Procedure: Serratus Anterior Block

The Procedure

Hello again from the Emergency Procedures team,

Serratus Anterior Plane Block

Today we’re exploring a technique for rib fracture pain: the Serratus Anterior Plane (SAP) block. As always, we’ve reviewed the latest evidence and translated it into practical bedside tips.

Detailed written instructions and explanation are available in our Free App (iOS and Android). This video is hot off the press and we want your help improving it. Drop us a line with any suggestions

So, without further ado…here is the video

The rationale…

What is the goal of this block?

To anaesthetise the lateral cutaneous branches of the thoracic intercostal nerves, typically from T2 to T9. It can provides significant pain relief to the ipsilateral hemithorax.

Where exactly do I inject the local anaesthetic?

There are two options: superficially between the latissimus dorsi and serratus anterior, or deeply between serratus anterior and the ribs. We recommend the superficial approach where tissue planes are visible. It’s easier to visualise with ultrasound and carries less risk of pneumothorax.

What kind of clinical improvements should I expect if the block works?

Most patients experience early pain relief to below moderate levels. You’ll also often see better incentive spirometry performance, increased oxygenation, and lower respiratory rates.

How worried should I be about local anaesthetic systemic toxicity (LAST)?

It’s rare — about 20 cases per 100,000 procedures — but potentially life-threatening. You can reduce the risk by using real-time ultrasound, injecting slowly, aspirating every 5 mL, and knowing how to treat it with  lipid rescue.

What does lipid rescue look like in practice?

For a 70 kg adult, draw up a 500 mL bag of 20% intralipid. Give two 50 mL boluses immediately, then infuse the rest at 1050 mL/hr. If there’s no response, up to two more boluses can be given.

Are there patients I should be extra cautious with?

Yes. People with severe hepatic failure (slower metabolism of local anaesthetics) or heart block without a pacemaker. Stick to maximum safe doses and monitor closely.

Can I add anything to extend the block?

You can add dexamethasone to bupivacaine to extend the block’s duration. Don’t mix dexamethasone with ropivacaine — it causes crystallisation.

I’ve spotted an improvement that could be made to your video and guide…..

Don’t be shy, let us know! Drop us a line

The App