by the time of recognition. It is not uncommon to begin with a wound that is caked with mud, manure, straw, and gravel. Often, by the time the wound is recognized, it is significantly later than the time of occurrence. This would therefore suggest that the wound has to heal by second-intention or delayed primary closure. A third option commonly involves initial primary skin closure to draw the wound margins closer together, providing initial protection over a wound ultimately destined to heal by second intention. The latter option is reasonable, provided adequate drainage occurs from the deep portions of the wound.

After hemorrhage control, initial wound management should focus on controlling the inflammatory process, reducing edema, assisting with wound debridement, and treating infection. With regard to inflammation, the goal should be to modulate the inflammatory process and not block it entirely. The aim should be to control an exaggerated systemic inflammatory response while not suppressing neutrophil migration and function within the wound as a normal part of the healing process. Glucocorticoids have been shown to downregulate L-selectin binding necessary for migration of neutrophils from capillary endothelium, as well as delay necessary neutrophil apoptosis for macrophage phagocytosis and sequential functions in the healing process.2,3 Nonsteroidal antiinflammatory drugs (NSAIDs) may more effectively modulate inflammation without deleterious effects on cellular function.⁴ Edema within a wound may be treated with compression wraps, when possible, as well as with hydrotherapy to increase perfusion and debride the wound.

Physical debridement of the wound should be undertaken with initial assessment, noting clinical characteristics, severity, structures involved, and estimating the duration (Figure 63-1). Gentle scrubbing of the wound initially with antiseptics will remove large debris. If povidone iodine is used for scrub or lavage, it should be a very dilute solution (<0.5%), as “free” iodine in solution is the basis for antimicrobial activity. Wound lavage with dilute antiseptic solution may then be used. Lavaging fresh, moderately contaminated wounds with antiseptic solution pressed from a 35-mL syringe through an 18-gauge needle provides tissue-friendly, targeted, focal hydropressure and debridement.

Infection should initially be treated empirically by utilizing broad-spectrum systemic antibiotics as well as topical antiseptic therapy. The wound should be reassessed frequently, and culture and sensitivity should guide antibiotic therapy when unresolved infection appears to be complicating the healing process (Figure 63-2 and 63-3). Intravenous (IV) regional antibiotic infusion is proposed by some in cases of distal limb wounds, in the belief that higher concentrations of drug could be achieved in the area of interest. However, the counter-argument would be that the antibiotics that are safe and legal to use in this manner, namely, β-lactams, have time above MIC dependent mechanisms of action, and are not concentration dependent.⁵ However, IV regional antibiotic perfusion should provide more rapid distribution of the dose within the area of concern.⁶ If this practice is followed, the tourniquet should remain in place for at least 30 minutes for effective distribution of antibiotic within tissue.

Primary Closure of Contaminated Wounds

Primary skin closure over a contaminated wound is a reasonable decision, provided adequate drainage occurs from the deep portions of the wound. Primary partial closure of gaping wounds will benefit the healing process later on by concentrating the time frame and distance covered during the proliferative stages and by decreasing the degree of wound contraction during remodeling. Portions of the wound should remain open to provide a portal for wound lavage and discharge of the products of inflammation. Consideration should be given to the orientation of the blood supply to the affected area with regard to the placement and type of tension-relieving suture patterns. Vertical mattress sutures (with and without stents) as well as near-far-far-near suture patterns are favored, whenever possible, to relieve tension, preserve collateral blood supply, and, in the cases of contaminated wounds, provide intermittent gaps for the escaping exudate.

Mastectomy

Diseases of the teat and udder in llamas and alpacas are not commonly recognized. Reports on these conditions are extremely limited compared with those in sheep, goats, and dairy cattle. However, these diseases are important and significant to llama and alpaca breeders because the consequences of poor mammary health may be perpetuated along family lines and complicate the successful rearing of thrifty crias. Mastitis may be a severe problem and is a cause of poor milk production and low weaning weights of crias. Problems of the teat and udder requiring surgery seem to be much less common. Udder amputation is perhaps the most common teat and udder surgery done in llamas and alpacas.⁷ Udder amputation is performed when the udder has been damaged beyond repair. The udder might be amputated after a long-term chronic mastitis that has left a nonsecretory fibrotic mass with or without abscesses within the udder. In these cases, the animal often suffers from chronic infection.

The two halves of the udder are distinctly separate from each other and are supplied by separate arteries, veins, and nerves.⁸ The main arterial blood supply to the udder is via the external pudendal artery, which courses through the inguinal ring after having originated from the pudendoepigastric trunk, which originates from the deep femoral artery, which originates from the external iliac artery, which originates from the abdominal aorta. The venous blood from the udder is drained by the external pudendal veins, the caudal superficial epigastric veins and the perineal veins. The iliohypogastric and ilioinguinal nerves provide nerve supply to the cranial udder. The genitofemoral nerve provides nerve supply to the caudal udder.

Udder amputation must be done cautiously because of the risk of untoward effects of surgery in an animal in poor physical condition from chronic infection and because of the risk of profuse, uncontrolled hemorrhage during surgery.7,8 The patient may be anemic because of the chronic nature of the infectious process. Removing a mass of the udder may result in severe hemorrhage and the creation of a large soft tissue defect that may be difficult to close completely. The owner must, therefore, be made aware of these potentially serious consequences. Amputation of the udder should be performed with the llama or alpaca under general anesthesia and with the appropriate facility to perform cardiopulmonary monitoring and intervention. A blood donor animal should be available, or blood should be harvested prior to surgery in case of life-threatening hemorrhage. If possible, the animal should be positioned in dorsal recumbency. This facilitates working on both sides of the udder simultaneously during surgery. If dorsal recumbency is not possible, the animal will need to be rolled from one side to the other during surgery, and the appropriate preparations should be made.

With udder amputation, the external pudendal artery should be ligated before any of the venous system is ligated. This gives the blood in the udder time to drain before the udder is removed. A skin incision is made parallel to the base of the udder and approximately 5 centimeters (cm) ventral to the region of attachment of the udder to the abdominal wall. This incision is extended circumferentially around the udder in an elliptical manner. Hemorrhage should be controlled by cautery or ligation. Once the incision has been made through skin, the incision is extended through the lateral suspensory ligament of the udder. Care should be taken as the external pudendal artery and vein lie directly beneath the lateral suspensory ligament. The external pudendal artery and vein is found coursing from the inguinal ring in a tortuous manner. The artery and vein should be separated and individually ligated using absorbable suture material (e.g., No. 2-0 polyglactin [PG]-910). Extreme care must be taken during this procedure to avoid rupturing the artery. The artery and vein may be ligated together en masse to avoid this possibility. A larger size (e.g., No. 0 PG-910) suture material is advisable to provide better ligature security. Once the artery and vein have been ligated on one side, the procedure should be repeated on the opposite side unless a hemimastectomy is being performed. Hemimastectomies are rarely done because of the nature of the disease being treated.

The circumferential incision is extended cranially, and the subcutaneous abdominal veins are ligated. Care should be taken to ensure that the ligation of these veins is done close enough to the udder so that the multiple branches of the veins are sealed. After the subcutaneous abdominal veins have been ligated, the skin incision is extended caudally, and the perineal veins are ligated. One perineal vein should be present for each side of the udder.

After ligating all the major vessels, the median suspensory ligament is cut near the abdominal wall. Ideally, 1 cm of the medial suspensory should remain on the abdomen to provide an anchor point for the subcutaneous sutures such that these obliterate dead space during closure. Once the udder has been amputated, the subcutaneous tissues and skin are closed. Simple interrupted sutures of an absorbable material are used to close dead space by placing stay sutures (“tacking sutures” or “walking sutures”) such that skin is firmly attached to the abdominal wall. This usually includes taking bites of the median suspensory ligament. Skin may be closed either using an interrupted, appositional suture pattern (e.g., simple interrupted, cruciate patterns) or a continuous appositional suture pattern (e.g., simple continuous, Mayo interlocking, or Ford interlocking suture patterns). A Penrose drain may be placed into the wound to provide drainage of dead space for 1 to 5 days following surgery. If this option is selected, a wound dressing should be used to protect the drainage site and prevent ascending infection alongside the drain.

Postoperatively, the patient should be confined to a stall or small pen for 14 days. During this period, antibiotics NSAIDs are administered at the discretion of the clinician.