Ultrasound for Evaluation of Peritonsillar Abscess

TaReva Warrick-Stone, DO | FMEM PGY3

The Article:

Impact of Transcervical Ultrasound for the Diagnosis of Pediatric Peritonsillar Abscesses on Emergency Department Performance Measures. Zhao et al. (2020). J Ultrasound Med. 39: 715-720.

The Idea:

To determine the effects of adopting transcervical US as the initial imaging study to diagnose pediatric peritonsillar abscesses on median ED length of stay as an indicator of performance.

The Study: 

A retrospective cohort study of all ED patients who had a CT or US scan performed on the neck region for suspected peritonsillar abscess at one freestanding tertiary care children’s hospital between Jan 2009 - Apr 2017. The institution adopted a protocol to use transcervical US first for the evaluation of PTAs in May 2013. The ED length of stay before and after implementation of the US-first approach were extracted from the EMR, along with imaging study performed and presence or absence of PTA on imaging. For patients with CT scans, they estimated the radiation dose, and for all patients, they estimated the amount billed and the amount reimbursed. As a balancing measure, they determined whether there were return patient visits within 2 weeks of the index ED visit related to head and neck infections or pain. All US studies were performed in the radiology department by board-certified sonographers trained in the transcervical technique. Images were reviewed and interpreted by pediatric radiologists. The CT studies were done with contrast and were obtained with a 64-slice system either in the ED or in the radiology department, and images were interpreted by pediatric radiologists. All abnormal findings were discussed between the ED physician and an ENT consultant regarding surgical or medical management.

The Findings:

Of the 962 ED patients who had neck imaging studies, 387 were included in the study; 286 were evaluated with US and 101 were evaluated with CT. None of the patients who had US scans required a subsequent CT scan. There were similar rates of positive results for CT (36, 35.6%) and US (99, 34.6%). The mean length of stay was significantly less for patients who had US (347 +/- 145 minutes) compared to CT (426 +/- 171 minutes), with an absolute difference of 79 minutes (95% CI, 44, 113 minutes). The difference was more pronounced in patients with negative results. Patients with negative CT results had a mean LOS of 115 minutes longer than in the US group (95% CI, 70, 160 minutes). The difference between the groups for patients with positive results was 12 minutes (95% CI, –40, 63 minutes), which was not statistically significant. Patients who were evaluated by US scan did not have a statistically significant increased rate of return visits within 2 weeks, 8.0% compared to 5.9% (P = 0.66). The median effective radiation dose of a neck CT scan was estimated at 3.9 mSV compared to no radiation exposure for US. At the time of this study, the mean billed cost of a neck CT scan was $2846, and the hospital was reimbursed on average $1138. The mean billed cost of a transcervical US scan was $1208, and the hospital was reimbursed on average $483 for each study. After implementation of the protocol, significantly more neck US (6.5) were ordered per month than neck CT (2.1) prior to the protocol with a mean difference in studies of 4.4 per month (95% CI, 3.5, 5.4).

The Takeaway:

A transcervical US-first strategy for the evaluation of pediatric peritonsillar abscess is associated with an overall decrease in the ED length of stay, however, this difference was only true for patients who had negative study results as there was no difference in LOS for those patients who were found to have PTAs.

Abscess Incision and Drainage With or Without Ultrasonography: A Randomized Controlled Trial

Elise Patel, D.O. FM PGY-3

The Article: Gaspari, R., Sanseverino, A. and Gleeson, T., 2019. Abscess Incision and Drainage With or Without Ultrasonography: A Randomized Controlled Trial. Annals of Emergency Medicine, 73(1), pp.1-7.

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:

1. Using POCUS prior to the I&D to visualize the abscess, but not using during or post-procedure,

2. Using POCUS dynamically: before, during, and post-procedure,

3. 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.

Bedside Evaluation of Femoral Nerve Block Versus Parenteral Opioids in Hip Fractures

Jeff Holoman, D.O. | EM/FM PGY 3

The Article:

Beaudoin, Francesca L., et al. “A Comparison of Ultrasound-Guided Three-in-One Femoral Nerve Block Versus Parenteral Opioids Alone for Analgesia in Emergency Department Patients With Hip Fractures: A Randomized Controlled Trial.” Academic Emergency Medicine, vol. 20, no. 6, 2013, pp. 584–591., doi:10.1111/acem.12154.

The Idea:

To compare the efficacy of US guided three-in-one femoral nerve blocks to standard treatment with IV morphine for pain control in elderly patients with hip fractures in the Emergency Department.

The Study:

A blinded, randomized control clinical trial at Rhode Island Hospital which included all patients over the age of 55 with radiographic findings of a femoral neck fracture or intertrochanteric fracture. Identified patients were also neurovascular intact, in moderate to severe pain (numerical pain rating scale > 5), and were able to consent to the study. After consent, the patients were randomized using sequentially numbered cards in sealed envelopes to one of two groups: femoral nerve block plus morphine (FNB) or standard care, morphine alone + sham injection (SC). Each participant in the FNB group received an US-guided femoral nerve block performed by physicians who had prior experience performing the technique and underwent a 30-minute training session to standardize the approach. FNB procedures were standardized according to patient positioning, injections of 25mL of bupivacaine, as well as holding manual pressure post injection for 5 minutes, 1 cm below the injection site. Each patient in the SC group received a sham injection that was intended to blind the participant and the treating physician. Set up and procedure of the SC group was also standardized to entail a 3mL 0.9% injection of saline, given subcutaneously over 5 minutes. Following administration of the FNB or sham injection, it was then left to the physician caring for the patient to choose analgesia dosing and frequency for the remainder of their ED stay. To assess the primary goal of pain relief, a patient reported pain scoring system was used. The summed pain-intensity difference (SPID) was used over a 4 hour study period. Trained professionals then asked participants to report their pain using an 11 point numerical rating scale (NRS), 0 being “no pain,” up to 10 being “worst pain imaginable.” Repeat measurements were then taken at the 15 minute, 1, 2 and 4 hour periods after the study procedure was performed. A pain – intensity difference (PID) was calculated at each time point. The PID was calculated as the change from baseline NRS for each measurement in time for the two groups. Secondly, review of the dose and amount of opioids used were measured to assess if those in the FNB group received less opioids. This secondary efficient variable was the total amount of opioid received after the study procedure, while the patient was in the Emergency Department. Rescue analgesia and SPID measurements for each group were also tested and compared.

The Findings:

Sixty-four patients were screened for the study with 38 being enrolled, with two patients from each arm dropping out after randomization. Eighteen patients in each arm completed the study. There was no significant difference between treatment groups with respect to age, sex, fracture type and vital signs or length of stay in the ED. There was also no significant difference between pre-enrollment analgesia or baseline pain intensity. Of note, there was a significant decrease in pain intensity in the patients in the FNB group over time ( p < 0.01 ), whereas those in the SC did not have any change in pain reduction over time ( p = 0.882 ). The SPID over 4 hours was significant greater in the FNB group ( 11.0 vs. 4.0). In addition, a significantly higher proportion of individuals in the FNB group achieved as least 33% reduction in pain intensity over time, 33% SPID, (12 vs. 0). 1/3 of the patients in the SC group had a negative %SPID, indicating that they had increasing pain throughout the study period. Regarding the second measure of the study, opioid use, patients in the FNB group received far less than the SC group (0.0 to 6.0 mg vs. 0.0 to 21.0 mg). Five patients in the FNB group received rescue analgesia versus 14 patients in the SC group. There was no significant association between dose of rescue analgesia and %SPID in the FNB group (r=-.-7, r^2=0.005) and only a weak association in the SC group (r=0.20 , r^2=0.04). There were no differences in the adverse effects of hypotension, hypoxia, or nausea/vomiting.

The Takeaway:

Usage of bedside US guided femoral three-in-one nerve blocks seemingly provides superior pain relief in comparison to parenteral opioids alone and requires less rescue analgesia while in the Emergency Department.

Review: Ultrasound-Guided LPs

Katelyn Hanson, DO

The Article: Millington S, Silva Restrepo M, Koenig S. Better With Ultrasound, Lumbar Puncture. CHEST 2018; 154(5):1223-1229

Overview: Lumbar puncture is a common procedure performed in both critical care and emergency medicine, and is typically associated with a high rate of success and favorable risk profile. However, as procedural ultrasound becomes more widely used in both specialties, it is reasonable to consider using ultrasound guidance to reduce the rate of failure and the risk of complications, especially in patients with difficult surface anatomy. 

Risks and Benefits: The authors of this review state that using ultrasound improves the rate of procedural success, reduces the number of required attempts, and decreases the incidence of specific complications that will be further described next. Ultrasound has been associated with a higher rate of first-pass success and lower risk of failure in all comers. They postulate that reducing the number of failed attempts and there for having fewer needle insertion attempts will lead to less incidence of postdural puncture headaches, back pain, spinal hematomas, epidural abscess and meningitis. They also suggest that injury to deep structures can be prevented by accurately quantifying the depth required to reach the subarachnoid space and avoiding excessive needle depth, and by accurately identifying the appropriate intervertebral spaces of L5-S1, L4-L5, or L3-L4.

Techniques:

#1 Identify Spinous Processes: It is recommended to use the curvilinear probe in the transverse plane with the probe marker position to the left of the screen. The first step is to identify the midline; it is recommended to start with traditional surface land marking by locating the superior aspects of the iliac crests to find the L4 spinous process. In cases where the iliac crests cannot be easily palpated, the authors recommend starting just above the intergluteal crest. The spinous process will appear as a peaked hyperechoic structure with acoustic shadow that will obscure deeper structures. Once the spinous process is identified in the exact middle of the screen, this location should be marked at the transducer midpoint with a skin pen to delineate the patient’s midline. The probe can then be moved cranially and caudally to identify neighboring spinous processes, and these should be marked with a skin pen as well, providing a map of L5, L4, and L3 spinous processes. Between the individual spinous processes will be the interspinous space, in which the hyperechoic spinous process will start to disappear and the hyperechoic articular processes will appear laterally, which is often referred to as the “bat sign.” The location of these articular processes can also be marked with a skin pen, and then a line between these landmarks is made, as well as a line between the superior and inferior spinous processes; the intersection between these two lines may represent the optimal site for needle insertion.

#2 Identify Intervertebral Levels: It is recommended to use the curvilinear probe in the sagittal plane with the probe marker position to the left of the screen. The first step is to identify the midline; see technique one for this part of the procedure. One the spinous processes have been located, the probe is moved caudally to identify the sacrum, which is seen as a roughly horizontal hyperechoic line. Once the sacrum is identified, the probe is moved cranially, and the first spinous process identified will be L5, with the space caudal to it the L5-S1 interspinous space. The process should be repeated for L4 and the L4-L5 interspinous space, and then center the L4-L5 interspace on the ultrasound screen and draw a line across this space with a skin marker. A line between the L4 and L5 spinous processes is also made, and the intersection between these two lines may represent the optimal site for needle insertion. 

In obese patients the spinous processes can be difficult to see from a midline approach. In these patients a paramedian approach can be used, where the procedure begins at the midline and then the probe is moved laterally 2-3cm until a hyperechoic saw-like pattern is seen, which would represent the articular processes. The probe is then moved caudally as described above to identify the sacrum, and then the specific L5 and L4 articular processes can be identified. The probe is then angled toward the midline to identify the lamina and L5-S1 and L4-L5 interlaminar spaces. Again, a line can be drawn horizontally across the interlaminar space, and then a line can be drawn from the 

#3 Estimate Required Depth for Needle Insertion: Using the paramedian approach described above in technique two, with the transducer in the sagittal plane, identify the posterior complex, which includes the ligamentum flavum, epidural space, and posterior dura. This complex will appear as a hyperechoic linear structure just deep to the lamina, and once identified its distance from the skin surface can be measured. The procedure can also be performed in the transverse plane from technique one, by identifying the desired spinous process and then moving the probe cranially or caudally to visualized the intervertebral space; the posterior complex can then be seen just deep to the lamina and its distance from the skin again measured; this value can be compared to the value obtained from the sagittal approach for a better estimate.

#4 Perform an Ultrasound-Assisted LP: Dynamic ultrasound guidance during the procedure is not recommended as it would require the operator to hold the transducer in their off hand during needle insertion, which would make the procedure unnecessarily complicated. After performing a thorough pre-procedural scan, set the set the probe aside and perform the procedure. 

Discussion: Point of care ultrasound has become an integral part of both emergency and critical care medicine. There are many procedures into which incorporating the use of ultrasound has already become the standard of care, and although this is not currently the case for performing lumbar punctures, it stands to reason that using ultrasound to better identify landmarks of the spine could improve patient outcomes, and thus should be considered a useful skill to learn to incorporate into regular practice. For more information, images corresponding to the procedures described above, and videos, see the original article cited above.