SA266 BITE WOUNDS & OTHER PENETRATING TRAUMAS Armelle de Laforcade, DVM, Dipl. ACVECC Tufts Cummings School of Veterinary Medicine North Grafton, MA, USA Trauma, including thoracic trauma, is an exceeding common presenting complaint in small animal emergency medicine. Following a primary survey that includes evaluation and stabilization of the major body systems, a secondary evaluation for specific injuries can be performed. This hour will focus on penetrating thoracic trauma with some specific discussion of bite wounds to the chest. Thoracic puncture wounds: All wounds located over the thorax should be explored and penetration into the thorax must be ruled out. Chest radiographs are always indicated for identification of pneumothorax, pulmonary contusion, and rib fractures. In some cases radiolucent gas patterns in the body wall can increase the index of suspicion for penetration into the thoracic cavity. In general, basic principles of wound management apply in the patient with wounds located over the thorax. With bite wounds in particular the extent of soft tissue injury may not be readily appreciated from visible puncture wounds and wound exploration under anesthesia is highly recommended. Trauma patients with wounds located over the chest should, however, always be intubated and closely monitored during the procedure. While it may seem extreme in some cases, it is not uncommon for manipulation of wound edges in severe trauma to result in a pneumothorax and controlling the airway makes it easy for manual positive pressure ventilation to be initiated. An exploratory thoracotomy is indicated when penetration into the thorax has been identified, so that the thoracic structures can be assessed for further damage. Penetrating thoracic foreign bodies: Penetrating foreign bodies over the thoracic cavity should be approached with caution. For example, the dog that presents with a stick protruding from the thoracic cavity should have minimal wound exploration performed prior to a thoracotomy. Instead, a primary survey should be performed and resuscitation should proceed prior to addressing the foreign body. With the airway captured a sterile prep can be performed the foreign body removed in an OR setting. This will allow for rapid hemostasis should a major vessel be affected, and additional foreign debris can be removed. Premature removal of the penetrating foreign body may lead to pneumothorax, hemothorax, and rapid cardiovascular decompensation. Bite wounds to the chest: Because dogs possess such powerful jaws, bite wounds inflicted by dogs typically cause severe crushing injury in addition to punctures and lacerations. Once the teeth penetrate through the skin, shaking and pulling frequently result in avulsion of the skin from its subcutaneous attachments and tearing of the subcutaneous tissue, muscle, vasculature, and underlying structures. The skin itself may still appear relatively intact as it tends to be more elastic and moveable than the underlying structures. For this reason, superficial-appearing skin wounds should be regarded as only “the tip of the iceberg”.

Western Veterinary Conference 2013

Bacteria from the attacker’s mouth, as well as hair and debris from the victim’s skin may be driven deep into the wounds, leading to contamination of devitalized tissues. The presence of dead space and accumulation of fluid or blood further contribute to the development of severe infections. Up to two-thirds of dog bite wounds in veterinary patients may become infected, frequently with multiple isolates. The most common aerobic isolates include Staphylococcus intermedius, Enterococcus, S. coagulase negative, and E. coli. There tends to be a predominance of anaerobes in the oral flora of dogs and cats, and as a result, Bacillus spp, Clostridium spp, and corynebacterium spp, have been frequently isolated from dog bite wounds as well. Cat bite attacks are more likely to result in small, deep puncture wounds because of their sharp, pointed teeth and lesser tendency to shake their victims. Cat bite wounds are also more likely than dog-inflicted wounds to become infected, with Pasteurella spp most commonly isolated. Antibiotic use should be strongly considered for moderate to severe bite wounds in veterinary patients. Although antibiotic therapy is considered controversial in human patients with dog-inflicted bite wounds, veterinary patients are more likely to have their wounds become contaminated with fur and debris, and may be at greater risk for sepsis. Because gram positive, gram negative, and anaerobic pathogens are frequently isolated from bite wounds, broad spectrum coverage with an antibiotic such as amoxicillin/clavulanate potassium is indicated. Alternatively, combined therapy with amoxicillin and enrofloxacin may be used. First generation cephalosporins alone are not considered appropriate therapy as they may not be effective against anaerobes or gram negative bacteria such as Pasteurella spp. Wound management: Appropriate management of thoracic wounds consists of clipping and cleansing, wound debridement, lavage, establishment of drainage, and antibiotic therapy (in most cases). All dog-inflicted bite wounds (with the possible exception of the distal extremities) should be surgically explored, as superficial skin wounds frequently hide more significant underlying damage. The practice of probing bite wounds with an instrument should not be performed as it frequently underestimates injury severity. Probes may not be able to follow the path of a bite wound through the various planes of moveable fascia and may therefore fail to identify large pockets of dead space. The cleaning and debridement process should proceed from the outside in (ie. starting with the skin and wound margins before moving on to the deeper portions of the wound) in order to avoid dragging contaminated material from the periphery deeper into the wound. A small amount of sterile, water-based jelly may first be applied to the wound to prevent contamination of the deeper tissues with hair and debris. Once the wound has been clipped, the skin surrounding the wound may then be scrubbed with a surgical scrub solution such as povidone-iodine or chlorhexidine. The interior of the wound should not be scrubbed with these preparations, as they may be irritating to the delicate tissues. Hydrogen peroxide is not considered an effective antimicrobial, and its use within wounds should also be avoided.

Sterile gloves and drapes should be used for wound debridement. The contaminated wound margins should be excised, and the incision extended if needed to facilitate exploration of the wound. All devitalized tissues should be excised using a scalpel blade or metzenbaum scissors. Lavage should be performed during the debridement process to facilitate removal of bacteria, hair, and debris from the wound. Sterile saline is typically adequate for this purpose. The addition of antibiotics to lavage solutions has not been shown to be beneficial. Lavage may be performed using a bulb syringe, a plastic 1 liter bottle of sterile saline with several holes punched in the lid, or a 35-ml syringe with 18 g needle. This syringe may be attached by 3-way stopcock to a bag of sterile saline in cases when copious lavage is needed. Once a wound has been adequately debrided, the decision can then be made as to whether the wound may be safely closed or should be left open for drainage. It is never appropriate to close bite wounds that have not been aggressively debrided. Wounds in which all devitalized tissue has been removed, with adequate blood supply, negligible dead space, and no evidence of infection may be closed primarily. More commonly, some form of drainage is needed because of the presence of dead space, compromised blood supply, or contamination. For wounds with moderate amounts of dead space, passive drainage using ¼” or ½” penrose drains may be employed. Following debridement, penrose drains are anchored at the dorsal aspect of the wound and allowed to exit from a separate site ventral to the wound. The drain should not be run directly underneath the suture line as this may decrease blood flow to the healing incision, nor should the drain exit directly from the wound. Closed-suction drains may also be used in large wounds. A “poor man’s” drain can be constructed from a butterfly catheter and vacutainer tube. The luer-lock is cut from the plastic tubing of the butterfly catheter, and the tubing is then fenestrated using a scalpel blade. The plastic tubing is inserted into the wound through a separate exit site, and a purse-stringed is used to secure it in place. Following wound closure, a vacutainer may be attached to the butterfly needle to provide continuous suction, and may be changed each time it becomes full. Larger closed-suction drainage systems are commercially available. Advantages to closed-suction drains include the provision of drainage in areas with poor dependent drainage, the ability to keep wounds and dressings dry, reduced risk of ascending infection, and the ability to quantitate discharge. Disadvantages include expense, need for in-hospital maintenance, and possible occlusion of drains as a result of kinking or thick discharge.