URGENT CARE Special Section Assessing and Managing Mammal Bites Animal bites can carry a serious risk of broken bones, neurovascular damage, infection, and psychological harm. Here’s how to size up the situation. Urgent Care Section umans interact with including wound care, infection other mammals ev- prophylaxis, and follow-up. H ery day: pets, farm livestock, service animals, zoo CASE #1: DOG BITE and laboratory animals, and A 5-year-old boy is bitten by a wild animals, both indigenous large neighborhood dog. The and nonindigenous. Add to that child’s parents, who witnessed Lisa D. Mills, MD Associate Professor the growing prevalence of non- the event, report that the dog Section of Emergency Medicine traditional companion animals held the boy’s arm and shook it Director, Emergency Ultrasound (NCAs), such as prairie dogs, violently. The dog is known to John Lilley, MD monkeys, and lemurs, and the have an up-to-date vaccination Resident Physician lifetime risk of being bitten by a profile. The child is tearful and Section of Emergency Medicine mammal rises to 50%. appears to be in pain. On exami- This article explores pertinent nation, you note that the forearm Louisiana State University Health Sciences Center aspects of managing mammal is bruised but the skin is intact, New Orleans, Louisiana bites in the urgent care setting, and there is reduced mobility in left) Inc (lower Researchers, © 2009 Photo right) © 2009 Phototake (upper left, www.emedmag.com JANUARY 2009 | EMERGENCY MEDICINE 35 MAMMAL BITES the shoulder. The rest of the exam is normal. The dogs, followed by cats. Bite wounds from mam- child has no medical problems and his immuni- mals that are not household pets or from NCA zations are up to date. Does this child need any mammals make up a minority of reported bites. further evaluation? What referrals should you However, they will be discussed in this article be- provide? cause, without proper care, these bites can cause significant morbidity and mortality. CASE #2: MONKEY BITE More than two-thirds of bite injuries occur in A 23-year-old woman reports that her pet green children younger than 10 years old—boys more monkey bit her on the chest earlier today. The often than girls. Children most commonly pre- patient recently had a tetanus immunization. On sent with bite wounds to the face, neck, and head. exam, you note a bruised area on the chest with Adults more commonly present with bites to the an associated superficial abrasion. Is any treat- extremities. ment indicated? HISTORY AND PHYSICAL EXAM TIPS CASE #3: CAT BITE Patients usually seek medical care after bites for A 45-year-old man presents with a bite wound on repair of the wound or because the wound has the forearm from his own cat. The cat is appropri- become infected. A thorough history of the event ately vaccinated. The wound is a small puncture includes asking about the timing of the injury, the without active bleeding. The arm is neurovascu- kind of animal involved, its health history (includ- larly intact. The man requests a tetanus shot. Is ing vaccination status and current health), and any further evaluation or treatment indicated? its behavior. Other important information about the animal includes whether it can be observed COMMON BUT OFTEN UNREPORTED or captured. About 1% of emergency department and urgent Thoroughly examine patients with bites. Bear care visits each year are for mammal bite injuries in mind that the most painful or obvious injury or their complications. Ten to 20 people die each may distract the patient from additional injuries, year from mammal bites. In 2006, 310,710 inju- so check areas adjacent to the bite as well. In ries from dog bites alone were reported to the particular, if the patient is a young child or has Centers for Disease Control and Prevention. The been mauled by an animal, check the entire body Urgent Care Section actual number of bite wounds from all mammals to identify additional injuries. is estimated to be around 2 million each year, Examine the wound itself meticulously. Many but that figure underestimates the true incidence aspects of mammal bites are not apparent on because most animal bites are unreported. cursory evaluation. Tears, punctures, and crush Animal bite injuries include lacerations, punc- wounds can have extensive subcutaneous in- tures, crush injuries, tears, rips, avulsions, frac- volvement. Flaps and avulsions may hide wound tures, hemorrhage, and contusions. The type contaminants and foreign bodies, such as teeth. and severity of injury depend on the location of Be alert for injuries to the vasculature, nerves, the bite, the species of animal, and size of the tendons, bones, and joints. Examine tendons patient. For instance, animals with large, strong along their full range of motion. A neurovascular jaws, especially large dogs, assessment of pulses, motor function, and sensa- >>FAST TRACK<< inflict crush, avulsion, and tion distal to wounds should precede and follow Many aspects of mammal tearing wounds. Dog bite all exploration and management. Neurovascular bites are not apparent on injuries are divided about structures and tendons can be exposed and in- cursory evaluation. equally among lacerations, jured in avulsions, large lacerations, punctures, puncture wounds, and su- and crush injuries. perficial abrasions. Feline and large rodent bites Bites from large mammals can damage and are more often deep puncture wounds as op- even fracture bone. Large dogs can produce bite posed to lacerations or tears. pressures in excess of 450 psi. The direct force The most common bite injuries are from of a bite can fracture delicate bones of the hand, 36 EMERGENCY MEDICINE | JANUARY 2009 www.emedmag.com MAMMALMAMMAL BITESBITES foot, and face. The crushing aspect of a large animal bite can fracture long bones. A detailed Animal Bites With a High Risk physical examination is needed to discover subtle for Infection fractures. Plain radiographs should be viewed af- ter the exam. Large mammals who bite and shake can dis- • crush injuries locate joints. Have patients perform active range- • hand wounds of-motion with joints that are near bite wounds. • puncture wounds Evaluate the joint for disruption of the capsule (open joint). Joint injection with methylene blue • wounds with extensive devitalized tissue is the most effective nonoperative assessment • heavily contaminated wounds technique for subtle capsule disruption. Maintain • prolonged time from injury to treatment: a low threshold for injecting joints. Missed open 6–12 hours on the body joints can lead to significant morbidity. 12–24 hours on the face Use plain radiography to assess for retained foreign bodies and skeletal injuries. Computed to- mography and magnetic resonance imaging have increased sensitivity for foreign bodies and subtle early suture removal. Inform patients that wound fractures. In cases of high suspicion and nega- infections may occur in spite of the appropriate tive plain films, use these imaging techniques. care. Advise all patients at discharge to look for Urgent Care Section Identifying foreign bodies requires careful exami- signs of infection, such as redness, increasing nation with ample light in a bloodless field. Plain pain, and purulent drainage. films of the affected area complement, but do not Some bite wounds have a higher risk of infection replace, exploration for foreign bodies. (see box). Puncture wounds, for instance, whether closed or left open, become infected more often REDUCING THE RISK OF INFECTION than other wounds. (Wounds that extend more Standard principles of wound care apply to mam- deeply than their length are considered puncture mal bites. (Routine cultures are not indicated and wounds, regardless of the size of the entry wound.) are poor predictors of infection.) Copiously irri- Crush wounds, even when debrided properly, also gate all bites; irrigation reduces the incidence of have an increased risk of infection. viral and bacterial infections. Debride the wound Location plays a significant role in determin- generously: Devitalized tissue does not function ing the management of bite wounds. The over- as a “biological dressing.” It acts as a nidus for all infection rate of head and neck wounds that infection and should not be retained. are primarily closed is low (1.4% to 6%). Despite Bites are tetanus-prone wounds. Patients who the risk of infection, primary closure may be have not had tetanus immunization within the necessary because most wounds to the face are last five years should receive appropriate tetanus in cosmetically sensitive areas. Bite wounds to prophylaxis. For patients without the primary se- the hands have a higher potential for infection ries of tetanus immunizations, refer to the CDC and significant morbidity guidelines. as a result of infection. >>FAST TRACK<< The practice pattern is to close the majority Although hand wounds of wounds primarily. When deciding to close the are still commonly closed, Maintain a low threshold wound, assess its location and size, degree of consider leaving high-risk for injecting joints. Missed contamination, functional impairment, cosmetic wounds open. open joints can lead to outcome, and time from injury. Uncomplicated Older wounds are also significant morbidity. wounds greater than 1.5 cm in cosmetically sensi- at higher risk for infec- tive areas can be primarily closed with minimal tion. As a guideline, a wound 6 to 12 hours from risk of infection. It’s expected that a small percent- the time of injury is considered old on the body. age of wounds will become infected and require Face wounds 12 to 24 hours after the incident are www.emedmag.com JANUARY 2009 | EMERGENCY MEDICINE 37 MAMMAL BITES Infectious Bacteria from Animal Bites considered old. These times are arbitrary, not absolute, and should be considered as only one Animal Bacteria factor in deciding whether to close the wound.