CHAPTER Animal Bites 17 Jeffrey D. Ferguson INTRODUCTION Animal bites are estimated to account for more than 1 million visits to physicians each year and account for 1% of emergency department (ED) visits. 1 The actual number of occurrences of animal-related injuries is impossible to calculate because many injuries go unreported. 1,2 Despite these high estimates, injuries from animals are not commonly encountered in most EMS systems. The infrequent nature of these calls, coupled with the excitement and emotion often found on scene, can lead to poor provider judgment or errors in proper care. This chapter focuses on the prehospital management of animal bites and injuries and highlights injuries likely to be encountered, with specific interventions where appropriate. GENERAL Scene Safety and Preplanning Similar to calls for assaults, shootings, or stabbings, calls for persons injured by an animal must be assumed to be inherently unsafe. First and foremost, the safety of the EMS provider must be considered. Additional resources should be summoned as necessary to either remove the patient to a safer environment or to secure any threatening animal. Potential resources for these tasks include, but are not limited to, animal control or law enforcement officers, dive or water rescue teams, or fire department personnel. Depending on local dispatch protocols, these agencies may already be summoned based on the provided call information, and their absence on scene arrival should raise concern about the safety of the environment. Additionally, many localities require reporting of animal bites or attacks as a public health and safety concern. Ensuring the early involvement of law enforcement or other appropriate agencies will satisfy this requirement as well as the need for holding or quarantining the offending animal. If a provider comes in contact with an animal while on scene, no attempt at contact or capture should be made. A retreat to a place of safety should become a priority to prevent a provider from becoming an additional victim. Even domestic, historically tame animals can be prone to aggression when cornered or confused. Attempting the capture of wild animals for the purposes of identification, quarantine, or testing should not be the primary concern of the EMS provider because it exposes him or her to undue risk. 3 Likewise, the transport of an animal, dead or alive, to the hospital for similar purposes is ill advised. Although stories by seasoned providers of evacuating ambulances due to resurrected or otherwise released animals in the truck make for good conversation, their lacking safety and sensibility is obvious. Such duties are best left to those properly trained and equipped to carry them out. Preplanning for animal attacks is encouraged. Interaction with facilities and staff that shelter animals, including zoos, wildlife centers, or pet stores, may identify animals capable of causing harm. In addition, resources such as wildlife experts or sources of antivenin for the animals should be sought. Poison Control Center contact information should be updated and readily available as resources for likely reactions to unusual exposures and stores of antivenin. 4 An EMS medical director should be prepared to be contacted as a resource for the community or ill-prepared hospitals or clinics during an event, and either have information 167
available or be able to forward the request to the appropriate public health authorities. A final consideration of preplanning is to be familiar with animals commonly found in the area. Lists of native species, often including hazard risks, are available from state wildlife or game agencies and often these groups also track migratory patterns of animals such as Africanized honeybees that may pose additional threats. These lists will allow for more species-specific protocol development that is addressed later in this chapter. General Management The majority of injuries from animal bites and attacks are not acutely life- or limb-threatening and can be cared for with standard wound care techniques. An attack that has resulted in significant fall or shaking, such as a large dog attack on a child, requires spinal precautions and immobilization. Airway and breathing assessment and monitoring are necessary for attacks to the face, neck, or chest. Moderate to severe bleeding should be immediately controlled in standard fashion. Any skin disruption from a bite, sting, or scratch should be grossly decontaminated by copious irrigation. Irrigants in decreasing order of preference include sterile normal saline, sterile water, potable (distilled, boiled but no longer hot or chemically treated) water, and any readily available water source. The exception is marine envenomation, which will be specifically discussed later in the chapter. Irrigation reduces the rate of infection from environmental or skin flora as well as animal specific organisms including rabies. 1,2 If available, a 1% povidone-iodine solution has demonstrated additional viricidal activity. 2,5 Following irrigation, a sterile bandage should be applied to prevent further contamination and promote continued hemostasis. Distal neurovascular function should be assessed and documented along with any visual evidence of envenomation. Palpable pulses should be marked to facilitate reassessment and areas of local erythema or edema should be outlined and time marked with a durable pen or marker. On assessment at the receiving hospital, extension of findings beyond this timed marking may be supporting evidence of envenomation or early infection. Immobilization of affected extremities should be performed to protect against further injuries to fractures or joint injuries or from foreign bodies. If not contraindicated, pain management should also be provided to minimize anxiety and psychologic trauma. Refusal Concerns Because of the innocuous appearance of many bite wounds, the tendency to downplay their risks may lead to patients trying to refuse treatment and transport by EMS. Refusal of transport by persons injured by animals should be discouraged and standing orders should reflect the real inherent risk present. These patients should be encouraged to seek immediate medical care to ensure proper assessment of risk of occult injury or envenomation as well as the need for postexposure prophylaxis of bacterial infection, tetanus, and rabies. ANIMAL-SPECIFIC CONCERNS Mammals Domesticated animals account for the vast majority of mammalian bite wounds, with dogs and cats representing 93% to 96% of mammalian bites. 2 Bites by both types of animals occur most frequently to the upper extremity, followed by the lower extremity, and finally the face and neck. 1 Acutely fatal wounds typically occur in the pediatric population and involve exsanguination from neck wounds. 1 Children are often familiar with the offending animal and are more prone to attacks to the face and neck. 1,6 In both animals, unique oral flora contribute to considerable infection risk. Although the majority of wounds do not become infected, those that do tend to require in-hospital therapy and at least one operative procedure. This is particularly true of penetrating wounds to the hand, which can be complicated further by tenosynovitis, abscess formation, osteomyelitis, and septic arthritis. 1 Two thirds of hand bites in one study required hospitalization for IV antibiotics and one third required at least one surgical procedure. 7 Systemic complications including endocarditis, meningitis, brain abscess, and sepsis must also be considered. 8 Bites inflicted by humans and pugilistic injuries resulting in injuries to the hand from striking teeth carry similar risk of complications as other mammalian bites. The latter become particularly worrisome when the metacarpal-phalangeal joint and overlying extensor tendons are involved. These wounds are especially prone to infection of the avascular tendon and sheath spaces, with more than 30% of these becoming infected, possibly resulting in decreased functional capacity. A final concern is the transmission of communicable 168 SECTION B Trauma and Environmental Incident Types
diseases such as human immunodeficiency virus (HIV) and hepatitis. 8 Their occurrence often coincides with intoxication and/or criminal activity that may act as a barrier to proper prehospital care through reluctance to disclose their true mechanism, patient refusal, or law enforcement custody. The discussion of poisonous mammals is popular trivia for physicians and EMS providers alike. In North America, poisonous mammals take the form of the short-tailed shrew, found in the central and eastern sections of North America. Several nonindigenous mammals have poisonous reputations. The solenodon, found in Central America, induces toxins in its saliva through grooved incisors. The platypus, found in Australia, has venomous glands introduced by spurs at the base of its hind feet. In all of these animals, the toxins serve the purposes of their own foraging and defense from predators. 9 Bites to humans result in unusually painful wounds with local edema, but typically lack serious or systemic effects. Wild mammal attacks are rare, accounting for less than 10% of animal bites in multiple studies 2 and requiring little specific intervention beyond that of appropriate trauma care described herein and elsewhere. The specific concern of rabies transmission from mammalian bites is discussed later in this chapter. Reptiles Snakebites and their treatment are the source of a great deal of mystery and myth. Of the estimated 45,000 annual snake bites in the United States, roughly 8,000 are reportedly from venomous snakes. There are 25 venomous species of snakes in the United States. The majority of these are in the subfamily of Crotalids (rattlesnakes, cottonmouths, and copperheads), and the remainder in the Elapid subfamily (coral snake). 10 This division also represents a large difference in their respective toxins. Crotalid envenomation produces symptoms that are largely a result of hemotoxins ranging from local swelling and ecchymosis to systemic coagulopathy, altered consciousness, and shock. The constellation of effects usually begins within minutes and steadily progresses to its maximal extent. In contrast, Elapid envenomations can remain relatively asymptomatic for up to 12 hours and then manifest as a curare-like neurotoxin ranging in severity from paresthesia to complete paralysis requiring ventilatory support. In either case, it is important to avoid underestimating the severity of a bite based on initial assessment of the patient at the scene. Any discussion of prehospital care of snakebites should begin with dispelling mythologic therapies. Cold therapy, arterial tourniquets, electricity (from TASERs or car batteries), incision of the wound, and suction (via commercially available device or oral) are popular lay therapies for snakebite that are without scientific backing and may lead to more local tissue damage. 3,10 13 Some recommended therapies, such as compression immobilization, traditional immobilization, and positioning at or below the heart, do have limited data to support them. 11 13 Compression immobilization has been shown in animal models to at least delay toxicity and mortality, perhaps at the cost of increasing regional tissue damage. 14,15 Antivenin therapy is not generally recommended in the prehospital setting. Animal serum-based preparations carry a high risk of anaphylaxis and although the Fab antivenin has less of an anaphylaxis risk, it still requires a significant amount of time and resources to prepare and administer. 3 Gila monsters also have venom in their saliva injected through grooved teeth and a reputedly vicious bite. Envenomation, however, is not lethal and usually causes only local inflammation. Other reptiles such as alligators or crocodiles have been involved in fatal attacks. Some turtles are also known to bite swimmers for no apparent reason or in self-defense. In all of these cases, no special prehospital care is required, but bites may be predisposed to specific types of infections. Marine Although not truly bites, many marine animals either sting or inject venom. North American examples of these include jellyfish, stonefish, catfish, and stingrays. In many if not all of these animals, the injected toxins are heat labile and respond to heat therapy for neutralization as well as pain reduction. 3,13,16 18 In the case of jellyfish, any tentacles or remaining nematocysts should be removed before applying heat. Other therapies are sourced in folklore, including the use of urine, sand, or meat tenderizer, all of which are inappropriate. Gloves or forceps should be used to manually remove visible tentacle remnants. A vinegar solution will stabilize remaining nematocysts, which can be removed by scraping with a tongue blade or similar object. 3,13,17,18 Impaled foreign bodies such as sea urchin spines or stingray barbs should not be routinely removed by prehospital provider because surgical debridement may be necessary. CHAPTER 17 Animal Bites 169
Spiders Most physicians are familiar with the frequency with which spiders are accused of inflicting soft tissue wounds that are ultimately attributable to folliculitis or other forms of soft tissue infections. However, there are three clinically significant species of spiders found in North America. Black widow spider bites are often unnoticed, but they may be experienced as a pinprick-type sensation that quickly resolves. Over the course of a few hours, calcium channel mediated neurotransmitter release of acetylcholine and sympathomimetics can result in muscle spasm, severe abdominal pain, hypertension, and diaphoresis. Fatalities are rare and therapy should be supportive. Opiods for pain and benzodiazepines for antispasmodics may be considered in the field. 3,19 Brown recluse and hobo spider bites can cause chronic, progressive soft tissue ulceration. Acute bites often go unnoticed, and there are no special considerations for prehospital care. 3,13,19 Insects Insect bites and stings are specifically covered elsewhere in Chapter 21, Allergies and Stings. SPECIAL CONSIDERATIONS Rabies Mammalian bites have the unique risk of rabies virus transmission. General meticulous wound care as previously discussed has been shown to minimize transmission. 5 Because rabies virus infection is almost universally fatal, 20,21 prevention is paramount. Current Centers for Disease Control and Prevention (CDC) guidelines recommend postexposure prophylaxis (PEP) including immunoglobulin administration and vaccination series for at risk bites in vaccine-naive individuals, and a modified vaccination series for those previously vaccinated. 22 Bites primarily from skunks, foxes, raccoons, bats, and some other carnivorous animals are considered at risk and should receive PEP immediately. Patients who have been bitten by dogs, cats, or ferrets should be immediately vaccinated if the animal is known or suspected to be rabid. If these domestic animals appear healthy and can be quarantined for 10 days, PEP can be withheld pending development of symptoms. Bites from other animals should be discussed with public health officials to determine the need for PEP. 22 Bats require special consideration because rabies transmission has occurred outside of recognized bites. Although data are conflicting and perhaps viewed as controversial, 22 PEP can be considered for persons who were in the same room as the bat and who might be unaware that a bite or direct contact had occurred (e.g., a sleeping person awakens to find a bat in the room or an adult witnesses a bat in the room with a previously unattended child, mentally disabled person, or intoxicated person) and rabies cannot be ruled out by testing the bat. 22 EMS personnel should encourage patients who are considering refusing care to seek advice regarding rabies prophylaxis at the ED. Anaphylaxis This immediately life-threatening condition will not be completely discussed here (see Chapter 21, Allergies and Stings). It is, however, important to recognize the potential for allergic and anaphylactic reactions to be precipitated not only by bees and ants, but from bites and stings from a diverse list of animals including several insects, marine animals, reptiles, and even some mammals. 24 Nonindigenous Animals This chapter has focused on species found in North America. It has been previously mentioned that preplanning in the form of familiarization of indigenous species and their clinical relevance is recommended. It is also important to recognize that exposure to nonindigenous animals can occur not only in zoos or known refuges, but in private collections or simply as pets. The best reports of nonindigenous bites in the literature involve venomous snakes. 10,12,25 The popularity of exotic pets seems to be increasing, judging anecdotally from news and entertainment sources. Because it would be nearly impossible to train every EMS provider for all possible species they may encounter in this manner, high-quality supportive care should be the standard, with local public health and poison control authorities guiding specific therapy. 170 SECTION B Trauma and Environmental Incident Types
SUMMARY Although not a frequent prehospital patient encounter, animal bites can be the source of significant injury and devastating sequelae. Prudent EMS care can lessen the possibility and severity of these as well as alleviate pain and anxiety in the acute setting. Medical directors should familiarize themselves with the commonly encountered animals of their region to educate and provide oversight for their providers. CLINICAL VIGNETTES Case 1 University Hospital, this is Air 1 transporting a 34-year-old male with a snake bite to his right hand that occurred approximately 1 hour ago. Animal control on scene reports this was a Canebrake Rattlesnake. First responders have placed a tourniquet below the elbow and had applied ice to the area of the bite. The patient s current vital signs include a blood pressure of 90/50, pulse of 116, and respirations of 20 with oxygen saturations of 100% on 15 L by mask. The patient appears uncomfortable, rating his pain as 8 out of 10. His right hand shows severe discoloration and edema. No pulses are present at the wrist and capillary refill is very delayed. Pulses and capillary refill are mildly diminished in other extremities. We have large-bore IV access in his unaffected arm and are starting a second liter of normal saline. We are requesting orders for further management of hypotension and pain. Our estimated time of arrival is 20 minutes. What Would Your Medical Oversight Orders Be to This Air Medical Crew? This patient has evidence of severe crotalid envenomation. Although the Canebrake is not a wellknown species, previous knowledge of its presence in your area (or zoo, if you live out West) has provided you with the information that this is one of the largest rattlesnakes in North America, with the largest fangs and highest venom load per bite. Even without this knowledge, this report is consistent with a critically ill patient with a life-threatening, and now limb-threatening, injury. Ice packs and the suspected arterial tourniquet should be discontinued. Compression immobilization in the form of circumferential wrapping with a hand-tightened elastic band and splinting should be performed if available. The affected limb should then be placed at or below the level of the heart. Although none of these therapies have been shown to prevent overall mortality, the risk of worsening local necrosis is likely acceptable to delay mortality in a patient with early systemic symptoms. IV fluids should be continued and pressor support considered if fluids alone do not correct hypotension. Epinephrine may be of particular benefit as systemic pathophysiology resembles anaphylaxis. Pain management is a reasonable request, but should be used judiciously in the setting of hypotension. Case 2 Community hospital, this is EMS 2. We are on scene with a 24-year-old male who has sustained a cat bite to his hand. Vital signs are stable and the patient is requesting no further treatment or hospital transport. He has two puncture wounds to his palm and the back of his hand over his little finger. There is no bleeding and his pulses, movement, sensation, and distal capillary refill are intact. We are requesting permission for no transport. What Would You Advise the Crew to Do? Bites involving the hand are at significantly increased risk for deep tissue infection and systemic complications. Patients should be fully informed of these risks, as well as those from tetanus and rabies, from such a seemingly innocuous injury to make an informed decision. The wound should be irrigated as discussed above, dressed in a sterile fashion, and further ED evaluation sought. CHAPTER 17 Animal Bites 171
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