Elise Patel, D.O. FM PGY-3
The Idea: This prospective randomized control trial sought to evaluate whether the use of point-of-care ultrasound (POCUS) in conjunction with incision and drainage (I&D) would improve uncomplicated abscess treatment outcomes. The hypothesis was that using POCUS in I&D for uncomplicated abscess would decrease the failure-rate of treatment which was defined by the need for a second I&D procedure within the ten days following the initial procedure.
The Study: Over the course of two years, 125 patients presenting to an academic institution with uncomplicated abscess were enrolled in the study and randomly assigned to either physical exam alone (control group) or physical exam with the addition of POCUS (experimental group) prior to I&D. After loss to follow-up, the final sample size of patients was 107. The physicians performing the procedures were emergency medicine physicians (residents and attendings) who had comparable experience in performing incision and drainage and soft-tissue POCUS as evidenced by the number of procedures they had logged prior to participation in the study. The physical-exam-only group had the abscess measured either by area of fluctuance or area of induration if fluctuance was absent. If there was doubt of the presence of abscess, ultrasound was utilized to confirm the presence of abscess, but the details of the ultrasound were kept from the physician performing the incision and drainage. The POCUS arm was not standardized in terms of how POCUS was utilized in the treatment course. There were three treatment strategies:
Using POCUS prior to the I&D to visualize the abscess, but not using during or post-procedure,
Using POCUS dynamically: before, during, and post-procedure,
Using POCUS pre-procedure and post-procedure, but performing the I&D itself without POCUS.
The patients and physicians performing the initial encounter were not blinded to which treatment arm a patient was included within, but the research staff and physicians performing the follow-up exams were blinded. The individual physicians performing the I&Ds were given liberty to decide whether to place packing and prescribe antibiotics. The patients were re-evaluated in-person by a blinded doctor on post-op day two or three, and blinded research staff reached out to patients via telephone and asked a standardized list of questions on post-op day seven through fourteen.
The Findings:
The primary outcome evaluated was the need for repeat I&D with purulent drainage expressed at the ten-day mark which was considered a failure of therapy. The total failure rate of the patients enrolled in the study was 10.3% [5.7-17.6% 95% CI] which was comparable to the rate previously given in the literature per the authors of this article. The failure rate in the POCUS group was 3.7%, and the failure rate in the control group was 17%, and the difference between the groups was 13.3% [0.0-19.4%]. The odds ratio was statistically significant with an odds ratio for failure of therapy of 0.19 in the ultrasound group [CI 0.04-0.97]. The secondary outcomes evaluated were need for additional antibiotics and symptoms at follow-up. There was no statistical significance between the groups for either of these outcomes.
Critiques:
The randomized control study is the first of its kind trying to evaluate the efficacy of POCUS in the treatment of abscesses, and the researchers did an excellent job in explaining their process and the methods taken to blind the evaluation of the outcomes to researcher bias. They also selected uncomplicated abscess patients which helped to select a more controlled population and also prevent harm from delay of care in the case of unstable patients. The authors reported that the use of POCUS improved outcomes compared to I&D with physical exam alone, but the confidence interval included zero which means that it could have potentially not been a statistically significant difference. The odds ratio did however reveal statistically significant benefit in outcomes with the use of POCUS. The sample size was the minimum needed to power the study, so it seems that the small sample size may have affected the ability of the study to demonstrate statistical significance. The control group had more men and more IVDA users which may have influenced the results. The method of POCUS was not standardized which could also have impacted the results of the study. In order to have a study that can clearly demonstrate the benefits of POCUS in treating abscesses, there needs to be additional research done with a larger sample size and more standardization of the methods and the two patient groups.
The Takeaway:
Utilization of POCUS in the performance of bedside I&D likely improves treatment outcomes, but further studies with larger sample sizes need to be performed to confirm these results.