Interscalene block

Surgical approach (context: typical operations where interscalene block is used)

• Shoulder arthroscopy (e.g. rotator cuff repair, subacromial decompression, labral repair)
  • Patient positioning: beach-chair or lateral decubitus; traction may be applied
  • Arthroscopic portals; irrigation fluid; potential for airway/ventilation effects from fluid extravasation (neck/chest swelling)
• Open shoulder surgery (e.g. arthroplasty, stabilization procedures)
  • More tissue trauma and blood loss than arthroscopy; longer duration
• Proximal humerus fixation / clavicle surgery (variable coverage)
  • Clavicle often needs additional superficial cervical plexus block or local infiltration (supraclavicular nerves C3–4)

Anaesthetic management (typical plan)

• Type of anaesthesia: regional (interscalene) + sedation, or GA + interscalene for analgesia
  • GA often preferred for arthroscopy (airway access, immobility, tolerance of irrigation/positioning)
• Airway: if GA, usually ETT (especially beach-chair, longer cases, aspiration risk); SGA possible for short low-risk cases with good access
  • Beach-chair: secure airway and vigilance for hypotension/cerebral perfusion
• Duration: commonly 1–3 hours (arthroscopy often 1–2 h; arthroplasty 2–3+ h)
• Pain: moderate–severe without regional; interscalene provides excellent analgesia for shoulder/proximal humerus
• Key perioperative risks to plan for: hemidiaphragmatic paresis, local anaesthetic systemic toxicity (LAST), recurrent laryngeal nerve block/hoarseness, Horner’s syndrome, pneumothorax (rare), nerve injury

Indications and dermatomal/myotomal coverage

• Best for: shoulder surgery (C5–6 predominant), proximal humerus
• Often incomplete for: ulnar nerve distribution (C8–T1) and medial arm/forearm
  • May need supplementation for distal arm/hand surgery (consider supraclavicular/infraclavicular/axillary approaches instead)
• Clavicle/AC joint: may require superficial cervical plexus block (supraclavicular nerves C3–4) ± local infiltration

Relevant anatomy (exam core)

• Target: brachial plexus roots/trunks between anterior and middle scalene muscles at level of cricoid cartilage (approx C6) or slightly caudad
• Ultrasound landmarks: SCM superficially; interscalene groove; hypoechoic round roots (often C5–C7) lateral to carotid; prevertebral fascia; transverse processes with anterior/posterior tubercles
• Nearby structures: phrenic nerve on anterior scalene (high incidence of blockade), vertebral artery (medial/deep), dorsal scapular and long thoracic nerves (within/near middle scalene), recurrent laryngeal nerve (medial spread), epidural/subarachnoid space (medial spread)
• Fascial planes: injection deep to prevertebral fascia around roots; avoid intraneural injection (high opening pressure, pain, swelling)

Contraindications and patient selection

• Absolute: patient refusal, true LA allergy, infection at site, uncorrected severe coagulopathy (follow regional anaesthesia anticoagulation guidance), inability to cooperate/consent
• Relative/important: significant respiratory disease (COPD, restrictive disease), contralateral diaphragmatic palsy, severe OSA, morbid obesity, severe pulmonary hypertension
  • Reason: hemidiaphragmatic paresis is common even with ultrasound and low volumes
• Caution: pre-existing neuropathy, anticoagulation/antiplatelets, difficult airway if planning sedation-only, inability to tolerate supine/semisupine positioning

Technique (ultrasound-guided) and practical steps

• Preparation: consent (including respiratory effects), IV access, monitoring, resuscitation drugs and intralipid available, asepsis, block performed in area with full monitoring
• Position: head turned away; semisupine; arm by side; optimize comfort and access
• Probe: high-frequency linear; scan at level of cricoid (C6) then adjust to best view of C5–C7 roots between scalene muscles
• Needle: in-plane lateral-to-medial commonly (keeps needle away from carotid/vertebral artery); aim for perineural spread around roots/trunks
  • Incremental injection with frequent aspiration; observe circumferential spread; stop if high resistance or patient reports severe pain/paraesthesia
• Volumes: aim for lowest effective volume to reduce phrenic palsy risk (often 5–10 mL for analgesia; 10–20 mL for dense surgical block depending on practice and LA choice)
• LA choices (typical): ropivacaine 0.2–0.5% or levobupivacaine 0.25–0.5%; consider lidocaine for rapid onset (mind total dose)
  • Always calculate maximum safe dose (mg/kg) and account for surgical infiltration and other blocks
• Adjuncts: perineural dexamethasone may prolong duration (local policy); avoid routine adrenaline if it obscures intravascular injection warning signs (practice varies)
• Catheter technique: can be used for continuous analgesia after major shoulder surgery; secure well; educate re limb protection and respiratory symptoms

Assessment of block and intraoperative management

• Expected sensory: C5–C6 (lateral shoulder/upper arm) most reliable; motor: deltoid weakness (axillary nerve), biceps weakness (musculocutaneous)
• If inadequate: allow time; top-up if safe; supplement with local infiltration, suprascapular/axillary nerve blocks, or convert to GA
• Sedation-only cases: maintain verbal contact; capnography; be ready to manage airway (block does not guarantee immobility or complete analgesia)

Complications (FRCA viva list) and management

• Hemidiaphragmatic paresis (phrenic nerve block): very common; may cause dyspnoea, reduced FVC/FEV1; usually resolves as block wears off
  • Management: reassure, sit upright, oxygen, consider NIV if needed; avoid/choose alternative block in high-risk respiratory patients
• Horner’s syndrome (stellate ganglion spread): ptosis, miosis, anhidrosis; benign and self-limiting
• Recurrent laryngeal nerve block: hoarseness; risk of airway compromise if contralateral vocal cord palsy
  • If stridor/airway concern: urgent airway assessment; consider ENT history; avoid in known contralateral palsy
• LAST (intravascular injection/overdose): tinnitus, metallic taste, agitation, seizures, arrhythmias, cardiovascular collapse
  • Immediate actions: stop injection, call for help, airway/100% O2, treat seizures (benzodiazepine), follow lipid rescue protocol, manage arrhythmias (avoid large doses of propofol if unstable; avoid vasopressin; use reduced-dose adrenaline)
• High spinal/epidural spread (rare): hypotension, bradycardia, respiratory insufficiency, loss of consciousness
  • Management: airway/ventilation, vasopressors, fluids, treat bradycardia; ICU support until resolution
• Nerve injury: intraneural injection, needle trauma, ischaemia, haematoma; persistent sensory/motor deficit
  • Prevention: ultrasound visualization, avoid paraesthesia/pain, low-pressure injection, incremental dosing; document neuro exam if concerns
• Pneumothorax: rare with interscalene (more with supraclavicular) but possible if very caudad/deep approach
  • Management: oxygen, assess (US/CXR), treat tension pneumothorax immediately, chest drain if indicated
• Vascular puncture/haematoma: carotid/IJV/vertebral artery (rare with US but serious)

Alternatives and modifications (to reduce phrenic palsy / tailor analgesia)

• Low-volume interscalene: reduces but does not eliminate phrenic palsy
• Suprascapular + axillary nerve blocks: good shoulder analgesia with less diaphragmatic involvement; may be preferred in respiratory compromise
• Superior trunk block: targets convergence of C5–6; may spare phrenic nerve more than classic interscalene (evidence evolving; still possible paresis)
• Local infiltration / surgeon-delivered periarticular infiltration: adjunct only; usually inferior to regional for severe pain

Consent points (what to mention)

• Benefits: superior analgesia, reduced opioids/PONV, improved early rehab, potential day-case facilitation
• Common/expected: numb arm/weakness, Horner’s, hoarseness, shortness of breath from hemidiaphragm paresis
• Serious/rare: LAST, nerve damage, pneumothorax, infection/bleeding, high neuraxial block
• Aftercare: limb protection (burns/trauma), sling use, when to seek help (progressive dyspnoea, chest pain, persistent deficit)