Answers for June 2015’s Clinical Image

2015_06

Human bite

While seemingly innocuous, human bites pose a great infection risk due to the polymicrobial oral flora of the human mouth. Most common microbes found from bite cultures include Streptococcus, Staphylococcus and Eikenella species with Streptococcus anginosus being the most common. Infection can lead to septic arthritis especially of MCP joint in closed fist injuries. There has been reported cases of injection with herpes and hepatitis but these are rare.

Assessment: includes thorough examination of wound site including: size, shape, location, depth of penetration, drainage, etc. Especially and specifically important in bite wounds include:

  • Timing of injury is important in dictating management
    • For fresh human bites ranging from minutes to hours, antibiotic therapy is not as important if irrigation is thorough and prompt
  • Assess for full range of motion of affected digit
  • Examine the bite in the position that it occurred to reveal injuries that may otherwise be concealed.  ie a fist w/ fingers fully flexed
  • MCP wounds: from closed-fist injury. Check for loss of knuckle height and integrity of extensor tendons
  • Chomping injuries of the finger: Check integrity of extensor and flexor tendons
  • Ear/nose bites: Loss of tissue and integrity of cartilage. Be sure to consult ENT

Labs and Imaging

  • Blood work: usually unwarranted in these scenarios unless you suspect the patient is septic
  • Imagining: radiographs are especially important in clenched fist and penetrating wounds to assess for fracture, foreign bodies (like retained tooth fragments) or osteomyelitis (in cases of late presentation).
    • Sidenote: for animal bites- it’s important to do a radiograph no matter the circumstance since animal teeth may fall out due to poor dental hygiene

 Management

  1. Wound cleaning: irrigate wound with saline or tap water
    • Tap water: run under high pressure sink
    • Saline: use a 30-60cc syringe through a decent angiocath OR 1L NS bag on a pressure bag w/ an 18g angiocath at the end and keep pumping the pressure bag
  2. Surgical debridement if necessary: may cause cosmetic defects when healing
  3. Wound closure: Do no close wounds to hands, puncture wounds, infected wounds or old wounds (greater than 12 hr) to decrease risk of infection. Head and neck wounds may be closed if cosmetic outcome is a concern. High vascularity in face and neck helps with healing. However, in these cases prophylactic antibiotics are necessary.  Stitches should be simple, interrupted and still allow for drainage.
  4. Administer tetanus shot if necessary: although risk of tetanus infection is low
  5. Prophylactic antibiotics:
    • Bites that do not penetrate the epidermis probably do not need antibiotic therapy unless they involve hands, feet, or joints or cartilaginous structures
    • Bites that break through the epidermis, involve joints, or cartilaginous structures is in a grey area for antibiotic prophylaxis- should be administered but evidence is not strong
    • Antibiotic prophylaxis should be giving with bites to the hand due to high risk of infection. If bite is less than 2 hours old, antibiotic treatment might not be necessary. If bite is more than 12 hours old, antibiotics should be given.

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From: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2776367/

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