Serratus Anterior Plane Blocks for rib fractures in the Emergency Department

One of the many jobs that I juggle is as a Major Trauma Consultant on the major trauma ward in Virchester. This involves overseeing and coordinating the care of major trauma patients who are cohorted in a single ward. We also input into critical care areas and the ED. It’s a really positive experience to see how patients progress through care and I love this, and also the interactions with other specialist teams. It’s great for my learning, good for patients, and I get some great insights into the complexities of my colleagues in surgery, anaesthesia and medicine.

One aspect of the job, which is incredibly important is pain management and we’ve had a real impact on how pain is managed for what are often complex patients with multisystem injury. In particular we spend a lot of time managing the pain from chest injury. Patients with such injuries (usually fractured ribs and thoracic spine) can really struggle with analgesia and as a result are prone to infection, a pretty awful experience, and in some cases death.

A number of options are available for chest wall analgesia, either alone or more commonly in some combination.

• Oral analgesia (PRN or regular)
• IV analgesia (PRN or regular)
• Patient controlled analgesia
• Regional blocks (we use erector spinae plane (ESP) blocks)
• Surgical fixation

At the moment we are recruiting to two randomised controlled trials for those with more severe rib injuries. ESPEAR is an RCT looking at erector spinae plane blocks and the ORIF trial which is looking at surgical fixation. Personally I’ve seen both in practice and there is no doubt that in some patients they appear to have an impact, but exactly which patients, when and why is yet to be clarified (hence the need for the trials).

If we look at the ESP block, it’s pretty good on the ward, but not always that great in the emergency department. The issue in the ED is positioning as to put an erector spinae plane block in getting the patient to sit up is helpful (you can do it in the lateral position but it’s trickier). However, a lot of our patient either have spinal fracture limiting movement OR are yet to have any such fractures/instability ruled out through MRI scans. Thus the ESP blockers are often frustrated in the first few hours/days. So wouldn’t it be better if there was a potential alternative.

The serratus anterior plane block can be achieved in the supine patient and can provide pretty good analgesia to the chest wall (though perhaps not as well to posterior ribs/transverse processes). The question is though, does it work in our ED trauma patients. This month we have a paper in JAMA surgery that attempts to answer that question. The abstract is below but as always please read the full paper yourself.

The Abstract – Serratus Anterior Plane Blocks for Early Rib Fracture Pain Management: The SABRE Randomized Clinical Trial¹

Importance: Rib fractures secondary to blunt thoracic trauma typically result in severe pain that is notoriously difficult to manage. The serratus anterior plane block (SAPB) is a regional anesthesia technique that provides analgesia to most of the hemithorax; however, SAPB has limited evidence for analgesic benefits in rib fractures.
Objective: To determine whether the addition of an SAPB to protocolized care bundles increases the likelihood of early favourable analgesic outcomes and reduces opioid requirements in patients with rib fractures.
Design, setting, and participants: This multicenter, open-label, pragmatic randomized clinical trial was conducted at 8 emergency departments across metropolitan and regional New South Wales, Australia, between April 12, 2021, and January 22, 2022. Patients aged 16 years or older with clinically suspected or radiologically proven rib fractures were included in the study. Participants were excluded if they were intubated, transferred for urgent surgical intervention, or had a major concomitant nonthoracic injury. Data were analyzed from September 2022 to July 2023.
Interventions: Patients were randomly assigned (1:1) to receive an SAPB in addition to usual rib fracture management or standard care alone.
Main outcomes and measures: The primary outcome was a composite pain score measured 4 hours after enrollment. Patients met the primary outcome if they had a pain score reduction of 2 or more points and an absolute pain score of less than 4 out of 10 points.
Results: A total of 588 patients were screened, of whom 210 patients (median [IQR] age, 71 [55-84] years; 131 [62%] male) were enrolled, with 105 patients randomized to receive an SAPB plus standard care and 105 patients randomized to standard care alone. In the complete-case intention-to-treat primary outcome analysis, the composite pain score outcome was reached in 38 of 92 patients (41%) in the SAPB group and 18 of 92 patients (19.6%) in the control group (relative risk [RR], 0.73; 95% CI, 0.60-0.89; P = .001). There was a clinically significant reduction in overall opioid consumption in the SAPB group compared with the control group (eg, median [IQR] total opioid requirement at 24 hours: 45 [19-118] vs 91 [34-155] milligram morphine equivalents). Rates of pneumonia (6 patients [10%] vs 7 patients [11%]), length of stay (eg, median [IQR] hospital stay, 4.2 [2.2-7.7] vs 5 [3-7.3] days), and 30-day mortality (1 patient [1%] vs 3 patients [4%]) were similar between the SAPB and control groups.
Conclusions and relevance: This randomized clinical trial found that the addition of an SAPB to standard rib fracture care significantly increased the proportion of patients who experienced a meaningful reduction in their pain score while also reducing in-hospital opioid requirements.

Partyka C, Asha S, Berry M, Ferguson I, Burns B, Tsacalos K, Gaetani D, Oliver M, Luscombe G, Delaney A, Curtis K. Serratus Anterior Plane Blocks for Early Rib Fracture Pain Management: The SABRE Randomized Clinical Trial. JAMA Surg. 2024 May

What kind of paper is this?

The Serratus Anterior Plane Blocks for Early Rib Fracture Pain Management trial (SABRE) is a randomised clinical trial which is an appropriate design for an intervention such as this. Patients were randomised in a 1:1 ratio using a secure online system.

Tell me about the patients and setting.

Patients were recruited in eight emergency departments in Australia. They were aged over 16 and had to have rib fractures. This implies that the patients had to have more than one rib fracture, but I can’t find that information in the paper, nor in the supplementary data (it may be there, but I cannot find it). Similarly, I can’t see any objective assessment of the rib fracture risk (such as the STUMBL score) that might help me understand the severity of injury of the patients in each group. There is some information in Table 1, but not in such a way to combine the various factors that are known to influence the severity and prognosis of chest injury.

This may not be an issue for the trial, but in my practice, we are only really considering serratus anterior plane blocks for the more severely injured patients, and I’m unclear how many of these patients are like the ones I see on the MT ward.

What about the intervention?

All patients had a standardised approach to chest wall injury. These are detailed in the supplementary data as they did vary between hospitals (though not dramatically so). The SAPB randomisation was in addition to the standard care in that hospital.

Serratus anterior plane blocks themselves are relatively straightforward to do. There are two approaches (deep and superficial), with the majority in this study being a superficial approach. The authors used a single shot technique, with an injection of LA, but no indwelling catheter. So in a way, it is akin to a fascia iliaca block for a hip fracture. A single injection of Ropivocaine 0.375% with a volume adjusted to weight (not exceeding 40ml) was used, and was hoped to achieve an analgesic effect for up to 12 hours.

If you want a reminder about how to an serratus anterior plane, then there is a good video below.

What about the outcomes?

Choosing an outcome in a trial like this is complex. The authors chose pain scores at 4-hours after enrolment (a reduction of pain score of 2 points on a 10-point scale, OR an absolute pain score <4). Patients with dementia were assessed using a different ‘Pain Assessment in Dementia Tool’ , this is worth highlighting as most studies exclude dementia patients as they are more difficult to recruit and/or measure. That inevitably means that they have less inclusion in trials and perhaps why dementia patients get poor analgesia in the ED. So well done to this group for including them.

There is some sense in using a 4-hour pain score as it is an outcome that is important to patients, and is directly related to what the intervention is trying to achieve (analgesia), but an alternative view would be that this is too short a time point, and that other aspects such as longer term pain, mobility, and complications such as pneumonia which are also important (and which are picked up in some of the secondary outcomes). The authors did follow up patients to 24 hours as a secondary outcome which is clearly important.

What about the results?

210 patients were recruited into the trial, 105 into each arm. In the block group 96 patients received a block, and in the control group 13 patients had a ‘rescue block’. Such cross-over is common in these trials, but we should still analyse on an intention to treat basis (ITT). Data for analysis was only available for 184 patients.

In terms of the primary outcome it was statistically and clinically different (RR, 0.73; 95%CI, 0.60-0.89; P=.001).

• 38 (41.3%) of patients in the block group achieved the primary outcome (good pain relief)
• 18 (19.6%) of patients in the control group achieved the primary outcome.

These reductions in pain were maintained up to 24 hours.

For the secondary outcomes the only significant difference was in the use of opioid medication which was less in the block group.

Another interesting and perhaps unexpected finding was that the SAPB appeared to be more effective for posterior and lateral fractures as opposed to anterior fractures. This is contrary to my past understanding of SAPB anatomy and may need some more explanation.

Are Serratus Anterior Plane blocks the solution to chest injury pain management?

One concern with the serratus anterior plane block is that it lasts for a few hours, and will then wear off, but in this study the effect appears to continue up to 24 hours.

Our usual approach in Virchester is to use an erector spinae plane, which is a catheter technique allowing a continuous infusion of local anaesthetic over several days. Obviously chest injuries do not resolve in a few hours (or days) and so both techniques require additional analgesia and forward planning. However, I can see a stat SAPB as a potential bridging technique to a subsequent erector spinae plane (with continuous infusion) or rib fixation.

The other issue worth noting is that the majority of patients in BOTH groups did not achieve the primary outcome and were therefore still in pain at the 4-hour mark. This suggests that this block is not a complete solution and that additional analgesia will be required, even if we adopt this technique. The authors rightly mention that rib injury is a significant injury and should be part of a chest wall injury management plan. These differ between units, but it’s a really important point to reiterate.

Final thoughts

This study supports the use of Serratus Anterior Plane Blocks in ED patients with significant chest injury. In Virchester it’s a bit hit and miss at the moment depending who is on, but there is a training program in place to upskill as many people as possible. This paper supports that project.

References and further reading

1. ORIF study.
2. ESPEAR study
3. Analgesia for rib fractures: a narrative review. 10.1007/s12630-024-02725-1
4. Partyka C, Asha S, Berry M, Ferguson I, Burns B, Tsacalos K, Gaetani D, Oliver M, Luscombe G, Delaney A, Curtis K. Serratus Anterior Plane Blocks for Early Rib Fracture Pain Management: The SABRE Randomized Clinical Trial. JAMA Surg. 2024 May 1:e240969. doi: 10.1001/jamasurg.2024.0969. Epub ahead of print. PMID: 38691350; PMCID: PMC11063926.
5. Dan Horner, “JC: What’s the ‘best’ test for a broken chest?,” in St.Emlyn’s, January 16, 2015, 
6. Simon Carley, “JC: Conservative management of chest trauma. St Emlyn’s,” in St.Emlyn’s, December 7, 2018
7. Simon Carley, “Chest drains & aspiration: Do it better with St.Emlyn’s,” in St.Emlyn’s, November 19, 2016
8. Harrington C, Bliss J, Lam L, Partyka C. Serratus Anterior Plane Block for Clinically Suspected Rib Fractures in Prehospital and Retrieval Medicine. Prehosp Emerg Care. 2024;28(1):30-35. doi: 10.1080/10903127.2022.2150344. Epub 2022 Dec 8. PMID: 36441609.
9. Surdhar I, Jelic T. The erector spinae plane block for acute pain management in emergency department patients with rib fractures. CJEM. 2022 Jan;24(1):50-54. doi: 10.1007/s43678-021-00203-x. Epub 2021 Oct 20. PMID: 34669173.