Dog Bites

The goal of this post is to discuss the management of dog bites including current controversies regarding closure of bite wounds and antibiotic prophylaxis.

Epidemiology

  • Dog bites account for 1% of injury related ED visits
  • Dogs comprise up to 90% of reported animal bites
  • Most dog bite victims are children
  • The most common location for dog bites are the extremities, followed by the face
  • Pit Bulls inflict the most bites of any breed by far
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Pit Bull

Wound Management

  • Initial management of wound should be stabilization
    • Direct pressure should be applied to actively bleeding wounds
    • Neurovascular assessment should be performed distal to wound
  • The majority of animal bites are puncture wounds
  • Large dogs are capable of causing crush injury with some bites as powerful as 400 psi
  • Order X-ray if any suspicion of fracture or foreign body!
  • Dog bites are dirty wounds and must be cleaned and sometimes debrided
    • The affected skin should be cleansed
    • The wound should be copiously irrigated with water, normal saline, or dilute providone iodine solution
    • You may want to inject lidocaine around the wound site before irrigating for pain control
  • After cleaning wound, carefully look for injury to underlying structures like fascia, tendon, and bone.

*Controversy*

Should dog bites be primarily closed?

  • The classic teaching is that dog bites should be left open to minimize infection unless the wound is gaping or on the face.
  • Keep in mind that the infection rate for all ED repaired lacerations is 3-7%
  • Primary closure will result in a better cosmetic result
  • A 2014 study titled Primary closure versus non-closure of dog bite wounds. A randomized controlled trial suggested that there was significant difference in infection rates between primary closure and secondary intent
    • 168 patients randomized to primary closure and secondary intent
    • All patients had wound cleaned with high pressure irrigation and providine iodine, and were given Augmentin prophylaxis
    • Overall infection rate: 8.7%
    • Primary closure infection rate: 9.7%
    • Secondary intent infection rate: 6.9%
    • Difference between groups not statistically significant
    • If wound was closed <8 hours: 4.5% infection rate
    • If wound was closed >8 hours: 22.2% infection rate
  • Based on this study it seems to be good practice to close dog bites if they are less than 8 hours old because they have a low risk of infection and yield a better cosmetic result. It also seems to be good practice to not close wounds greater than 8 hours old due to the high risk of infection. Other factors should be considered when deciding whether to close or not, including size, tissue loss, location, and comorbid conditions.

 

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Dog bite puncture wound

 

 

 

 

 

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Dog bite with fracture
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Dog bite 2 months after primary closure

 

 

Infection

  • Pastuerella is the most common pathogen in dog bites
  • 64 species of bacteria have been isolated from dog mouths and many infections are polymicrobial
  • Amoxicillin-clavulonate (AKA Augmentin, AKA “Dogmentin”) is the antibiotic of choice

*Controversy*

Should all dog bites be prophylaxis with antibiotics?

  • Classic teaching is that all dog bite patients should receive prophylactic antibiotics
  • A 2008 paper titled Antibiotic prophylaxis for mammalian bites (review) examined this question
    • Meta analysis of six dog bite studies comparing antibiotic prophylaxis with placebo
    • In these studies, the majority of wounds were left to heal by secondary intention
    • Prophylactic antibiotic infection rate: 5.5%
    • Placebo infection rate: 4%
    • The difference in infection rates was not statistically significant
    • The paper also looked at infection rates by bite location and included human and cat bites along with dog bites. Hand bites with antibiotic prophylaxis had an infection rate of 2%, while hand bites with placebo had an infection rate of 28%.
  • The paper suggests that antibiotic prophylaxis of dog bites is not necessary, but maybe it should be considered for bites on the hand. There is not enough data change practice regarding wound closed by primary intention
  • Once again, would size, shape, patient comorbidities, and other factors should be taken into account
  • Clinical manifestations of bite wound infections may include fever, erythema, swelling, purple not discharge and lymphangitis
  • Complications of infection include abscess, septic arthritis, osteomyelitis, and bacteremia
  • If infection is suspected, remove sutures, draw wound cultures and blood cultures, and start empiric antibiotics
  • Ask about tetanus vaccine history
    • Give tetanus vaccine if patient has not received dose within last five years
  • Dogs in the US very rarely carry rabies. Rabid dogs much more common in Asia and Africa
    • If the dog is suspected to have rabies, immediately begin rabies prophylaxis with both rabies vaccine and immunoprophylaxis
    • If the dog is not suspected to have rabies, it should be observed for the next ten days if possible, to look for development of rabies symptoms. Decision to initiate prophylaxis should be made based on risk. (Rabid dogs more common in Southwestern United States, head and neck bites allow rabies to reach CNS more quickly)

ABX

bite2
Hand infection following dog bite

PTSD

  • Over half of pediatric dog bite victims develop symptoms of PTSD 2-9 months after sustaining the injury

Laws and Regulations

  • Many jurisdictions in the US require physicians to report dog bites
  • Rabies is a reportable disease and any suspected animals should be sent for testing

 

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References

  1. Ellis, Robert, and Carrie Ellis. “Dog and cat bites.” American family physician90.4 (2014).
  2. Chen E et al. Primary Closure of Mammalian Bites. Acad EM 2000; 7(2): 157- 162.
  3. Medeiros IM, Saconato H. Antibiotic prophylaxis for mammalian bite (Review). Cochrane Database of Systematic Reviews 2008 (3);
  4. Fleisher, Gary Robert. “The management of bite wounds.” New England Journal of Medicine 340 (1999): 138-140.
  5. http://rebelem.com/myths-management-dog-bites/
  6. http://www.uptodate.com/contents/initial-management-of-animal-and-human-bites?source=search_result&search=dog+bite+wound&selectedTitle=1~150#H27

Matthew Turner

MS4

Columbia University College of Physicians and Surgeons

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