Your 78-year-old fell off a ladder hanging Christmas lights. She has six rib fractures, splints every time she breathes, and her sats are creeping down despite a non-rebreather. You can keep stacking dilaudid and hope she doesn't end up tubed in the ICU, or you can grab the ultrasound, find the latissimus, and give her an actual shot at breathing again. A new RCT in Academic Emergency Medicine just landed on serratus anterior plane blocks (SAPB) done by EM physicians, and the results are worth five minutes of your attention.
Why Rib Fractures Are a Big Deal (Especially in Grandma)
Rib fractures are deceptively dangerous. The fractures themselves don't kill people; the splinting, atelectasis, and pneumonia that follow do. In patients over 65, mortality climbs roughly 19% for each additional rib fractured, and the risk of pneumonia roughly doubles. The mechanism is straightforward: pain leads to shallow breathing, shallow breathing leads to atelectasis, atelectasis leads to pneumonia, pneumonia leads to the ICU.
The treatment paradigm has historically been "opioids and incentive spirometry," which works about as well as it sounds. IV opioids blunt respiratory drive, cause delirium in the elderly, and don't reliably break the splinting cycle. We need something better, and regional anesthesia has been quietly sitting in our toolbox for years.
The Block, in 60 Seconds
The serratus anterior plane block was first described in 2013 by Blanco et al. as a simpler, safer alternative to thoracic epidurals and paravertebral blocks. You're depositing local anesthetic in the fascial plane between the latissimus dorsi and serratus anterior muscles, around the mid-axillary line at the 4th or 5th rib. The lateral cutaneous branches of the intercostal nerves (T2-T9) run through this plane, so a well-placed injection of 20-40 mL of dilute local anesthetic gives you broad coverage of the hemithorax.
The advantages over a thoracic epidural are obvious: no neuraxial risks, no sympathetic blockade dropping the pressure, no need to sit a polytrauma patient upright. Compared to paravertebral blocks, the target is superficial and the landmarks are forgiving. If you can do a peripheral nerve block, you can do this.
Technique in brief: linear probe in the mid-axillary line at the 5th rib, identify lat dorsi superficially and serratus anterior deep to it, in-plane needle from anterior to posterior, hydrodissect the plane with saline first, then inject your local. Ropivacaine 0.25-0.5% or bupivacaine 0.25% are the usual suspects. Catheter techniques exist but aren't realistic for most EDs.
The New RCT: What They Found
The study (Mowery et al., Academic EM, 2024) randomized ED patients with acute rib fractures to either standard care plus an ED-performed SAPB or standard care alone. The block group got ultrasound-guided SAPB with ropivacaine performed by trained emergency physicians.
The headline results: SAPB patients had clinically meaningful reductions in pain scores at multiple time points post-block, with the effect sustained for hours beyond what a single dose of IV opioid would provide. Opioid consumption in the first 24 hours was lower in the block group. Incentive spirometry volumes, a proxy for pulmonary function and the thing we actually care about, improved more in the block arm.
No serious complications. No pneumothoraces from the block itself (the needle stays well superficial to the pleura when done correctly). No local anesthetic systemic toxicity.
A few honest caveats. The trial was modestly sized and single-center, so we shouldn't pretend this is a 5,000-patient pragmatic mega-trial. It builds on a growing pile of observational and smaller RCT data pointing in the same direction, including prior work showing reduced pneumonia rates and shorter LOS in blocked patients. The signal is consistent. The magnitude is debatable. The direction is not.
Who Gets the Block?
Good candidates: multiple rib fractures (especially 3 or more), elderly patients, anyone splinting or with declining incentive spirometry volumes, patients you're worried about admitting to the floor versus the ICU, patients with contraindications to opioids or NSAIDs.
Relative contraindications: coagulopathy (though the plane is compressible and superficial, so this is softer than for neuraxial), local infection over the site, allergy to amides, and the patient who can't hold still for five minutes. Bilateral fractures are tricky because you'd need bilateral blocks and you have to watch your total LA dose. Calculate max dose by weight before you draw up, every time.
The "I don't have time" excuse deserves a direct response. The block itself takes about five minutes once you're set up. The patient who avoids intubation saves you, the ICU team, and the hospital roughly a week of downstream work. The math is not close.
Should This Be a Core EM Skill?
Yes. Full stop. Regional anesthesia is no longer the exclusive domain of anesthesiology, and the SAPB is arguably the easiest, highest-yield block in our practice. ACEP's policy statement on ED ultrasound-guided nerve blocks already includes fascial plane blocks as within our scope. Residency programs that aren't teaching this are behind.
If you're an attending who didn't learn this in training, the learning curve is genuinely short. Workshops at SAEM, ACEP, and Highland's regional anesthesia courses will get you most of the way there. A handful of supervised reps and you're functional. Your geriatric trauma patients will thank you, even if they don't know why.
The Bottom Line
- A new RCT supports what the prior literature has been saying: ED-performed SAPB reduces pain and opioid use in acute rib fracture patients without serious complications.
- The block targets the fascial plane between latissimus dorsi and serratus anterior at the mid-axillary line, well away from the pleura.
- Prioritize SAPB in elderly patients with 3+ rib fractures, those splinting, or anyone with declining IS volumes. These are your future ICU admissions.
- Calculate max local anesthetic dose by weight every time, especially if you're considering bilateral blocks.
- "I don't have time" is no longer a defensible answer. The block takes five minutes. The admission it prevents takes a week.
Sources
- Mowery NT, et al. Serratus Anterior Plane Block for Acute Rib Fractures in the Emergency Department: A Randomized Controlled Trial. Academic Emergency Medicine. 2024. https://onlinelibrary.wiley.com/doi/10.1111/acem.70338
- Blanco R, Parras T, McDonnell JG, Prats-Galino A. Serratus plane block: a novel ultrasound-guided thoracic wall nerve block. Anaesthesia. 2013;68(11):1107-1113.
- Bulger EM, et al. Rib fractures in the elderly. Journal of Trauma. 2000;48(6):1040-1046.
- ACEP Policy Statement: Ultrasound-Guided Nerve Blocks. American College of Emergency Physicians. https://www.acep.org/patient-care/policy-statements/ultrasound-guided-nerve-blocks/
- Hernandez N, et al. Impact of serratus plane block on pain scores and incentive spirometry volumes after chest trauma. Local and Regional Anesthesia. 2019;12:59-66.
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