Regional Anesthesia Techniques in Orthopaedic Surgery

Regional anesthesia in orthopaedics includes neuraxial (spinal/epidural) and peripheral nerve blocks for upper limb (interscalene for shoulder, supraclavicular/infraclavicular for elbow/forearm, axillary for hand) and lower limb (femoral, adductor canal, sciatic, popliteal). Ultrasound guidance is now standard, reducing complications by 65%. The critical complication is LAST (Local Anesthetic Systemic Toxicity), which presents with CNS symptoms first (perioral numbness, tinnitus, seizures) before cardiovascular collapse - treatment is 20% lipid emulsion (1.5 mL/kg bolus). Adductor canal block is preferred over femoral nerve block for TKA as it preserves quadriceps strength and enables early mobilisation.

Regional anesthesia encompasses neuraxial (spinal, epidural) and peripheral nerve block techniques that provide targeted anesthesia and analgesia for orthopaedic procedures. These techniques have become integral to Enhanced Recovery After Surgery (ERAS) protocols and multimodal analgesia.

Benefits in orthopaedic surgery:

• Superior analgesia compared to systemic opioids
• Reduced opioid consumption by 30-50%
• Earlier mobilization with motor-sparing blocks
• Reduced hospital length of stay
• Lower incidence of PONV (postoperative nausea and vomiting)
• Improved patient satisfaction

Evolution of practice:

• Landmark-based techniques (1970s-1990s): anatomical landmarks, nerve stimulator
• Ultrasound guidance (2000s-present): direct visualization, real-time needle placement
• Motor-sparing blocks (2010s-present): adductor canal, IPACK, PENG blocks
• Continuous catheter techniques: prolonged analgesia for complex surgery

Spinal Anesthesia (Subarachnoid Block)

Technique:

• Level: L3-L4 or L4-L5 interspace (below conus medullaris at L1-L2)
• Position: Sitting or lateral decubitus
• Needle: 25G or 27G pencil-point (Whitacre, Sprotte) reduces PDPH
• Local anesthetic: Bupivacaine 0.5% heavy (10-15 mg for lower limb)
• Onset: 5-10 minutes
• Duration: 90-150 minutes (plain), 120-180 minutes (heavy with opioid)

Indications in orthopaedics:

• Total hip arthroplasty
• Total knee arthroplasty
• Lower limb fracture fixation
• Foot and ankle surgery

Advantages:

• Rapid onset
• Dense motor and sensory block
• Predictable duration
• Reduced blood loss (controlled hypotension)

Disadvantages:

• Fixed duration (single-shot)
• Hypotension (sympathetic blockade)
• Urinary retention
• Headache risk if dural puncture with large needle

Epidural Anesthesia

Technique:

• Level: Lumbar (L2-L3, L3-L4) for lower limb, thoracic for upper abdominal/thoracic
• Loss of resistance technique to identify epidural space
• Catheter placement: allows continuous infusion
• Local anesthetic: Bupivacaine 0.25-0.5%, ropivacaine 0.2-0.5%
• Onset: 15-30 minutes
• Duration: Continuous (with catheter)

Indications:

• Major lower limb surgery (bilateral TKA, complex trauma)
• Postoperative analgesia after spine surgery
• Rib fractures (thoracic epidural)

Advantages:

• Titratable anesthesia
• Continuous technique (catheter)
• Can be used for postoperative analgesia
• Cardiovascular stability (gradual onset)

Disadvantages:

• Slower onset than spinal
• More drug required
• Epidural hematoma risk (anticoagulation)
• Patchy block (5-10% failure rate)

Combined Spinal-Epidural (CSE)

Technique:

• Needle-through-needle or separate spaces
• Spinal component for rapid onset
• Epidural catheter for prolonged analgesia

Indications:

• Long or unpredictable duration surgery
• Postoperative analgesia required (THA, TKA)

Benefits of Ultrasound

Improved outcomes:

• Success rates: 95% vs 80% with nerve stimulator
• Onset time: 30% faster
• Block quality: improved density and coverage
• Local anesthetic volume: 30% reduction
• Complications: 65% reduction

Safety advantages:

• Direct visualization: nerves, vessels, pleura, peritoneum
• Real-time needle tracking: prevents vascular puncture
• Spread confirmation: ensures adequate distribution
• Avoidance of injection: if intravascular or intraneural

Ultrasound Techniques

Probe selection:

• High-frequency linear (8-15 MHz): Superficial structures (under 4 cm)
• Low-frequency curvilinear (2-5 MHz): Deep structures (over 4 cm)

Needle approaches:

• In-plane: Needle parallel to probe, entire shaft visible
• Out-of-plane: Needle perpendicular to probe, only cross-section visible

Nerve identification:

• Hyperechoic: Bright, fascicular structure
• Honeycomb appearance: Multiple hypoechoic fascicles
• Adjacent structures: Arteries (pulsatile, compressible), veins, muscles

Signs of successful injection:

• Circumferential spread: "donut sign" around nerve
• Nerve expansion: slight distension during injection
• Separation: nerve separates from adjacent structures

Training and Competency

Learning curve:

• Basic skills: 20-30 blocks
• Competency: 50-100 blocks
• Expert level: 200+ blocks

Recommended pathway:

• Didactic learning (anatomy, physics)
• Simulation and phantom practice
• Supervised clinical practice
• Independent practice with backup

Common Agents

Mechanism of Action

Sodium channel blockade:

• Local anesthetics bind to voltage-gated sodium channels
• Block propagation of action potentials
• Prevent depolarization of nerve fibers

Differential blockade:

• Small fibers blocked first: Pain (C fibers), temperature (A-delta)
• Large fibers blocked last: Motor (A-alpha), proprioception
• Explains sensory block before motor block

Adjuncts

Epinephrine (1:200,000 to 1:400,000):

• Vasoconstriction: prolongs duration by 30-50%
• Reduces systemic absorption: lowers LAST risk
• Marker of intravascular injection: tachycardia if IV
• Avoid: in digital blocks, ISB (phrenic palsy duration)

Dexamethasone (4-8 mg):

• Prolongs duration: 30-50% increase
• Anti-inflammatory: reduces postoperative pain
• Perineural or IV: both effective

Clonidine (1-2 mcg/kg):

• Alpha-2 agonist: prolongs sensory and motor block
• Side effects: hypotension, sedation
• Less commonly used with longer-acting agents

Mechanism and Risk Factors

Pathophysiology:

• CNS toxicity: Inhibition of inhibitory neurons first (excitation), then all neurons (depression)
• Cardiac toxicity: Blockade of cardiac sodium and potassium channels, calcium dysregulation
• Lipid sink theory: Lipid emulsion creates a "sink" to sequester LA from tissues

Risk factors:

• High total dose: exceeding maximum recommended
• Accidental intravascular injection: especially into artery
• Highly vascular site: intercostal, paracervical blocks
• Patient factors: extremes of age, cardiac disease, hepatic dysfunction, low protein states

Relative toxicity (most to least):

1. Bupivacaine: highest cardiotoxicity
2. Ropivacaine: intermediate
3. Lidocaine: least toxic

Clinical Presentation

Progression of LAST:

Stage 1 - CNS excitation:

• Perioral numbness
• Metallic taste
• Tinnitus
• Visual disturbances
• Agitation, confusion
• Muscle twitching

Stage 2 - CNS depression:

• Seizures
• Loss of consciousness
• Respiratory depression
• Coma

Stage 3 - Cardiovascular toxicity:

• Bradycardia
• Hypotension
• Arrhythmias (ventricular tachycardia, fibrillation)
• Cardiac arrest (often resistant to standard ACLS)

Management of LAST

Immediate actions:

1. STOP injecting local anesthetic immediately
2. Call for help - LAST is a team emergency
3. Airway management: 100% oxygen, ventilate if needed
4. Suppress seizures: Benzodiazepines (NOT propofol initially)

Lipid emulsion therapy:

• First-line treatment for LAST
• Intralipid 20% or equivalent lipid emulsion

Dosing protocol:

• Bolus: 1.5 mL/kg over 1 minute (approximately 100 mL for 70 kg adult)
• Infusion: 0.25 mL/kg/min
• Repeat bolus: if cardiovascular instability persists after 5 minutes
• Continue infusion: for at least 10 minutes after cardiovascular stability
• Maximum dose: 10 mL/kg over first 30 minutes

Cardiac arrest management:

• Start CPR immediately with ACLS protocol
• Continue lipid emulsion throughout resuscitation
• Use epinephrine in small doses (under 1 mcg/kg)
• AVOID vasopressin (may worsen cardiac toxicity)
• AVOID propofol (is NOT lipid emulsion therapy)
• Prolonged resuscitation: may require over 60 minutes, do not give up early

Post-resuscitation:

• Observe 4-6 hours minimum (12-24 hours if severe)
• Monitor: ECG, cardiac enzymes, lipid levels
• Risk of recurrence: as LA redistributes from tissues

Prevention Strategies

Reduce risk of LAST:

• Use ultrasound guidance: reduces accidental intravascular injection
• Aspirate before injection: check for blood
• Fractionated dosing: inject 3-5 mL aliquots with pauses
• Test dose: with epinephrine (will cause tachycardia if IV)
• Maximum dose limits: calculate and respect limits
• Avoid bupivacaine for IVRA: use lidocaine or prilocaine
• Communicate with patient: ask about symptoms during injection

Absolute Contraindications

All regional blocks:

• Patient refusal
• Infection at injection site
• Allergy to local anesthetic (rare - true allergy under 1%)

Neuraxial specific:

• Therapeutic anticoagulation (see timing guidelines)
• Coagulopathy or thrombocytopenia (under 80,000)
• Elevated intracranial pressure
• Hypovolemic shock

Relative Contraindications

Consider risks vs benefits:

• Pre-existing neurological deficit (medicolegal)
• Sepsis (bacteremia risk of seeding)
• Severe spinal deformity (difficult technique)
• Prior spine surgery at level (altered anatomy)
• Prophylactic anticoagulation (timing critical)

Anticoagulation Guidelines

Neuraxial anesthesia timing:

Catheter removal timing:

• Remove catheter before restarting anticoagulation
• Wait same interval as for block placement after removal
• Observe for 4 hours after removal for signs of hematoma

Complications by Block Type

Neuraxial complications:

• Epidural hematoma: under 1 in 150,000 (higher with anticoagulation)
• Epidural abscess: under 1 in 50,000
• Post-dural puncture headache: 0.5-1% (lower with pencil-point needles)
• Total spinal: 1 in 1,000 (high epidural injection)
• Urinary retention: 10-30% (resolves as block wears off)
• Hypotension: 20-40% (treat with fluids, vasopressors)

Peripheral nerve block complications:

• Nerve injury: under 1 in 1,000 (lower with ultrasound)
• Vascular injury: under 1 in 500 (usually self-limiting hematoma)
• Pneumothorax: under 1% for SCB with ultrasound
• LAST: 0.2% with ultrasound (0.6% without)
• Phrenic nerve palsy: 100% with ISB (temporary)
• Horner syndrome: 25-75% with ISB (temporary)

Risk minimization:

• Use ultrasound guidance
• Avoid injection if high resistance
• Stop if patient reports severe pain
• Respect anatomy and avoid excessive force
• Use atraumatic needles

PBS and Medications

Local anesthetics on PBS:

• Bupivacaine: PBS listed for regional anesthesia
• Ropivacaine: PBS listed, preferred for motor-sparing blocks
• Lidocaine: Widely available, low cost
• Levobupivacaine: PBS listed, less cardiotoxic alternative

Lipid emulsion availability:

• Intralipid 20%: Should be stocked in all areas performing regional anesthesia
• ANZCA guidelines: Recommend immediate availability of lipid rescue kit

ANZCA Guidelines

Regional anesthesia standards:

• Consent: Specific consent for regional technique required
• Monitoring: Standard monitoring during block performance and initial phase
• Resuscitation: Immediate access to resuscitation equipment and lipid emulsion
• Training: Structured training programs and credentialing

Safe Practice:

• Ultrasound: Recommended for all peripheral nerve blocks
• Checklist: Use of WHO checklist for procedural safety
• Anticoagulation: Follow ANZCA/ASRA guidelines for timing

ERAS Protocols in Australia

Enhanced Recovery After Surgery:

• Regional anesthesia is cornerstone of ERAS protocols
• Reduces opioid use and enables early mobilization
• Improves patient satisfaction scores
• Reduces hospital length of stay by 1-2 days

Common ERAS combinations:

• THA: PENG block or fascia iliaca + multimodal analgesia
• TKA: ACB + IPACK or periarticular infiltration + multimodal
• Shoulder arthroplasty: ISB + multimodal analgesia

Regional anesthesia is a cornerstone of modern orthopaedic perioperative care, offering superior analgesia, reduced opioid consumption, and facilitation of early mobilization. The evolution from landmark-based techniques to ultrasound-guided approaches has dramatically improved safety and efficacy.

Key exam points:

• LAST is a life-threatening complication treated with lipid emulsion 20%
• Ultrasound guidance is now standard of care for peripheral nerve blocks
• Motor-sparing blocks (ACB, IPACK, PENG) enable ERAS protocols and same-day mobilization
• Block selection must match surgical site and patient goals
• Anticoagulation timing is critical for neuraxial safety

Future directions include development of novel motor-sparing blocks, longer-acting local anesthetics, and integration of continuous catheter techniques with ambulatory surgery protocols.