Hi Everyone,
I hope you had a wonderful holiday with loved ones! Today's POTD addresses a subject matter that I hope everyone avoided while at home with family fighting over food and attention: dog bites. Fur babies are well known to the streets of NYC, and sometimes their bite marks can find their way into our ED. How do we manage these bites? And what does the evidence say we should be doing?
The Current Dogma of Antibiotics
The classical practice we learn in EM training is to give antibiotics for any dog bite given the copious amounts of bacteria swirling around in a dog's mouth. The easy memory trick is to give Augmentin aka Dogmentin for any dog bite wound. But is this really helping prevent infection? See the studies below for evidence
Coyle, C., Shi, J., & Leonard, JC. (2024). Antibiotic prophylaxis in pediatric dog bite injuries: Infection rates and prescribing practices. Journal of the ACEP Open: Antibiotics did not change the rate of infection in pediatric dog bite injuries, with overall infection rate of about 5.2%. TLDR of the paper: a 2024 retrospective study demonstrated prophylactic antibiotics did not affect the infection risk for dog bites.
Quinn, JV., McDermott, D., Rossi, J., Stein, J., & Kramer, N. (2010). Randomized control trial of prophylactic antibiotics for dog bites with refined cost model. Western Journal of Emergency Medicine: Antibiotics did not reduce the rate of infection from dog bites. There is separate analysis of the paper that states giving antibiotics is cost effective if the infection rate is greater than 5%, but that's not the primary focus for us. TLDR of the paper: a 2010 RCT demonstrated prophylactic antibiotics did not affect the infection risk for dog bites.
Saconato, H., & Medeiros, I. (2001). Antibiotic prophylaxis for mammalian bites. Cochrane Database Systematic Review: Antibiotics did not reduce the rate of infection from dog or cat bites. However, antibiotics for hand wounds specifically, which have higher infection rates at baseline, did appear to decrease the infection rate, with a number needed to treat of 4. TLDR of the paper: a 2001 systematic review demonstrated prophylactic antibiotics did not affect the infection risk for dog bites, with the exception of bites on the hand.
Cummings, P. (1994). Antibiotics to prevent infection in patients with dog bite wounds: a meta-analysis of randomized trials. Annals of Emergency Medicine: Antibiotics did reduce the rate of infection from dog bites. Relative risk of infection with antibiotics was 0.56. TLDR of the paper: a 1994 meta-analysis demonstrated prophylactic antibiotics did decrease the infection risk for dog bites.
So a 1994 meta-analysis, which seemingly included similar studies to a 2001 systematic review, came to the opposite conclusion... how? There appears to be one study that is the major difference between the two reviews, which is below.
Brakenbury, PH., Muwanga, C. (1989). A comparative double blind study of amoxicillin/clavulanate vs placebo in the prevention of infection after animal bites. Archives of Emergency Medicine: Infection occurred in 33% of patients given augmentin vs. 60% of patients given placebo, a staggering and statistically significant result that suggests antibiotics did reduce the rate of infection. However, the paper includes a loose definition of what was classified as infection, stating "infection was defined as the presence of erythema and tenderness beyond that expected 24 hours after the injury with or without purulent discharge, cellulitis or lymphangitis." TLDR of the paper: a 1989 RCT demonstrated that augmentin did decrease the infection risk in dog bites, but with a lenient definition of infection.
This paper alone is what drove the statistical significance of the 1994 meta-analysis. So, to put it plainly, if you believe in the definition of infection stated by this 1989 paper and the significance of this single RCT, give antibiotics! If you don't, the evidence would support your decision to hold off on prophylactic antibiotics. When considering antibiotics, also think about side effects, allergies, resistance, and shared-decision making.
Getting Closure on Closure
So we have figured out our antibiotics, but what about suturing the wound? The thought is that suturing close these bacteria-prone wounds makes it a nidus for abscess formation. Does that play out in the literature? There are a few studies that address this.
Paschos, NK., Makris, EA., Gantsos, A., & Georgoulis, AD. (2014). Primary closure versus non-closure of dog bite wounds. A randomised controlled trial. Injury: There was no difference in infection rate between primary closure vs. non-closure. Whether or not the patient presented before or after 8 hours did affect infection risk, but closure played no role. Cosmetic outcome, however, was better in primary closure group. Important groups that were excluded from the study were immunocompromised patients and complex wounds. TLDR of the paper: a 2014 RCT demonstrated that closing dog bite wounds did not change infection outcomes, but it did improve cosmetic outcomes.
Wu, PS., Beres, A., Tashjian, DB., & Moriarty, KP. (2011). Primary repair of facial dog bite injuries in children. Pediatric Emergency Care: There were no infections in a group of pediatric patients with dog bite wounds to the face who had their laceration repaired either in the ED or the OR. TLDR of the paper: a 2011 retrospective study demonstrated that closing dog bite wounds did not change infection outcomes, either in the ED or the OR.
Chen, E., Hornig, S., Shepherd, SM., & Hollander, JE. (2000). Primary closure of mammalian bites. Academic Emergency Medicine: There was a 5.5% change of developing infection in a group of patients who had primary closure of their dog bite wound and received prophylactic antibiotics. TLDR of the paper: a 2000 observational study demonstrated that closing dog bite wounds was associated with a similar baseline infection risk to that seen in other studies.
Maimaris, C. & Quinton, DN. (1988). Dog-bite lacerations: a controlled trial of primary wound closure. Archives of Emergency Medicine: Suturing dog bite wounds neither increased infection rate nor improved cosmetic outcomes, and no prophylactic antibiotics were given. TLDR of the paper: a 1988 RCT demonstrated that closing dog bite wounds did not change infection outcomes.
It looks like the current evidence is suggesting that primary closure is safe when it comes to infection risk in dog bites, but to take into account the clinical characteristics of your patients (i.e. immunocompetence), characteristics of the wound (i.e. complexity and depth), and cosmetic preferences.
Keeping UpToDate With The Dog Bites
This really goes against how most of us have been practicing: antibiotics and leave open. When it comes down to it, the evidence really does point one way: no antibiotics and close. That seems radical to me. And that's what UpToDate seems to agree with at the moment; the algorithm does in fact give the option of antibiotics or no antibiotics (in very particular cases) and closing or not closing (in other very particular cases), but there's currently no pathway that is suggesting no antibiotics and closing.
