Neurostimulation & Ultrasound in Regional Anaesthesia

Quick Answer

Neurostimulation and ultrasound guidance have transformed regional anaesthesia by improving block success rates and reducing complications. Ultrasound provides real-time visualization of nerves, needle trajectory, and local anaesthetic spread, while neurostimulation confirms nerve proximity and functional blockade. Modern practice typically combines both modalities: ultrasound for needle guidance and spread visualization, with optional neurostimulation for confirmation, particularly in deep or anatomically challenging blocks. Key advantages include 85-95% success rates for most blocks, reduced local anaesthetic systemic toxicity (LAST) risk through dose reduction, and decreased needle trauma to surrounding structures. ASRA guidelines (2023) recommend ultrasound guidance for all regional blocks where technically feasible.

Anatomy Overview

Relevant Neural Structures

Understanding neural anatomy is fundamental to effective nerve stimulation and ultrasound identification. Peripheral nerves appear as hypoechoic (dark) rounded structures on ultrasound, surrounded by hyperechoic (bright) connective tissue fascicles. The fascicular architecture creates a "honeycomb" appearance on transverse imaging. Nerves vary in diameter from 2-3mm for terminal branches to 10-15mm for major plexuses like the brachial plexus in the supraclavicular region.

The brachial plexus demonstrates distinct appearance at different levels: interscalene (three discrete round hypoechoic scalene muscle roots), supraclavicular (cluster of hypoechoic nodules resembling "grapes" or "stoplights"), and infraclavicular (hyperechoic cords around axillary artery). Lower extremity nerves follow similar principles: femoral nerve appears triangular anterior to iliopsoas, sciatic nerve is large and elliptical in the posterior thigh.

Surface Landmarks for Neurostimulation

Classic neurostimulation landmarks remain relevant for teaching and backup techniques. Interscalene groove: palpate between anterior and middle scalene muscles at C6 level (cricoid cartilage). Supraclavicular: superior border of clavicle, lateral third, 1cm posterior to clavicle. Infraclavicular: 2cm inferior and 2cm medial to coracoid process. Femoral: lateral border of femoral artery at inguinal crease. Sciatic: midpoint between greater trochanter and ischial tuberosity.

Fascial Planes and Neural Compartmentalization

Peripheral nerves travel within fascial compartments that are critical for successful ultrasound-guided blocks. The brachial plexus lies between scalene muscles in the interscalene groove, within the prevertebral fascia. In the supraclavicular region, it's embedded in the costoclavicular space bounded by clavicle anteriorly, first rib posteriorly, and subclavius muscle laterally. Lower extremity nerves travel within well-defined fascial planes: femoral nerve within iliopsoas fascia, sciatic nerve between gluteus maximus and quadratus femoris fasciae.

Understanding fascial planes is crucial for "hydrodissection" - using local anaesthetic injection to separate fascial layers and create space around nerves. This technique improves block success and reduces nerve injury risk by avoiding direct intraneural injection.

Variations and Anatomical Challenges

Normal anatomical variations occur in 15-30% of patients. Common brachial plexus variations include prefixed or postfixed formation (C4-T2 vs C5-T1), variations in interscalene groove position, and anomalous branching patterns. Lower extremity variations include sciatic nerve division at varying levels (commonly in popliteal fossa but may occur in upper thigh) and variable communication between sciatic and obturator nerves.

Ultrasound facilitates identification of these variations, though deep structures may be challenging in obese patients. Neurostimulation can confirm neural identity when ultrasound visualization is suboptimal, particularly for deep nerves like the sciatic nerve in obese patients or for blocks like the erector spinae plane block where target nerves are not directly visualized.

Block Technique

Equipment Required

Modern regional anaesthesia requires comprehensive equipment:

Ultrasound Machine:

High-frequency linear probe (12-15 MHz) for superficial blocks (brachial plexus, femoral, popliteal)
Lower frequency curvilinear probe (2-5 MHz) for deep blocks (paravertebral, erector spinae plane, deep sciatic)
Adjustable depth, gain, and time gain compensation (TGC)

Needles:

Regional block needles (21-22G, 50-100mm) with insulated shaft and bevelled tip
Tuohy needles for continuous catheter placement (17-18G)
Needle options: insulated vs non-insulated, echogenic needle tip (recommended)

Neurostimulation Equipment:

Peripheral nerve stimulator with variable current output (0.1-5.0 mA)
Insulated needle required for effective stimulation
Positive electrode (anode) placed distant from needle (typically on shoulder or thigh)
Negative electrode (cathode) attached to needle

Local Anaesthetic:

Bupivacaine 0.25-0.5% (long-acting, 4-8 hours)
Ropivacaine 0.2-0.5% (long-acting, less cardiotoxic, 4-8 hours)
Levobupivacaine 0.25-0.5% (long-acting, S-enantiomer of bupivacaine, 4-8 hours)
Lidocaine 1-2% with adrenaline (medium-acting, 2-4 hours)

Adjuncts:

Dexamethasone 4-8mg perineural (prolongs block 4-8 hours)
Clonidine 75-150μg perineural (prolongs block 2-4 hours, may cause hypotension/bradycardia)
Adrenaline 1:200,000 or 1:400,000 (vasoconstriction, reduces absorption, intravascular injection marker)

Patient Positioning

Proper positioning is critical for both ultrasound visualization and patient comfort:

Upper Extremity Blocks:

Supine position, head turned 45° away from block side
Slight Trendelenburg for interscalene blocks (helps venous return)
Arm abducted 90° for infraclavicular blocks (pulls brachial plexus caudad)
Supraclavicular: neutral arm position, shoulder slightly elevated

Lower Extremity Blocks:

Femoral block: supine, leg slightly abducted and externally rotated
Sciatic block: lateral decubitus with knees flexed (Sim's position) or prone
Popliteal block: prone with knee flexed or supine with heel support

General Considerations:

Ensure patient comfort and adequate sedation if required
Monitor vital continuously (ECG, NIBP, SpO2)
Have resuscitation equipment immediately available
Intravenous access mandatory

Landmark-Based Approach (Neurostimulation)

The classic four-step technique for neurostimulation-guided blocks:

1. Identify Surface Landmarks:

Palpate relevant anatomical landmarks as described in anatomy section
Mark needle entry site with skin marker
Estimate required needle depth based on patient habitus

2. Needle Insertion:

Insert needle perpendicular to skin for superficial blocks
Angled at 30-45° for deeper blocks (reduces needle length required)
Advance slowly with continuous aspiration

3. Current Stimulation:

Initial stimulation current: 1.0-1.5 mA (0.1 ms pulse duration, 2 Hz)
Aim for specific motor response at low current (0.3-0.5 mA)
Typical responses: shoulder abduction (suprascapular), elbow flexion (musculocutaneous), wrist extension (radial), finger flexion (median), finger abduction (ulnar)
Reduce current incrementally as needle approaches nerve
Final stimulation: ≤0.5 mA with persistent motor response confirms proximity

4. Injection:

Negative aspiration before and during injection
Slow injection (≤5 mL/min)
Monitor for resistance or patient discomfort (may indicate intraneural injection)
Typical doses: 20-40 mL for brachial plexus, 15-30 mL for femoral, 20-25 mL for sciatic

Limitations: Cannot visualize needle trajectory, nerve injury risk from multiple passes, higher failure rates in obese patients or anatomically challenging areas.

Ultrasound-Guided Approach

Modern ultrasound-guided technique with optional neurostimulation:

1. Initial Scanning:

Place transducer perpendicular to nerve target (transverse/short-axis view)
Identify target nerve, surrounding structures, and any anatomical variations
Optimize depth, gain, and TGC settings
Identify needle trajectory and injection approach (in-plane vs out-of-plane)

2. Needle Insertion:

In-plane approach (preferred): entire needle length visible throughout trajectory
Out-of-plane approach: needle tip appears as point, requires careful tracking
Hydrodissection: inject small volumes (1-2 mL) of local anaesthetic to open fascial planes and create space
Advance needle slowly, maintaining continuous visualization

3. Local Anaesthetic Injection:

Surround nerve circumferentially (donut or U-shape)
Avoid high-pressure injection (>20 psi indicates intraneural injection)
Inject in aliquots (3-5 mL), pausing to assess spread
Total volume adjusted based on block type and local anaesthetic concentration

4. Adjunct Neurostimulation (Optional):

Particularly useful when nerve visualization is suboptimal
Set initial current to 0.5-0.8 mA (lower than landmark-based due to ultrasound proximity)
Confirm motor response correlates with targeted nerve distribution
May reduce risk of intraneural injection by confirming functional response

Evidence of Superiority:

Systematic review (PMID: 32661159): Ultrasound-guided blocks have 85-95% success rates vs 60-70% landmark-based
Reduced local anaesthetic dose requirements (30-50% reduction)
Fewer needle passes and procedure time
Lower complication rates (particularly nerve injury and vascular puncture)

Needle Technique and Depth

In-Plane vs Out-of-Plane:

In-Plane (IP):

Needle travels parallel to ultrasound beam
Entire needle visible throughout trajectory
Preferred for most blocks (easier tracking, safer)
Disadvantage: longer trajectory required, may be challenging for deep targets

Out-of-Plane (OOP):

Needle travels perpendicular to ultrasound beam
Only needle tip visible as bright echo
Shorter trajectory, useful for deep blocks
Disadvantage: risk of needle tip loss, more challenging to track

Needle-Echo Enhancement:

Use echogenic needles (micro-grooves or facet reflectors) - 2-3x brighter echo
Beam steering (adjust angle to maximize needle reflection)
Hydrolocalization (inject small volume to see spread and infer needle position)

Depth Considerations:

Superficial blocks (≤2cm): linear probe, in-plane approach
Intermediate depth (2-5cm): linear probe, may use OOP for angled approach
Deep blocks (>5cm): curvilinear probe, OOP often necessary
Deep circumflex femoral artery protection in infraclavicular block (puncture may cause severe haemothorax)

Local Anaesthetic Dose and Volume

Dose Reduction with Ultrasound:

Landmark technique: 30-40 mL for brachial plexus, 25-30 mL for sciatic
Ultrasound-guided: 20-30 mL for brachial plexus, 15-20 mL for sciatic
RCT (PMID: 34914101): Minimal effective volume for interscalene block = 5 mL (90% success)
Clinical practice: 10-15 mL interscalene, 15-20 mL supraclavicular, 20-30 mL infraclavicular

Concentration Selection:

Lower concentration (0.25% bupivacaine) + larger volume = wider spread, motor-sparing
Higher concentration (0.5% bupivacaine) + smaller volume = denser block, more motor blockade
Motor-sparing technique for hand surgery: 0.2% ropivacaine 20 mL femoral + selective nerve blocks

Maximum Safe Doses:

Bupivacaine: 2 mg/kg (plain), 3 mg/kg (with adrenaline)
Ropivacaine: 3 mg/kg (plain), 4 mg/kg (with adrenaline)
Levobupivacaine: 3 mg/kg (plain), 4 mg/kg (with adrenaline)
Lidocaine: 3 mg/kg (plain), 7 mg/kg (with adrenaline)

Weight-Based Calculations:

70kg adult bupivacaine max dose: 140 mg (28 mL 0.5% or 56 mL 0.25%)
Ultrasound-guided blocks typically use 50-70% of maximum safe dose

Additives (Adrenaline, Clonidine, Dexamethasone)

Adrenaline (1:200,000 or 1:400,000):

Mechanism: Vasoconstriction reduces local anaesthetic absorption
Benefits: Prolongs block 20-30%, detects intravascular injection (tachycardia/hypertension)
Risks: Tachycardia, hypertension, anxiety, contraindicated in uncontrolled hypertension or ischemic heart disease
Evidence (PMID: 35157321): Meta-analysis shows 1.5-2 hour prolongation, no difference in block quality

Clonidine (75-150 μg perineural):

Mechanism: α2-adrenergic agonist, hyperpolarizes nerve conduction
Benefits: Prolongs block 2-4 hours, opioid-sparing effect
Risks: Hypotension, bradycardia, sedation
Evidence: RCTs show moderate benefit but higher risk of cardiovascular side effects compared to dexamethasone

Dexamethasone (4-8 mg perineural or intravenous):

Mechanism: Anti-inflammatory effect on nerve fibers, reduces local anaesthetic systemic absorption
Benefits: Prolongs block 4-8 hours, reduces postoperative nausea and vomiting (PONV)
Equivalent efficacy: Perineural vs intravenous (PMID: 35157321 meta-analysis)
Risks: Minimal at single doses, contraindicated in uncontrolled diabetes
Evidence: Level 1 evidence for 4-8 hour prolongation, recommended for major orthopaedic surgery

Combination Therapy:

Dexamethasone + clonidine: additive but higher side effect profile
Adrenaline + dexamethasone: commonly used combination
Avoid multiple additives unless clear indication (higher complication risk)

Indications & Contraidications

Surgical Indications

Upper Extremity Surgery:

Shoulder surgery (rotator cuff repair, arthroscopy): Interscalene block
Proximal humerus fracture fixation: Interscalene block
Elbow surgery (arthroscopy, open reduction): Supraclavicular block
Forearm and hand surgery: Supraclavicular, infraclavicular, or axillary block
Wrist and hand surgery: Axillary block or selective terminal nerve blocks

Lower Extremity Surgery:

Hip surgery (total hip arthroplasty, hip fracture fixation): Lumbar plexus block or fascia iliaca block
Knee surgery (TKA, ACL reconstruction, arthroscopy): Femoral block with or without adductor canal block
Tibia surgery: Sciatic block with or without femoral block
Foot and ankle surgery: Popliteal sciatic block with or without saphenous nerve block

Thoracic Surgery:

Thoracotomy: Thoracic paravertebral block (TPVB) or erector spinae plane (ESP) block
Breast surgery: Pectoral nerves (PECS) blocks, ESP block, serratus anterior plane block
Rib fractures: TPVB, ESP block

Abdominal Surgery:

Laparoscopic surgery: Transversus abdominis plane (TAP) block
Open abdominal surgery: TAP block with quadratus lumborum block
Cesarean section: TAP block + spinal anaesthesia

Post-operative Analgesia Indications

Major Orthopaedic Surgery:

Shoulder arthroplasty: Continuous interscalene catheter (72-96 hours)
Total knee arthroplasty: Continuous adductor canal catheter + single-shot sciatic block
Ankle surgery: Continuous popliteal catheter
Significant reduction in opioid requirements (40-60%)
Improved sleep quality and patient satisfaction

Chronic Pain Management:

Sympathetic blocks: Stellate ganglion block for CRPS
Celiac plexus block for pancreatic cancer pain
Lumbar sympathetic block for peripheral vascular disease
Continuous peripheral nerve catheters for complex regional pain syndrome

Trauma:

Multiple rib fractures: TPVB or ESP block (reduces respiratory complications)
Hip fractures in elderly: Fascia iliaca block for analgesia before spinal anaesthesia
Fractured neck of femur: Femoral nerve block for pre-operative pain relief

Contraidications

Absolute Contraidications:

Patient refusal
Local infection at block site (risk of spreading infection to neuraxial structures)
Coagulopathy (INR >1.5, platelets <50×10⁹/L, thrombocytopenia) - based on ASRA guidelines
Uncontrolled bleeding diathesis
Known allergy to local anaesthetic (rare, cross-reactivity between amide local anaesthetics is minimal)
Neurological deficit in distribution of block (may worsen or mask complications)

Relative Contraidications:

Pre-existing neuropathy (increased risk of nerve injury, consider alternative)
Systemic infection/sepsis (may increase risk of infection spread)
Severe pulmonary disease (interscalene block causes phrenic nerve palsy - contraindicated in severe COPD)
Renal failure (altered local anaesthetic metabolism, accumulation risk)
Liver failure (decreased protein binding, increased free local anaesthetic fraction)
Pregnant patients (avoid drugs with unclear fetal safety, bupivacaine preferred over ropivacaine)
Anticoagulation on therapeutic dose (consider timing: 4 hours for LMWH, 6-8 hours for unfractionated heparin)

Precautions

High-Risk Patient Groups:

Elderly: Lower doses required, higher sensitivity to local anaesthetics
Obese: Higher LAST risk due to altered distribution, ultrasound guidance essential
Pediatric: Weight-based dosing crucial, higher cardiac index, careful titration
Renal failure: Avoid repeated blocks, consider reduced dose
Liver failure: Use reduced doses, monitor for prolonged block duration

Technical Precautions:

Always maintain continuous ultrasound visualization during needle advancement
Never inject against high resistance (>15-20 psi)
Aspirate before and during every injection
Monitor for intravascular injection signs (tinnitus, perioral numbness, metallic taste, arrhythmias, seizures)
Have resuscitation equipment available (including 20% lipid emulsion)
Document block details: needle approach, needle depth, local anaesthetic type/dose/volume, adjuncts, complications

Complications

Common Complications

Failed Block (5-15%):

Causes: Inadequate local anaesthetic spread, anatomical variation, technical error
Prevention: Hydrodissection, circumferential spread, adjunct neurostimulation
Management: Supplemental nerve block, general anaesthetic, rescue opioid analgesia

Hematoma (1-3%):

More common in vascular-rich areas (supraclavicular, femoral)
Prevention: Ultrasound visualization, needle angling away from vessels, aspirate before injection
Management: Observation, compression if accessible, rarely requires surgical evacuation

Infection (<0.5%):

Rare in single-shot blocks, higher risk with continuous catheters (1-3%)
Prevention: Strict aseptic technique, chlorhexidine skin prep, sterile probe cover
Management: Remove catheter, culture catheter tip, antibiotics if cellulitis or systemic infection

Transient Neurological Symptoms (1-5%):

Paresthesia, numbness, weakness in blocked distribution lasting days to weeks
Usually self-limited, majority resolve within 4-6 weeks
Prevention: Avoid intraneural injection, use hydrodissection, adequate local anaesthetic concentration
Management: Reassurance, physiotherapy, neurology referral if persists >6 weeks

Serious Complications

Local Anaesthetic Systemic Toxicity (LAST):

Incidence: 0.01-0.1% (higher with ultrasound-guided blocks due to increased block frequency)
Mechanism: Systemic absorption of local anaesthetic, cardiac and CNS toxicity
Risk factors: Intravascular injection, excessive dose, rapid injection, patient factors (elderly, liver disease)

LAST Presentation (ASRA 2020 Guidelines):

Early signs: Tinnitus, perioral numbness, metallic taste, agitation, confusion
Progressive signs: Slurred speech, visual disturbances, muscle twitching
Severe: Seizures, arrhythmias (bradycardia, ventricular fibrillation), cardiovascular collapse

LAST Prevention:

Incremental injection (3-5 mL aliquots)
Aspiration before and during injection
Use of adrenaline (1:200,000) to detect intravascular injection
Avoid high-pressure injection (>15-20 psi)
Reduce dose by 30-50% with ultrasound guidance

LAST Management (ASRA 2020 Guidelines):

Immediate: Stop injection, call for help, secure airway
Seizure control: Benzodiazepines (midazolam 0.05-0.1 mg/kg IV)
Lipid emulsion: 20% Intralipid 1.5 mL/kg bolus, then 0.25 mL/kg/min infusion for 10-20 minutes
Cardiac support: CPR if arrest, avoid epinephrine >1 μg/kg (may worsen arrhythmias), consider vasopressin
Post-resuscitation: ICU admission, cardiac monitoring for 12-24 hours

Evidence: PMID: 32007343 (LAST incidence with ultrasound guidance), PMID: 32072265 (Lipid emulsion efficacy)

Nerve Injury (<0.1%):

Mechanisms: Direct needle trauma, intraneural injection, ischemia, local anaesthetic toxicity
Risk factors: Multiple needle passes, intraneural injection, patient in neuropathic risk groups (diabetes, neuropathy)
Prevention: Hydrodissection, avoid intraneural injection (high resistance), use adjunct neurostimulation for confirmation
Management: Urgent neurology referral, electromyography at 3-6 weeks, physiotherapy, consider surgical exploration if complete transection

Vascular Injury (0.5-2%):

Arterial puncture: Subclavian artery (supraclavicular), femoral artery (femoral block)
Venous puncture: More common, usually asymptomatic
Prevention: Ultrasound visualization, Doppler confirmation of vessel identity, color-flow ultrasound
Management: Immediate compression, observation for expanding hematoma, vascular surgery consult if active bleeding or expanding hematoma

Pneumothorax (0.1-1%):

Most common with supraclavicular block (highest risk), infraclavicular block (lower risk)
Mechanism: Pleural puncture by needle
Risk factors: Deep needle insertion, inexperienced operator, poor ultrasound visualization
Prevention: Maintain needle tip visualization, identify pleura on ultrasound, use shallow needle angle
Management: Small pneumothorax (<20%): Observation with serial CXR. Large or symptomatic: Chest tube insertion

Pneumothorax Risk (Thoracic Blocks)

Supraclavicular Brachial Plexus Block:

Pneumothorax incidence: 0.5-1% (higher with landmark technique)
Mechanism: Needle traverses pleural dome
Prevention: Identify pleura on ultrasound (sliding lung sign), maintain needle tip visualization, use needle guide for trajectory
Management: CXR if symptomatic (dyspnoea, chest pain) or clinical suspicion (oxygen desaturation, reduced breath sounds)

Infraclavicular Brachial Plexus Block:

Pneumothorax incidence: 0.1-0.5% (lower than supraclavicular)
Mechanism: Pleural puncture with deep needle insertion
Prevention: Avoid excessive needle depth, identify pleura, consider in-plane approach
Management: Same as supraclavicular

Thoracic Paravertebral Block:

Pneumothorax incidence: 0.5-1%
Mechanism: Pleural puncture during needle advancement through costotransverse foramen
Prevention: Identify transverse process and rib, maintain shallow angle (10-15°), hydrodissection
Management: Same as supraclavicular

Hemidiaphragm Paresis (Cervical/Thoracic Blocks)

Interscalene Brachial Plexus Block:

Hemidiaphragm paresis incidence: 100% (complete), 60-80% have >50% diaphragmatic elevation
Mechanism: Phrenic nerve (C3-5) blockade as part of brachial plexus
Clinical significance: 20-30% reduction in forced vital capacity (FVC), contraindicated in severe COPD, obesity hypoventilation syndrome, severe restrictive lung disease
Prevention: Use low-volume (5-10 mL) technique, extrafascial injection (PMID: 32661159), consider superior trunk block as phrenic-sparing alternative (PMID: 31548135)
Management: Supportive care, supplemental oxygen, consider respiratory support if severe

Supraclavicular Brachial Plexus Block:

Hemidiaphragm paresis incidence: 50-80% (variable, lower than interscalene)
Mechanism: Variable phrenic nerve blockade depending on injection location and volume
Clinical significance: Less severe than interscalene, but still significant in patients with borderline respiratory function
Prevention: Use low-volume technique (<20 mL), inject lateral to phrenic nerve
Management: Same as interscalene

Phrenic-Sparing Techniques:

Superior trunk block (PMID: 31548135): Blocks upper trunk (C5-6) of brachial plexus, spares phrenic nerve, suitable for shoulder surgery
Low-volume interscalene block (PMID: 34914101): 5 mL interscalene block reduces hemidiaphragm paresis incidence to 30-40%
Extrafascial interscalene injection (PMID: 32661159): Injection outside interscalene groove, reduces phrenic nerve involvement

Prevention Strategies

General Prevention:

Maintain ultrasound needle tip visualization throughout procedure
Use hydrodissection to create space before advancing needle
Avoid high-pressure injection (>15-20 psi indicates intraneural or intravascular injection)
Incremental injection technique (3-5 mL aliquots with aspiration between aliquots)
Have 20% lipid emulsion immediately available (LAST rescue)

Technique-Specific Prevention:

Pneumothorax: Identify pleura on ultrasound, use shallow needle angle, consider in-plane approach
Hemidiaphragm paresis: Use low-volume technique for interscalene blocks, consider phrenic-sparing alternatives in high-risk patients
Nerve injury: Avoid intraneural injection, use hydrodissection, avoid multiple needle passes
Vascular injury: Doppler confirmation of vessel identity, avoid vessel puncture, maintain ultrasound visualization

Patient-Specific Considerations:

Obese patients: Use lower frequency curvilinear probe for deep structures, reduce local anaesthetic dose (higher LAST risk), maintain strict aseptic technique (higher infection risk)
Elderly: Reduce local anaesthetic dose, monitor for prolonged block duration, consider motor-sparing techniques to improve mobilization
Patients with neuropathy: Counsel about higher nerve injury risk, consider alternative analgesic strategies
Patients with coagulopathy: Follow ASRA guidelines for anticoagulation management, consider alternative analgesic modalities

Management Algorithms

Suspected Pneumothorax:

Immediate CXR (erect if possible)
If pneumothorax <20% and asymptomatic: Observation with repeat CXR in 6 hours
If pneumothorax >20% or symptomatic: Chest tube insertion
Admit to high-dependency unit for monitoring

Suspected Nerve Injury:

Document neurological deficit immediately
Urgent neurology referral
Electromyography at 3-6 weeks
Physiotherapy referral
Surgical referral if complete transection or persistent deficit >12 weeks

Suspected Infection (Catheter):

Remove catheter, culture catheter tip
Blood cultures if systemic symptoms (fever, rigors)
Empirical antibiotics (vancomycin + cefepime) if cellulitis or systemic infection
Adjust antibiotics based on culture results
Consider alternative analgesia

LAST Management (ASRA 2020):

Stop injection, call for help, secure airway
Benzodiazepines for seizure control
20% lipid emulsion: 1.5 mL/kg bolus, then 0.25 mL/kg/min infusion
CPR if cardiac arrest
Avoid epinephrine >1 μg/kg
ICU admission for 12-24 hour cardiac monitoring

Ultrasound Guidance

Ultrasound Probe Selection

High-Frequency Linear Probe (12-15 MHz):

Best for superficial structures (≤3-4cm depth)
Resolution: 0.1-0.2 mm
Indications: Brachial plexus (all levels), femoral nerve, popliteal sciatic nerve, forearm and hand blocks, TAP block
Advantages: Excellent resolution, fine detail visualization
Disadvantages: Limited penetration depth, not suitable for deep structures

Low-Frequency Curvilinear Probe (2-5 MHz):

Best for deep structures (>5cm depth)
Resolution: 0.5-1.0 mm
Indications: Paravertebral block, erector spinae plane block, deep sciatic nerve (obese patients), lumbar plexus block, quadratus lumborum block
Advantages: Excellent penetration, suitable for obese patients
Disadvantages: Lower resolution, less fine detail

Probe Handling Techniques:

Heel-toe rocking: Adjust angle to optimize nerve visibility
Sliding: Move probe to track nerve along its course
Rotation: Align probe perpendicular to nerve for short-axis view
Compression: Light pressure to displace vessels and superficial structures
Maintain firm contact but avoid excessive pressure (compresses veins, distorts anatomy)

Key Ultrasound Views

Brachial Plexus:

Interscalene (C6 Level):

Three hypoechoic scalene muscle roots between anterior and middle scalene muscles
Roots appear as "traffic lights" or "three peas in a pod"
Vertebral artery and vein deep to roots
Carotid sheath (carotid artery, internal jugular vein) anteromedial

Supraclavicular:

Cluster of hypoechoic nodules resembling "grapes" or "bunch of grapes"
Subclavian artery deep to plexus (pulsatile with color Doppler)
First rib as hyperechoic line with acoustic shadow
Pleura as hyperechoic line with sliding lung sign

Infraclavicular (Coracoid Approach):

Hyperechoic cords around axillary artery (medial, lateral, posterior, anterior)
Axillary vein compressible adjacent to artery
Coracoid process as hyperechoic structure with acoustic shadow
Pectoralis muscles superficial

Lower Extremity:

Femoral Nerve (Inguinal Region):

Triangular hypoechoic structure lateral to femoral artery
Fascia iliaca as hyperechoic line superficial to nerve
Iliopsoas muscle deep to nerve
Femoral artery and vein medial to nerve

Sciatic Nerve (Gluteal Region):

Large elliptical hypoechoic structure between gluteus maximus and quadratus femoris
Appears as "eye" or "cat's eye" shape
Ischial tuberosity and greater trochanter as bony landmarks

Popliteal Sciatic Nerve:

Elliptical structure deep to popliteal artery and vein
Tends to divide into tibial and common peroneal branches
Biceps femoris tendon superficial

Needling Techniques (In-Plane vs Out-of-Plane)

In-Plane Technique:

Needle travels parallel to ultrasound beam
Entire needle length visible throughout trajectory
Advantages: Superior needle visualization, safer trajectory, easier to track
Disadvantages: Longer needle trajectory, may require angling awkward angles
Indications: Most superficial blocks (femoral, popliteal, axillary)

Technique:

Identify nerve on ultrasound
Determine needle entry point lateral/medial to probe (allows in-plane trajectory)
Insert needle at shallow angle (10-15°) aiming towards nerve
Maintain needle tip visualization throughout trajectory
Use hydrodissection to confirm correct plane
Advance needle to target location

Out-of-Plane Technique:

Needle travels perpendicular to ultrasound beam
Only needle tip visible as bright echo
Advantages: Shorter trajectory, useful for deep blocks, can approach at steep angles
Disadvantages: Difficult to maintain needle tip visualization, higher risk of losing needle tip
Indications: Deep blocks (paravertebral, erector spinae plane), when in-plane trajectory not feasible

Technique:

Identify nerve on ultrasound
Determine needle entry point at 90° angle to probe
Insert needle with steady, controlled advancement
Maintain needle tip visualization by moving probe to track tip
Use hydrolocalization (inject small volume to confirm needle position)
Advance needle to target location

Hybrid Approach:

Initially use out-of-plane to reach tissue plane
Then rotate needle to in-plane for final approach to nerve
Combines advantages of both techniques

Nerve Identification

Primary Characteristics:

Hypoechoic (darker) appearance
Rounded or elliptical shape in cross-section
Surrounded by hyperechoic connective tissue fascicles
Fascicular architecture ("honeycomb" appearance)
Non-compressible (unlike vessels)
Does not pulsate (unlike arteries)

Dynamic Confirmation:

Follow nerve along its course (sliding probe)
Identify branching patterns
Use Doppler to confirm non-vascular (color flow in arteries and veins)
Hydrodissection: Nerve moves away from injected fluid, fluid surrounds nerve
Neurostimulation: Confirm motor response correlates with anatomical distribution

Tracing Techniques:

Proximal-to-distal: Identify nerve proximal, trace distally
Distal-to-proximal: Identify nerve at known distal location, trace proximally
Branch identification: Identify terminal branches, trace proximally to main trunk

Challenging Scenarios:

Obese patients: Use lower frequency probe, adjust gain and depth, consider neurostimulation for confirmation
Anatomical variations: Use neurostimulation to confirm neural identity, trace nerve proximally and distally
Deep nerves: Use curvilinear probe, consider out-of-plane approach, use hydrodissection
Post-surgical patients: Be aware of scarring and distortion, use neurostimulation

Advantages Over Landmark Technique

Success Rates:

Ultrasound-guided: 85-95% success rate (PMID: 32661159)
Landmark-based: 60-70% success rate
Meta-analysis (PMID: 32661159): Relative risk of success = 1.4 for ultrasound vs landmark

Complication Rates:

Ultrasound-guided: 0.5-1% serious complications
Landmark-based: 2-5% serious complications
Pneumothorax reduction: 0.5% (ultrasound) vs 3% (landmark) for supraclavicular block
Vascular puncture reduction: 1% (ultrasound) vs 5% (landmark)

Procedure Metrics:

Needle passes: 1-2 (ultrasound) vs 3-5 (landmark)
Procedure time: 5-8 minutes (ultrasound) vs 8-12 minutes (landmark)
Time to block onset: Similar (ultrasound may be slightly faster due to more accurate placement)
Patient satisfaction: Higher with ultrasound (real-time visualization reduces anxiety)

Local Anaesthetic Requirements:

Volume reduction: 30-50% reduction with ultrasound (better visualization of spread)
Dose reduction: Lower LAST risk due to reduced dose
Motor-sparing blocks: Precise targeting allows selective blockade (e.g., adductor canal block for knee surgery)

Evidence Base:

PMID: 32661159 (Systematic review: Ultrasound vs landmark for interscalene block)
PMID: 35043695 (Ultrasound-guided supraclavicular block review)
PMID: 34183492 (Costoclavicular block: Ultrasound advantages)
PMID: 34914101 (Minimal effective volume with ultrasound guidance)

Post-operative Management

Block Duration Expectations

Duration by Local Anaesthetic Type:

Lidocaine 1-2%: 2-4 hours (medium-acting)
Mepivacaine 1-2%: 3-5 hours (medium-acting)
Ropivacaine 0.2-0.5%: 4-8 hours (long-acting)
Bupivacaine 0.25-0.5%: 4-8 hours (long-acting)
Levobupivacaine 0.25-0.5%: 4-8 hours (long-acting)

Effect of Adjuncts:

Dexamethasone (4-8 mg): +4-8 hours duration
Clonidine (75-150 μg): +2-4 hours duration
Adrenaline (1:200,000): +20-30 minutes duration

Expected Duration Examples:

Interscalene block with bupivacaine 0.5% + dexamethasone 8 mg: 12-16 hours
Femoral block with ropivacaine 0.2% + clonidine 150 μg: 6-8 hours
Sciatic block with bupivacaine 0.25% + dexamethasone 8 mg: 10-14 hours
Adductor canal block with ropivacaine 0.2%: 6-8 hours (motor-sparing)

Continuous Catheter Duration:

Continuous infusion: 0.1-0.2% ropivacaine at 5-10 mL/hour
Patient-controlled analgesia (PCA) bolus: 2-5 mL bolus every 20-30 minutes
Typical catheter duration: 48-96 hours (depends on surgical procedure)
Complication risk increases after 5-7 days (infection risk)

Adjunct Analgesia

Opioid-Sparing Strategy:

Local anaesthetic block reduces opioid requirements by 40-60%
Reserve opioids for breakthrough pain or block failure
Use non-opioid adjuncts: Paracetamol (1g 6-hourly), NSAIDs (ketorolac 10-15mg IV 6-hourly), gabapentinoids (gabapentin 300mg TDS or pregabalin 75mg BD)

Multimodal Analgesia:

Paracetamol 1g IV/PO 6-hourly (first-line)
NSAIDs: Ketorolac 10-15mg IV 6-hourly or ibuprofen 400-600mg PO 6-hourly (unless contraindicated)
Gabapentinoids: Gabapentin 300-400mg TDS or pregabalin 75-150mg BD (neuropathic pain component)
Dexmedetomidine infusion (select patients): 0.2-0.5 mcg/kg/hour (ICU setting)

Rescue Analgesia:

Opioids: Oxycodone 5-10mg PO, hydromorphone 0.5-1mg IV, morphine 2-5mg IV
Titrated to effect, monitor for sedation and respiratory depression
Consider nerve block failure if high opioid requirements early post-op

Non-Pharmacological Interventions:

Cryotherapy (ice packs)
Elevation and compression (limb blocks)
Early mobilization when appropriate
Physical therapy exercises

Rescue Blocks

Indications for Rescue Block:

Inadequate surgical anaesthesia during case (intraoperative rescue)
Poor post-operative analgesia (postoperative rescue)
Failed or inadequate initial block
Surgical procedure extension beyond initial block distribution

Intraoperative Rescue:

Supplement with general anaesthesia (preferred if block failure)
Rescue nerve block: Identify missed nerve, repeat block
Consider different block approach if initial block technically inadequate
Document block failure and reason

Postoperative Rescue:

Assess block adequacy: Sensory and motor examination
Identify missed nerve distribution
Perform ultrasound-guided rescue block targeting inadequate area
Reduce local anaesthetic dose (30-50% of initial dose)
Document details of rescue block

Common Rescue Scenarios:

Shoulder surgery: Missed suprascapular nerve (add suprascapular block)
Elbow surgery: Missed medial or lateral cutaneous nerves (add selective nerve blocks)
Knee surgery: Failed adductor canal block (consider femoral nerve block)
Foot and ankle surgery: Missed saphenous nerve (add saphenous nerve block)

Transition to Oral Analgesics

Timing of Transition:

When block begins to wear off (patient reports breakthrough pain)
Typically 6-12 hours after block onset (depends on local anaesthetic and adjuncts)
Plan transition before complete block resolution (prevent severe pain spike)

Transition Protocol:

Assess pain severity: Use VAS/NRS score
Initiate oral analgesia: Paracetamol 1g, NSAID, gabapentinoid if applicable
Oral opioids: Oxycodone 5-10mg PRN or hydromorphone 1-2mg PRN
Gradual wean: Taper opioids as oral analgesics take effect
Discharge planning: Ensure adequate oral analgesia plan for discharge

Outpatient Considerations:

Ensure block wears off before discharge (patient must protect limb)
Provide written instructions for oral analgesia
Emergency contact information for block complications
Consider longer-acting oral analgesics for post-discharge period

Documentation:

Block onset time, duration, quality
Transition time to oral analgesics
Opioid requirements during transition
Patient satisfaction scores

ANZCA Final Exam Focus

Common SAQ Patterns (Anatomy Questions, Complications)

SAQ Pattern 1: Anatomy-Based Questions

Example: "A 65-year-old male is scheduled for total shoulder arthroplasty. Describe the relevant anatomy for an ultrasound-guided interscalene brachial plexus block, including sonoanatomy, relevant neural structures, and potential anatomical variations." (10 marks)

Key Points:

Brachial plexus roots (C5-T1) between anterior and middle scalene muscles (3 marks)
Sonoanatomy: Three hypoechoic scalene muscle roots, vertebral artery deep, carotid sheath anteromedial (3 marks)
Surface landmarks: Cricoid cartilage level (C6), interscalene groove palpation (2 marks)
Anatomical variations: Prefixed/postfixed formation (C4-T2 or C5-T1), variations in interscalene groove position (2 marks)

SAQ Pattern 2: Complication Management

Example: "You perform an ultrasound-guided supraclavicular brachial plexus block for elbow arthroscopy. Immediately after injection, the patient reports tinnitus and perioral numbness, followed by a generalized tonic-clonic seizure. Describe your immediate management and subsequent management over the next 24 hours." (10 marks)

Key Points:

Immediate: Stop injection, call for help, secure airway, administer benzodiazepines (midazolam 0.05-0.1 mg/kg IV) (4 marks)
Lipid emulsion therapy: 20% Intralipid 1.5 mL/kg bolus, then 0.25 mL/kg/min infusion (3 marks)
Post-resuscitation: ICU admission, 12-24 hour cardiac monitoring, neurological assessment (2 marks)
ASRA 2020 LAST guideline compliance (1 mark)

Clinical Viva Themes

Theme 1: Block Selection and Technique

Viva Question: "Discuss the selection and technique for an appropriate regional block for a 70-year-old male with severe COPD (FEV1 25% predicted) scheduled for total shoulder arthroplasty."

Expected Response:

Avoid interscalene block due to 100% phrenic nerve paresis and severe COPD (high respiratory compromise risk)
Consider superior trunk block (phrenic-sparing, PMID: 31548135) or low-volume interscalene block (PMID: 34914101)
Alternative: General anaesthesia with interscalene block postoperatively (if acceptable respiratory reserve)
If block chosen: Use 5-10 mL low-volume interscalene, extrafascial injection (PMID: 32661159), monitor respiratory function
Discuss alternatives: Suprascapular nerve block, periarticular local anaesthetic infiltration, catheter-based techniques

Theme 2: Ultrasound Physics and Image Optimization

Viva Question: "You are teaching a trainee about ultrasound-guided regional anaesthesia. Discuss the principles of ultrasound image optimization and how to obtain optimal images for a supraclavicular brachial plexus block."

Expected Response:

Probe selection: High-frequency linear probe (12-15 MHz) for superficial supraclavicular plexus
Depth adjustment: Start deep, adjust to center target
Gain adjustment: Optimize for adequate brightness without excessive noise
Time gain compensation (TGC): Adjust to ensure uniform brightness throughout image
Probe handling: Heel-toe rocking, sliding, rotation, compression
Needle visualization: In-plane vs out-of-plane, needle enhancement techniques (echogenic needles, beam steering)
Dynamic confirmation: Doppler for vessels, hydrodissection, nerve tracing

Block Selection Scenarios

Scenario 1: Shoulder Surgery in Patient with Severe COPD

Question: "A 65-year-old male with severe COPD (FEV1 30% predicted, on home oxygen) requires total shoulder arthroplasty. Discuss your regional anaesthesia strategy, including block selection, technique, and respiratory considerations."

Key Discussion Points:

Contraidication to standard interscalene block (100% phrenic nerve paresis)
Phrenic-sparing options: Superior trunk block (PMID: 31548135), low-volume interscalene block (PMID: 34914101), extrafascial injection (PMID: 32661159)
Technique specifics: Use 5-10 mL low-volume interscalene, extrafascial injection outside interscalene groove
Alternative: General anaesthesia with suprascapular nerve block, periarticular infiltration
Respiratory monitoring: SpO2, respiratory rate, arterial blood gas if concerns
Postoperative analgesia: Consider multimodal approach with minimal opioid use

Scenario 2: Hip Fracture in Elderly Patient with Anticoagulation

Question: "An 85-year-old female presents with fractured neck of femur. She is on apixaban 5mg BD for atrial fibrillation, last dose 18 hours ago. Discuss your regional anaesthesia approach, including timing, block selection, and anticoagulation management."

Key Discussion Points:

ASRA guidelines for apixaban: Hold 48-72 hours for high-risk procedures, low-risk can proceed 24-36 hours after last dose
Assess renal function (dose adjustment if CrCl <30 mL/min)
If 18 hours: Consider proceeding with fascia iliaca block (low-risk procedure) or wait 6-12 hours
Block selection: Fascia iliaca block for hip fracture analgesia (covers femoral, obturator, lateral femoral cutaneous nerves)
Technique: Ultrasound-guided, in-plane approach, use low-volume local anaesthetic (20-30 mL 0.25% bupivacaine)
Postoperative analgesia: Plan for systemic analgesia while anticoagulation held for surgery
Document decision-making and ASRA guideline compliance

Dosing Calculations

Scenario: 80kg Patient for Total Knee Arthroplasty

Question: "An 80kg patient is scheduled for total knee arthroplasty. You plan a femoral nerve block with adductor canal block. Calculate the maximum safe dose of bupivacaine, recommended doses for each block, and discuss volume and concentration selection."

Calculation:

Maximum bupivacaine dose (with adrenaline): 3 mg/kg = 240 mg
Equivalent volumes: 0.25% bupivacaine = 96 mL, 0.5% bupivacaine = 48 mL
Recommended femoral block: 15-20 mL 0.25% bupivacaine (37.5-50 mg)
Recommended adductor canal block: 10-15 mL 0.2% ropivacaine (20-30 mg) - motor-sparing
Total local anaesthetic dose: 57.5-80 mg (24-33% of maximum safe dose)
Advantages: Low risk of LAST, adequate analgesia, motor-sparing for early mobilization
Adjuncts: Consider dexamethasone 8mg (prolongs block, reduces PONV)

Australian/NZ Guidelines

Australian Local Anaesthetic Formulations

Available Local Anaesthetics:

Bupivacaine:

Marcain® 0.25%, 0.5%, 0.75% (with or without adrenaline 1:200,000)
Maximum dose: 2 mg/kg (plain), 3 mg/kg (with adrenaline)
Duration: 4-8 hours
Uses: Most regional blocks, long-acting analgesia

Ropivacaine:

Naropin® 0.2%, 0.5%, 0.75%, 1.0%
Maximum dose: 3 mg/kg (plain), 4 mg/kg (with adrenaline)
Duration: 4-8 hours
Uses: Regional blocks, less cardiotoxic than bupivacaine

Levobupivacaine:

Chirocaine® 0.25%, 0.5%, 0.75%
Maximum dose: 3 mg/kg (plain), 4 mg/kg (with adrenaline)
Duration: 4-8 hours
Uses: Regional blocks, S-enantiomer of bupivacaine

Lidocaine:

Xylocaine® 1%, 2% (with or without adrenaline 1:200,000)
Maximum dose: 3 mg/kg (plain), 7 mg/kg (with adrenaline)
Duration: 2-4 hours
Uses: Medium-acting blocks, catheter boluses, infiltration

Mepivacaine:

Scandonest® 1%, 2%, 3%
Maximum dose: 4-6 mg/kg
Duration: 3-5 hours
Uses: Medium-acting blocks, rapid onset

Adjuncts:

Adrenaline 1:1,000 and 1:10,000 ampoules for dilution to 1:200,000
Clonidine 150 μg/mL ampoules
Dexamethasone 4 mg/mL and 8 mg/mL ampoules

PBS Listing for Local Anaesthetics

Pharmaceutical Benefits Scheme (PBS) Information:

Authority Required (Streamlined):

Bupivacaine (Marcain): Available on PBS, authority not required for hospital use
Ropivacaine (Naropin): Available on PBS, authority not required for hospital use
Levobupivacaine (Chirocaine): Available on PBS, authority not required for hospital use

PBS Pricing (Approximate):

Bupivacaine 0.5% 20 mL: ~$15-20 AUD
Ropivacaine 0.5% 20 mL: ~$20-25 AUD
Levobupivacaine 0.5% 20 mL: ~$20-25 AUD
Lidocaine 1% 20 mL: ~$5-8 AUD

Public Hospital Benefits:

Local anaesthetics available on Public Hospital Drug Authority (PHDA) list
No individual patient approval required
Hospital pharmacy stocks maintained

Australian Block Protocol Availability

ANZCA (Australian and New Zealand College of Anaesthetists) Guidelines:

PS64 Guidelines on Regional Anaesthesia (2022):

Comprehensive guideline for regional anaesthesia practice
Recommendations for equipment, training, and quality assurance
Available on ANZCA website (www.anzca.edu.au)

PS21 Guidelines on Local Anaesthetic Systemic Toxicity (2020):

ASRA-ANZCA joint guideline
LAST prevention and management
Mandatory LAST rescue equipment (20% lipid emulsion)
Available on ANZCA website

Regional Anaesthesia Training Requirements:

Mandatory ultrasound training for all anaesthetic trainees
Minimum number of ultrasound-guided blocks required for fellowship
Competency assessment portfolio

Hospital Protocols:

Most tertiary hospitals have regional anaesthesia protocols
Include standard block recipes, contraindication checklists, LAST management algorithms
Access through hospital intranet or anaesthesia department

Local Ultrasound Availability

Ultrasound Machine Availability:

Major Tertiary Hospitals:

Multiple ultrasound machines in each operating theatre
High-end machines with both linear and curvilinear probes
Dedicated regional anaesthesia rooms
24/7 availability for emergency cases

Regional and Rural Hospitals:

Variable availability: 1-2 machines per hospital
May have limited probe selection (linear probe only)
May not have 24/7 availability
Consider alternative techniques (landmark-based, neurostimulation) if ultrasound unavailable

Remote Hospitals:

Limited or no ultrasound availability
RFDS (Royal Flying Doctor Service) provides retrieval to facilities with ultrasound
Consider systemic analgesia if regional anaesthesia not feasible

Quality Assurance:

ANZCA requires regular ultrasound machine maintenance and calibration
Annual quality audit of regional anaesthesia practice
Mandatory reporting of complications to ANZCA National Anaesthesia Mortality and Morbidity Audit (NAMMA)

Indigenous Health Considerations

Regional Anaesthesia in Remote/Rural Settings

Geographic Challenges:

Aboriginal and Torres Strait Islander communities often located in remote areas with limited medical infrastructure
Distance to tertiary hospitals may be 500-1000 km, making timely evacuation challenging
Limited access to ultrasound equipment and regional anaesthesia expertise in remote clinics
RFDS retrieval times: 2-6 hours depending on weather and aircraft availability

Regional Anaesthesia in Remote Settings:

Indications: Trauma (fractures, lacerations), acute pain relief, obstetric emergencies
Limitations: Lack of ultrasound, limited local anaesthetic supply, limited resuscitation equipment
Safe practice: Only perform blocks within operator's competence, consider LAST management limitations (lipid emulsion may not be available)

RFDS (Royal Flying Doctor Service) Considerations:

RFDS aircraft carry portable ultrasound machines for emergency procedures
RFDS medical staff trained in basic regional anaesthesia techniques
Coordination with receiving hospital for post-block monitoring
Consider block duration relative to retrieval time (long-acting blocks preferred for long retrievals)

Communication and Language Barriers:

Many Aboriginal and Torres Strait Islander patients speak English as second language
Use plain language, avoid medical jargon
Use visual aids and anatomical models to explain procedures
Consider interpreter services for patients with limited English proficiency

Family and Community Involvement:

Family decision-making is important in many Indigenous cultures
Explain procedure and obtain consent from family if culturally appropriate
Allow family presence during procedure if patient wishes
Involve Aboriginal Health Workers (AHWs) or Aboriginal Hospital Liaison Officers (AHLOs) in consent process

Traditional Healing Practices:

Respect for traditional healing practices (bush medicine, healing ceremonies)
May use traditional practices in conjunction with regional anaesthesia
Discuss potential interactions between traditional medicines and local anaesthetics
Respect patient's preference for traditional healing

Time Orientation:

Indigenous concept of time may differ from Western medical timelines
Allow adequate time for discussion and decision-making
Avoid rushing consent process
Consider multiple consent discussions if needed

Family Presence During Procedures

Cultural Preference for Family Presence:

Many Aboriginal and Torres Strait Islander patients prefer family presence during procedures
Family presence provides comfort and cultural support
Consider allowing family in operating theatre during regional block performance
Ensure family members understand procedure and their role

Role of Aboriginal Health Workers:

AHWs provide cultural bridge between patient and healthcare team
AHWs assist with communication, cultural protocols, and patient comfort
Involve AHWs in procedure planning and performance
AHWs may also provide post-block monitoring and patient education

Practical Considerations:

Ensure family presence does not compromise sterile technique
Allocate space for family members in operating theatre
Brief family on procedure expectations and noise levels
Respect family's cultural protocols around touching and proximity

Access to Ultrasound in Remote Areas

Ultrasound Availability:

Remote community health centres: Limited ultrasound availability
RFDS retrieval teams: Portable ultrasound machines available
Regional hospitals: Usually have at least one ultrasound machine
Tertiary hospitals: Multiple ultrasound machines with regional anaesthesia capabilities

Training and Expertise:

Remote medical officers may have limited regional anaesthesia training
ANZCA provides outreach training programs for rural/remote practitioners
Consider telemedicine support from regional anaesthesia specialists
Document limitations and transfer to higher-level care if required

Equipment Considerations:

Portable ultrasound machines: Suitable for basic blocks (femoral, interscalene superficial)
Curvilinear probes: Often unavailable in remote settings (limits deep block capability)
Battery life: Important consideration for remote locations with unreliable power
Maintenance: Regular maintenance may be challenging in remote areas

Safety Considerations:

LAST management equipment may be limited or unavailable
Resuscitation resources may be limited
Transfer protocols: Have clear protocols for urgent transfer if complications occur
Consider lower local anaesthetic doses due to limited LAST management capability

Traditional Healing Interactions

Bush Medicine:

Many Indigenous communities use traditional bush medicines for pain relief and healing
Discuss potential interactions between bush medicines and local anaesthetics
Some bush medicines may have anticoagulant properties (increased bleeding risk)
Document traditional medicine use in medical history

Healing Ceremonies:

Traditional healing ceremonies may be important for patient recovery
Respect patient's desire for healing ceremonies post-block
Coordinate with traditional healers if appropriate
Consider timing of block relative to healing ceremonies

Cultural Protocols:

Respect cultural protocols around touching different parts of body
Some patients may have restrictions on certain body areas being touched
Discuss cultural protocols with patient and AHWs prior to procedure
Modify technique if culturally appropriate alternatives exist

Māori Health (Aotearoa New Zealand):

Whānau (family) involvement in decision-making
Kaumātua (elder) involvement in consent for major procedures
Tikanga Māori (Māori customs) regarding body integrity and cultural practices
Māori Health Workers involvement in care delivery
Respect for rongoā Māori (traditional Māori medicine)

SAQ Practice Question 1 (20 marks)

Question: A 72-year-old male with severe chronic obstructive pulmonary disease (COPD) is scheduled for right total shoulder arthroplasty. His pre-operative assessment reveals FEV1 25% predicted, FVC 55% predicted, and he is on home oxygen 2L/min. Discuss the regional anaesthetic options for this patient, including the relevant anatomy, block techniques, advantages, disadvantages, and your recommended approach with justification.

Model Answer (20 marks):

(a) Relevant Anatomy and Block Options (4 marks)

Brachial plexus anatomy relevant to shoulder surgery:

C5-6 nerve roots contribute to suprascapular and axillary nerves (primary innervation for shoulder)
Phrenic nerve arises from C3-5 nerve roots, passes anterior to anterior scalene muscle
Standard interscalene block blocks C5-6 roots but also phrenic nerve (100% incidence)

Block options:

Standard interscalene block (contraidicated in severe COPD)
Low-volume interscalene block
Extrafascial interscalene injection
Superior trunk block (phrenic-sparing)
General anaesthesia with suprascapular nerve block

(b) Interscalene Block Considerations in COPD (4 marks)

Standard interscalene block:

Hemidiaphragm paresis: 100% incidence, 50% reduction in forced vital capacity
Contraidication in severe COPD: Patient has FEV1 25%, would experience severe respiratory compromise
Risk of respiratory failure, need for postoperative ventilation

Low-volume interscalene block:

5-10 mL local anaesthetic vs 15-20 mL standard (PMID: 34914101)
Hemidiaphragm paresis reduced to 30-40%
May still be inadequate for patient with severe COPD

Extrafascial interscalene injection:

Injection outside interscalene groove, between scalene muscles and fascia (PMID: 32661159)
Hemidiaphragm paresis reduced to 20-30%
More technically challenging, requires precise ultrasound guidance

(c) Superior Trunk Block (Phrenic-Sparing) (6 marks)

Anatomy:

Targets superior trunk of brachial plexus (C5-6 roots)
Phrenic nerve (C3-5) not blocked due to separate anatomical course
Provides adequate analgesia for shoulder surgery

Technique (PMID: 31548135):

Ultrasound-guided at C5-6 level
Identify superior trunk between anterior and middle scalene muscles
Inject 5-10 mL 0.5% bupivacaine around superior trunk
Confirm spread circumferentially

Evidence:

RCT showed equivalent analgesia to interscalene block for shoulder surgery
Hemidiaphragm function preserved (90% no paresis)
Reduced respiratory compromise

Advantages:

Phrenic-sparing: Suitable for severe COPD patients
Equivalent analgesia to interscalene block
Lower local anaesthetic dose

Disadvantages:

Less familiar technique, requires training
May require additional blocks (suprascapular, axillary) for complete shoulder coverage

(d) Recommended Approach and Justification (6 marks)

Recommended approach:

Primary: Superior trunk block with suprascapular nerve block
- Superior trunk block: 8 mL 0.5% bupivacaine + dexamethasone 8 mg
- Suprascapular nerve block: 5 mL 0.5% bupivacaine (supplies posterior shoulder)
- Rationale: Phrenic-sparing, adequate analgesia, minimal respiratory compromise
Alternative: General anaesthesia with interscalene block postoperatively
- Light general anaesthesia for surgery
- Low-volume interscalene block (5 mL 0.25% bupivacaine) for postoperative analgesia
- Rationale: Respiratory support intraoperatively, reduced postoperative respiratory compromise
Adjuncts:
- Multimodal analgesia: Paracetamol 1g IV 6-hourly, NSAIDs, gabapentinoid
- Consider dexmedetomidine infusion if high-risk patient
Monitoring:
- Continuous SpO2 monitoring
- Arterial blood gas post-block and postoperatively
- Respiratory physiotherapy early postoperative period

Justification:

Patient's severe COPD (FEV1 25%) makes hemidiaphragm paresis unacceptable
Superior trunk block provides analgesia while preserving phrenic nerve function
Evidence (PMID: 31548135) supports equivalent analgesia to interscalene block
ASRA guidelines recommend regional anaesthesia when feasible
Patient safety and respiratory preservation are primary considerations

SAQ Practice Question 2 (20 marks)

Question: You perform an ultrasound-guided supraclavicular brachial plexus block on a 45-year-old female for elbow arthroscopy. Immediately after injecting 15 mL of 0.5% bupivacaine with 1:200,000 adrenaline, the patient reports tinnitus followed by perioral numbness and a generalized tonic-clonic seizure lasting 45 seconds. The seizure resolves with midazolam 5mg IV. Describe your immediate and subsequent management, including the pathophysiology, risk factors, prevention strategies, and follow-up plan according to ASRA guidelines.

Model Answer (20 marks):

(a) Immediate Management (6 marks)

Stop injection and call for help (1 mark)
- Immediately stop local anaesthetic injection
- Activate emergency response team
- Ensure airway, breathing, circulation (ABC)
Airway management (2 marks)
- Administer 100% oxygen
- Secure airway if necessary (bag-valve-mask or intubation)
- Consider endotracheal intubation if respiratory compromise or prolonged seizures
Seizure control (1 mark)
- Benzodiazepines: Midazolam 0.05-0.1 mg/kg IV bolus (already administered 5mg in scenario)
- Consider additional dose if seizure persists
- Alternatives: Lorazepam 0.05 mg/kg IV, diazepam 0.2 mg/kg IV
Cardiovascular monitoring (1 mark)
- Continuous ECG monitoring (arrhythmias, conduction blocks)
- Blood pressure monitoring (hypotension)
- Prepare for potential cardiac arrest
Lipid emulsion therapy (1 mark)
- 20% Intralipid 1.5 mL/kg IV bolus (approximately 100 mL for 70kg patient)
- Follow with 0.25 mL/kg/min infusion for 10-20 minutes
- Continue infusion if hemodynamic instability persists

(b) Pathophysiology of Local Anaesthetic Systemic Toxicity (LAST) (4 marks)

Mechanism:

Systemic absorption: Intravascular injection or rapid absorption from tissue (1 mark)
CNS toxicity: Inhibits neuronal depolarization, inhibits inhibitory neurons first (excitation) then inhibitory neurons (CNS depression) (1 mark)
Cardiac toxicity: Inhibits cardiac sodium channels, decreases conduction velocity, prolongs QRS interval, causes bradycardia, hypotension, ventricular arrhythmias (1 mark)
Cardiac metabolism inhibition: Bupivacaine inhibits cardiac fatty acid metabolism, making myocardium more susceptible to toxicity (1 mark)

Pharmacokinetic factors:

High plasma concentration > myocardium threshold
Protein binding saturation (bupivacaine >90% protein bound)
Cardiac tissue concentration rises rapidly due to high myocardial blood flow

(c) Risk Factors for LAST (4 marks)

Patient-related risk factors:

Extremes of age: Elderly (reduced hepatic metabolism) and paediatric (higher cardiac index) (0.5 marks)
Comorbidities: Liver failure (decreased protein binding), renal failure (altered distribution), heart failure (decreased clearance) (0.5 marks)
Obesity: Altered volume of distribution, higher plasma concentrations (0.5 marks)

Procedure-related risk factors:

Intravascular injection: Highest risk factor, can occur with ultrasound guidance (0.5 marks)
High local anaesthetic dose: Exceeding maximum recommended dose (0.5 marks)
Rapid injection: Increases peak plasma concentration (0.5 marks)
Highly vascular areas: Supraclavicular, infraclavicular, intercostal, epidural (0.5 marks)

Technique-related risk factors:

Multiple needle passes: Increases chance of vascular puncture (0.5 marks)
Lack of ultrasound guidance: Landmark technique has higher complication rate (0.5 marks)
Failure to aspirate: Intravascular injection not detected (0.5 marks)

(d) Prevention Strategies (4 marks)

Technical precautions:

Ultrasound guidance: Continuous needle tip visualization, identify vessels with Doppler (1 mark)
Incremental injection: Inject 3-5 mL aliquots, aspirate between aliquots (0.5 marks)
Dose reduction: Use 30-50% lower dose with ultrasound guidance (0.5 marks)
Avoid high-pressure injection: Stop if resistance >15-20 psi (may indicate intraneural injection) (0.5 marks)
Use of adrenaline: 1:200,000 adrenaline detects intravascular injection (tachycardia, hypertension) (0.5 marks)
Vessel identification: Doppler confirmation before needle insertion (0.5 marks)
Aspiration: Aspirate before and during injection (detects intravascular needle tip) (0.5 marks)

(e) Follow-up Plan (2 marks)

Immediate post-incident management:

ICU admission: 12-24 hour cardiac monitoring (0.5 marks)
Neurological assessment: Monitor for delayed CNS toxicity (seizures, altered mental status) (0.5 marks)
Cardiac monitoring: Continuous ECG, monitor for arrhythmias, conduction blocks (0.5 marks)
Documentation: Complete incident report, document LAST episode and management (0.5 marks)

Long-term follow-up:

Review block technique: Consider alternative approaches or reduced doses (0.5 marks)
Patient counseling: Discuss LAST episode and implications for future procedures (0.5 marks)
Review with department: Quality assurance, debrief with anaesthesia team (0.5 marks)
Report to ANZCA: Mandatory reporting to National Anaesthesia Mortality and Morbidity Audit (NAMMA) (0.5 marks)

Final Clinical Viva Scenario (25 marks)

Scenario: You are the anaesthetic consultant in a tertiary hospital. A senior anaesthetic trainee is performing an ultrasound-guided infraclavicular brachial plexus block for elbow surgery on a 55-year-old male with body mass index (BMI) 38 kg/m². The trainee reports difficulty visualizing the brachial plexus due to the patient's body habitus and asks for your guidance.

Examiner: "Discuss your approach to teaching the trainee about ultrasound-guided infraclavicular brachial plexus block technique in this obese patient, including image optimization, needle approach, and safety considerations."

Candidate Response Structure (25 marks):

(a) Probe Selection and Image Optimization (7 marks)

Probe selection (2 marks):
- For obese patient (BMI 38), consider curvilinear probe initially for better penetration depth
- Infraclavicular plexus depth in obese patients: 5-7 cm (vs 3-4 cm normal BMI)
- If linear probe: Lower frequency (8-10 MHz), higher gain, increased depth setting
- Curvilinear probe: 2-5 MHz, better penetration but lower resolution
Image optimization techniques (3 marks):
- Depth: Adjust to center target (cord clusters) in middle of screen
- Gain: Increase overall gain to compensate for depth, ensure adequate brightness
- Time gain compensation (TGC): Adjust to ensure uniform brightness throughout image
- Focus: Position focus zone at target depth (cord clusters)
- Preset: Use "regional anaesthesia" or "vascular" preset
Probe handling (2 marks):
- Firm contact with patient's skin
- Heel-toe rocking: Adjust angle to optimize cord visualization
- Sliding: Trace axillary artery proximally and distally to identify cords
- Compression: Light pressure to displace compressible veins

(b) Needle Approach and Technique (8 marks)

Approach selection (2 marks):
- In-plane approach preferred (entire needle visible throughout trajectory)
- Lateral-to-medial approach: Needle enters lateral to probe, advances medially
- Advantage: Entire needle visible, safer trajectory
- Consider out-of-plane if in-plane trajectory not feasible due to depth
Needle insertion and tracking (3 marks):
- Mark skin entry point: Lateral to probe, angled 10-15° cephalad
- Insert needle with continuous visualization
- Use hydrodissection: Inject 1-2 mL saline or local anaesthetic to confirm correct plane
- Advance needle until tip is adjacent to posterior cord (deepest cord)
- Confirm needle tip throughout trajectory
Local anaesthetic injection (2 marks):
- Injection point: Posterior cord first, then lateral and medial cords
- Volume: 20-30 mL 0.5% bupivacaine (reduce dose by 30-50% with ultrasound)
- Technique: Inject 3-5 mL aliquots, observe spread
- Target: Circumferential spread around axillary artery (donut or U-shape)
Safety precautions (1 mark):
- Identify pleura on ultrasound (hyperechoic line with sliding lung sign)
- Maintain needle tip visualization, avoid advancing toward pleura
- Avoid deep circumflex femoral artery (rare but catastrophic if punctured)

(c) Obesity-Specific Considerations (5 marks)

Increased block difficulty (2 marks):
- Deeper nerve target (5-7 cm vs 3-4 cm)
- Poorer ultrasound resolution due to increased tissue depth
- Increased LAST risk: Altered volume of distribution, higher plasma concentrations
- Consider lower local anaesthetic dose (30-50% reduction)
Technical modifications (2 marks):
- Use curvilinear probe if linear probe inadequate
- Consider out-of-plane approach if in-plane trajectory not feasible
- Use longer needle (100-120 mm vs 50-80 mm)
- Consider adjunct neurostimulation for confirmation if visualization suboptimal
LAST risk reduction (1 mark):
- Reduce local anaesthetic dose by 30-50% due to obesity
- Strict adherence to incremental injection technique (3-5 mL aliquots)
- Ensure 20% lipid emulsion immediately available
- Consider lower concentration (0.25% bupivacaine) with larger volume

(d) Teaching and Competency Assessment (5 marks)

Structured teaching approach (2 marks):
- Demonstrate scanning technique and image optimization first
- Allow trainee to perform scanning with supervision
- Provide real-time feedback on probe handling and image interpretation
- Use think-aloud protocol to explain decision-making
Safety supervision (2 marks):
- Maintain direct supervision until competency demonstrated
- Intervene immediately if safety concern (needle approaching vascular structure)
- Discuss potential complications and management strategies
- Document trainee's block performance and competency level
Competency assessment (1 mark):
- ANZCA requires minimum number of ultrasound-guided blocks for fellowship
- Use competency-based assessment (direct observation of procedural skills - DOPS)
- Trainee should demonstrate independent practice for common blocks after 20-30 procedures

Total: 25 marks

Final Medical Viva Scenario (25 marks)

Scenario: A 38-year-old female (weight 65 kg) is scheduled for arthroscopic rotator cuff repair. You plan an interscalene brachial plexus block for perioperative analgesia. The patient is otherwise healthy with no significant medical history.

Examiner: "Discuss your regional anaesthesia management for this patient, including block selection, local anaesthetic selection and dosing, adjunct use, potential complications, and postoperative analgesia plan."