Clinical assessment and risk stratification

Patients should be assessed with a validated risk score, for example Battle et al.’s STUMBL (STUdy of the Management of BLunt chest wall trauma) score;⁶ this predicts the risk of complications secondary to the rib injury, using patient age, number of fractures, underlying lung disease, anti-coagulant use and SpO2. The patient’s pain score should also be assessed.

Management is decided by the risk score and pain score, according to local rib fracture pathways. For example, low risk scores may be considered for oral analgesia and discharge; moderate risk scores for admission, PCA, and consideration of a nerve block procedure / anaesthetic team review; and higher risk scores for critical care review. Physiotherapy, high-flow nasal oxygenation, and pain team involvement may also be helpful.

Patients with anterior lateral rib fractures with a moderate / higher risk score or high pain score, those with more posterior fractures in whom the lateral or sitting position to allow more posterior nerve block techniques is not possible or these techniques are contraindicated, or in those in whom a chest drain is inserted, may benefit from SAPB as part of multimodal analgesia.

Advantages of SAPB

• Technically easy and superficial block.
• Performed with patient supine.
• Suitable for patients with associated spinal trauma or head injuries where paravertebral and epidural blocks may be contraindicated.
• Can be inserted in patients with a coagulopathy.⁷
• Can form part of an opiate sparing analgesic strategy.⁸

Contraindications to SAPB

There are few contraindications to performing the block.

Absolute

• Patient refusal
• Local anaesthetic allergy
• Infection at needle insertion point

Relative

• Distorted anatomy e.g. surgical emphysema

Complications of SAPB⁹

• Pneumothorax – due to puncture of the pleura
• Vascular puncture – the thoracodorsal artery lies medially
• Nerve damage – unlikely with a plane block however the thoracodorsal nerve does run with the thoracodorsal artery
• Failure/inadequate block
• Local anaesthetic systemic toxicity (LAST)
• Infection