IJ
Joined: 26 Nov 2002
Posts: 2544
Location: Boston |
Good stuff. Issues to think about:
Depth:
the deeper the easier something can fester. Abrasions can give you a cellulitis, but are generally easy to clean right away.
Source:
cat worse than dog, because cats transmit more dangerous bacteria (especially pasturella and staph) and inoculate deeper with their needle teeth. Peopel maybe worse. Researchers have isolated 42 bacteria from the human mouth. The average infection has 4-5 isolated; I've heard there've been up to 16 recovered from a nasty wound. nothing suggests your own mouth is safer than another.
Site:
The hand has a lot of interconnecting compartments that allow movement but facilitate bacterial spread like a subway. The forearm is more tightly packed with meat and gristle that present barriers. Illustrated somewhat by this case?
Joints are vulnerable because they can't open and drain, and neither their space nor the cartilage that makes up the bone contact points nor the capsule around it are well vascularized. Infection fighting cells can't get in there well.
Vaccination:
rabies for pets may be an issue. With any wound, an extra tetanus never hurt anyone. In general, go get another unless you're darned sure when you got your last and it was recent (depends on the wound how much so, but if the wound is concerning you should be at the doc's anyway).
The odds.
We've all had human bites to our cheeks, lips and most of us have sucked on a wound, generally without any difficulty. The studies I'll mention are limited because they only assess injuries that people bring in. Lots of minor abrasions never see a doctor and do quite well. Do they therefore all need antibiotics?
"If for any reason you get a bite wound or hurt yourself on someone's teeth (however that may happen), seek medical attention immediately. You need prophylactically to be put on a broad-spectrum antibiotic AT ONCE."
This is genreally good advice, and the sooner a wound is irrigated and antibiotics are in the bloodstream, the better. However it's not absolute for everyone; a good online resource for MDs (up to date) notes:
"Antibiotic prophylaxis — Some patients present early after being bitten and before there is evidence of infection. It is not clear that such patients require antibiotics. A prospective, double blind, placebo-controlled trial found that infection rates were low, with or without antibiotics (combination of cephalexin and penicillin), in 127 immunocompetent adults with low-risk wounds who presented within 24 hours of sustaining a human bite [10]. Low-risk wounds were those that only involved the epidermis and did not involve the hands, feet, or skin overlying joints or cartilaginous structures.
In comparison, antibiotic prophylaxis was beneficial in a small randomized trial of human bites involving the hand [11]. This finding is consistent with a meta-analysis from the Cochrane database [12]. Using data from the above trial of human bites and three trials of dog bites involving the hand, antibiotic prophylaxis significantly reduced the rate of infection (2 versus 28 percent with placebo, odds ratio 0.10, 95% CI 0.01-0.86). A limitation to these observations is that most of the studies were small and/or methodologically deficient.
In addition to hand bites, antibiotic prophylaxis is also recommended in selected other high-risk bites. These include:
Deep puncture wounds
Wounds requiring surgical debridement
Older patients
Immunocompromised patients
A bite wound near or in a prosthetic joint
Bite wound in an extremity with underlying venous and/or lymphatic compromise (eg, following mastectomy)
If patients are to receive antimicrobial prophylaxis, the first dose should be given parenterally, if feasible, to obtain effective tissue levels as early as possible. If parenteral therapy cannot be given, appropriate oral antibiotics should be given and continued for at least three to five days [1,11]."
Here's the abstract from that prophylaxis paper. Note that HAND BITES WERE EXCLUDED as being too high risk not to treat:
TI Low risk of infection in selected human bites treated without antibiotics.
AU Broder J; Jerrard D; Olshaker J; Witting M
SO Am J Emerg Med 2004 Jan;22(1):10-3.
To assess the need for antibiotics in low-risk human bite wounds, a prospective, double-blind, placebo-controlled study involving 127 patients presenting with low-risk human bite wounds over 2 years to a 40,000 visit per year major academic ED was performed. Low-risk bites penetrated only the epidermis and did not involve hands, feet, skin, overlying joints, or cartilaginous structures. Exclusion criteria included age less than 18 years, puncture wounds, immunocompromise, allergy to penicillin or related compound, or bites greater than 24 hours old. Patients were randomly assigned to receive either a cephalexin/penicillin combination or placebo. One hundred twenty-five patients completed the study. Infection developed in 1 of 62 patients receiving placebo (1.6%, 95% confidence interval CI, 0-7.3%). Infection developed in 0 of 63 patients receiving the cephalexin/penicillin combination (0%, 95% CI, 0-4.6%). Antibiotic treatment of some low-risk human bite wound could be unnecessary. Infection rates appear similar in low-risk human bite wounds whether treated with antibiotics or placebo.
Note the difference when you study hand wounds, albeit in smaller numbers:
TI Management of early human bites of the hand: a prospective randomized study.
AU Zubowicz VN; Gravier M
SO Plast Reconstr Surg 1991 Jul;88(1):111-4.
A prospective, randomized study was undertaken to determine if mechanical care of early human bites alone is sufficient therapy in the compliant patient or if prophylactic antibiotics (oral versus parenteral) are indicated. Beginning in June of 1985, patients presenting with human bites of the hand were entered into the study if (1) the bite was less than 24 hours old, (2) the patient was free of infection, (3) the bite did not penetrate the joint capsule, and (4) there was no injury to tendon. Forty-eight patients were ultimately segregated into one of three study groups after standardized ER mechanical wound care. Fifteen patients received an oral placebo, with 7 developing infection (46.7 percent). Sixteen patients received an oral antibiotic, and 17 patients received parenteral antibiotics. No infections were found in either of these latter groups. The results statistically substantiate that mechanical wound care alone is insufficient therapy. Oral antibiotics appear to be equal to intravenous antibiotics for prophylaxis. From a cost-benefit standpoint, vigorous cleaning, debridement, and coverage with a broad-spectrum oral antibiotic are adequate care for an uncomplicated bite in the compliant patient.
Here's the take from the infectious disease society of america, 2005 practice guidelines:
"Animal bites account for 1 percent of all emergency department visits, and dog bites are responsible for 80 percent of such cases. ...cat and dog bites contain an average of 5 different aerobic and anaerobic bacteria per wound.... The decision to administer oral or parenteral antibiotics depends on the depth and severity of the wound and on the time since the bite occurred. Patients not allergic to penicillin should receive treatment with oral amoxicillin-clavulanate or with intravenous ampicillin-sulbactam or ertapenem (B-II), because agents such as dicloxacillin, cephalexin, erythromycin, and clindamycin have poor activity against Pasteurella multocida. Although cefuroxime, cefotaxime, and ceftriaxone are effective against P. multocida, they do not have good anaerobic spectra. Thus, cefoxitin or carbapenem antibiotics could be used parenterally in patients with mild penicillin allergies. Patients with previous severe reactions can receive oral or intravenous doxycycline, trimethoprim-sulfamethoxazole, or a fluoroquinolone plus clindamycin.
Human bites may occur from accidental injuries, purposeful biting, or closed fist injuries. The bacteriologic characteristics of these wounds are complex but include infection with aerobic bacteria, such as streptococci, S. aureus, and Eikenella corrodens, as well as with multiple anaerobic organisms, including Fusobacterium, Peptostreptococcus, Prevotella, and Porphyromonas species. E. corrodens is resistant to first-generation cephalosporins, macrolides, clindamycin, and aminoglycosides. Thus, intravenous treatment with ampicillin-sulbactam or cefoxitin is the best choice (B-III)"
"HUMAN BITES — Human bite wounds often result from aggressive behavior and are frequently more serious than animal bites. Wounds may be either occlusive injuries, in which the teeth actually bite the body part, or clenched-fist injuries, which occur when the fist of one person strikes the teeth of another. Between 10 and 20 percent of occlusive wounds occur during sexual interactions. Bite wounds in children may be associated with sports-related activity (look for imbedded teeth) but should also alert the clinician to possible child abuse....
The IDSA agrees with Bill on antibiotics (if not the other way around):
"Evaluation and treatment should follow the general principles outlined for animal bites, with irrigation and topical wound cleansing,
except that prophylactic antimicrobials should be given as early as possible to all patients regardless of the appearance of the wound
(show table 6). An expert in hand care should evaluate clenched-fist injuries for penetration into the synovium, joint capsule, and the bone (B-III). These wounds, although often quite small, may extend deeply into the hand tissues, and relaxation of the fist may carry organisms into the deep compartments and potential spaces of the hand. Exploration under tourniquet control may be necessary. Clenched-fist injuries often require hospitalization and intravenous antimicrobial therapy with agents such as (shop talk ensues)."
_________________
--Ian
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