Management of Skin Trauma: Bites and Burns

Part 1: Animal and Human Bites

Ellie J. C. Goldstein

Five million animal bites, leading to 800,000 medical encounters, occur in the United States each year. Patients often present to the primary physician for advice and therapy. Patients may appear shortly after injury concerned about rabies, tetanus, or the repair of a disfiguring tear. Sometimes, they delay seeking care, only to present later with infection. The primary physician must provide first aid and tetanus prophylaxis, decide whether antibiotics are necessary, and estimate the risk for rabies. Human bites are less common but potentially more serious. Particularly treacherous are clenched-fist injuries, which result from striking the teeth. Bites in children and the elderly should be evaluated for abuse potential. Occlusional bites and paronychial injuries may also result in infection.

PATHOPHYSIOLOGY AND CLINICAL PRESENTATION (1, 2, 3, 4, 5, 6, 7, 8, 9, 10 and 11)

Most bites result in minor trauma. Approximately 80% of patients neither need nor seek medical care. Bite wounds that produce a break in the skin allow the inoculation of bacteria that normally inhabit the skin or, more usually, the oral cavity of the biting animal. Conditions favoring infection include prior splenectomy, liver disease, immune compromise, crush injury, edema, wounds to the hand, and multiple punctures. Patients with established infection usually present more than 8 hours after having sustained an injury. Patients with preexisting edema (e.g., persons with congestive heart failure or chronic venous insufficiency, women who have undergone radical or modified mastectomy) are at risk for more severe infection.

Animal Bites

In animal bites, the wound itself may or may not be problematic, depending on how much tearing of the skin occurs. The infecting organisms are usually the normal oral flora of the biting animal. Pasteurella species, including Pasteurella multocida, are present in 50% of animal oral cavities and in 50% of dog and 75% of cat bite wounds. Cat bites are more prone to infection than are dog bites and may lead to severe cellulitis and approximately 20% present as abscesses. Catscratch disease is caused by Bartonella henselae and Bartonella quintana, fastidious gram-negative rods; it often presents with fever and lymphadenopathy and is more frequently seen during the cold-weather months. Any patient who has undergone splenectomy or has alcoholic liver disease is prone to sepsis with Capnocytophaga canimorsus (formerly DF-2).

Human Bites

Human bites, especially clenched-fist injuries, in which damage is inflicted while the tendons and other tissues of the exterior area of the finger are stretched to full length, can be serious because they result not only in breakage of the skin but also in exposure of the tendon and possibly the joint. As the fingers are straightened, the damaged parts relax, and infecting organisms are carried into the tissues, producing infection in wounds that may initially appear minor. If the joint capsule is penetrated, septic arthritis or osteomyelitis is a risk.

The oral flora in humans is more abundant than that in most animals and includes Streptococcus viridans, Haemophilus influenzae, Eikenella corrodens, Prevotella species, Porphyromonas species, anaerobic diphtheroids, fusobacteria, and spirochetes. Wounds may also be infected by skin flora, such as a group A β-hemolytic streptococci (Streptococcus pyogenes) or staphylococci (Staphylococcus aureus). Streptococcus anginosus may be present in approximately 50% of wounds, S. aureus and E. corrodens in 30%, and anaerobes in approximately 55%, especially Fusobacterium nucleatum in approximately 30% and Prevotella melaninogenica in 20%. The presence of anaerobic bacteria is associated with more severe infection and may lead to abscess formation. Human bites are responsible for most severe bite wound infections, accounting for greater than 50% of clenched-fist injuries and 45% of occlusional bite wounds in adults requiring hospitalization. In children, bites may occur during play, but only 14% may require hospitalization. Many patients initially deny that a human bite was a cause of injury.

PRINCIPLES OF THERAPY (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 and 15)

Basic elements of management include characterization of the injury, vigorous cleansing, elevation, tetanus prophylaxis, and the administration of appropriate antibiotics.

Animal Bites

It is important to elicit a history of the circumstances surrounding the injury. If an animal bite occurred, the type of animal and its behavior need to be detailed, as well as whether the animal had been vaccinated and whether the attack was provoked or unprovoked. The wound should be diagrammed in the chart, with proximity to bones or joints noted. Minor animal puncture wounds should be cleansed with soap and water and treated expectantly without antibiotics. Copious irrigation of wounds with normal saline solution is an important therapeutic adjunct. Animal puncture wounds that are small and clean require no other treatment.

Rabies

Since 1967, only one or two cases of rabies in humans have been documented each year in the United States. No cases of rabies have occurred in New York City or Los Angeles for many years. Raccoon rabies is epidemic in all states along the entire eastern seaboard. In most other states, skunks and bats are the most common rabid animals. Rabies is more prevalent in cats than in dogs in the United States. Rabies is a concern if the attack is unprovoked, occurs in a rural setting, or involves a raccoon, a bat, a skunk, or an animal that is behaving in a peculiar manner. The local health department provides data regarding the local incidence of rabies and should be notified for follow-up and documentation. Patients with bat exposure, even without a known bite, should be considered for prophylaxis because a bat bite or exposure has been the most common cause for clinical rabies in humans in the United States. If rabies is considered a possibility, human diploid cell vaccine should be given along with rabies immune globulin without delay (see Chapter 6). If a person is bitten by a pet, the animal should be watched at home by the owner for 2 weeks and the bite reported to the local health department.

Tetanus

It is important to determine whether the patient has had an initial series of tetanus shots and a booster within the last 10 years. Those who have not had an initial series should be given both tetanus toxoid and tetanus immune globulin (see Chapter 6). For persons who have had the initial series but no booster in 10 years, 0.5 mL of tetanus toxoid should be administered intramuscularly.

Tear Wounds

Therapy for tear wounds is problematic. No controlled trials of closure versus nonclosure, with or without antibiotics, have been undertaken. The principles of therapy are to cleanse and debride the wound cautiously. After the wound has been left open for 24 hours, the edges can be approximated with adhesive strips or sutured and a 3- to 5-day course of amoxicillin/clavulanate prescribed (875 mg thrice daily for 3 to 5 days if the patient’s weight is greater than 125 lb) taken with food. Secondary closures can be performed if no infection is apparent. Facial wounds may be closed and antibiotics given. It is useful to refer these patients to a plastic surgeon.

Infected Wounds

Patients who present with infection should receive debridement, drainage, cleansing, and antibiotics. Amoxicillin/clavulanic acid is effective against most animal bite pathogens. In penicillin-allergic patients, doxycycline is preferred because P. multocida is often resistant to erythromycin and cephalexin. Penicillin and amoxicillin are effective against P. multocida, streptococci, anaerobes, and E. corrodens but are ineffective against S. aureus. In vitro and anecdotal clinical data exist for moxifloxacin, which also covers most pathogens. Oral second-generation cephalosporins, such as cefuroxime, are active against P. multocida but not anaerobes.

Human Bites

Human bites are usually located on an extremity; hand wounds are the most serious. The same principles of cleansing, drainage, and debridement apply. Human bites should not be closed primarily, although edges can be approximated if the tear is severe. Antibiotics should be instituted after wound cultures are taken. Amoxicillin/clavulanic acid (ampicillin/sulbactam, intravenously) should be administered pending culture results to cover β-lactamase-producing oral anaerobes and gram-positive cocci, particularly S. aureus. Ertapenem and other intravenous carbapenems can be used but are more expensive alternatives. Infrequently, the presence of a gram-negative organism necessitates a change in antibiotic regimen. All patients previously immunized who have not had a booster in 5 years should be given 0.5 mL of tetanus toxoid. Follow-up is essential because of the potential for late serious infection. A risk exists for the transmission of viral pathogens such as hepatitis A, B, and C viruses and less for HIV.

Clenched-Fist Injuries

These usually require specialized care. Radiographs should be taken to rule out fractures and provide a baseline for future assessment of osteomyelitis. Extension and flexion of digits should be carefully checked and sensation tested. The third metacarpophalangeal joint is most often affected. The integrity of the joint capsule must be determined, and this may require an experienced surgeon. If the capsule is intact, the hand is cleaned, debrided, immobilized, and elevated. Ampicillin/sulbactam, cefoxitin, or ertapenem should be started and tetanus toxoid administered. Patients seen within 8 hours of injury with intact joint capsules can be managed as outpatients with careful follow-up. Those with torn capsules need to be admitted for surgery and treatment with intravenous antibiotics. Patients who present after 8 hours should be admitted for observation to determine whether the capsule is intact or interrupted.

Only gold members can continue reading. Log In or Register to continue