Axillary block

Surgical approach

Not an operation, a regional anaesthetic technique for forearm/hand surgery (e.g. tendon repair, ORIF wrist/hand, carpal tunnel release, Dupuytren’s, hand trauma washout).
Typical surgical steps (examples):
- Tourniquet applied to upper arm (often required) → exsanguination → incision/repair/fixation → dressing/splint.
- Position: supine, arm abducted on arm board, surgeon works distal to elbow.

Anaesthetic management

Type of anaesthesia: Regional (axillary block) ± sedation, can convert to GA if inadequate/urgent.
Airway: usually none (spontaneous ventilation) or nasal cannulae/face mask, if deep sedation/GA → SGA/ETT as indicated.
Duration: block performance 10–20 min, onset 10–30 min depending on LA, surgical duration commonly 0.5–2 hours (varies widely).
How painful: surgery itself can be well covered, tourniquet pain may limit tolerance (often begins 30–60 min).
Analgesia plan: multimodal (paracetamol/NSAID if appropriate) + opioid rescue, consider adjuvants/long-acting LA for prolonged analgesia.
Monitoring/standards: full AAGBI monitoring, IV access, resus drugs incl. Intralipid immediately available.

Indications and coverage

Indications: surgery/analgesia for elbow to hand, especially forearm, wrist, hand procedures.
Dermatomal/nerve coverage: terminal branches of brachial plexus at axilla: median, ulnar, radial, musculocutaneous.
Important: intercostobrachial nerve (T2) supplies medial upper arm/tourniquet area → not blocked by axillary block, may need separate subcutaneous ring infiltration or specific block.
Less reliable for: proximal arm/shoulder surgery (need supraclavicular/interscalene).

Relevant anatomy (exam-focused)

Axillary artery is the key landmark, nerves are arranged around it (variable):
- Median: often anterolateral/anterior to artery.
- Ulnar: often medial to artery.
- Radial: often posterior/posterolateral to artery.
- Musculocutaneous: typically leaves sheath early, lies in/near coracobrachialis between biceps and coracobrachialis (often not adjacent to artery).
Axillary sheath: fascial extension of prevertebral fascia, contains artery and many nerves, but septations and early exit of musculocutaneous contribute to patchy block.
Structures at risk: axillary artery/vein, lymphatics, median nerve injury risk with intraneural injection, pleura is remote (lower pneumothorax risk than supraclavicular).

Contraindications

Absolute: patient refusal, LA allergy (true IgE rare), infection at site, inability to cooperate/consent, uncontrolled bleeding diathesis (relative/absolute depending on severity).
Relative: anticoagulation (follow RA-UK/ASRA principles, axillary is compressible but still caution), pre-existing neuropathy, severe PVD/AV fistula limb, inability to abduct arm, sepsis, significant respiratory compromise is usually less relevant than for proximal blocks.

Technique (ultrasound-guided preferred)

Position: supine, arm abducted 90°, elbow flexed, forearm supinated, comfortable head/neck position.
Probe: high-frequency linear, scan transverse in axilla to identify axillary artery (pulsatile) and surrounding nerves, use colour Doppler to identify veins.
Needle approach: in-plane (commonly) from anterior/superior aspect, aim for perineural spread around each nerve (or around artery with targeted deposits).
Musculocutaneous nerve: identify in coracobrachialis, inject separately (common cause of sparing if missed).
Volume strategy (typical adult): total 20–40 mL depending on LA/concentration and number of injections, ultrasound allows lower volumes but ensure adequate spread.
Safety steps: incremental aspiration, frequent verbal contact, avoid high injection pressure, stop if pain/paraesthesia or resistance, document neuro status pre/post.

Alternative techniques

Nerve stimulator technique: seek motor responses (e.g. median: wrist/finger flexion, ulnar: 4th/5th finger flexion, radial: wrist/finger extension, musculocutaneous: elbow flexion).
Transarterial technique (historical): through axillary artery with injection posterior/anterior, higher vascular puncture/haematoma risk, largely replaced by ultrasound.
Perivascular single-injection techniques can be less reliable due to septations and musculocutaneous exit, multiple targeted injections improve success.

Local anaesthetic choices (typical examples, adjust to patient and dose limits)

Shorter procedures: lidocaine 1–2% (± adrenaline) for faster onset, consider alkalinisation (e.g. bicarbonate) per local practice.
Longer analgesia: ropivacaine 0.5% or levobupivacaine 0.25–0.5%.
Dose safety: calculate maximum safe dose (consider lean body weight, comorbidities, pregnancy, age), remember cumulative dose if also infiltrating tourniquet area.
Adjuvants: adrenaline reduces systemic absorption and helps detect intravascular injection, perineural dexamethasone may prolong duration (off-label, local policy). Avoid mixing without clear rationale.

Assessment of block

Sensory testing (cold/light touch/pinprick) in nerve territories:
- Median: palmar index finger.
- Ulnar: palmar little finger.
- Radial: dorsal first web space.
- Musculocutaneous: lateral forearm (lateral cutaneous nerve of forearm).
Motor testing (optional): thumb opposition (median), finger abduction (ulnar), wrist extension (radial), elbow flexion (musculocutaneous).
Tourniquet: test medial upper arm sensation, consider intercostobrachial infiltration if needed.

Complications and management

Local anaesthetic systemic toxicity (LAST): tinnitus, metallic taste, agitation → seizures → cardiovascular collapse.
- Immediate actions: stop injection, call for help, airway/oxygen/ventilate, treat seizures (benzodiazepine), manage arrhythmias (avoid large doses propofol in instability), start lipid emulsion early per guideline, CPR if needed.
Vascular puncture/haematoma: commoner than proximal blocks, apply firm pressure, caution anticoagulated patients.
Nerve injury: intraneural injection, high pressure, needle trauma, neurotoxicity, ischaemia, document, reassure, follow local nerve injury pathway, urgent review if severe pain, progressive deficit, or compartment syndrome suspected.
Infection: rare, asepsis essential.
Block failure/patchy block: common causes include missed musculocutaneous nerve, inadequate spread, septations, insufficient onset time, manage with supplementation or convert to GA.
Pneumothorax: very rare with axillary approach (more relevant to supraclavicular).

Sedation and perioperative considerations

Sedation: minimal/moderate preferred, maintain verbal contact during injection, avoid deep sedation that masks intraneural pain or early LAST symptoms.
Tourniquet pain management: reassurance, light sedation/analgesia, consider additional blocks/infiltration, if severe and prolonged, may need GA.
Post-op: sling advice (protect insensate limb), written instructions, warn about burns/trauma, time course of block resolution, safety-net for persistent numbness/weakness.

Test yourself…

Describe the anatomy relevant to an axillary brachial plexus block.

Focus on terminal branches, their relationship to the axillary artery, and why the block can be patchy.

Brachial plexus cords divide into terminal branches in/near the axilla: median, ulnar, radial, musculocutaneous.
Axillary artery is central, nerve positions are variable but classically: median anterior, ulnar medial, radial posterior, musculocutaneous often within coracobrachialis.
Axillary sheath may be septated, musculocutaneous exits early → single perivascular injection may miss nerves → patchy block.
Intercostobrachial nerve (T2) supplies medial upper arm/tourniquet area and is not part of brachial plexus → requires separate coverage.

What are the indications and contraindications for an axillary block?

Give a structured answer: indications, absolute contraindications, relative contraindications.

Indications: surgery/analgesia for forearm, wrist, hand, useful when avoiding GA or for day-case analgesia.
Absolute contraindications: refusal, infection at site, true LA allergy, inability to cooperate/consent.
Relative contraindications: anticoagulation/bleeding risk, pre-existing neuropathy, inability to abduct arm, significant local trauma/distortion, sepsis.

How would you perform an ultrasound-guided axillary block?

Examiners want: positioning, scanning, identification of nerves, needle approach, LA deposition, safety.

Position patient supine, arm abducted 90°, elbow flexed, apply full monitoring and IV access, asepsis, resus drugs and lipid available.
Use linear high-frequency probe in axilla, identify axillary artery and veins (Doppler).
Identify nerves around artery, locate musculocutaneous in/near coracobrachialis.
In-plane needle, inject incrementally with aspiration, aim for perineural spread around median/ulnar/radial and separate injection for musculocutaneous, total volume commonly 20–40 mL depending on LA and patient factors.
Stop if severe pain/paraesthesia or high resistance, reassess needle tip, avoid intraneural injection.

Why might an axillary block fail, and how would you manage a patchy block intraoperatively?

Include technical, anatomical, and time-related causes, then a pragmatic rescue plan.

Causes: missed musculocutaneous nerve, inadequate LA spread due to septations, insufficient volume, intravascular injection, not allowing enough onset time, anatomical variation.
Management: re-assess sensory distribution, top-up targeted nerves under ultrasound, infiltrate surgical field as appropriate, address tourniquet pain (intercostobrachial infiltration, analgesia/sedation).
If still inadequate or urgent surgery: convert to GA (with appropriate fasting/airway plan) and document.

How would you assess whether the block is working before allowing surgery to start?

Give specific sensory points and relate them to nerves, mention tourniquet area.

Test sensory loss to cold/light touch/pinprick in: median (palmar index), ulnar (palmar little), radial (dorsal first web space), musculocutaneous (lateral forearm).
Optional motor: thumb opposition (median), finger abduction (ulnar), wrist extension (radial), elbow flexion (musculocutaneous).
Check medial upper arm sensation for tourniquet tolerance, consider intercostobrachial coverage if needed.

Discuss tourniquet pain in the context of axillary block and how you would manage it.

Tourniquet pain is a common viva theme in upper limb regional anaesthesia.

Mechanism: not fully abolished by peripheral nerve block, contributions from unblocked cutaneous nerves (e.g. intercostobrachial T2) and deep ischaemic pain pathways.
Prevention: ensure intercostobrachial nerve covered (subcutaneous ring infiltration medial upper arm), minimise tourniquet time/pressure where possible, choose LA with adequate duration.
Treatment: reassurance, analgesia (opioid), light sedation (e.g. propofol/remifentanil per local practice), consider additional local infiltration, convert to GA if severe/prolonged.

What complications can occur with axillary block, and how would you recognise and manage LAST?

Expect a structured list plus a clear LAST algorithm.

Complications: vascular puncture/haematoma, infection, nerve injury, block failure, LAST, pneumothorax is rare with axillary approach.
Recognise LAST: perioral numbness, tinnitus, metallic taste, agitation/confusion → seizures → arrhythmias/hypotension/cardiac arrest.
Manage: stop injection, call for help, airway/100% O2/ventilate, treat seizures (benzodiazepine), start lipid emulsion early, follow local/RA-UK guidance, CPR if required.

Compare axillary block with supraclavicular and interscalene blocks for upper limb surgery.

A common FRCA-style comparison: coverage, risks, and suitability.

Axillary: best for forearm/hand, lower risk of pneumothorax/phrenic palsy, may miss musculocutaneous and intercostobrachial, tourniquet pain common.
Supraclavicular: dense block for arm distal to shoulder, faster onset, higher pneumothorax risk than axillary, possible phrenic nerve involvement (less than interscalene).
Interscalene: best for shoulder/proximal humerus, high incidence of phrenic nerve palsy and hoarseness, less reliable ulnar distribution, not ideal for severe respiratory disease.

A patient on anticoagulants requires wrist surgery. Would you perform an axillary block?

Answer should be principle-based: compressibility, bleeding risk, guideline adherence, and shared decision-making.

Assess anticoagulant type, dose, timing, renal function, and indication, check platelet count/coagulation if relevant, follow current regional anaesthesia anticoagulation guidance.
Axillary site is relatively compressible compared with deep plexus blocks, but bleeding/haematoma can still occur, use ultrasound to avoid vessels, apply prolonged pressure if puncture occurs.
Discuss risks/benefits and alternatives (GA, local infiltration), document shared decision and post-block neurovascular observations.

Describe the nerve supply of the hand relevant to axillary block and how you would troubleshoot a specific nerve sparing.

Examiners like targeted troubleshooting: identify which nerve is spared and how to rescue it.

Median: palmar lateral 3½ digits, thenar motor, sparing → pain in index/middle/thumb, rescue with targeted median perineural injection under ultrasound.
Ulnar: palmar/dorsal medial 1½ digits, intrinsic hand muscles, sparing → little finger pain/weak finger abduction, rescue with targeted ulnar injection medial to artery.
Radial: dorsal radial hand sensation, wrist/finger extension motor, sparing → dorsal web space pain, rescue with targeted radial injection posterior to artery.
Musculocutaneous: lateral forearm sensation, elbow flexion, sparing → lateral forearm pain with incision/traction, rescue by injecting in/near coracobrachialis.

You are asked to provide anaesthesia for a hand trauma washout in a patient with COPD. Discuss the advantages and disadvantages of an axillary block and how you would conduct the case.

Structure: suitability, benefits/risks, conduct, failure plan, post-op.

Suitability: procedure distal to elbow, COPD makes avoidance of GA desirable, axillary block avoids phrenic palsy risk seen with interscalene and has very low pneumothorax risk compared with supraclavicular.
Benefits: spontaneous ventilation, excellent analgesia, reduced opioids, day-case potential, haemodynamic stability.
Disadvantages/risks: block failure/patchiness, tourniquet pain, LAST, vascular puncture, nerve injury, time to perform/onset.
Conduct: consent (incl. nerve injury, failure, LAST), monitoring/IV access, ultrasound-guided multi-injection technique including musculocutaneous, calculate LA dose, minimal sedation, confirm block before incision, cover intercostobrachial if tourniquet planned.
Failure plan: targeted top-ups, surgeon infiltration, convert to GA with COPD-appropriate strategy (lung-protective ventilation, avoid excessive opioids, consider SGA if appropriate).
Post-op: multimodal analgesia, limb protection advice, neuro checks, safety-net for persistent symptoms.

Outline the complications of brachial plexus blocks and how you would minimise the risk when performing an axillary block.

Examiners expect general complications plus axillary-specific emphasis (vascular puncture, missed nerves, tourniquet).

Complications: LAST, nerve injury, vascular puncture/haematoma, infection, block failure, allergic reaction, local tissue injury, (pneumothorax/phrenic palsy mainly proximal approaches).
Risk reduction: ultrasound guidance, identify vessels with Doppler, incremental injection with aspiration, avoid high pressure, minimal sedation, adhere to max LA dose, lipid available, asepsis, document baseline neuro status.
Axillary-specific: ensure musculocutaneous block, consider intercostobrachial coverage for tourniquet, apply pressure after any vascular puncture.

A patient develops a seizure shortly after injection during an axillary block. Describe your immediate management.

This is essentially a LAST emergency viva, prioritise ABC and lipid therapy.

Stop LA injection, call for help, commence ABC approach with 100% oxygen, maintain airway and support ventilation to avoid hypoxia/hypercarbia/acidosis.
Terminate seizure: benzodiazepine (e.g. midazolam), consider small propofol doses only if haemodynamically stable, avoid large doses in instability.
Start lipid emulsion promptly per guideline, continue supportive care and treat arrhythmias/hypotension, prepare for CPR if deterioration.
Post-event: ICU/HDU observation, document, report, counsel patient, review LA dosing and technique.