Forearm blocks (median, ulnar, radial)

Surgical approach (context: typical cases using forearm blocks)

Common procedures: laceration repair, tendon repair, foreign body removal, incision & drainage, carpal tunnel release (median), trigger finger, Dupuytren’s (often more proximal), hand fracture manipulation, nailbed repair, hand burns dressing changes
Typical operative steps (varies by procedure): tourniquet (upper arm/forearm), skin prep/drape, local infiltration by surgeon sometimes, incision, haemostasis, repair (tendon/nerve/skin), dressing/splint
- Tourniquet pain may limit purely distal blocks; consider additional analgesia/sedation or more proximal block/GA

Anaesthetic management (for surgery on hand/wrist using forearm blocks)

Type of anaesthesia: regional (forearm peripheral nerve blocks) ± sedation; GA if prolonged, uncooperative patient, extensive debridement, or tourniquet intolerance
Airway: usually none (spontaneous breathing). If GA required: SGA often suitable; ETT if aspiration risk, long case, prone/awkward access, or need controlled ventilation
Duration: blocks provide surgical anaesthesia for minor/moderate hand surgery; typical surgical time 15–90 min; block duration depends on LA (lidocaine 2–4 h; bupivacaine/ropivacaine 6–12 h)
How painful: skin incision and deep manipulation can be painful if incomplete coverage; tourniquet pain is common with forearm/hand blocks (unblocked intercostobrachial/medial cutaneous nerves; deep ischaemic pain)
- Plan: multimodal analgesia, minimal sedation (titrate), consider tourniquet alternatives (WALANT) or more proximal block/GA
Monitoring and safety: standard monitoring, IV access, full asepsis, resuscitation equipment and intralipid immediately available; document neuro exam if possible

Overview and indications

Forearm blocks target terminal nerves: median, ulnar, superficial radial (sensory) ± radial nerve deep branch not required for cutaneous anaesthesia
Used for: hand/wrist surgery, analgesia for fractures/soft tissue injury, ED wound management; can be combined with digital blocks
Advantages vs brachial plexus: less motor block proximally, less risk of phrenic palsy/pneumothorax, lower LA volume, can preserve elbow/shoulder function
Limitations: may not cover tourniquet pain; may miss cutaneous territories (e.g., medial cutaneous nerve of forearm, intercostobrachial); incomplete coverage if anatomical variation

Contraindications and cautions

Absolute: patient refusal, true LA allergy (rare), infection at injection site, inability to cooperate/maintain position safely
Relative: anticoagulation/coagulopathy (lower risk than deep plexus blocks but still consider haematoma/compartment risk), pre-existing neuropathy, severe peripheral vascular disease, inability to assess neuro status, sepsis
Caution with high-pressure injection (intraneural risk) and in patients with tight casts/compartment syndrome risk (masking pain)

Relevant sensory distribution (exam essentials)

Median nerve: palmar thumb, index, middle, radial half of ring finger; dorsal distal phalanges of index/middle (nail beds); thenar eminence (palmar cutaneous branch arises proximal to carpal tunnel)
Ulnar nerve: palmar and dorsal ulnar side of hand; little finger and ulnar half of ring finger
Superficial radial nerve: dorsolateral hand and dorsal thumb/index proximal phalanges; NOT usually nail beds (median supplies distal dorsal index/middle)
Important gaps: medial cutaneous nerve of forearm (medial forearm skin), lateral cutaneous nerve of forearm (cephalic side), intercostobrachial (upper medial arm) for tourniquet

Local anaesthetic choice and dosing (typical forearm block volumes)

Technique is low volume: typically 3–5 mL per nerve with ultrasound; 5–10 mL with landmark techniques depending on spread
LA options: lidocaine 1–2% (fast onset), ropivacaine 0.2–0.5% or bupivacaine/levobupivacaine 0.25–0.5% (longer duration)
Additives: adrenaline (reduce systemic uptake/marker of intravascular injection; avoid end-artery myths—evidence supports safety in digits in appropriate concentrations but follow local policy), dexamethasone (prolongs duration; perineural vs IV varies by policy)
Always calculate maximum safe dose (weight-based) and consider cumulative dose if multiple injections; use incremental injection with aspiration and ultrasound visualisation

Preparation, positioning, and equipment

Consent: explain benefits/risks (failure, nerve injury, infection, bleeding, LAST), duration of numbness, limb protection advice
Position: supine, arm abducted on arm board, forearm supinated for median/ulnar at wrist; pronation may help superficial radial at distal forearm
Equipment: high-frequency linear ultrasound probe, sterile cover/gel, 22–25G 50 mm needle (or 25G for wrist), chlorhexidine/alcohol prep, labelled syringes, intralipid available
Safety: perform a block “stop” check, monitor throughout, communicate with patient (paresthesia/pain on injection = stop and reposition)

Median nerve block (forearm/wrist) — anatomy and technique

Anatomy at wrist: median nerve lies between palmaris longus and flexor carpi radialis tendons (often just deep to palmaris longus) and superficial to flexor tendons; accompanies no major artery at the wrist (unlike ulnar)
Landmark technique (wrist): identify palmaris longus (absent in ~10–20%); insert needle just ulnar to FCR or between PL and FCR, advance slowly until just deep to fascia; inject 3–5 mL after negative aspiration
- If palmaris longus absent: use FCR tendon (radial) and FCU tendon (ulnar) as references; median is usually just ulnar to FCR
Ultrasound technique: probe transverse at distal forearm/wrist crease; identify FCR, PL, flexor tendons; median nerve appears hyperechoic oval/triangular; in-plane needle; deposit LA to surround nerve (avoid intraneural injection)
Block assessment: loss of cold/pinprick in median distribution; motor: thumb opposition/abduction (recurrent branch) may be reduced

Ulnar nerve block (forearm/wrist) — anatomy and technique

Anatomy at wrist: ulnar nerve lies ulnar to ulnar artery within Guyon’s canal region; more superficial at wrist; at distal forearm it is deep to FCU tendon
Landmark technique (wrist): palpate ulnar artery at wrist; insert needle just ulnar to the artery, advance 0.5–1 cm; aspirate and inject 3–5 mL
- Avoid intravascular injection: ulnar artery is close; aspirate frequently and inject incrementally
Ultrasound technique: probe transverse at wrist/distal forearm; identify ulnar artery (Doppler helpful) and nerve (hyperechoic, often small) ulnar to it; deposit LA around nerve, not around artery
Block assessment: loss of sensation little finger/ulnar half ring finger; motor: finger abduction/adduction (interossei), thumb adduction (Froment’s sign)

Radial nerve (superficial radial) block — anatomy and technique

Target for cutaneous anaesthesia is superficial radial nerve (SRN), not the deep motor branch
Anatomy: SRN emerges between brachioradialis and extensor carpi radialis longus in distal forearm; becomes subcutaneous ~5–10 cm proximal to radial styloid; runs with/near cephalic vein
Landmark field block (common): subcutaneous ring/line of LA over dorsolateral distal forearm from radial styloid towards brachioradialis tendon; 5–10 mL in a fan
- This is often a subcutaneous infiltration rather than a perineural injection; lower nerve injury risk but may be patchy
Ultrasound technique: probe transverse at distal forearm; identify brachioradialis; SRN is small hyperechoic structure superficial/lateral; inject 3–5 mL to surround; avoid cephalic vein
Block assessment: loss of sensation dorsolateral hand and thumb web space; motor function preserved (unless more proximal radial nerve blocked)

Coverage planning (which nerves for which surgery)

Palmar hand surgery: usually median + ulnar; add SRN if dorsal extension or radial-sided dorsum involved
Dorsal hand surgery: usually SRN + ulnar (dorsal ulnar cutaneous) ± median for nailbed/distal dorsal index/middle
Thumb: median (palmar) + SRN (dorsal); consider digital blocks for complete circumferential anaesthesia
If tourniquet used: consider additional analgesia/sedation, or more proximal block (e.g., axillary) and/or block intercostobrachial/medial cutaneous nerve of arm depending on tourniquet site

Complications and management

Local anaesthetic systemic toxicity (LAST): risk increased with intravascular injection (especially ulnar near artery) and multiple injections
- Management: stop injection, call for help, airway/oxygen/ventilation, treat seizures (benzodiazepine), lipid emulsion, manage arrhythmias (avoid large doses propofol in unstable patient; avoid lignocaine as antiarrhythmic in LAST)
Nerve injury: intraneural injection/high pressure, needle trauma, ischaemia; minimise by ultrasound, low pressure, avoid paresthesia pain, incremental injection
Vascular puncture/haematoma: ulnar artery proximity; compress and reassess; consider anticoagulation status
Infection: asepsis; avoid through cellulitis
Block failure/patchy block: anatomical variation, inadequate LA spread; troubleshoot with ultrasound top-up, supplementary infiltration/digital blocks, or convert to GA
Masking evolving compartment syndrome: avoid dense prolonged analgesia in high-risk injuries without clear monitoring plan; educate team and document

Troubleshooting and tips

If median block spares thenar eminence: consider palmar cutaneous branch (arises proximal to carpal tunnel) — ensure injection is proximal enough or supplement subcutaneous infiltration over thenar area
If ulnar block incomplete on dorsoulnar hand: dorsal ulnar cutaneous branch arises proximal to wrist; perform block slightly more proximal in distal forearm
If SRN block patchy: use a subcutaneous fan technique and ensure coverage across dorsolateral forearm; avoid intravascular injection into cephalic vein
Tourniquet pain: treat early (opioid, ketamine low-dose, propofol infusion titrated) or change plan (release/deflate, convert to GA, more proximal block)

Talk me through how you would provide regional anaesthesia for a laceration repair on the palmar aspect of the hand.

Aim: surgical anaesthesia of palmar hand with minimal proximal motor block; anticipate tourniquet needs.

Assess site: palmar hand usually needs median + ulnar; add superficial radial if dorsoradial extension/first web space involved
Check contraindications, consent, baseline neurovascular exam (document), allergy/anticoagulation status
Plan: ultrasound-guided wrist/forearm blocks with low volumes (3–5 mL per nerve) using ropivacaine 0.5% or lidocaine depending on duration; incremental injection with aspiration
Tourniquet: if forearm/upper arm tourniquet planned, warn about possible pain; consider sedation or alternative (WALANT) or more proximal block/GA if needed
Confirm block: sensory loss in relevant distributions before incision; supplement with local infiltration/digital blocks if needed

Describe the ultrasound anatomy and technique for a median nerve block at the wrist.

Key is identifying flexor tendons and placing LA around the median nerve without intraneural injection.

Probe: high-frequency linear, transverse at wrist crease/distal forearm; optimise depth and gain
Identify structures: FCR tendon (radial), palmaris longus (if present), flexor tendons; median nerve is hyperechoic oval/triangular between/near PL and FCR, superficial to flexor tendons
Needle: in-plane (lateral-to-medial or medial-to-lateral), advance to just adjacent to nerve; inject small aliquots to achieve circumferential spread
Volume: typically 3–5 mL; avoid high-pressure injection and stop if patient reports sharp paresthesia/pain

How would you perform an ulnar nerve block at the wrist using landmarks? What are the hazards?

Ulnar nerve is close to the ulnar artery: safety is about avoiding intravascular injection and haematoma.

Palpate ulnar artery at wrist; insert needle just ulnar to the artery at the proximal wrist crease; advance 0.5–1 cm
Aspirate and inject incrementally 3–5 mL LA; apply pressure if arterial puncture occurs
Hazards: intravascular injection → LAST; arterial puncture/haematoma; intraneural injection; incomplete block if injected too distal (dorsal ulnar cutaneous branch arises proximal)

A patient has numbness over the dorsum of the thumb but still feels pain at the nail bed during surgery. Explain why and what you would do.

Dorsal thumb skin is often superficial radial; nail bed sensation can be median (and digital nerves).

Explain anatomy: superficial radial supplies dorsolateral hand/thumb skin; median nerve supplies dorsal distal phalanges/nail beds of index/middle and contributes via digital nerves
Action: assess which digit; supplement with median nerve block (if not done) and/or digital nerve block of the affected finger; ensure adequate time for onset
If tourniquet pain or deep pain persists: provide titrated analgesia/sedation or convert to GA if required

How do you minimise the risk of nerve injury during forearm blocks?

Prevent mechanical and chemical injury: visualise needle, avoid intraneural injection, avoid high pressure, and use appropriate LA/volume.

Use ultrasound where possible; keep needle tip in view; aim for perineural spread rather than intraneural
Avoid paresthesia or pain on injection; stop and reposition if occurs
Inject incrementally with frequent aspiration; use low opening injection pressure; avoid large volumes in tight fascial planes
Document pre-existing neuropathy and postoperative neuro symptoms; provide limb protection advice

Your patient develops tinnitus and perioral tingling during an ulnar nerve block. What is happening and what do you do next?

This suggests early LAST; act immediately to prevent progression to seizures/cardiovascular collapse.

Stop injecting immediately; call for help; maintain verbal contact
Airway/oxygen/ventilation: 100% oxygen; avoid hypercapnia/acidosis; prepare for airway support
Treat seizures if occur: benzodiazepine first line; consider small propofol doses only if haemodynamically stable
Start lipid emulsion therapy as per guideline; manage arrhythmias (avoid lignocaine; use amiodarone if needed); continue CPR modifications if arrest
Post-event: monitor (HD/ICU depending severity), document, report, and counsel patient

Which nerves must be blocked to provide complete anaesthesia for the hand? What areas might still be painful?

Hand cutaneous supply is mainly median, ulnar, and superficial radial, but there are important exceptions.

Core: median + ulnar + superficial radial cover most palmar and dorsal hand skin
Potential gaps: thenar eminence (palmar cutaneous branch of median), dorsoulnar hand (dorsal ulnar cutaneous branch if blocked too distal), medial/lateral forearm skin (cutaneous nerves), and tourniquet pain (intercostobrachial/medial cutaneous arm)
Deep pain: periosteal/tendon manipulation may require supplementation even with good cutaneous block

Compare forearm blocks with an axillary brachial plexus block for hand surgery.

Trade-off between simplicity/coverage and proximal effects/risks.

Forearm blocks: lower LA volume, fewer proximal complications, preserve elbow/shoulder movement; but can be patchy and don’t address tourniquet pain well
Axillary block: more reliable for multiple nerve territories and can include musculocutaneous; still may not fully cover tourniquet (upper arm) without additional blocks; higher LA volume and more motor block
Choice depends on surgery extent, tourniquet plan, patient factors, and operator skill

You are asked to provide regional anaesthesia for a day-case carpal tunnel decompression. Discuss your anaesthetic technique and perioperative management.

Carpal tunnel decompression is median-nerve territory surgery; consider surgeon preference (WALANT vs tourniquet) and postoperative analgesia.

Preop: assess comorbidities (OSA, diabetes/neuropathy), anticoagulants, baseline neuro symptoms; consent including risk of transient worsening/diagnostic confusion post-op
Technique options: (1) Median nerve block at wrist/forearm ± local infiltration by surgeon; (2) WALANT (surgeon infiltration with lidocaine + adrenaline); (3) GA if anxious/uncooperative
If tourniquet used: warn about discomfort; consider light sedation; forearm blocks may not prevent deep tourniquet pain
LA choice: short case—lidocaine; if analgesia desired—ropivacaine/levobupivacaine; keep volumes low and within max dose
Intraop: standard monitoring, IV access, incremental injection, readiness for LAST; confirm sensory block before incision
Postop: limb protection advice, avoid heat/trauma until sensation returns; simple analgesia; safety-net for persistent numbness/weakness

Describe the complications of peripheral nerve blocks in the forearm and how you would reduce their incidence.

Structure answer into: neurological, systemic toxicity, vascular/bleeding, infection, block failure, and patient factors.

Neurological: neuropraxia, intraneural injection, neuritis; reduce with ultrasound, low pressure, avoid paresthesia pain, appropriate needle handling, avoid high concentration/large volume around small nerves
Systemic: LAST; reduce with dose calculation, incremental injection/aspiration, adrenaline marker, ultrasound, avoid intravascular injection (ulnar artery proximity)
Vascular/bleeding: haematoma/arterial puncture; reduce with ultrasound/Doppler, compression, consider anticoagulation
Infection: asepsis; avoid infected sites
Failure/patchy: anatomical variation, inadequate spread; reduce with ultrasound, adequate time, correct nerve selection; manage with top-ups or conversion plan
Other: masking compartment syndrome; reduce by careful patient selection, documentation, and monitoring plan

Explain the sensory innervation of the hand and how it informs your choice of blocks for dorsal hand surgery.

Examiners want accurate territories plus acknowledgement of overlap and nailbed exceptions.

Dorsum: superficial radial supplies dorsolateral hand; ulnar supplies dorsoulnar hand; median contributes to dorsal distal phalanges/nail beds of index/middle via digital nerves
For dorsal surgery: plan SRN + ulnar; add median if incision involves index/middle nail bed/distal dorsal phalanx or if uncertain
Supplementation: digital blocks for circumferential finger surgery; local infiltration for small gaps