Managing simple cutaneous abscesses was as straightforward a complaint as there was in emergency medicine — until recently. Incision and drainage was all that was required. Packing, irrigation, and antibiotics had all but been discredited by those in the evidence-based know. At least that was until someone went and studied it.
A recent trial by Talan, et al., examined the utility of enteral antibiotic therapy when added to incision and drainage (I&D) for managing simple cutaneous abscesses. (New Engl J Med 2016;374:823.) The authors randomized 1,265 patients presenting to the emergency department with cutaneous abscesses to I&D and placebo or I&D and a seven-day course of trimethoprim-sulfamethoxazole. Patients randomized to the seven-day course of antibiotics had a clinical cure rate of 80.5 percent vs. only 73.6 percent in the patients who received I&D alone.
The use of trimethoprim-sulfamethoxazole was also found to be superior in a number of secondary endpoints, resulting in lower rates of subsequent surgical drainage procedures (3.4% vs. 8.6%), skin infections at new sites (3.1% vs. 10.3%), and infections in household members (1.7% vs. 4.1%) seven to 14 days after the treatment period. These improvements in cure rates came at the price of a small increase in gastrointestinal distress, with a 6.5 percent absolute increase in the rate of GI complaints in patients randomized to receive trimethoprim-sulfamethoxazole.
This was a methodologically rigorous trial, with statistically significant results. Its findings may lead to a global shift in practice toward prescribing antibiotics for all simple cutaneous abscesses, but is such a change in practice justifiable, despite the strength of these findings?
This was a pragmatic trial, in which the authors enrolled all patients over 12 presenting to the ED with surgically confirmed abscesses larger than 2 cm in diameter conducive to outpatient treatment. Exclusion criteria were minimal, and this practical design ensured a heterogeneous cohort of abscesses, a large portion of which had significant concomitant cellulitis. The median area of surrounding cellulitis was 20 cm2, with approximately 20 percent of the cohort presenting with a surrounding cellulitic area of greater than 75 cm2. Eleven percent of the patients had diabetes, and 18 percent had a fever in the days leading up to their presentation to the ED.
Resolved with I&D
Essentially, this was not a cohort made up entirely of simple cutaneous abscess. It contained a large quantity of infections that would likely benefit from antibiotics. Despite this, the majority of patients experienced resolution of their abscess with I&D alone. Very few of the patients deemed a clinical failure required further medical therapy; their abscesses ultimately resolved with no further treatment. There was only a 5.6 percent increase in the number of patients who required additional surgical drainage and a seven percent increase in the number of patients started on additional antibiotics at the follow-up visit between seven and 21 days.
The pragmatic design of this study makes for an easy translation to our general ED population. Unfortunately, this very same pragmatism limits a finer, more granular interpretation of the data. In a population that includes abscesses of various shapes and sizes with varying degrees of surrounding cellulitis, a seven-day course of trimethoprim-sulfamethoxazole provides a moderate degree of clinical value above I&D alone. But it can also be said that the vast majority of patients presenting with cutaneous abscesses will fare equally as well with simple surgical drainage.
The question remains, are the patients who failed I&D alone clinically predictable? Were these the patients who had significant surrounding cellulitis, systemic symptoms (fever, malaise), or baseline immune-compromised conditions (diabetes, etc.)? Furthermore, this trial fails to address the more subtle unattended consequences of empirically treating all simple cutaneous abscesses with trimethoprim-sulfamethoxazole. This trial was severely underpowered to assess the rate of rare reactions such as Steven-Johnson's syndrome associated with the use of trimethoprim-sulfamethoxazole. (Arch Dermatol 1990;126:43.) Nor can it evaluate the effects such a change in practice will have on current antibiotic resistance.
Talan, et al., clearly demonstrate that the majority of patients with simple cutaneous abscesses will improve with I&D alone. The ones who do fail are likely clinically predictable upon presentation. Most will resolve with no further management, with a small minority requiring further surgical drainage or the addition of antibiotics. For the well-appearing patient presenting with a simple cutaneous abscesses with minimal cellulitis, a trial of I&D alone seems reasonable.
Clinical medicine is far more complex than the yes-no dichotomy mandated by frequentist methodology. And while the Talan, et al., trial has provided us with clear evidence that some abscesses will benefit from antibiotics, it does not demonstrate that all do.
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