Superior Trunk Block - ARiRA Pro Tips
Indications: Recommended for surgeries involving the shoulder and proximal humerus, especially when sparing the phrenic nerve, is a priority.
Anatomy: Focuses on the superior trunk of the brachial plexus, formed by the convergence of the C5 and C6 nerve roots, positioned between the anterior and middle scalene muscles.
Patient Positioning: Ensure the patient is supine, with the head turned away from the block side for optimal access. Elevating the ipsilateral shoulder slightly can improve ergonomics for needle placement.
Ultrasound Technique: A high-frequency linear probe is used to scan transversely at the C6 level to identify the "traffic light" appearance of the C5 and C6 nerve roots. Then, move the probe slightly distally to visualise the superior trunk, identified as a hypoechoic, oval structure encased in a connective tissue sheath. Depending on individual anatomy and ultrasound settings, it may sometimes appear as a cluster or "bunch" of hypoechoic structures, representing the bundled nerve fascicles within the trunk. This is the optimal site for performing the superior trunk block, proximal to the takeoff of the suprascapular nerve.
Needle Insertion: Perform an in-plane approach, introducing the needle laterally and directing it medially. If possible, avoid traversing the middle scalene muscle to reduce the risk of trauma to the dorsal scapular and long thoracic nerves.
Injection Volume: Administer 5–15 mL of local anaesthetic, depending on the desired spread and the patient's anatomy. Lower volumes may further reduce the likelihood of phrenic nerve involvement.
Phrenic Nerve Sparing: Compared to interscalene blocks, this approach reduces the risk of phrenic nerve blockade, offering a safer option for patients with compromised respiratory function.
Optimising Coverage: For enhanced shoulder analgesia, consider a supplemental injection targeting the supraclavicular nerves over the middle scalene muscle.
Interscalene Brachial Plexus Block – FAQs
Q: What is the superior trunk brachial plexus block?
A: The superior trunk brachial plexus block is a regional anaesthesia technique targeting the upper trunk of the brachial plexus, formed by the C5 and C6 nerve roots. It provides anaesthesia and analgesia for surgeries involving the shoulder and upper arm.
Q: How does the superior trunk block compare to the interscalene block in terms of efficacy?
A: The superior trunk block provides comparable analgesia to the interscalene block for shoulder surgeries. However, it is associated with a much lower risk of phrenic nerve involvement, occurring in about 5% of cases compared to over 70% with the interscalene block. This makes it a safer choice for patients with respiratory conditions.
Q: What are the potential complications associated with the superior trunk block?
A: While generally safe, potential complications include vascular puncture, inadvertent nerve involvement (e.g., recurrent laryngeal nerve), local anaesthetic systemic toxicity (LAST), and, rarely, hemidiaphragmatic paralysis.
Q: Are there any contraindications for the superior trunk block?
A: Contraindications include patient refusal, allergy to local anaesthetics, infection at the injection site, coagulopathy, and significant anatomical abnormalities of the brachial plexus. Caution is advised in patients with severe pulmonary disease.
Q: How long does the block typically last?
A: The duration depends on the local anaesthetic used. For example, bupivacaine or ropivacaine provides adequate analgesia for 6–18 hours.
Q: Is this block suitable for patients with respiratory compromise?
A: Yes, the superior trunk block is often favoured for patients with respiratory issues because it spares the phrenic nerve in most cases, lowering the risk of hemidiaphragmatic paralysis.
Q: Can this block be used for outpatient surgeries?
A: Absolutely. Its effectiveness and reduced respiratory risk make it ideal for outpatient shoulder surgeries.
Q: How do you enhance analgesia for the shoulder region?
A: Adding a small-volume injection (3–5 mL) targeting the supraclavicular nerve branches can improve coverage of the shoulder's cutaneous areas.
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This content has been specifically tailored for healthcare professionals, focusing on unique strategies to optimise safety and efficacy during superior trunk block procedures. Always apply clinical judgment tailored to individual patient needs.