Interscalene Brachial Plexus Block - ARiRA Pro Tips
Key Points
Indications: Provides anaesthesia for shoulder, clavicle, and upper arm surgeries.
Anatomy: Targets the brachial plexus roots (C5-C7), located between the anterior and middle scalene muscles at the level of the cricoid cartilage (C6).
Position the patient supine with the head turned away from the side to be blocked, ensuring easy access to the neck.
Ultrasound Guidance
Probe Selection: Use a high-frequency linear transducer.
Imaging Tips: Position the probe transversely over the neck at the C6 level to visualise the brachial plexus as a cluster of hypoechoic round structures, often described as ‘traffic lights’ due to their distinctive arrangement.
Identify the brachial plexus between the anterior and middle scalene muscles using an ultrasound probe placed transversely at the level of C6.
To enhance safety, always use in-plane needle insertion, visualising the needle throughout its trajectory.
Optimise the image by adjusting the depth and gain to improve the visibility of the nerve structures and surrounding muscles.
Reverse-Plexus Trace Technique
Tip for Enhanced Visualisation: When locating the brachial plexus between the anterior and middle scalene muscles is challenging at the C6 level, reposition the ultrasound probe to the supraclavicular fossa. At this level, identify the brachial plexus posterior and superficial to the subclavian artery. Once visualised, gradually move the transducer cranially along the neck to follow the nerve structures to the desired level for the interscalene block.
Injection Techniques
Always aspirate before injecting to avoid intravascular injection.
Inject in small aliquots (1–2 mL at a time) and observe the spread of local anaesthetic around the nerve roots.
The volume of injection is 5-20 ml, depending on the desired extent of anaesthesia and patient-specific factors. Balancing the volume is essential to achieving effective nerve blockade while minimising potential complications.
Precautions
Monitor for signs of intravascular injection or local anaesthetic systemic toxicity (LAST).
Avoid injecting near the vertebral artery or the dural sleeve of the spinal cord.
Use colour Doppler to visualise and avoid blood vessels.
Complications
Transient Phrenic nerve blockade leads to hemidiaphragmatic paralysis, typically resolving as the block wears off.
Temporary Horner’s Syndrome: Caused by inadvertent stellate ganglion blockade, presenting with ptosis, miosis, and anhidrosis; resolves as the block regresses.
Vascular Puncture: The vertebral artery is particularly at risk during needle advancement. Maintain constant ultrasound needle tip visualisation and exercise caution to minimise the likelihood of accidental puncture.
Pneumothorax, though rare, is a possible risk with deep needle insertion.
Interscalene Brachial Plexus Block – FAQs
Q: What surgeries are most suitable for the interscalene block?
A: It is ideal for procedures involving the shoulder, clavicle, and upper arm, including shoulder arthroscopy, clavicle fixation, and proximal humerus surgeries.
Q: How long does the anaesthetic effect typically last?
A: The duration depends on the local anaesthetic used. For example, bupivacaine or ropivacaine can provide anaesthesia lasting 6–18 hours, whereas shorter-acting agents like lidocaine may wear off in 1.5–4 hours.
Q: What are the key precautions during this block?
A: Precautions include:
Continuous ultrasound guidance to avoid vascular or neural injury.
Frequent aspiration to prevent intravascular injection.
Monitoring for signs of local anaesthetic systemic toxicity (LAST).
Q: How can you optimise the ultrasound-guided technique?
A: Use a high-frequency linear probe to visualise the brachial plexus at the C6 level, ensuring clear identification of the nerve roots between the anterior and middle scalene muscles. Adjust gain and depth for better visualisation of surrounding structures.
Q: Are there any long-term risks associated with this block?
A: Long-term complications are rare, but there is a small risk of persistent neuropathy, which usually resolves within weeks.
Q: Can the block be combined with sedation or general anaesthesia?
A: Yes, the interscalene block is often used as a primary anaesthetic with sedation or as part of a multimodal approach with general anaesthesia for extended postoperative analgesia.
Q: How can phrenic nerve paralysis be minimised?
A: Phrenic nerve involvement can be reduced by lowering the volume of local anaesthetic (e.g., 5–8 mL) or by modifying the needle trajectory to target the upper trunk selectively.
Q: What should be done if the patient reports persistent numbness or weakness? A: Persistent symptoms beyond 24–48 hours should prompt a detailed neurological assessment and consideration of additional investigations if necessary.
Q: Are there alternative blocks for shoulder surgery?
A: Alternatives include superior trunk block, supraclavicular or combined suprascapular and axillary nerve blocks, depending on the surgical site and desired distribution of anaesthesia.
Q: Why does hoarseness occur after an interscalene brachial plexus block?
A: Hoarseness can occur due to the unintended blockade of the recurrent laryngeal nerve or due to laryngeal hyperaemia.
Recurrent Laryngeal Nerve Block: The recurrent laryngeal nerve may be affected during an interscalene brachial plexus block due to the anatomical proximity of the nerve to the injection site. The Spread of the local anaesthetic along the fascial planes can inadvertently block the recurrent laryngeal nerve, which is located near the trachea and oesophagus. This can result in temporary hoarseness due to partial paralysis of the vocal cord muscles innervated by the nerve.
Laryngeal Hyperaemia: Laryngeal hyperaemia can occur due to the vasodilatory effects of the local anaesthetic. The local anaesthetic can influence nearby blood vessels, leading to increased blood flow and engorgement in the laryngeal tissues. Hyperaemia may also be linked to inadvertent blockade of sympathetic nerve fibres, altering vascular tone and increasing perfusion in the region.
Q: What causes Horner’s syndrome after an interscalene brachial plexus block?
A: Horner’s syndrome occurs due to the unintended blockade of the stellate ganglion, a sympathetic ganglion located at the level of the C7 vertebra. The stellate ganglion may get blocked during an interscalene block when local anaesthetic spreads inferiorly or along fascial planes to the area of the ganglion. This results in temporary interruption of sympathetic nerve function, causing classic symptoms such as ptosis (drooping eyelid), miosis (constricted pupil), and anhidrosis (loss of sweating) on the affected side. These effects typically resolve as the block wears off.
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This content is intended for healthcare professionals to enhance procedural understanding and safety. Clinical judgement and patient-specific factors must guide all decisions.