Author: Katie Colton, MD (EM Resident Physician, PGY-2, NUEM) // Edited by: Quentin Reuter, MD (EM Resident Physician, PGY-3, NUEM) // Expert Commentary: Matt Levine, MD
Citation: [Peer-Reviewed, Web Publication] Colton K, Reuter Q (2017, January 31). Nibbles & Bits: Management of Dog Bite Wounds [NUEM Blog. Expert Commentary By Levine M]. Retrieved from http://www.nuemblog.com/blog/dog-bites
Introduction
Every year in the United States, there are 2-5 million annual animal bites that present to emergency departments (ED), approximately 1% of all ED visits (1, 2). Most bite injuries seen in the ED are inflicted by dogs (60 to 90 percent), with the remainder caused by cats (5 to 20 percent), rodents (2 to 3 percent), humans (2 to 3 percent), and rarely, other animals (3).
The Case
A 23 year-old male presents to the ED with a dog bite to the cheek 6 hours post injury. His vital signs are normal. Physical exam reveals a 3cm gaping laceration to the cheek with minimal active bleeding; there is no bony or muscle disruption appreciated. Should you close his wound?
To close or not to close?
Some elements of wound care remain standard – vigorous irrigation, debridement of nonviable tissue, and antibiotic coverage when appropriate. The classic teaching is that bite wounds should not be closed due to concern for infection; however, several studies have challenged this dogma, particularly in low-risk wounds and patients.
Here is the crux of the issue: should this wound be closed? It is widely accepted that wound closure will improve the cosmetic outcome, but what is the increased risk of infection associated with closing a dog bite injury? The following four papers delve into the infection risk of primary closure.
Maimaris et al: This was a prospective randomized trial in which 169 dog bites were managed by leaving the wound open (92) versus closure with sutures (77). All wounds were thoroughly irrigated but no antibiotics were given to either group. 13 wounds (7.7%) became infected, seven from the sutured group, six from the open group. Wounds repaired > 10 hours post injury had an increased risk of infection. Of note, 9/13 infections were on the hands.
Chen et al: Prospective observational cohort study of 145 mammalian bites that were closed primarily: 88 dog, 45 cat, 12 human. Wounds were irrigated, 81% put on antibiotics. There were 8 subsequent wound infections (5.5%). This is comparable to the clean laceration infection rate typically quoted at 3-7%. Seven of the eight wound infections had been placed on amoxicillin/clavulanate. This paper doesn’t compare these patients to the rest of dog bites patients that were not closed, introducing obvious selection bias.
Rui-Feng et al: This is a large study of immediate primary closure for facial dog bites. It is an RCT with 600 patients randomized to closure versus no closure. Patients only received antibiotics if they presented with evidence of infection. Wounds were aggressively cleaned with a combination of soapy saline, hydrogen peroxide/saline, and iodine/saline solutions for a total of at least 15 minutes. There was no statistically significant difference in wound infection between closed and open wounds (6.3 and 8.3%, respectively).
Paschos et al: This study was an RCT of dog bite wound management. All patients were immunocompetent, presented within 48 hours, and had non-complicated wounds (no damage to deep structures). One group (82 patients) had their wounds sutured, while the other (86 patients) had their wounds left open. All patients had their wounds irrigated under pressure and received amoxicillin/clavulanate. There was no statistically significant difference in the rate of infection (8 vs 6 patients respectively) but a significantly improved cosmetic outcome in patients whose wounds were sutured. Timing was also key with only 4.5% of patients developing an infection if presenting <8 hours vs 22.5% of patients presenting > 8 hours developing an infection. Unfortunately, this study was powered to detect a difference in cosmetic outcome, not infection rate, so take it with a grain of salt.
Wounds NOT to close
- Crush injuries involving damage to deep structures such as muscles and tendons
- Puncture wounds: these have an increased risk of infection due to penetration of deep structures
- Bites involving the hands and feet (due to high infection rates and easily damaged complex structures) (8)
- Wounds more than 12 hours old (or potentially 24 hours old on the face)
- Cat or human bites (consider risk/benefit in facial wounds)
- Wounds in immunocompromised patients
Is the face less risky than other locations? Yes, maybe…
Wu et al: 86 pediatric patients with facial lacerations from dog bites. Wound were repaired in the ED (46%), the OR (51%), and outpatient settings (3%). All patients received antibiotics. No lacerations became infected.
Paschos et al: None of the 41 wounds to the face (sutured or left open) became infected.
It is thought that the large amount of blood flow to the face offers some protection against infection. The cosmetic benefit of closure likely outweighs the risk of infection, but consider having a discussion with patients about the potential harm of closure vs no closure.
So what is the take home?
No randomized controlled trial has shown a statistically significant increase in infection rates with closing dog bites versus leaving them open. There is reasonable evidence that dog bite wounds closed after copious irrigation have better cosmetic outcomes without a higher risk of infection. Debride non-viable tissue and foreign bodies, irrigate under high pressures, and consider prophylactic antibiotics (typically amoxicillin/clavulanate). Wounds presenting >8 hours after injury have a higher risk of infection, so be sure to document a risk-benefit conversation with your patients if you choose to close these wounds.
Summary of Trials Discussed
Expert Commentary
Thank you Dr. Reuter and Dr. Colton for taking an evidence-based approach to address the dogma that dog bite lacerations should not be sutured.
It is unlikely that a single study can definitively answer the question: “Is it safe to close dog bite wounds?” Even the best of RCTs is likely to have some heterogeneity in the patient population such as:
- Age of the wound
- Patient comorbidities
- Antibiotic selection, usage rates, and compliance
- Cleansing techniques
- Wound differences in location, length, depth, and soft tissue damage
- Appropriately matched control groups
However, these studies do reveal useful information to help clinicians address this question. Namely, whatever the true rate of wound infection is after a dog bite, these data reveal a much lower infection rate than one would infer from such a stringent dogma. Also, hands get infected more than faces.
So perhaps the dogma should really be: “Dog bite wounds of the face must be meticulously irrigated and the risk of poor cosmetic outcome vs infection should be weighed when considering closure.” Leaving a gaping dog bite to the face open guarantees a poor cosmetic outcome 100% of the time. Meticulous wound care, closure, and antibiotics will lead to a <100% poor cosmetic outcome (actually far less!). So the choice seems obvious to me. I suspect it will seem even more obvious to most of your patients, since they are usually more concerned about facial scarring than infections.
I would have a detailed discussion with the patient about infection risk, and then recommend closure and antibiotics of their gaping facial dog bite laceration, with very careful return instructions of course. I would have that same conversation, and then recommend against closure of most (but not necessarily all) hand dog bite wounds, since cosmetic outcome of the hand is seldom an issue to the patient. I would be open to shared decision making for those patients with cosmetic concerns about their hand. However, I would not share this decision with the patient if I am convinced it is absolutely contraindicated because the risk of infection of their hand wound is too high (i.e an elderly diabetic vasculopath with a 10 hour old dog bite to the hand with tissue crush). I would make this decision myself.
At the end of the day, closure decisions for dog bite wounds are much like other decision-making scenarios in medicine. Each case is unique. Each patient has his/her own set of co-morbidities, level of cosmetic concern, and even antibiotic allergies. Each wound has its own age, location, length, and depth. There is no binary “yes” or “no” blanket answer to the question: “Should dog bite wounds be sutured?” But in most cases, after carefully considering all of these factors, the answer for each case is quite apparent.
Matt Levine, MD
Assistant Professor
Director of Trauma Services, Department of Emergency Medicine
Northwestern Memorial Hospital
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References
- Weiss HB, Friedman DI, Coben JH. Incidence of dog bite injuries treated in emergency departments. JAMA. 1998 Jan 7;279(1):51-3.
- Hollander JE, Singer AJ, Valentine S, Henry MC.Wound registry: development and validation. Ann Emerg Med. 1995 May;25(5):675-85.
- Endom, EE. Initial Management of Animal and Human Bites. Uptodate.com 2016.
- Maimaris C, Quinton DN. Dog-bite lacerations: a controlled trial of primary wound closure. Arch Emerg Med. 1988;5(3):156.
- Chen E, Hornig S, Shepherd SM, Hollander JE. Primary closure of mammalian bites. Acad Emerg Med. 2000;7(2):157.
- Paschos NK, Makris EA, Gantsos A, Georgoulis AD. Primary closure versus non-closure of dog bite wounds. a randomised controlled trial. Injury. 2014 Jan; 45(1):237-40.
- Wu PS, Beres A, Tashjian DB, Moriarty KP. Primary repair of facial dog bite injuries in children. Pediatr Emerg Care. 2011 Sep;27(9):801-3.
- Kennedy SA, Stoll LE, Lauder AS. Human and other mammalian bite injuries of the hand: evaluation and management. J Am Acad Orthop Surg.. 2015 Jan;23(1):47-57. doi: 10.5435/JAAOS-23-01-47.
- Rui-feng C, Li-song H, Ji-bo Z, Li-qiu W. Emergency treatment on facial laceration of dog bite wounds with immediate primary closure: a prospective randomized trial study. BMC Emerg Med.2013;13(Suppl 1):S2.