Serratus Anterior Plane Blocks for Rib Fractures in the ED
/Kring, R. M. et al. Ultrasound‐Guided Serratus Anterior Plane Block (SAPB) Improves Pain Control in Patients With Rib Fractures. J. Ultrasound Med. 41, 2695–2701 (2022).
Broad strokes
In this prospective, non-randomized study published by Kring et al in January 2022 out of Maine Medical Center, researchers compared mean pain scores at rest and during incentive spirometry before, at 15 minutes after, and then 60 minutes after treatment with a serratus anterior plane block.
Why do we care?
This topic is important because of the high incidence of rib fractures in trauma patients and their association with increased morbidity and mortality. According to this paper, rib fractures occur in up to 10% of all traumatically injured patients and these fractures are frequently associated with respiratory complications such a pneumonia. In the ED, our typical protocol to decrease the incidence of these respiratory complications is early initiation of aggressive pain control and pulmonary hygiene. These patients often will receive systemic analgesia with opiates to decrease the incidence of these respiratory complications, which leads to its own set of opiate associated-complications, including constipation, delirium and dependence.
The thought with introducing the serratus anterior plane block was that regional anesthesia is well within the purview of EM physicians and can offer a safe alternative to systemic pain medications.
Materials and Methods
It was an interventional study at a single tertiary care referral center with a level I trauma designation and an approximate annual ED census of 90,000.
A group of 6 emergency medicine physicians (3 senior residents, 2 ultrasound fellows and 1 attending physician) completed a 1 hour didactic and hands-on training in performing the serratus anterior plane block under ultrasound guidance. They then enrolled patients in the study, using the trauma team activation paging system for notification and reviewing the EMR for details of injuries.
Inclusion criteria:
Patient >18 years of age with acute trauma injuries including (but not limited to) >2 unilateral fractures of anterior or lateral rib 2 to 9 with plan for admission to trauma service.
Exclusion criteria:
The exclusion criteria was strict and excluded patients who would be unable to accurate report their pain scores before and after treatment with the plane block, including the following:
Intubated patients
Patients with clinically significant ICH or TBI
Patients with significant distracting injuries
Patients who were clinically intoxicated
Patients who were planned to go to the OR emergently
Patients with pre-existing chest tubes or those who were anticipated to have one placed
Researchers asked patients to report their chest wall pain on the 11-point numeric rating scale (NRS 11) (where pain is rated from 0 (no pain) to 10 (worst pain imaginable)). Patients were asked to do the same while using an incentive spirometer to their maximal vital capacity.
Researchers then performed the serratus anterior plane block. 15 and 60 minutes after the SAPB was performed, patients were again asked to report their NRS11 pain scale at rest and then during IS. The thought behind obtaining both time values is that at 15 minutes, the block is just starting to take effect and at 60 minutes, the block is at full effect.
For the 24 hours after the block was performed, patients were managed by the trauma service and followed by investigators, using chart review to determine any complications.
The primary outcome in this study was a change in pain score at rest 60 minutes after block. Secondary outcomes were changes in pain scores at rest at 15 minutes, during incentive spirometry at both time points and then change in maximum vital capacity.
Results
24 patients were eligible during the study period from January 2019 to June 2020 and 20 patients age 33-95 were ultimately enrolled by the 6 operators. 50% were male, 50% were female and they had a median # of 4 rib fractures with a range 2-8.
Mean and median pain score at rest prior to SAPB were 5.4 (SD 3.28) and 6.5, respectively. With IS, the pain mean pain score was 6.9. Mean pain scores at rest after the block decreased at both 15 and 60 minutes, with a mean decrease in pain score at 60 minutes of 2.5.
They also noted that there was an increase in mean vital capacity at 60 minutes post-block of 232 mL (pre block mean vital capacity was 1545mL)
No complications were identified in the study population in the first 24 hours.
Discussion
The study authors state that their data supports the use of SAPB as an adjunct for pain control in patients with multiple anterior and lateral rib fractures. Benefits to this is that the SAPB is relatively simple to perform and does not require delivery of anesthetic to a particular nerve but rather to an entire plane. With minimal training, study investigators performed the SAPB with 0 complications attributed to block identified over the study period (24 hours).
Limitations the study identified were the small sample size and single center, nonrandomized design. Enrollment was hindered by relatively restrictive exclusion criteria (used to ensure patients could accurately report their pain).
Some major limitations I identified and that were discussed during journal club was the lack of knowledge regarding what other multi-modal pain medications the patients received and how that related to their improved pain and IS (did they receive fentanyl at 50 minutes after block and that contributed to their significantly improved pain at time 60 compared to time 15?).
There additionally was no control group for this study, which may have been able to be overcome by chart biopsy or data collection even on days when the primary proceduralists/investigators were not present. Additionally, there was no way to control for placebo effect.
They additionally did not provide further patient data information regarding the change in vital capacity. For example, the mean increase in vital capacity was a little over 200 mL and the age of patients ranged from 33-95. While 200mL increase in vital capacity may not make a huge impact on an otherwise healthy 30-year-old man, it may be clinically significant for a 95-yo woman.
Regarding downstream outcomes, the paper acknowledge it did not study factors such as pain control after hospital admission, incidence of pneumonia, delirium, length of hospital stay, discharge disposition or mortality. While the primary outcomes that the paper did look at certainly matter (pain scores following treatment at 60 minutes), the reason that the pain scores matter and why we care and admit patients to the hospital for improved pain control is to improve vital capacity and decrease incidence of pneumonia.
Finally, we discussed whether we would expect this paper to change our practice pattern. While it is certainly a good skill to have in your armamentarium and can be used in conjunction with other multi-modal pain control agents, the consensus was that there was not enough information to routinely make this a part of clinical care. Additionally, this information/improvement of pain scores would do nothing to change our disposition for the patient. We discussed that this might be beneficial procedure to help pain control for a patient discharging, but the decision regarding discharge or admission would be made prior, as using it as a clinical deciding factor would increase the risk of discharged patients representing, potentially with worse respiratory complications.
Overall, the paper showed that this procedure does help with pain scores in patients, particularly at 60 minutes post-procedure, but significant further study (particularly in regard to downstream effects) is required before it becomes part of our routine clinical practice.
Authorship
Written by Olivia Gobble, MD, PGY-3, University of Cincinnati Department of Emergency Medicine
Peer Review, Editing, and Posting by Jeffery Hill, MD MEd, Associate Professor, University of Cincinnati Department of Emergency Medicine
Cite As: Gobble, O. Hill, J. Serratus Anterior Plane Blocks for Rib Fractures in the ED. TamingtheSRU. www.tamingthesru.com/blog/journal-club/serratus-anterior. 11/3/2023
