10.19 Bites
===========

agk's Library of Common Simple Emergencies

Presentation
------------

Histories of animal bites are usually 
volunteered, but the history of a human bite, 
such as one obtained over the knuckle during a 
fight, is more likely to be denied or explained 
only after questioning. A single bite may 
contain various types of injury, including 
underlying fractures and tendon and nerve 
injuries, not all of which are immediately 
apparent.

What to do:
-----------

- Obtain a complete history, including the type 
    of animal that bit, whether or not the 
    attack was provoked, what time the injury 
    occurred, the current health status and 
    vaccination record of the animal, and 
    whether or not the animal has been captured 
    and is being held for observation. report 
    the bite to police or appropriate local 
    authorities.
- Assess the wound for any damage to deep 
    structures, any need for surgical 
    consultation, and any risk of infection. 
    Look for bone and joint involvement and, if 
    present, obtain appropriate imaging studies 
    (dog bites have caused open depressed skull 
    fractures in small children). Examine for 
    nerve and tendon injury and be aware that 
    crush and puncture wounds as well as bites 
    on the hands, wrists and feet are at higher 
    risk for development of infection and 
    significant complications such as 
    tenosynovitis, septic joints, osteomyelitis 
    and sepsis. Bites from cats, humans, other 
    primates are also associated with higher 
    rates of infection. If tissue damage is 
    extensive, then obtain vascular, 
    orthopedic, otorhinolaryngologic, 
    reconstructive or other consultation.
- For crush wounds and contusions, elevate 
    above the heart and apply cold packs.
- If the wound requires debridement, or will be 
    painful to cleanse and irrigate, 
    anesthetize with buffered lidocaine 
    (epinephrine will slightly increases 
    infection rates).
- If there are already signs of infection, 
    obtain aerobic and anaerobic cultures of 
    any pus.
- Cleanse the wound with antiseptic (10% 
    povidone-iodine solution, diluted 1:10 in 
    normal saline) and sharply debride any 
    debris and non-viable tissue.
- Irrigate the wound, using a 20ml syringe, a 
    19 gauge needle or an irrigation shield 
    (Zerowet), and at least 200ml of sterile 
    saline or the diluted 1% povine-iodine 
    solution. This technique demonstrably 
    reduces microscopic debris and bacteria. 
    You can use an intravenous setup to 
    irrigate a large area.
- Prepare every wound as if you were going to 
    suture it.
- For animal bite wounds that are clean, 
    uninfected lacerations located anywhere 
    other than the hand or foot, you may 
    staple, tape, or suture them closed. 
    Prophylactic antibiotics are not necessary. 
    Infection rates in sutured dog bite wounds 
    have compared favorably with those for 
    unsutured wounds and with non-bite 
    lacerations.
- If the wound is infected when first seen, 
    plan either a delayed repair after three to 
    five days of saline dressings or secondary 
    wound healing without closure. Prescribe 
    antibiotics (see below) for seven to ten 
    days. Severe infections require 
    hospitalization for elevation, 
    immobilization, intravenous antibiotics and 
    surgical consultation.
- With human bites, animal bites that are 
    punctures or located on the hand, wrist or 
    foot, or bites more than 12 hours old, in 
    most cases, you should leave the wounds 
    open and apply a light dressing or saline 
    dressing and consider delayed primary 
    closure after two to three days. Wounds 
    should also be left open on debilitated and 
    patients with diabetes, alcoholism, chronic 
    steroid use, organ transplants, vascular 
    insufficiency, splenectomy, HIV or other 
    immunocompromising condition.
- Start prophylactic antibiotics in the ED on 
    these wounds (see above) and in patients 
    with artificial or damaged heart valves and 
    implanted prosthetic devices. The most 
    effective dose is the one you can give now. 
    Augmentin 500 mg tid for three to five days 
    is the current CDC recommendation for all 
    bites. Alternatives for prophylaxis 
    include:
    - dog bites: clindamycin (Cleocin) 150-300 
        mg and ofloxacin (Floxin) 400 mg bid 
        for adults, clindamycin and 
        trimethoprim/sulfamethoxazole for 
        children
    - cat bites: penicillin V 500 mg qid, 
        doxycycline 100 mg bid for adults, or 
        ceftriaxone 500-2000 mg im/iv
    - human bites: cefoxitin 2000 mg q8h iv
- If the patient has had no [tetanus] toxoid in 
    the past 5-10 years, provide prophylaxis.
- If the patient was bitten by an oddly 
    behaving domestic animal, or a bat, coyote, 
    fox, opossum, raccoon, or skunk, you should 
    start rapid [rabies] vaccination with 
    20IU/kg of rabies immune globulin and the 
    first of five l mL doses of human diploid 
    strain rabies vaccine. Reassure the patient 
    that bites of rodents and lagomorphs, 
    including rats, squirrels, hamsters, and 
    rabbits, in America do not usually transmit 
    rabies. Such bites also have a low 
    incidence of secondary infection and do not 
    require prophylactic antibiotics.
- Provide hepatitis prophylaxis for patients 
    who have been bitten by known carriers of 
    hepatitis B. Administer hepatitis B immune 
    globulin 0.06ml/kg im at the time of injury 
    and schedule a second dose in 30 days. 
    Follow standard guidelines applicable to 
    contaminated needle sticks.
- Minimize edema (and infection) of hand wounds 
    by splinting and elevation.
- Have patient return for a wound check in two 
    days, or sooner if there is any sign of 
    infection. Explain the potential for 
    serious complication such as septic 
    arthritis, osteomyelitis and tenosynovitis 
    (evident when a finger becomes diffusely 
    swollen, immobile, tender along the flexor 
    surface or painful on passive extension) 
    which will require specialty consultation.

What not to do:
---------------

- Do not overlook a puncture wound. 
- Do not suture debris, non-viable tissue, or a 
    bacteria innoculum into a wound.
- Do not use buried absorbable sutures, which 
    act as a foreign body and cause a reactive 
    inflammation for about a month and increase 
    the risk of infection.
- Do not waste time and money obtaining 
    cultures and Gram stains of fresh wounds. 
    The results of these tests do not correlate 
    well with the organisms that subsequently 
    cause infection.
- Do not routinely suture human bites.

Discussion
----------

Animal bites are often brought promptly to the 
ED, if only because of a legal requirement to 
report the bite, or because of fear of rabies. 
Bite wounds account for 1% of all ED visits in 
the US, most caused by dogs and cats. Most dig 
bites are from household pets rather than 
strays. A disproportionate number of dog bites 
are from German shepherds.

Bites occur most commonly among young, poorly 
supervised children who disturb the animals 
while they are sleeping or feeding, separate 
them during a fight, try to hug or kiss an 
unfamiliar animal or accidently frighten it. 
Malpractice claims and other civil lawsuits 
often follow bite injuries.

Dog and cat bites both show high rates of 
infection with staphylococcus and streptococcus 
species, as well as Pasteurella multocida and 
many different gram-negative and anaerobic 
bacteria. In addition to these organisms, 
10-30% of all human bites are infected with 
Eikenella corrodens, which sometimes show 
resistance to the semisynthetic penicillins, 
but sensitivity to penicillin. Adequate 
debridement and irrigation are clearly more 
effective than prophylactic antibiotics, and 
except in wounds that are at high risk for 
developing infection are often all that is 
required to prevent infection of bites.

Less than 0.1% of all animal bites result in 
rabies. For questions of local rabies risk, 
local public health services may be available 
and valuable support as sources of information 
regarding the area's prevalence of rabies in an 
involved species.

References:
-----------

- Rosen RA: The use of antibiotics in the 
    initial management of recent dog-bite 
    wounds. *Am J Emerg Med* 1985;3:19-23.
- Elenbaas RM, McNabney WK, Robinson WA: 
    Evaluation of prophylactic oxacillin in cat 
    bite wounds. *Ann Emerg Med* 
    1984;13:155-157.
- Dire DJ, Hogan DE, Riggs MW: A prospective 
    evaluation of risk factors for infections 
    from dog-bite wounds. *Acad Emerg Med* 
    1994;1:258-266.

 ----------------------------------------------------
 from Buttaravoli & Stair: COMMON SIMPLE EMERGENCIES
 Longwood Information LLC 4822 Quebec St NW Wash DC
 1.202.237.0971 fax 1.202.244.8393 electra@clark.net
 ----------------------------------------------------