• "Paper 1, Question 5" (Brachial plexus anatomy and routes)
• "Paper 2, Question 3" (Interscalene block and phrenic nerve palsy)
• "Section 11, Paper 1, Question 1" (Epidural space anatomy)
• Or just name the topic directly - e.g., "TAP block", "PENG block", "LAST management"

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ANATOMY OF THE BRACHIAL PLEXUS: VARIOUS ROUTES OF BLOCKING AND COMPLICATIONS

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1. INTRODUCTION

• The brachial plexus is the primary neural network supplying the entire upper extremity
• Brachial plexus block (BPB) provides surgical anaesthesia and/or analgesia for procedures on the shoulder, arm, elbow, forearm, wrist and hand
• It is one of the most commonly performed peripheral nerve blocks worldwide and forms the cornerstone of upper extremity regional anaesthesia
• Local anaesthetic may be deposited at any level along the plexus; choice of approach determines the level and distribution of the block

Exam Tip: The question asks for (a) Anatomy, (b) Various routes, and (c) Complications — answer all three parts for full marks.

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2. ANATOMY OF THE BRACHIAL PLEXUS

2.1 Overview: "ROOTS, TRUNKS, DIVISIONS, CORDS, BRANCHES" — Mnemonic: "Robert Taylor Drinks Cold Beer"

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2.2 Roots

• Emerge from intervertebral foramina C5–T1
• Travel in grooves between anterior and posterior tubercles of transverse processes
• Pass between scalenus anterior and scalenus medius muscles
• C5 root — also receives contribution from C4 (prefixed plexus)
• T1 root — also receives contribution from T2 (postfixed plexus)
• Phrenic nerve (C3, C4, C5) — descends anterior to scalenus anterior; always at risk during proximal approaches

Viva Pearl: The phrenic nerve arises predominantly from C4 (with contributions from C3 and C5). It runs anterior to scalenus anterior and is blocked in virtually 100% of interscalene blocks, producing ipsilateral hemidiaphragmatic paresis.

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2.3 Trunk Formation

• The trunks cross the base of the posterior triangle of the neck and the first rib
• Upper and middle trunks pass above the subclavian artery; lower trunk passes behind or below it

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2.4 Divisions

• Each trunk divides into anterior and posterior divisions at the lateral border of the first rib/posterior to clavicle
• Total: 6 divisions (3 anterior + 3 posterior)
• Anterior divisions supply flexor compartments; posterior divisions supply extensor compartments

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2.5 Cord Formation

• Cords are grouped around the 2nd part of the axillary artery (posterior to pectoralis minor)
• Surrounded by the axillary sheath (continuation of prevertebral fascia)

Exam Tip: Cord nomenclature is based on position relative to the 2nd part of the axillary artery, not the arm.

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2.6 Terminal Branches (Mnemonic: "My Aunt Regularly Urges Me")

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2.7 Branches Arising Proximal to Terminal Branches

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2.8 Cutaneous Dermatomes of Upper Extremity

Exam Tip: The intercostobrachial nerve (T2) is NOT part of the brachial plexus. It is NOT blocked by any brachial plexus approach. Tourniquet pain is mediated partly through T2.

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2.9 Key Anatomical Diagram Description

• Vertebral column (C5–T1) on left
• Roots emerging between scalenus anterior and medius
• 3 trunks crossing posterior triangle with subclavian artery below
• Clavicle crossing
• 6 divisions behind clavicle
• 3 cords around axillary artery (label medial, lateral, posterior)
• 5 terminal branches emerging below pectoralis minor
• Label phrenic nerve on anterior scalenus anterior
• Label first rib as inferior boundary of supraclavicular fossa
• Label "interscalene" → "supraclavicular" → "infraclavicular" → "axillary" levels with arrows

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3. VARIOUS ROUTES OF BLOCKING THE BRACHIAL PLEXUS

Classification of Approaches

BRACHIAL PLEXUS BLOCK APPROACHES
              |
    __________|__________
    |                   |
ABOVE CLAVICLE      BELOW CLAVICLE
(Supraclavicular)   (Infraclavicular)
    |                   |
1. Interscalene     3. Infraclavicular
2. Supraclavicular  4. Axillary
                    5. Costoclavicular (novel)

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3.1 INTERSCALENE BRACHIAL PLEXUS BLOCK (ISB)

Level of Block

• Trunks (superior and middle) in the interscalene groove

Indications

• Shoulder surgery (arthroscopy, arthroplasty, rotator cuff repair)
• Proximal humerus fractures
• Clavicle surgery (partial)
• Acute shoulder pain / trauma

Patient Position

• Supine, head turned 30–45° to contralateral side, slight reverse Trendelenburg

Surface Anatomy / Landmarks

• Cricoid cartilage (C6 level) — identifies the level of the interscalene groove
• Posterior border of sternocleidomastoid (SCM)
• External jugular vein (often crosses at this level)
• Chassaignac's tubercle (anterior tubercle of C6 transverse process)

Ultrasound Technique

• Probe: High-frequency linear (10–15 MHz)
• Position: Transverse, lateral neck at C6 level
• Sonoanatomy:
  • Identify carotid artery and internal jugular vein medially
  • Identify scalenus anterior and scalenus medius muscles
  • Brachial plexus roots/trunks appear as "traffic light" or "stoplight" sign — 3 hypoechoic round structures between the scalene muscles (C5 upper, C6 middle, C7 lower)
  • Note: Vertebral artery lies medial and deep — must be avoided
• Needle: 22G, 50mm, short bevel or echogenic
• Approach: In-plane (lateral to medial) or out-of-plane
• Volume: 10–20 mL (5 mL may be sufficient for analgesia with reduced phrenic nerve block risk)
• Endpoint: Spread of LA seen around trunks; aspiration negative before each increment

Nerve Stimulator Endpoint

• Stimulation of upper trunk (C5, C6): deltoid contraction, shoulder abduction, or elbow flexion
• Acceptable at 0.2–0.5 mA

What is Blocked / What is Missed

Key Complications

• Ipsilateral phrenic nerve block (100%) — hemidiaphragmatic paresis → absolute contraindication in contralateral phrenic nerve palsy or single lung
• Horner's syndrome — stellate ganglion block (25%)
• Pneumothorax (rare with US guidance)
• Vertebral artery injection → immediate CNS toxicity
• Intraspinal/epidural spread
• Subarachnoid injection → high/total spinal

Viva Pearl: ISB is the ONLY brachial plexus block where bilateral performance is absolutely contraindicated (bilateral phrenic nerve palsy → respiratory arrest).

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3.2 SUPRACLAVICULAR BRACHIAL PLEXUS BLOCK

Level of Block

• Trunks and divisions at the first rib, as they cluster together before dividing
• Called the "spinal anaesthesia of the arm" — most complete and consistent block for the upper limb

Indications

• All surgeries below the mid-humerus (elbow, forearm, wrist, hand)
• Not ideal for shoulder surgery (C5, C6 proximal branches may be missed)

Patient Position

• Supine, head turned to contralateral side; arm adducted

Surface Anatomy / Landmarks

• Posterior border of SCM at clavicle
• Clavicle
• Subclavian artery pulsation in supraclavicular fossa

Ultrasound Technique

• Probe: High-frequency linear (12–15 MHz)
• Position: Parallel to and just above clavicle, coronal oblique
• Sonoanatomy:
  • Subclavian artery — pulsatile, circular, anechoic
  • First rib — hyperechoic line with acoustic shadow below the artery
  • Pleura — bright hyperechoic line, deeper to first rib, with lung sliding
  • Brachial plexus = "cluster of grapes" — multiple hypoechoic nodules lateral and superficial to the subclavian artery
• Needle: 22G, 50mm echogenic
• Approach: In-plane, lateral to medial
• Volume: 20–30 mL
• Corner pocket technique: LA deposited in the "corner pocket" between subclavian artery and first rib — achieves superior spread to lower trunk (prevents ulnar sparing)

Key Complications

• Pneumothorax — most significant risk (0.1–0.4% with US guidance)
• Phrenic nerve block (50–60%)
• Horner's syndrome
• Subclavian artery puncture/haematoma

Exam Tip: The pneumothorax risk is lower with US guidance but never zero — rib and pleura must be identified before needle insertion.

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3.3 INFRACLAVICULAR BRACHIAL PLEXUS BLOCK

Level of Block

• Cords around the 2nd part of the axillary artery

Indications

• Procedures at or distal to the elbow
• Catheter placement (more comfortable than axillary)
• Obese patients, restricted neck movement
• When tourniquet is applied above elbow

Patient Position

• Supine, arm slightly abducted or at side

Surface Anatomy / Landmarks

• Coracoid process — medial border
• Infraclavicular fossa — below clavicle, medial to coracoid

Ultrasound Technique

• Probe: High-frequency linear or lower-frequency curvilinear (depending on depth)
• Position: Parasagittal below clavicle, medial to coracoid process
• Sonoanatomy:
  • Axillary artery — round, pulsatile, anechoic, at 3–5 cm depth
  • Axillary vein — compressible, medial
  • Cords: Lateral cord = superficial/lateral (10 o'clock), Posterior cord = deep/posterior (6 o'clock), Medial cord = medial (8 o'clock) relative to artery
  • Pectoralis major and minor muscles overlying
• Needle: 22G, 80–100mm echogenic
• Approach: In-plane (cephalad-to-caudad direction)
• Volume: 20–35 mL
• Endpoint: U-shaped (posterior) or circumferential spread around axillary artery

Key Complications

• Pneumothorax (less than supraclavicular)
• Axillary vessel puncture
• Infraclavicular haematoma
• No phrenic nerve risk

Viva Pearl: Infraclavicular block has lower phrenic nerve block rate and is preferred in patients with moderate pulmonary compromise. Catheter placement is more stable here than at axillary level.

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3.4 AXILLARY BRACHIAL PLEXUS BLOCK

Level of Block

• Terminal nerves (median, ulnar, radial, musculocutaneous) in the axilla

Indications

• Forearm, wrist and hand surgery
• Day-case surgery
• Paediatric upper limb surgery
• High-risk pulmonary patients (no phrenic nerve risk)

Patient Position

• Supine, arm abducted 90° and externally rotated, elbow flexed

Surface Anatomy / Landmarks

• Axillary artery pulse (palpated in axilla)
• Anterior edge of axillary hair line

Ultrasound Technique

• Probe: High-frequency linear (12–15 MHz)
• Position: Transverse, in the axilla, high as possible
• Sonoanatomy:
  • Axillary artery — central reference landmark
  • Median nerve — superficial, lateral to artery (hyperechoic honeycomb, 11–1 o'clock)
  • Ulnar nerve — medial, superficial to artery (9–11 o'clock)
  • Radial nerve — deep/posterior to artery (5–7 o'clock)
  • Musculocutaneous nerve — NOT periarterial; lies within coracobrachialis muscle or between coracobrachialis and biceps (must be blocked separately)
  • Axillary vein — medial, compressible
• Needle: 22G, 50mm
• Approach: In-plane, lateral
• Volume: 5 mL per nerve (total 15–20 mL) — selective 4-injection technique

What is Missed

• Musculocutaneous nerve — exits plexus proximal to axilla; must be separately blocked in coracobrachialis
• Intercostobrachial nerve (T2) — requires subcutaneous infiltration along axilla
• Medial cutaneous nerve of arm — subcutaneous ring at axillary crease

Key Complications

• Axillary artery/vein puncture (most common)
• Haematoma
• No phrenic nerve risk
• No pneumothorax risk

Exam Tip: The axillary block is the safest BPB approach but least complete (musculocutaneous and intercostobrachial nerves missed). Requires 4-injection technique with US for best results.

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3.5 COSTOCLAVICULAR BRACHIAL PLEXUS BLOCK (Novel/Recent)

Level of Block

• Cords in the costoclavicular space (between clavicle and first rib)

Sonoanatomy

• Probe: Linear, high-frequency, parallel to clavicle
• Cords appear as compact cluster lateral to subclavian artery in costoclavicular space
• Axillary artery and subclavian vein are medial

Advantages

• Cords more compact here than at infraclavicular level → single injection technique
• Excellent for catheter insertion
• Lower phrenic nerve block rate than supraclavicular/interscalene
• Suitable when arm cannot be moved (trauma, fracture)

Volume: 20–30 mL

Viva Pearl (2024–2026): Meta-analysis by Amaral et al. (2024) comparing costoclavicular vs. infraclavicular approaches found comparable efficacy with potentially lower complication rates for costoclavicular. Koo et al. (2023) confirmed significantly lower hemidiaphragmatic paralysis rate with costoclavicular versus interscalene block.

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Comparison Table of All Approaches

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4. LOCAL ANAESTHETIC DRUGS

• Dexamethasone 4–8 mg (IV or perineural) — extends block duration by 6–8 hours
• Dexmedetomidine 0.5–1 mcg/kg — extends sensory block by 2–4 hours
• Clonidine 75–150 mcg — modest prolongation
• Buprenorphine 0.3 mg — prolongs analgesia

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5. PATIENT PREPARATION

• Consent: Informed written consent; explain procedure, risks, alternatives
• Monitoring: ECG, SpO2, NIBP, IV access mandatory
• Sedation: Midazolam 1–2 mg IV + fentanyl 25–50 mcg IV titrated (conscious sedation)
• Positioning: As per approach (detailed per block above)
• Asepsis: Sterile field, ultrasound probe sterile cover, skin antisepsis (chlorhexidine)
• Resuscitation: Lipid emulsion 20% intralipid must be available at point of care
• WHO block checklist: Patient identity, site marking, timeout, anticoagulation status

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6. ASSESSMENT OF BLOCK

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7. COMPLICATIONS

Classification

COMPLICATIONS OF BRACHIAL PLEXUS BLOCK
            |
     _______|_______
     |             |
  SYSTEMIC      LOCAL
     |             |
   LAST        Nerve injury
   Seizure      Haematoma
   Cardiac      Pneumothorax
   arrest       Infection
              Phrenic palsy
              Horner syndrome
              Vascular injury

Systematic Complications Table

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8. MANAGEMENT OF LAST (LOCAL ANAESTHETIC SYSTEMIC TOXICITY)

RECOGNITION
Neurological: perioral tingling, tinnitus, metallic taste, confusion, seizures
Cardiac: arrhythmia, bradycardia, VT/VF, cardiovascular collapse
                    ↓
STOP INJECTION immediately
Call for help
                    ↓
AIRWAY MANAGEMENT
100% O2 via mask → intubate if seizures or unconscious
Prevent hypoxia (worsens LAST)
                    ↓
SEIZURE MANAGEMENT
Benzodiazepine FIRST: Midazolam 1–2 mg IV
or Propofol 0.5–1 mg/kg (if not cardiovascularly compromised)
Avoid large doses propofol (worsens cardiac depression)
                    ↓
CARDIOVASCULAR COLLAPSE
Epinephrine: small doses (10–100 mcg boluses)
Avoid vasopressin, calcium channel blockers, beta-blockers
                    ↓
LIPID EMULSION (20% Intralipid) — ASRA 2020
Bolus: 1.5 mL/kg IV over 1 minute
Infusion: 0.25 mL/kg/min
Repeat bolus ×2 if no improvement (at 3–5 min)
Double infusion rate to 0.5 mL/kg/min if persistent
Maximum dose: 12 mL/kg
                    ↓
CPR if cardiac arrest
Prolonged CPR (>60 minutes) with lipid emulsion
Consider cardiopulmonary bypass if available
                    ↓
POST-EVENT MONITORING
ICU/HDU for minimum 4–6 hours after bupivacaine toxicity
12 hours after cardiac arrest

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9. ANTICOAGULATION AND BRACHIAL PLEXUS BLOCK

Important: For peripheral nerve blocks without deep planes (e.g., axillary, femoral), ASRA considers the risk of haematoma lower than neuraxial. Non-compressible sites (infraclavicular, paravertebral) require similar caution to neuraxial.

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10. RECENT ADVANCES (2024–2026)

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11. CURRENT GUIDELINES SUMMARY

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12. CLINICAL PEARLS

1. "Stoplight" sign on US = 3 hypoechoic nodules between scalene muscles at interscalene level = C5 (superior), C6 (middle), C7 (lower)
2. "Cluster of grapes" sign = brachial plexus at supraclavicular level
3. At supraclavicular level, the entire plexus is most compact — hence "spinal of the arm"
4. C8, T1 (lower trunk/medial cord) is MOST COMMONLY missed in interscalene and (sometimes) supraclavicular blocks — always supplement ulnar nerve for hand surgery
5. Phrenic nerve is blocked in 100% of ISBs — always ask about contralateral phrenic palsy, COPD severity, and BMI
6. The musculocutaneous nerve exits the plexus high in the axilla and must be separately blocked in the coracobrachialis muscle during axillary block
7. Intercostobrachial nerve (T2) is never blocked by any BPB — supplement subcutaneous ring for tourniquet pain
8. Never direct the needle medially during interscalene block — vertebral artery and intervertebral foramina lie medially; even 1 mL intrathecally causes total spinal
9. Opening injection pressure > 15 psi suggests intraneural placement — stop injection immediately
10. 20% Intralipid must be drawn up before every brachial plexus block — not just available in pharmacy
11. For infraclavicular catheter placement, aim for the posterior cord position (6 o'clock behind artery) — single injection produces circumferential spread
12. Ropivacaine 0.5% is the drug of choice for single-injection BPB balancing onset, duration and safety profile
13. Dexamethasone 8 mg IV prolongs block duration comparably to perineural dexamethasone with a better safety profile
14. Bilateral ISB is absolutely contraindicated — bilateral phrenic nerve palsy = respiratory arrest
15. The costoclavicular approach is the fastest-emerging infraclavicular technique — cords are most compact here; single injection, no arm movement required

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13. COMMON VIVA QUESTIONS

• Roots: C5–T1; Trunks: Upper (C5+C6), Middle (C7), Lower (C8+T1); Cords: Lateral (C5–C7), Posterior (C5–T1), Medial (C8, T1)

• Both phrenic nerves are blocked → bilateral hemidiaphragmatic paresis → respiratory failure requiring ventilation

• LA deposited in the groove between the subclavian artery and the first rib → ensures spread to lower trunk (C8, T1) preventing ulnar nerve sparing

• Sonographic appearance of brachial plexus at interscalene level: 3 round hypoechoic structures arranged vertically between anterior and middle scalene muscles

• It exits the brachial plexus proximal to the axilla, enters coracobrachialis muscle, and lies outside the axillary sheath at the level of block

• The initial pressure required to inject LA around the nerve. Pressure > 15 psi suggests intraneural needle tip position → risk of nerve damage → stop injection

• Local anaesthetic systemic toxicity from intravascular injection or systemic absorption. Treatment: stop injection, airway, oxygen, seizure management, 20% Intralipid bolus 1.5 mL/kg then infusion 0.25 mL/kg/min

• Ulnar nerve (C8, T1 from lower trunk) — lower trunk lies below and behind the subclavian artery, away from the primary injection site in the interscalene groove

• Ptosis, miosis, anhidrosis, enophthalmos from stellate ganglion block. Most common with interscalene block (25–75%). Transient, requires only reassurance.

• Same fascial compartment — it is the prevertebral fascia that surrounds the plexus from the interscalene groove proximally and continues as the axillary sheath distally. LA spreads proximally or distally within this sheath.

• Supraclavicular (0.1–0.4% with US guidance; historically up to 6% with landmark technique) due to proximity of pleural apex

• Separate injections for median nerve, ulnar nerve, radial nerve, and musculocutaneous nerve (in coracobrachialis) rather than single periarterial injection → higher success rate

• Infraclavicular catheter is more stable (less head movement), no phrenic nerve risk, better for hand/forearm surgery; interscalene catheter better for shoulder surgery but causes persistent phrenic palsy

• Anterior suprascapular nerve block; combined axillary nerve + suprascapular nerve block; sub-pectoral (subomohyoid) ISB with reduced volume (5 mL); costoclavicular block

• Patient refusal; infection at injection site; allergy to local anaesthetics; bilateral interscalene block; contralateral phrenic nerve palsy (for ISB/supraclavicular); coagulopathy (relative for most approaches)

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14. HIGH-YIELD FACTS

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15. RAPID REVISION BOX

BRACHIAL PLEXUS — ONE PAGE REVISION
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
ANATOMY MNEMONIC: Robert Taylor Drinks Cold Beer
Roots (C5–T1) → Trunks (3) → Divisions (6) → Cords (3) → Branches (5)

TRUNKS:  Upper=C5+C6 | Middle=C7 | Lower=C8+T1
CORDS:   Lateral=C5-C7 | Posterior=C5-T1 | Medial=C8,T1

TERMINAL NERVES (My Aunt Regularly Urges Me):
M-Musculocutaneous | A-Axillary | R-Radial | U-Ulnar | M-Median

APPROACH SELECTION:
Shoulder → INTERSCALENE (trunks) — phrenic risk!
Arm/Elbow → SUPRACLAVICULAR (divisions) — "spinal of arm"
Elbow/Hand → INFRACLAVICULAR or COSTOCLAVICULAR (cords)
Hand/Wrist → AXILLARY (terminal nerves) — safest

VOLUMES: ISB 10-20mL | Supraclav 20-30mL | Infraclav 20-35mL | Axillary 15-20mL

KEY COMPLICATIONS:
1. LAST → Intralipid 1.5 mL/kg bolus + 0.25 mL/kg/min
2. Phrenic palsy → O2, PPV if needed (ISB 100%, Supraclav 50-60%)
3. Pneumothorax → Supraclavicular (highest risk)
4. Horner → ISB/Supraclav (25-75%, transient)
5. Vertebral artery → ISB (never direct needle medially)
6. Intraspinal → ISB (catastrophic)

MISSED NERVES:
ISB → C8/T1 ulnar territory
Axillary → Musculocutaneous (block separately in coracobrachialis)
All BPBs → Intercostobrachial T2 (subcutaneous ring block)

BILATERAL ISB = ABSOLUTELY CONTRAINDICATED

INJECTION PRESSURE > 15 psi = STOP (intraneural)

LAST TREATMENT: Stop → Airway → O2 → Seizure Rx →
INTRALIPID 20% → 1.5 mL/kg bolus → 0.25 mL/kg/min infusion → CPR

ULTRASOUND SIGNS:
ISB: "Stoplight" (3 nodes between scalenes)
Supraclav: "Cluster of grapes" lateral to subclavian artery
Infraclav: Cords at 3, 6, 9 o'clock around axillary artery
Axillary: Median (11), Ulnar (9-11), Radial (5-7) around artery

RECENT ADVANCES (2024-2026):
Costoclavicular block | Liposomal bupivacaine | AI-US | Pressure monitoring
Phrenic-sparing ISB | Continuous catheters | Handheld US (Butterfly iQ+)
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

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• Miller's Anesthesia 10e, Chapter 42 (Upper Extremity Blocks)
• Barash Clinical Anesthesia 9e, Chapter 36 (Brachial Plexus)
• Morgan & Mikhail Clinical Anesthesiology 7e, Chapter on Regional Anaesthesia
• Amaral et al. "Infraclavicular versus costoclavicular approaches...systematic review and meta-analysis." Braz J Anesthesiol 2024 [PMID: 37748644]
• Oliver-Fornies et al. "Hemidiaphragmatic paralysis after ultrasound-guided brachial plexus blocks." J Clin Anesth 2025 [PMID: 40494113]
• Koo et al. "Hemidiaphragmatic paralysis after costoclavicular approach vs other brachial plexus blocks." Korean J Anesthesiol 2023 [PMID: 37127532]
• ASRA LAST Guidelines 2020 | ASRA Anticoagulation Guidelines 2022 | ESRA 2023 Consensus---

• Full anatomy with mnemonic, roots → trunks → divisions → cords → terminal branches with tables
• All 5 approaches (Interscalene, Supraclavicular, Infraclavicular, Axillary, Costoclavicular) with US technique, volumes, indications
• Comprehensive comparison table
• Complete complications with mechanism, prevention, management
• Full ASRA LAST algorithm with drug doses
• Anticoagulation guidelines (ASRA 2022 / ESRA 2023)
• Recent advances up to 2026 with supporting evidence
• 15 viva questions with model answers
• One-page rapid revision box

📋 QUESTION TRACKER

✅ DISCUSSED

🔄 IN PROGRESS NOW

⏳ REMAINING (from your list)

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TRUNCAL REGIONAL NERVE BLOCKS

Enumerate Truncal Blocks — Discuss ESP Block, Serratus Anterior Plane Block, and Paravertebral Block

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PART A: ENUMERATION OF TRUNCAL REGIONAL NERVE BLOCKS

Classification

TRUNCAL REGIONAL NERVE BLOCKS
            |
   _________|__________
   |                   |
NEURAXIAL            PERIPHERAL
(Epidural/Spinal)     Truncal Blocks
                       |
         ______________|_______________
         |              |              |
   PARAVERTEBRAL   INTERFASCIAL    INTERCOSTAL
   BLOCKS          PLANE BLOCKS    BLOCKS
         |              |
    Thoracic PVB   ESP Block
    Lumbar PVB     TAP Block
                   QL Block
                   PECS I / II
                   SAP Block
                   Serratus Ant. Block
                   Parasternal Block

Complete Enumeration Table

Exam Tip: In the exam, enumerate ALL truncal blocks first in a table — this scores well even if you only discuss 2–3 in detail. Always state whether a block has somatic only or somatic + visceral + sympathetic coverage.

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BLOCK 1: ERECTOR SPINAE PLANE (ESP) BLOCK

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1. DEFINITION AND INTRODUCTION

• Definition: A fascial plane block in which local anaesthetic is deposited deep to the erector spinae muscle group and superficial to the transverse process of the vertebra
• First described by Forero et al., 2016 for neuropathic chest pain (thoracic T5 level)
• Mechanism: LA spreads within the ESP fascial plane → permeates anteriorly through the intertransverse connective tissue → enters the paravertebral space → blocks dorsal rami, ventral rami, and sympathetic nerve fibres
• The ESP plane runs from cervical spine to sacrum bilaterally

Viva Pearl: The exact mechanism of the ESP block remains incompletely understood. Proposed pathways include: (1) direct paravertebral spread via intertransverse ligament, (2) retrolaminar spread, (3) neural soaking of dorsal rami at transverse process level.

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2. RELEVANT ANATOMY

Erector Spinae Muscle Group (Mnemonic: "I Love Spine")

• The 3 muscles lie bilaterally alongside the vertebral column
• High thoracic (T1–T6): Lie deep to trapezius and rhomboid muscles
• Low thoracic (T7–T12): Lie deep to latissimus dorsi muscle
• Lumbar: Covered by thoracolumbar fascia

Key Relationships at the Transverse Process Level

SKIN
  ↓
Subcutaneous fat
  ↓
Trapezius / Rhomboid / Latissimus dorsi
  ↓
ERECTOR SPINAE MUSCLE GROUP
  ↓
[ESP FASCIAL PLANE] ← TARGET injection plane
  ↓
TRANSVERSE PROCESS (osseous backstop)
  ↓
Intertransverse ligament
  ↓
PARAVERTEBRAL SPACE (LA spreads here)
  ↓
Spinal nerve (dorsal + ventral rami + sympathetics)

Important Anatomical Points

• The transverse process acts as the osseous backstop — protects from inadvertent pleural puncture
• At thoracic levels: TP is at 2.5–3 cm depth
• Lateral border of TP is the danger zone for advancing too deep → paravertebral space, pleura
• The dorsal scapular artery and posterior intercostal arteries are nearby

Dermatomes Covered

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3. SURGICAL AND CLINICAL INDICATIONS

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4. SONOANATOMY AND ULTRASOUND-GUIDED TECHNIQUE

Probe

• Linear high-frequency probe (13–6 MHz) — routine adults
• Curvilinear (8–3 MHz) — obese patients or deep thoracic levels

Patient Position

• Sitting (preferred) — with head flexed forward, arms across chest
• Lateral decubitus or prone (alternative)

Scanning Protocol

Sonographic Landmarks

PARASAGITTAL US VIEW (thoracic ESP):
─────────────────────────────────────
[Skin]
[Trapezius / Rhomboids / Lat dorsi]
[ERECTOR SPINAE MUSCLE] ← striated, hypoechoic
[ESP PLANE] ← bright fascial line = TARGET
[TRANSVERSE PROCESS] ← hyperechoic shelf + acoustic shadow
                        (NOT the rib — rib is lateral and deeper)
─────────────────────────────────────

Exam Tip — Common Mistake: Confusing the transverse process with the rib on US. TP = rectangular, more medial, with broad acoustic shadow. Rib = curved, lateral, deeper.

Needle Technique

• Needle: 22G 80–100 mm echogenic block needle
• Approach: In-plane (cranio-caudal OR caudo-cranial)
• Direction: Needle tip contacts periosteum of TP
• Hydrodissection: Inject 1–2 mL saline — erector spinae muscle lifts off TP = correct plane confirmed
• Injection: 20–30 mL LA (single injection); 30–50 mL for extended coverage
• Spread: Watch LA lift erector spinae off TP and track cranially + caudally along the plane

Drug Choice and Volumes

• Bilateral ESP: Halve volumes per side (max 10–15 mL per side)
• Continuous catheter: Ropivacaine 0.2% at 5–10 mL/h

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5. ASSESSMENT OF BLOCK

• Sensory: Pin-prick testing along dermatomes T3–T9 (depending on injection level)
• Motor: No motor block expected (fascial plane block — purely somatic +/- visceral)
• Onset: 15–30 minutes for full sensory blockade
• Duration: 12–24 hours with long-acting LA

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6. ADVANTAGES AND DISADVANTAGES

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7. COMPLICATIONS

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8. RECENT EVIDENCE (2024–2026)

• Yang et al. Network Meta-analysis, Pain Physician 2024 [PMID: 39621976]: For thoracic surgery analgesia — PVB ranked superior to ESP; ESP was superior to intercostal and systemic analgesia
• Gamberini et al. Bayesian Network Meta-analysis, Am J Emerg Med 2025 [PMID: 39740311]: In blunt thoracic trauma — PVB ranked highest; ESP block was effective and superior to systemic analgesia for rib fractures
• ESAIC 2024: Endorses ESP as first-line option where PVB expertise is unavailable; recommends pressure monitoring and US guidance as standard of care

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BLOCK 2: SERRATUS ANTERIOR PLANE BLOCK (SAP BLOCK)

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1. DEFINITION AND INTRODUCTION

• Definition: An ultrasound-guided interfascial plane block in which local anaesthetic is deposited superficial or deep to the serratus anterior muscle at the mid-axillary line to anaesthetise the lateral chest wall
• First described by Blanco et al., 2013
• Primarily blocks the lateral cutaneous branches of the intercostal nerves (T2–T9)
• Two variants: Superficial SAP (between latissimus dorsi and serratus anterior) and Deep SAP (between serratus anterior and ribs)

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2. RELEVANT ANATOMY

Serratus Anterior Muscle

• Origin: Lateral surfaces of upper 8–9 ribs
• Insertion: Medial border of scapula (anterior/costal surface)
• Innervation: Long thoracic nerve (C5, C6, C7)
• Function: Protracts and rotates scapula; stabilises scapula during arm movements
• Relations:
  • Superficial: Latissimus dorsi (posterolaterally), pectoralis major/minor (anteriorly)
  • Deep (internal surface): Ribs and intercostal spaces, parietal pleura
  • In the plane: Thoracodorsal artery (between latissimus dorsi and serratus anterior — Doppler essential)
  • Intercostobrachial nerve (ICBN), T2–T9 lateral cutaneous branches run within/between these fascial planes

Nerves Blocked

Viva Pearl: SAP block does not cover the medial chest wall, anterior chest, or visceral pain. Medial branch (costomediastinal) is not covered. Hence not adequate as sole anaesthetic for thoracotomy.

Cutaneous Coverage

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3. CLINICAL INDICATIONS

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4. SONOANATOMY AND ULTRASOUND-GUIDED TECHNIQUE

Probe

• Linear high-frequency (13–6 MHz) — standard
• Transverse orientation at mid-axillary line

Patient Position

• Supine with arm abducted (ipsilateral arm above head) — preferred
• Lateral decubitus (alternative)

Scanning at Mid-Axillary Line, 4th–5th Rib Level

LATERAL CHEST WALL US (Transverse view at mid-axillary line):
─────────────────────────────────────────────────────────────
[Skin]
[Subcutaneous fat]
[LATISSIMUS DORSI MUSCLE] ← superficial layer
[SUPERFICIAL SAP PLANE] ← between LD and SAM = Target 1
[SERRATUS ANTERIOR MUSCLE] ← scalloped/fan-shaped
[DEEP SAP PLANE] ← between SAM and rib = Target 2
[RIB] ← hyperechoic curved surface + acoustic shadow
[PLEURA] ← bright hyperechoic line between rib shadows
─────────────────────────────────────────────────────────────
DOPPLER: Thoracodorsal artery in superficial plane — AVOID

Technique Steps

Clinical Pearl: Always perform Deep SAP before Superficial SAP — once superficial plane is filled with LA, it becomes difficult to visualise deep structures.

Drug Doses

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5. ADVANTAGES AND DISADVANTAGES

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6. COMPARISON: SAP vs. PVB (from Wang & Li, BMC Anesthesiol 2025 [PMID: 41087941])

• SAP block and PVB showed comparable postoperative pain scores (VAS/NRS) at 6h and 24h
• PVB had superior analgesia at 12h
• SAP had lower complication rates (no pneumothorax, no hypotension)
• Conclusion: SAP is a safer alternative where PVB expertise is unavailable

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BLOCK 3: THORACIC PARAVERTEBRAL BLOCK (TPVB)

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1. DEFINITION

• Definition: Injection of local anaesthetic into the thoracic paravertebral space (TPVS) — a wedge-shaped anatomical compartment lateral to the vertebral body — producing ipsilateral somatic and sympathetic nerve block over multiple contiguous thoracic dermatomes
• Often described as a unilateral, segmental epidural equivalent with superior haemodynamic profile

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2. ANATOMY OF THE THORACIC PARAVERTEBRAL SPACE

Boundaries (Mnemonic: "SPAM" — Superior, Posterior, Anterior, Medial)

Contents of the TPVS

• Spinal nerve (at intervertebral foramen)
• Dorsal ramus (posterior primary rami)
• Ventral ramus (anterior primary rami) — main target
• Sympathetic chain (anteriorly, near vertebral body)
• Intercostal vessels
• Loose areolar fatty tissue
• Endothoracic fascia (separates pleural from extrapleural compartment)

Key Anatomical Points

• TPVS is a wedge-shaped space — apex medially at IVF, base laterally at pleura
• Communicates freely with adjacent levels — hence single injection can spread multiple levels
• At thoracic levels: TPVS depth from skin = 4–5 cm in average adults
• The superior costotransverse ligament (SCL) is the key posterior boundary — a firm fibrous band between the transverse process and the rib above
• Endothoracic fascia divides the PVS into anterior (pleural) and posterior (extrapleural) compartments

Exam Tip: The paravertebral space communicates medially with the epidural space (especially if large volumes used) — this explains ipsilateral and occasionally bilateral blocks with PVB.

Diagram Description — Draw in Exam

CROSS-SECTION OF THORACIC PARAVERTEBRAL SPACE:

        [Spinous process]
               |
        [Lamina + Ligamentum flavum]
               |
        [EPIDURAL SPACE]
               |         IVF
        [Vertebral body] — [SPINAL NERVE] ——→ PARAVERTEBRAL SPACE
               |                              |
               |                    [Superior Costotransverse Lig.]
               |                              | (posterior wall)
               |                    [Rib — head and neck]
               |                              |
               |                    [PARIETAL PLEURA]
               |                        (anterior wall)
               ↓
         Sympathetics (anterolateral)

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3. SURGICAL AND CLINICAL INDICATIONS

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4. LANDMARK-BASED TECHNIQUE

Patient Position

• Sitting, spine flexed forward; or lateral decubitus

Surface Anatomy

• Identify spinous processes (count from C7 prominens downwards for thoracic)
• Mark a point 2.5 cm lateral to the midpoint of the superior edge of each spinous process
• Important: At thoracic levels, due to the steep caudal angulation of spinous processes, the T4 nerve root is accessed lateral to T3 spinous process

Needle Technique (Classic/Landmark)

STEP 1: Insert 20G Tuohy needle PERPENDICULAR to skin
STEP 2: Contact TRANSVERSE PROCESS at 2.5–4 cm depth
STEP 3: Walk needle CAUDALLY off the TP
STEP 4: Advance 1–1.5 cm BEYOND TP tip → "loss of resistance"
         through superior costotransverse ligament
STEP 5: Aspiration — negative blood and air
STEP 6: Inject LA — observe "clicks" as plunger advances (loss of resistance)
STEP 7: Volume 3–5 mL per level (landmark technique)

Viva Pearl: The loss of resistance in PVB occurs as the needle passes through the superior costotransverse ligament — this is the classical tactile endpoint (like epidural LOR technique). However, US guidance has made this more reliable.

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5. ULTRASOUND-GUIDED TECHNIQUE

Probe

• Linear probe (13–6 MHz) — standard
• Curvilinear for deeper structures in obese patients

Probe Position and Views

• Probe perpendicular to spine at target level
• Identify: spinous process (medial), transverse process, costotransverse joint, rib (lateral), parietal pleura (anterior to rib)
• TPVS seen as wedge-shaped hypoechoic space between SCL and pleura

• Probe 2–3 cm lateral to midline
• See: erector spinae muscles, transverse processes, ribs, TPVS, and pleura
• LA injection: watch anterior displacement of pleura = correct TPVS injection confirmed

Needle Technique (US-Guided)

Drug Doses and Volumes

• Mastectomy (T2–T6): 3 injections at T3, T4, T5 or single catheter at T4
• Rib fractures: Level of each fractured rib

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6. COMPLICATIONS OF TPVB

Exam Tip: The most feared complication of TPVB is pneumothorax — always identify pleura on US BEFORE needle insertion. Anterior displacement of pleura during injection is the confirmation sign.

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7. ANTICOAGULATION CONSIDERATIONS FOR TPVB

• TPVB is classified as a deep, non-compressible block by ASRA 2022
• Therefore, applies similar anticoagulation rules as neuraxial blocks
• LMWH therapeutic dose: Wait 24 hours before performing TPVB
• Warfarin: INR ≤ 1.5 before performing
• DOACs (rivaroxaban, apixaban): Wait 48 hours

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8. COMPARISON OF ALL THREE BLOCKS

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9. RECENT ADVANCES (2024–2026)

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10. CURRENT GUIDELINES

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11. CLINICAL PEARLS

1. PVB is the gold standard for unilateral thoracoabdominal analgesia — but requires expertise
2. ESP block is the safest to learn — the transverse process is an osseous backstop that prevents pleural puncture
3. SAP block uses the rib as backstop — virtually zero pneumothorax risk; ideal for trainees
4. LA spread in ESP is unpredictable — always use a sufficient volume (20–30 mL) and confirm spread under US
5. Anterior displacement of pleura on US = the confirmatory sign of correct TPVS injection
6. For mastectomy: T2–T6 coverage needed; PVB at T3 and T5 or SAP block for lateral coverage + PECS II for medial coverage
7. Bilateral PVB = bilateral sympathectomy → significant hypotension risk; reduce volumes, have vasopressors ready
8. For rib fractures: PVB or ESP preferred over intercostal blocks (longer duration, fewer injections needed)
9. Deep SAP block first when doing dual-plane technique — superficial injection obscures deep anatomy
10. The thoracodorsal artery lies in the superficial SAP plane — always use colour Doppler before injection
11. Continuous PVB catheters outperform single-shot for thoracotomy analgesia — plan catheter at time of surgery
12. ESP at T4 level covers T2–T6 → suitable for breast surgery when PVB not available
13. Lumbar PVB (L1–L3) covers lumbar plexus — indicated for inguinal hernia, renal surgery (not psoas compartment block)
14. ERAS protocols: ESP/PVB combined with dexamethasone, NSAIDs, and paracetamol = opioid-free thoracic anaesthesia
15. If bilateral ESP is needed, total volume must not exceed 3 mg/kg ropivacaine — LAST risk is real with bilateral injections

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12. COMMON VIVA QUESTIONS

• Posterior: Superior costotransverse ligament; Anterolateral: Parietal pleura; Medial: Vertebral body + IVF; Superior/Inferior: Heads of ribs

• Loss of resistance through SCL (landmark technique); Anterior displacement of parietal pleura on US (gold standard)

• LA deposited deep to erector spinae over TP → diffuses through intertransverse connective tissue → enters paravertebral space → blocks dorsal rami, ventral rami, and sympathetic fibres over multiple levels

• PVB directly blocks sympathetic chain in the TPVS → sympatholysis; ESP block produces sympathetic block only if LA diffuses anteriorly to reach the paravertebral space — this is variable

• When LA is injected into the TPVS under US guidance, the parietal pleura is displaced anteriorly (away from the SCL) as the TPVS expands with LA = confirmatory sign of correct placement

• Lateral cutaneous branches of T2–T9, intercostobrachial nerve (T2), long thoracic nerve, thoracodorsal nerve; does NOT block medial chest wall or visceral pain

• PVB has superior analgesia at 12h but SAP has lower complication profile. For lateral chest wall coverage SAP is excellent; for complete breast coverage, PVB or PECS II + SAP combined is preferred (Wang & Li, BMC Anesthesiol 2025)

• Superficial: LA between latissimus dorsi and serratus anterior; Deep: LA between serratus anterior and rib. Efficacy is similar but deep SAP should be performed first

• Approximately 0.5–1% (much lower than historical 2–5% with landmark technique)

• Thoracic surgery (mastectomy, VATS): T4–T5 level; Abdominal surgery: T7–T8 level; Lumbar (spine/hip): L2–L3 level

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13. RAPID REVISION BOX

TRUNCAL BLOCKS — ONE PAGE REVISION (ESP + SAP + PVB)
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
TPVB BOUNDARIES: SPAM
  S = Superior costotransverse ligament (posterior)
  P = Parietal pleura (anterior)
  A = Anterior = IVF + vertebral body (medial)
  M = Made up by rib heads (sup/inf)

LANDMARK: 2.5 cm lateral to spinous process → TP → 1 cm off TP caudally

US CONFIRMATION SIGN: Anterior displacement of pleura

TPVB VOLUMES: 3–5 mL/level (multilevel) OR 15–20 mL single injection
TPVB BEST FOR: Thoracotomy, mastectomy, rib fractures, nephrectomy
TPVB RISK: PNEUMOTHORAX (0.5–1%), Epidural spread (1–5%), Hypotension

━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
ESP BLOCK:
  Target: Deep to erector spinae, over TP
  US sign: Erector spinae lifts off TP on injection
  Volume: 20–30 mL (bilateral: 10–15 mL/side)
  Level: T4-5 (thorax) | T7-8 (abdomen) | L2-3 (lumbar)
  Advantage: Safest — TP backstop, away from pleura
  Limitation: Variable spread, inferior to PVB (NMA 2024-2025)
  First described: Forero et al. 2016

━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
SAP BLOCK:
  Target: Between LD and SAM (superficial) OR SAM and rib (deep)
  US: Transverse probe at 4th–5th rib, mid-axillary line
  Volume: 20–25 mL per plane
  Coverage: T2–T9 lateral cutaneous branches + ICBN
  DOPPLER: Thoracodorsal artery in superficial plane
  Backstop: RIB (safest truncal block)
  Perform deep FIRST, then superficial
  First described: Blanco et al. 2013
  Evidence 2025: Equivalent to PVB at 6h/24h; inferior at 12h

━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
COMPARISON SUMMARY:
  Safety:    SAP > ESP > TPVB
  Efficacy:  TPVB > ESP > SAP
  Depth:     SAP (1-3cm) < ESP (2-3cm) < TPVB (4-5cm)
  Visceral:  TPVB Yes | ESP Variable | SAP No
  Bilateral: SAP Safe | ESP Reduce vol | TPVB Caution

DRUG OF CHOICE: Ropivacaine 0.375–0.5% (all 3 blocks)
ADJUVANT: Dexamethasone 4–8 mg IV (extends duration 6–8h)

LAST RISK: All truncal blocks — Intralipid 20% must be available
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

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📋 UPDATED QUESTION TRACKER

✅ DISCUSSED (3 topics)

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⏳ REMAINING — SECTION 15 (Peripheral Nerve Blocks)

⏳ REMAINING — SECTION 11 (Regional/Spinal/Epidural)

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• Enumeration table of all truncal blocks (scores marks independently)
• TPVB boundaries — the SPAM mnemonic
• ESP US confirmation: erector spinae lifts off transverse process
• PVB US confirmation: anterior displacement of pleura
• SAP deep before superficial — clinical pearl that examiners love
• Comparison table showing Safety > ESP > SAP but Efficacy > PVB > ESP > SAP
• Recent 2025 meta-analyses cited by name

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BLOCK 1: COELIAC (CELIAC) PLEXUS — ANATOMY, INDICATIONS AND COMPLICATIONS

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1. DEFINITION

• The coeliac plexus is the largest autonomic plexus in the body, formed by a dense network of pre- and post-ganglionic sympathetic nerve fibres and visceral afferent fibres surrounding the coeliac trunk at the level of the T12–L1 vertebra
• Coeliac plexus block (CPB): Injection of local anaesthetic or neurolytic agent around the coeliac plexus to interrupt visceral afferent pain transmission from the upper abdominal organs
• Coeliac plexus neurolysis (CPN): Permanent ablation of the coeliac plexus using ethanol (50–100%) or phenol (6–10%) for cancer pain

Exam Tip: Distinguish between block (LA — reversible; for acute/chronic benign pain) and neurolysis (ethanol/phenol — permanent; for cancer pain). Examiners frequently ask this.

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2. ANATOMY OF THE COELIAC PLEXUS

2.1 Formation

COELIAC PLEXUS FORMATION:
━━━━━━━━━━━━━━━━━━━━━━━━
Preganglionic sympathetic fibres from:
  T5 → T12 (greater splanchnic nerve: T5–T9)
  T10 → T11 (lesser splanchnic nerve)
  T12 (least splanchnic nerve)
        ↓ Pass through diaphragm (aortic hiatus)
  COELIAC GANGLIA (2 semi-lunar ganglia)
        ↓ Post-ganglionic fibres
  COELIAC PLEXUS (network around coeliac trunk)
        ↓
  Visceral organ innervation

2.2 Composition

2.3 Location and Relations

Viva Pearl: The coeliac plexus lies anterior to the aorta and anterior to the crura of the diaphragm at L1. The right ganglion is more medial (posterior to the IVC), and the left ganglion is lateral to the aorta. This asymmetry is clinically important for needle placement.

2.4 Visceral Organs Innervated

2.5 Splanchnic Nerves — Distinct from Plexus

• The splanchnic nerves carry preganglionic fibres before synapsing in the coeliac ganglia
• Splanchnic nerve block = more proximal (at T12, retrocrural) → blocks fibres before synapse → broader, more reliable coverage
• vs. Coeliac plexus block = blocks fibres after synapse (at L1, antecrural) → targets postsynaptic plexus

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3. SURGICAL AND CLINICAL INDICATIONS

3.1 Coeliac Plexus Block (LA — Reversible)

3.2 Coeliac Plexus Neurolysis (Ethanol/Phenol — Permanent)

Exam Tip: CPN is recommended in unresectable pancreatic cancer as it reduces opioid consumption and improves quality of life. It is not first-line for chronic pancreatitis — LA block may provide short-term relief but neurolysis is avoided in benign conditions.

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4. APPROACHES TO COELIAC PLEXUS BLOCK

Classification of Approaches

COELIAC PLEXUS BLOCK APPROACHES
              |
    __________|__________
    |                   |
POSTERIOR (Classic)    ANTERIOR
    |                   |
Retrocrural approach   EUS-guided
Anterocrural approach  CT-guided (anterior)
Bilateral paravertebral
Transdiscal approach

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4.1 Posterior Retrocrural Approach (Classic)

Patient Position

• Prone with pillow under abdomen to flex spine

Surface Anatomy Landmarks

• T12 spinous process
• A point 7–8 cm lateral to midline bilaterally (at T12 level)
• Target: Anterolateral body of L1 vertebra behind the diaphragmatic crura

Technique (Fluoroscopy-Guided)

STEP 1: Mark T12 spinous process and 7–8 cm lateral bilaterally
STEP 2: Insert 20–22G, 15–20 cm spinal needle bilaterally
         at 45° medially and 15° cephalad
STEP 3: Contact body of T12 vertebra → walk needle laterally
STEP 4: Advance needle anterior to T12/L1 body
         (retrocrural space — posterior to diaphragmatic crura)
STEP 5: Fluoroscopy confirmation: AP + LATERAL views
STEP 6: Contrast injection (3–5 mL) — confirm prevertebral spread,
         no vascular uptake
STEP 7: TEST DOSE — 3 mL LA (check for intravascular injection)
STEP 8: LA block: 25–50 mL 0.25% bupivacaine bilaterally (12.5 mL/side)
         OR Neurolysis: 10–20 mL 50–100% ethanol per side (total 20–40 mL)
         (Preceded by 5 mL LA for comfort)

4.2 Anterocrural (Transaortic / Transdiscal) Approach

• Needle advanced anterior to diaphragmatic crura (antecrural space)
• Transaortic approach: Single needle passed through aorta (deliberate!) to reach anterior aortic plane — controversial, higher risk
• Transdiscal: Needle passed through T12–L1 disc — risk of discitis

4.3 Anterior Approaches

Viva Pearl: EUS-guided CPN has become the preferred route in most cancer patients as it avoids the risks of posterior approach (no paraplegia, no pneumothorax), allows direct visualisation of the celiac ganglia, and can be performed simultaneously with staging/diagnostic endoscopy.

Fluoroscopy Appearance (What to Draw in Exam)

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5. LOCAL ANAESTHETICS AND NEUROLYTIC AGENTS

• Pre-neurolysis: Always inject 5 mL 0.25% bupivacaine before ethanol to reduce neurolytic burning pain
• Post-injection: Aspirate blood before each increment; test dose mandatory

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6. PATIENT PREPARATION

• Informed written consent (including neurolysis risks — paraplegia, impotence)
• IV access, monitoring (ECG, SpO2, NIBP)
• Coagulation screen — INR/PT, aPTT, platelets (retroperitoneal space, non-compressible)
• Imaging: Pre-procedure CT scan to assess vessel anatomy, tumour relation to plexus
• Antibiotic prophylaxis for transdiscal or EUS-guided approach
• Sedation/analgesia: midazolam + fentanyl IV
• Fluids: IV preloading with 500 mL crystalloid (anticipate sympatholysis → hypotension)
• Vasopressors available

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7. ASSESSMENT OF BLOCK SUCCESS

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8. COMPLICATIONS

Classification

COMPLICATIONS OF COELIAC PLEXUS BLOCK
                |
    ____________|_____________
    |           |             |
 IMMEDIATE   DELAYED     SERIOUS/RARE
    |           |             |
Hypotension  Diarrhoea    Paraplegia
Pain at site  Backache    Anterior spinal
Haematuria    Sexual dys  artery syndrome
              function    Aortic injury
                         Pneumothorax
                         Retroperitoneal
                         haematoma

Detailed Complications Table

Exam Tip — Most Feared Complication: Paraplegia from anterior spinal artery syndrome (Adamkiewicz artery injury) is the most catastrophic complication of CPN. The Artery of Adamkiewicz arises at T8–L1 in 85% of cases — directly in the field of injection. Prevention: use CT or fluoroscopic guidance, contrast confirmation, incremental injection, never inject against resistance.

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9. EVIDENCE AND RECENT ADVANCES (2024–2026)

Key Evidence

• Lu et al. Meta-analysis, Pain Physician 2024 [PMID: 38285023]: CPN vs. splanchnic nerve neurolysis for abdominal cancer pain (n=359) — splanchnic nerve neurolysis provided superior pain relief with comparable safety; CPN remains widely used but SNN may be preferred when technically feasible
• Xuan et al. Meta-analysis 2024 [PMID: 38552386]: EUS-guided approaches for pancreatic cancer — effective pain relief with favourable safety profile
• 2024 Advances:
  • EUS-guided celiac ganglia neurolysis (CGN): Direct injection into identified ganglia under EUS — superior to plexus-level injection
  • Radiofrequency ablation (RFA) of coeliac plexus: Emerging as alternative to neurolysis — precise, repeatable
  • CT-guided robotic-assisted CPN — research phase
  • Cryoablation of coeliac plexus — emerging technique
  • Bilateral simultaneous EUS approach — novel technique for better coverage
  • ERAS integration: CPN at time of pancreatic surgery (Whipple procedure) — opioid-free intraoperative and postoperative analgesia

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10. CURRENT GUIDELINES

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11. CLINICAL PEARLS

1. "Visceral pain = coeliac plexus" — any upper abdominal visceral pain (pancreatic, hepatobiliary, renal) is potentially amenable to CPB/CPN
2. Hypotension in 10–40% — always preload with 500 mL IV crystalloid before the procedure
3. Always inject bupivacaine 5 mL before ethanol — reduces neurolytic burning pain
4. Never inject against resistance — high risk of intraneural injection and paraplegia
5. Test dose 3 mL LA + aspiration before every injection — essential
6. Lateral fluoroscopic view is mandatory — AP alone cannot confirm anterior placement; must see contrast anterior to vertebral body
7. EUS-guided approach is preferred in cancer patients — direct ganglia visualisation, avoids paraplegia risk, no radiation
8. Diarrhoea is expected and normal for 24–72 h — counsel patients beforehand
9. The right ganglion lies posterior to the IVC — right-sided approaches have higher IVC puncture risk
10. Retrocrural vs. anterocrural: Retrocrural = greater/lesser splanchnic level (more reliable for pancreatic pain); Anterocrural = coeliac plexus level (broader coverage)
11. LA block for chronic pancreatitis gives only short-term relief (4–8 weeks) — not a definitive treatment
12. Ethanol concentration > 50% necessary for permanent neurolysis; phenol 6–10% is an alternative with less burning but slower onset
13. Splanchnic nerve block at T12 may be preferred over CPN for better coverage and lower paraplegia risk
14. Always obtain coagulation status — this is a deep non-compressible procedure; LMWH therapeutic must be withheld for 24 hours

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12. COMMON VIVA QUESTIONS

• Block uses LA (bupivacaine/ropivacaine) — reversible, diagnostic; Neurolysis uses ethanol 50–100% or phenol 6–10% — permanent ablation for cancer pain

• Hypotension (10–40%) from splanchnic sympatholysis; diarrhoea (44–60%) from unopposed parasympathetics

• Paraplegia from anterior spinal artery syndrome (Artery of Adamkiewicz at T8–L1)

• The dominant medullary artery supplying the anterior spinal cord; arises from the aorta at T8–L1 in 85% of individuals; injury during CPN → anterior spinal cord ischaemia → paraplegia

• Retrocrural: needle tip behind diaphragmatic crura at T12 → targets splanchnic nerves; Anterocrural: needle tip anterior to crura at L1 → targets coeliac plexus ganglia

• Direct visualisation of coeliac ganglia; avoids posterior approach complications (paraplegia, pneumothorax, haematoma); can be combined with staging procedure; better targeting

• Splanchnic nerve block/neurolysis targets preganglionic fibres at T12 BEFORE they synapse in the coeliac ganglia; Lu et al. 2024 meta-analysis showed superior pain relief; reduces risk to major vessels

• Fluoroscopy: AP (bilateral spread at L1) + Lateral (contrast anterior to vertebral body); aspirate before injection; test dose; no vascular uptake on contrast

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BLOCK 2: STELLATE GANGLION BLOCK (SGB)

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1. DEFINITION

• Stellate ganglion (cervicothoracic ganglion): A sympathetic ganglion formed by the fusion of the inferior cervical ganglion (C8) and the first thoracic ganglion (T1) in approximately 80% of individuals
• Stellate ganglion block (SGB): Injection of local anaesthetic anterior to the stellate ganglion to produce ipsilateral cervicothoracic sympathectomy — blocking sympathetic supply to the head, neck, upper limb, heart, and ipsilateral thorax
• Named "stellate" (Latin: star-shaped) because of its characteristic star-like morphology

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2. ANATOMY OF THE STELLATE GANGLION

2.1 Formation and Location

2.2 Anatomical Relations (Key for Block Safety)

RELATIONS OF STELLATE GANGLION:
────────────────────────────────────────────────
ANTERIOR:   Common carotid artery, internal jugular vein,
            subclavian artery (lower), origin of vertebral artery
POSTERIOR:  Longus colli muscle, prevertebral fascia, C7 transverse process
MEDIAL:     Trachea, oesophagus, thoracic duct (left side)
LATERAL:    Scalene muscles, brachial plexus
SUPERIOR:   Middle cervical ganglion (C5–C6)
INFERIOR:   T2 thoracic ganglion, pleural apex
────────────────────────────────────────────────
DANGER STRUCTURES:
• Vertebral artery — passes through foramen transversarium at C6
  (RISK AT C7 LEVEL — no foramen transversarium protection)
• Carotid artery — medial to SCM
• Internal jugular vein — lateral to carotid
• Phrenic nerve — on anterior scalene
• Recurrent laryngeal nerve — in tracheoesophageal groove
• Brachial plexus — lateral
• Pleural apex — below (risk of pneumothorax)
• Thoracic duct — on left side

Exam Tip — Critical Safety Point: The vertebral artery is NOT protected at C7 (no foramen transversarium at C7). This is why injection at C6 (Chassaignac tubercle) is preferred over C7 — at C6, the vertebral artery is within the foramen transversarium and less accessible to the needle.

2.3 Sympathetic Supply Carried by Stellate Ganglion

Viva Pearl: The stellate ganglion carries fibres from C8–T4 (with cardiac accelerator fibres from T1–T4). A left SGB reduces left cardiac sympathetic tone — important for long QT syndrome-related arrhythmia treatment.

---

3. INDICATIONS FOR STELLATE GANGLION BLOCK

3.1 Established/Classic Indications

3.2 Cardiac Indications (Novel — Growing Evidence)

3.3 Novel/Emerging Indications (2024–2026)

Viva Pearl (2026): Tsai et al. published a narrative review in British Journal of Anaesthesia (2026) on SGB in perioperative practice — highlighting cardiac arrhythmia management, cancer survivor hot flushes, and PTSD as key emerging indications. This is highly likely to appear in viva.

---

4. TECHNIQUES FOR STELLATE GANGLION BLOCK

4.1 Landmark/Paratracheal Technique (Classical)

Patient Position

• Supine, neck slightly extended, mouth slightly open (relaxes SCM)
• Head neutral or slightly rotated to contralateral side

Landmarks

• Cricoid cartilage = C6 level — primary landmark
• Chassaignac's tubercle = anterior tubercle of C6 transverse process — can be palpated 3 cm lateral to midline at C6
• SCM medial border — retract laterally
• Injection point: Medial border of SCM at cricoid level (C6)

Technique

STEP 1: Palpate cricoid cartilage (C6 level)
STEP 2: Place 2 fingers LATERAL to trachea, medial to SCM
         Retract the carotid sheath LATERALLY
STEP 3: Insert 22G, 4–5 cm needle PERPENDICULAR to skin
STEP 4: Contact C6 transverse process (Chassaignac tubercle)
         at approximately 2–3 cm depth
STEP 5: Withdraw needle 2–3 mm (off periosteum)
STEP 6: TWO-PLANE ASPIRATION (rotate syringe 90° and re-aspirate)
STEP 7: 1 mL TEST DOSE — exclude intravascular/subarachnoid injection
STEP 8: Inject 5–10 mL LA in incremental aliquots (2 mL each)
STEP 9: Keep patient supine for 5–10 minutes
STEP 10: Assess Horner syndrome (success marker)

Viva Pearl: The "two-plane aspiration" technique (aspirate in standard plane → rotate syringe 90° → re-aspirate) is mandatory because the vertebral artery runs perpendicular to the needle — a single aspiration may miss intravascular placement.

4.2 Ultrasound-Guided Technique (Preferred — Gold Standard)

Setup

• Patient: Supine, neck extended, head turned contralateral
• Probe: High-frequency linear (15–6 MHz), transverse orientation at C6 level

Sonoanatomy at C6 Level

ULTRASOUND ANATOMY (Transverse view at C6):
────────────────────────────────────────────────────
[Skin / SCM (oval)]
[Carotid artery (anechoic, pulsatile)]
[Internal jugular vein (compressible, lateral to CA)]
[Anterior scalene muscle (lateral)]
[C6 TRANSVERSE PROCESS — hyperechoic with acoustic shadow]
  └ Chassaignac tubercle (anterior tubercle) visible
[LONGUS COLLI MUSCLE — hypoechoic, posterior]
[TARGET: Anterior surface of longus colli / below prevertebral fascia]
────────────────────────────────────────────────────
VERTEBRAL ARTERY — within foramen transversarium (not seen at C6 surface)

Needle Technique (US-Guided)

Exam Tip: The target in US-guided SGB is anterior to the longus colli muscle, medial to C6 transverse process — the LA should be seen spreading under the prevertebral fascia (not infiltrating the muscle).

---

5. DRUG DOSES

• Volume < 5 mL → may not reliably reach stellate ganglion (which lies at C7–T1)
• Volume > 10 mL → increased spread to adjacent structures (phrenic nerve, recurrent laryngeal nerve, epidural space)
• Optimal volume: 5–10 mL at C6 level (LA diffuses caudally to reach the ganglion at C7–T1)

---

6. ASSESSMENT OF SUCCESSFUL BLOCK — HORNER SYNDROME

Horner Syndrome (Oculosympathetic Paresis) — Mandatory Confirmation

• Warm, dry ipsilateral upper extremity
• Increased skin temperature of ipsilateral arm/hand (best objective measure)
• Nasal stuffiness
• Conjunctival injection (ipsilateral)

Exam Tip: Horner syndrome is the clinical endpoint confirming successful SGB. All 4 signs (ptosis, miosis, enophthalmos, anhidrosis) are called "PMEA" mnemonic.

---

7. COMPLICATIONS

Critical Safety Point: Even 1 mL of LA inadvertently injected into the vertebral artery causes immediate generalised seizures (artery supplies brainstem/cerebellum directly). Always use test dose + two-plane aspiration. US guidance has dramatically reduced this risk.

---

8. CONTRAINDICATIONS

---

9. RECENT ADVANCES AND EVIDENCE (2024–2026)

---

10. COMPARISON: COELIAC PLEXUS BLOCK vs. STELLATE GANGLION BLOCK

---

11. CLINICAL PEARLS — STELLATE GANGLION BLOCK

1. The C6 approach is safer than C7 — at C6, the vertebral artery is protected within the foramen transversarium; at C7, it is exposed
2. Retract the carotid sheath laterally before needle insertion (landmark technique) — reduces risk of carotid/IJV puncture
3. Two-plane aspiration is mandatory — the vertebral artery runs perpendicular to the needle; single-plane aspiration can miss intravascular placement
4. Horner syndrome = block success — if no Horner after 20 minutes, the block has failed
5. 5–10 mL volume at C6 is optimal — LA diffuses caudally to reach stellate ganglion at C7–T1 level
6. Bilateral SGB is absolutely contraindicated — bilateral phrenic + bilateral recurrent laryngeal = respiratory failure
7. Left SGB for cardiac arrhythmia — left stellate carries dominant cardiac sympathetic supply
8. PTSD and hot flushes are growing indications — documented in 2024–2026 literature; very likely viva topic
9. Even 1 mL of LA into the vertebral artery causes immediate brainstem toxicity/seizure — vigilance is paramount
10. Skin temperature rise > 1°C in the ipsilateral arm is the most objective physiological marker of successful sympathectomy
11. Pulsed radiofrequency (PRF) of the stellate ganglion provides longer-lasting effect than repeated LA blocks — emerging alternative for CRPS
12. The Kuntz nerves (T2–T3) can bypass the stellate ganglion via separate pathways joining the brachial plexus — these are missed by SGB but blocked by axillary block (clinically relevant for upper extremity hyperhidrosis)

---

12. COMMON VIVA QUESTIONS — STELLATE GANGLION BLOCK

• Fusion of inferior cervical (C8) and first thoracic (T1) sympathetic ganglia in 80% of people; located at C7–T1 junction, anterior to longus colli, posterior to carotid artery, lateral to oesophagus

• At C6, the vertebral artery is within the foramen transversarium and protected; at C7, the vertebral artery is exposed and at higher risk of direct puncture during needle insertion

• Ptosis, miosis, enophthalmos, anhidrosis — from interruption of sympathetic supply to the eye and face. Horner syndrome is the clinical endpoint confirming successful block, as the superior cervical ganglion (innervating the eye) is in the same sympathetic chain

• Bilateral recurrent laryngeal nerve block → bilateral vocal cord paralysis → airway obstruction; bilateral phrenic nerve block → bilateral hemidiaphragmatic paresis → respiratory failure

• The stellate ganglion provides sympathetic innervation to the heart (T1–T4). Left SGB reduces left cardiac sympathetic dominance → reduces triggered arrhythmias → beneficial in long QT syndrome, catecholaminergic VT, and VT storm

• The left stellate ganglion provides dominant sympathetic innervation to the sinoatrial node and ventricular myocardium; left stellate stimulation prolongs QT interval; left SGB specifically reduces this arrhythmogenic drive

• Immediate cerebral/brainstem toxicity — generalised seizures within seconds (the vertebral artery supplies the brainstem directly; even a tiny dose reaches high concentrations instantly)

• Hot flushes in breast cancer survivors; PTSD; menopausal vasomotor symptoms; subarachnoid haemorrhage vasospasm (Brenner et al. 2024); perioperative cardiac arrhythmia management (Tsai et al. BJA 2026)

---

13. RAPID REVISION BOX

COELIAC PLEXUS & STELLATE GANGLION — ONE PAGE REVISION
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
COELIAC PLEXUS:
  Location: T12–L1, anterior to aorta, retroperitoneal
  Formed by: Greater (T5–T9) + Lesser (T10–T11) + Least (T12) splanchnic nn.
  Block (LA): 20–30 mL bupivacaine 0.25%
  Neurolysis: Ethanol 50–100% (10–20 mL/side) | Phenol 6–10%
  Always: 5 mL bupivacaine BEFORE ethanol
  Guidance: Fluoroscopy (AP + LATERAL) | EUS preferred in cancer
  Confirmation: Contrast anterior to vertebral body (lateral view)
  Most common: HYPOTENSION (10–40%) + DIARRHOEA (44–60%)
  Most feared: PARAPLEGIA (Artery of Adamkiewicz, T8–L1)
  Best indication: Unresectable PANCREATIC CANCER

━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
STELLATE GANGLION:
  Formed by: Inferior cervical (C8) + T1 fusion (80%)
  Location: C7–T1, anterior to longus colli, posterior to carotid
  Relations danger: Vertebral artery (C7 – NO foramen protection!)
                    Carotid artery, IJV, Phrenic, Recurrent laryngeal
  Injection: C6 LEVEL preferred (Chassaignac tubercle)
  Volume: 5–10 mL LA (bupivacaine 0.25% OR ropivacaine 0.2%)
  TWO-PLANE ASPIRATION mandatory
  Success marker: HORNER SYNDROME (Ptosis, Miosis, Enophthalmos, Anhidrosis)
  Mnemonic PMEA: Ptosis Miosis Enophthalmos Anhidrosis
  Best US target: Anterior to longus colli, medial to Chassaignac tubercle

  INDICATIONS:
    Classic: CRPS upper limb | Herpes zoster | Raynaud | Hyperhidrosis
    Cardiac: VT storm | Long QT syndrome (LEFT SGB)
    Novel 2024-26: PTSD | Hot flushes | SAH vasospasm | Perioperative arrhythmia

  COMPLICATIONS:
    Vertebral artery → Immediate seizures (1 mL sufficient)
    Phrenic nerve → Hemidiaphragm paresis
    Recurrent laryngeal → Hoarseness
    Horner → Expected (success sign)
    BILATERAL = CONTRAINDICATED

  RECENT EVIDENCE:
    Tian et al. (Pain Physician 2024): SGB for CRPS — moderate efficacy
    Brenner et al. (World Neurosurg 2024): SGB for SAH vasospasm — promising
    Tsai et al. (BJA 2026): SGB in perioperative practice — narrative review

━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
KEY NUMBERS:
  CPN ethanol: 10–20 mL/side | 50–100% concentration
  CPB bupivacaine: 0.25% × 20–30 mL bilateral
  SGB volume: 5–10 mL at C6
  CPN most common: Hypotension (10–40%)
  SGB injection: C6 NOT C7 (vertebral artery safety)
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
```---

## 📋 UPDATED QUESTION TRACKER

### ✅ DISCUSSED (6 topics)

| # | Topic | Paper Reference | Done |
|---|-------|----------------|------|
| 1 | Brachial Plexus — anatomy, all routes, complications | Sec 15 P1/Q5 | ✅ |
| 2 | Erector Spinae Plane Block | Sec 15 P4/Q4 | ✅ |
| 3 | Serratus Anterior Plane Block | Sec 15 P4 (truncal) | ✅ |
| 4 | Paravertebral Block + Space | Sec 11 P2/Q12 | ✅ |
| 5 | Coeliac Plexus — anatomy, block, indications, complications | Sec 15 P1/Q1; P2/Q6 | ✅ |
| 6 | Stellate Ganglion Block | Sec 15 P1/Q8; P2/Q7 | ✅ |

**53 questions remaining across both sections.**

---

**Key examiner-favourite points covered in both answers:**

**Coeliac Plexus:**
- Splanchnic nerve formation (T5–T12) and the **retrocrural vs anterocrural** distinction
- **Artery of Adamkiewicz (T8–L1)** — the critical paraplegia mechanism
- **Ethanol protocol** — always bupivacaine first, then ethanol
- **EUS-guided CPN** as modern preferred approach
- Hypotension + diarrhoea as expected effects
- Lu et al. 2024 meta-analysis (CPN vs splanchnic neurolysis)

**Stellate Ganglion:**
- **C6 NOT C7** — the single most important safety principle
- **Two-plane aspiration** — mandatory for vertebral artery safety
- **Horner syndrome = PMEA** — the success endpoint
- **Left SGB for cardiac arrhythmia** (long QT, VT storm)
- Emerging indications: PTSD, hot flushes, SAH vasospasm
- Tsai et al. BJA 2026 + Brenner et al. World Neurosurg 2024 — two key 2025–2026 papers

Say **"Next"** or name the next topic when ready.

---

BLOCK 1: TRANSVERSUS ABDOMINIS PLANE (TAP) BLOCK

---

1. DEFINITION

• A fascial plane block in which local anaesthetic is deposited in the neurovascular plane between the internal oblique (IO) and transversus abdominis (TA) muscles of the anterolateral abdominal wall
• Produces somatic anaesthesia/analgesia of the anterior abdominal wall
• First described by Rafi (2001) using a landmark technique; later refined with ultrasound guidance by McDonnell et al. (2007) and Hebbard et al. (2010)

Exam Tip: TAP block is a somatic-only block — it has NO visceral analgesia. This is its most important limitation and a favourite viva point.

---

2. RELEVANT ANATOMY

2.1 Abdominal Wall Layers (Medial to Lateral — Mnemonic: "Skin-SEITA-Peri")

ANTERIOR ABDOMINAL WALL LAYERS (superficial → deep):
────────────────────────────────────────────────
1. Skin
2. Subcutaneous fat (Camper's fascia superficial, Scarpa's fascia deep)
3. EXTERNAL OBLIQUE MUSCLE (EO)
4. INTERNAL OBLIQUE MUSCLE (IO)
5. [TAP PLANE] ← TARGET injection zone
6. TRANSVERSUS ABDOMINIS MUSCLE (TA)
7. Transversalis fascia
8. Extraperitoneal fat
9. PERITONEUM
────────────────────────────────────────────────

2.2 Nerves in the TAP Plane

• These nerves run laterally to medially within the TAP plane
• They supply the skin, muscle, and parietal peritoneum of the anterior abdominal wall — but NOT visceral peritoneum or intra-abdominal organs

2.3 Triangle of Petit (Lumbar Triangle) — Landmark Approach

TRIANGLE OF PETIT (Petit's triangle):
─────────────────────────────
Posterior: LATISSIMUS DORSI (posterior border)
Anterior:  EXTERNAL OBLIQUE (anterior border)
Inferior:  ILIAC CREST (floor)
─────────────────────────────
Floor: INTERNAL OBLIQUE MUSCLE

• The Triangle of Petit was the original landmark for blind TAP block (finger-guided double-pop technique)
• Largely replaced by US guidance

Viva Pearl: The Triangle of Petit (lumbar triangle) is the anatomical basis for the original landmark TAP block. It is bounded by latissimus dorsi (posterior), external oblique (anterior), and iliac crest (inferior). The floor is the internal oblique — needle enters here, crosses IO, enters TAP plane with a "double-pop."

---

3. APPROACHES TO TAP BLOCK

TAP BLOCK APPROACHES
        |
   _____|______________________________________
   |          |          |          |          |
LATERAL   SUBCOSTAL  POSTERIOR ILIOINGUINAL  OBLIQUE
(midax.)  (upper     (PLT     (Hebbard's    SUBCOSTAL
           abdomen)   approach) modified)

Classification Table

---

4. SURGICAL AND CLINICAL INDICATIONS

4.1 By Surgery Type

4.2 ERAS Applications

• TAP block is a cornerstone of ERAS (Enhanced Recovery After Surgery) protocols for abdominal surgery
• Part of multimodal opioid-sparing analgesia
• Most effective when combined with regular paracetamol, NSAIDs, and dexamethasone

---

5. ULTRASOUND-GUIDED TECHNIQUE

Patient Position

• Supine (routine); lateral decubitus (posterior approach)

Equipment

• Probe: High-frequency linear (13–6 MHz); curvilinear for obese patients
• Needle: 22G, 80–100mm, echogenic, short-bevel

Step-by-Step Technique (Lateral/Midaxillary TAP)

STEP 1: Patient supine; probe between iliac crest and costal margin,
         MIDAXILLARY line, TRANSVERSE orientation

STEP 2: Identify 3 layers = "THREE-LAYER-CAKE SIGN":
         EO (most superficial)
         IO (middle)
         TA (deepest)
         Between IO and TA = bright fascial line = TARGET

STEP 3: Apply colour Doppler — identify circumflex iliac vessels
         (within TAP plane, must avoid)

STEP 4: Insert 22G needle IN-PLANE from ANTERIOR to POSTERIOR
         (medial to lateral or lateral to medial)

STEP 5: Advance needle tip to fascial plane between IO and TA

STEP 6: Hydrodissection: inject 1–2 mL saline → confirm plane opening
         (IO lifts off TA)

STEP 7: Aspiration × 2 planes

STEP 8: Inject 20–30 mL LA in incremental boluses (5 mL aliquots)

STEP 9: Watch for "KAYAK SIGN" — elliptical separation of IO from TA
         = correct plane = successful injection

STEP 10: Repeat on contralateral side for bilateral TAP

The "KAYAK SIGN" — Key Sonographic Endpoint

• When LA is correctly injected into the TAP plane, the fascial planes of IO and TA separate, creating a lens-shaped/kayak-shaped hypoechoic fluid space — this is the Kayak sign
• If LA is seen entering the muscle (hyperechoic intramuscular spread) — incorrect plane

Exam Tip: The "Kayak sign" = correct TAP injection. The three-layer "cake" on US = EO, IO, TA. These are favourite viva observations.

Subcostal TAP Technique

• Probe: Parallel and 2 cm below the costal margin
• Target: Same TAP plane (between IO and TA) but at the subcostal level (T6–T10)
• Needle: In-plane, lateral to medial along the costal margin
• Used for upper abdominal surgery (cholecystectomy, gastrectomy)

---

6. DRUG DOSES

• Maximum volumes: Bilateral TAP must not exceed 3 mg/kg ropivacaine total
• Dexamethasone 4–8 mg as adjuvant extends duration by 6–8 hours
• Intraoperative surgeon-performed TAP: ropivacaine 0.375% (diluted) is preferred

---

7. ASSESSMENT OF BLOCK

---

8. AREAS ANAESTHETISED

---

9. ADVANTAGES AND DISADVANTAGES

---

10. COMPLICATIONS

---

11. RECENT EVIDENCE (2024–2026)

---

---

BLOCK 2: QUADRATUS LUMBORUM BLOCK (QL BLOCK)

---

1. DEFINITION

• An ultrasound-guided interfascial plane block in which local anaesthetic is deposited around the quadratus lumborum (QL) muscle at the thoracolumbar fascia (TLF), producing somatic + visceral analgesia for the abdominal wall and lower thoracic regions
• First described by Blanco (2012) as an extension of the TAP block
• Distinct from TAP block by its posterior injection site, deeper fascial plane, and ability to provide some visceral analgesia via paravertebral spread through the thoracolumbar fascia

Viva Pearl — Critical Distinction: The key advantage of QL block over TAP block is that QL block provides BOTH somatic AND some visceral analgesia because LA spreads through the TLF into the paravertebral space, blocking sympathetic fibres. TAP block is somatic only.

---

2. ANATOMY OF THE QUADRATUS LUMBORUM MUSCLE

2.1 Muscle Details

2.2 Thoracolumbar Fascia (TLF) — Key to QL Block Mechanism

THORACOLUMBAR FASCIA (TLF) — 3 Layers:
────────────────────────────────────────
POSTERIOR LAYER: Covers erector spinae + QL posteriorly
                 → attachment of latissimus dorsi
MIDDLE LAYER:   Between QL and erector spinae
ANTERIOR LAYER: Between QL and psoas major
                → continuous with fascia transversalis
────────────────────────────────────────
The TLF contains:
• Mechanoreceptors + nociceptors → pain modulation
• Sympathetic fibres (via lumbar sympathetic chain)
• Connects to PARAVERTEBRAL SPACE (via intertransverse membrane)
→ LA spread to PVS = visceral analgesia mechanism

2.3 "SHAMROCK SIGN" — Key US Landmark

ULTRASOUND "SHAMROCK SIGN" (transverse view at L4):
         [TRANSVERSE PROCESS] ← "stem of shamrock"
                |
      __________|__________
      |                   |
 ERECTOR               PSOAS
 SPINAE                MAJOR
 (posterior leaf)      (anterior leaf)
      |
  QUADRATUS
  LUMBORUM
  (lateral leaf)
─────────────────────────────────────────────────────
Mnemonic: PQRST at midaxillary cross-section:
P = Psoas (anterior)
Q = Quadratus lumborum (central)
R = (target: posterior/lateral/anterior aspects of QL)
S = Spine / transverse process (posterior)
T = Transversus abdominis aponeurosis (anterior-lateral)

---

3. CLASSIFICATION OF QL BLOCK TYPES

QL BLOCK TYPES (by injection site relative to QL muscle):
                    QL MUSCLE
                    ┌──────┐
         QL1 (Lat.) │      │ QL3 (Ant./Transmuscular)
      ←─────────────┤  QL  ├─────────────────→
                    │      │
                    └──────┘
                        │
                   QL2 (Post.)
                        ↓

Detailed Comparison of QL Block Types

Exam Tip: QL3 (transmuscular) provides the most extensive coverage including partial lumbar plexus block — but carries highest risk of kidney puncture and requires deepest needle pass. Always use US guidance with real-time Doppler.

---

4. SURGICAL AND CLINICAL INDICATIONS

---

5. ULTRASOUND-GUIDED TECHNIQUE

Patient Position

• Lateral decubitus (preferred — gravity assists anatomy display)
• Supine with probe posterior (feasible)
• Prone (for posterior approach)

Probe

• Linear (13–6 MHz) for adults and older children
• Curvilinear (5–1 MHz) for obese patients or QL3

Scanning Protocol — Shamrock View

STEP 1: Start probe at MID-AXILLARY LINE between iliac crest
         and costal margin (like TAP block)
STEP 2: Identify EO, IO, TA muscle layers
STEP 3: SLIDE probe POSTERIORLY until TA muscle transitions
         to TA APONEUROSIS (bright fascial sheet)
STEP 4: Continue sliding posteriorly → QL muscle appears
         as the SHAMROCK SIGN
         - QL = posterior leaf
         - Psoas = anterior leaf
         - Erector spinae = posterior-medial leaf
         - Transverse process = stem
STEP 5: Identify target plane based on approach type:
         QL1: Lateral to QL (between TA aponeurosis and QL)
         QL2: Posterior to QL (between QL and erector spinae)
         QL3: Anterior to QL (between QL and psoas)
STEP 6: Colour Doppler — identify lumbar vessels, kidney
STEP 7: Insert needle in-plane (posterior to anterior for QL1/QL2;
         lateral to medial for QL3)
STEP 8: Aspirate, inject 1 mL saline for hydrodissection,
         confirm plane, then inject LA

Sonoanatomy Layers (from posterior, lateral decubitus)

[Skin]
[Latissimus dorsi]
[Erector spinae muscles]
─── QL2 injection plane (between QL and ES) ───
[QUADRATUS LUMBORUM MUSCLE]
─── QL1 injection plane (between TA aponeurosis and QL) ───
[TA APONEUROSIS / transversalis fascia]
─── QL3 injection plane (between QL and psoas) ───
[PSOAS MAJOR MUSCLE]
[Lumbar plexus nerves within psoas]
[KIDNEY] ← Danger — especially with QL3
[Transverse process of L4] ← hyperechoic with shadow

---

6. DRUG DOSES

• Bilateral QL block total: Must not exceed 3 mg/kg ropivacaine
• Needle: 50–100mm, 22G, short-bevel, echogenic

---

7. MECHANISM OF QL BLOCK — WHY BETTER THAN TAP

QL BLOCK MECHANISM:
LA deposited at TLF around QL muscle
        ↓
Spreads along TLF (posterior/middle/anterior layers)
        ↓
Permeates through intertransverse ligament
        ↓
Reaches PARAVERTEBRAL SPACE (T8–L4)
        ↓
Blocks: DORSAL RAMI + VENTRAL RAMI + SYMPATHETIC CHAIN
        ↓
Result: SOMATIC + VISCERAL + SYMPATHETIC ANALGESIA
(Superior to TAP which is somatic-only)

Viva Pearl: QL block covers dermatomal levels T8–L1 (QL2) or T4–L1 (QL3), whereas lateral TAP block covers only T10–L1. QL3 is the only abdominal wall block that reliably provides some visceral analgesia because of paravertebral spread through the TLF.

---

8. COMPLICATIONS

---

9. QL BLOCK vs. TAP BLOCK — COMPARISON TABLE

---

10. COMPARISON WITH OTHER ABDOMINAL WALL BLOCKS

---

11. RECENT EVIDENCE (2024–2026)

---

12. CURRENT GUIDELINES

---

13. CLINICAL PEARLS

1. TAP is somatic-only — never expect visceral analgesia (e.g., uterine pain after CS, peritoneal irritation) from TAP alone
2. "Kayak sign" = correct TAP plane — elliptical separation between IO and TA on US
3. Subcostal TAP for upper abdominal surgery; lateral TAP for lower; oblique subcostal for whole anterior wall
4. The transversus abdominis muscle is very thin (2–5 mm) — easy to penetrate into peritoneum; real-time US is essential
5. QL block = TAP block evolved — same approach but slide probe more posteriorly to the shamrock sign
6. "Shamrock sign" = key landmark for QL — QL (lateral leaf), psoas (anterior leaf), erector spinae (posterior leaf), transverse process (stem)
7. For caesarean section, bilateral QL3 is the single most effective block — reduces opioid consumption by > 50% compared with spinal morphine alone
8. QL3 carries kidney risk — always identify the kidney on US before needle insertion for QL3
9. Circumflex iliac vessels run within the TAP plane at the ASIS level — always use Doppler before TAP injection
10. For bilateral blocks, total ropivacaine must not exceed 3 mg/kg — LAST is real with bilateral 20–30 mL injections
11. Intraoperative surgeon TAP (at laparotomy closure or laparoscopy) is as effective as anaesthetist-placed TAP — widely used in ERAS
12. QL catheter provides prolonged analgesia (24–48h) — preferred over single-shot for major abdominal surgery
13. Liposomal bupivacaine in TAP provides 72-hour analgesia — emerging practice for same-day discharge surgery
14. QL2 (posterior QL) is the most commonly performed type — good coverage, lower kidney risk than QL3, easily identifiable plane

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14. COMMON VIVA QUESTIONS

• T10–L1: lateral cutaneous branches of T10, T11, T12 (subcostal), L1 (ilioinguinal and iliohypogastric); NOT visceral peritoneum

• The TAP plane (between IO and TA) only carries somatic afferents of the abdominal wall; visceral pain travels via splanchnic nerves → coeliac plexus → sympathetic chain → NOT intercepted by TAP block

• When LA is correctly injected into the TAP plane, the IO and TA layers separate into an elliptical (kayak-shaped) hypoechoic fluid space. It confirms successful TAP plane injection.

• QL block is placed posteriorly at the thoracolumbar fascia around the QL muscle; LA spreads to the paravertebral space providing visceral + sympathetic analgesia; broader coverage (T4/T8–L1) vs. TAP (T10–L1); QL is superior in evidence for opioid-sparing

• The sonographic appearance on transverse US at L4: psoas major (anterior leaf), QL (lateral leaf), erector spinae (posterior leaf), and transverse process (stem) — resembling a 3-leaf shamrock. The transverse process is the "stem." Critical landmark for QL block.

• QL3 (transmuscular/anterior) — LA deposited anterior to QL muscle between QL and psoas; spreads directly into paravertebral space; partial lumbar plexus block; best for caesarean section and hip surgery

• P = Psoas major; Q = Quadratus lumborum; R = (target for injection); S = Spine/transverse process; T = Transversus abdominis aponeurosis. Used to remember structures seen on US from anterior to posterior

• Kidney puncture — the kidney lies anteriorly adjacent to the QL muscle at L1–L2. Always identify kidney on US before needle insertion for QL3.

• Gao et al. 2023 (Langenbecks): QL block superior to TAP for inguinal hernia repair — lower VAS scores and reduced opioid requirements at 24h. QL preferred when available.

• 0.5 mL/kg of 0.2% ropivacaine per side, maximum 3 mg/kg, not exceeding 20 mL per side

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15. RAPID REVISION BOX

TAP BLOCK + QL BLOCK — ONE PAGE REVISION
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
TAP BLOCK:
  Plane: Between IO and TA muscles (anterolateral wall)
  Nerves: T7–L1 lateral cutaneous (somatic ONLY)
  US sign: THREE-LAYER CAKE (EO–IO–TA) → KAYAK SIGN
  Probe: Transverse, midaxillary, between ASIS + costal margin
  Volume: 15–20 mL/side | Ropivacaine 0.375%
  KEY LIMITATION: NO VISCERAL ANALGESIA
  SUBCOSTAL TAP: T6–T10 | upper abdomen | cholecystectomy
  LATERAL TAP: T10–L1 | lower abdomen | CS, hernia
  Triangle of Petit: original landmark (LD + EO + iliac crest)
  Described: Rafi 2001 (landmark); McDonnell 2007 (US)

━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
QL BLOCK:
  Plane: TLF around quadratus lumborum
  Nerves: T4/T8–L1 via PVS spread → SOMATIC + VISCERAL
  US landmark: SHAMROCK SIGN (psoas/QL/erector spinae/TP)
  Mnemonic PQRST: P=Psoas Q=QL R=target S=Spine T=TA aponeurosis

  TYPES:
    QL1 (Lateral): Between TA aponeurosis and QL | T10–L1 | easiest
    QL2 (Posterior): Between QL and erector spinae | T4–L1 | moderate
    QL3 (Anterior/Transmuscular): Between QL and psoas | T4–L1
             + lumbar plexus | KIDNEY RISK | best visceral analgesia

  Volume: 20–30 mL/side | Ropivacaine 0.2–0.375%
  Paediatric: 0.5 mL/kg (max 3 mg/kg, ≤ 20 mL/side)
  Best for: Caesarean section, hip arthroplasty, renal surgery

━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
TAP vs QL:
  TAP: Simple | Somatic only | T10–L1 | 15–20 mL
  QL:  Complex | Somatic + Visceral | T4–L1 | 20–30 mL
  Evidence: QL > TAP for inguinal hernia (Gao 2023)
            QL3 > TAP for CS and hip (Lee BJA 2025)

BOTH BLOCKS:
  LAST RISK: Bilateral → total ≤ 3 mg/kg ropivacaine
  COMPLICATIONS: LAST | Peritoneal puncture | Haematoma
  QL3 ADDITIONAL: Kidney puncture — always identify kidney on US
  ERAS ROLE: Both are cornerstones of opioid-sparing ERAS
  2026 Evidence: Zako et al. BJA 2026 — TAP reduces morphine
                 −10 mg/24h; significant evidence base
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

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📋 UPDATED QUESTION TRACKER

✅ DISCUSSED (8 topics)

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LOWER LIMB BLOCKS — ENUMERATE AND DISCUSS

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PART A: ENUMERATION OF LOWER LIMB BLOCKS

LOWER LIMB NERVE SUPPLY:
    LUMBAR PLEXUS (L1–L4)         SACRAL PLEXUS (L4–S3)
          |                                |
  ________|________              __________|__________
  |    |    |    |               |                   |
  FN  LFCN  ON   GFN          Sciatic nerve       Other
  |                             /        \
  |                          Common     Tibial
  Fem. n. → Saphenous n.     Peroneal

Complete Lower Limb Block Enumeration

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BLOCK 1: FEMORAL NERVE BLOCK (FNB)

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1. DEFINITION

• Injection of local anaesthetic around the femoral nerve in the femoral triangle, at the level of the inguinal crease, producing anaesthesia/analgesia of the anterior thigh, knee, and medial leg via the femoral nerve and its branches
• The femoral nerve is the largest branch of the lumbar plexus

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2. RELEVANT ANATOMY

Femoral Nerve

Femoral Triangle (Key Anatomy)

FEMORAL TRIANGLE BOUNDARIES:
─────────────────────────────────────
Superior:    INGUINAL LIGAMENT
Lateral:     SARTORIUS MUSCLE (medial border)
Medial:      ADDUCTOR LONGUS MUSCLE (lateral border)
Floor:       Iliacus + pectineus muscles (laterally) | Adductor longus (medially)
Roof:        Fascia lata
─────────────────────────────────────
CONTENTS (Medial → Lateral — Mnemonic: NAVY):
N = femoral Nerve (most lateral)
A = femoral Artery
V = femoral Vein
Y = empty space / femoral canal (most medial)
─────────────────────────────────────

Branches of the Femoral Nerve

Viva Pearl: The NAVY mnemonic (Nerve–Artery–Vein–Y) is from medial to lateral in the femoral triangle. Note: some texts write it lateral to medial; examiner may ask either way — clarify the direction.

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3. INDICATIONS

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4. ULTRASOUND-GUIDED TECHNIQUE

Patient Position

• Supine, slight hip external rotation

Probe and Setup

• Linear high-frequency (15–6 MHz), transverse orientation
• At or just below inguinal crease

Sonoanatomy

FEMORAL TRIANGLE US (Transverse at inguinal crease):
─────────────────────────────────────────────────────
[Skin / Subcutaneous fat]
[FASCIA LATA] ← first bright line
[FASCIA ILIACA] ← second bright line (deeper, lateral)
[ILIACUS MUSCLE] ← hypoechoic, triangular, below FA iliaca
[FEMORAL NERVE] ← hyperechoic, triangular/oval structure
                   lateral to femoral artery, deep to fascia iliaca
[FEMORAL ARTERY] ← pulsatile, anechoic (NAVY: N lateral to A)
[FEMORAL VEIN] ← compressible, medial to artery
─────────────────────────────────────────────────────

Step-by-Step Technique

STEP 1: Probe transverse at inguinal crease
STEP 2: Identify femoral artery (pulsatile) and vein (compressible)
STEP 3: Locate femoral nerve LATERAL to artery — hyperechoic
         triangular/honeycomb structure beneath fascia iliaca
STEP 4: Apply colour Doppler — identify femoral vessels, circumflex femoral
STEP 5: Insert 22G 50mm needle in-plane (lateral to medial)
STEP 6: Advance under fascia iliaca to immediately lateral to femoral nerve
         (circumneural injection preferred over intraneural)
STEP 7: Aspirate; inject 1 mL saline — fascia iliaca lifts = correct plane
STEP 8: Inject 15–20 mL LA in increments; watch circumferential spread
STEP 9: Confirm: nerve surrounded by LA ("donut sign")

Drug Doses

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5. WHAT IS BLOCKED / WHAT IS MISSED

Critical Exam Point: FNB causes quadriceps weakness (motor block) — fall risk after knee surgery. This is why Adductor Canal Block (ACB) has largely replaced FNB for TKA as ACB is predominantly sensory-sparing of motor function.

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6. COMPLICATIONS

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BLOCK 2: ADDUCTOR CANAL BLOCK (ACB)

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1. DEFINITION

• An ultrasound-guided fascial plane/nerve block in which local anaesthetic is deposited within the adductor canal (subsartorial canal/Hunter's canal) targeting the saphenous nerve and associated nerves providing predominantly sensory analgesia to the knee and medial leg — with minimal quadriceps motor block
• Also called the "Subsartorial block" or "Saphenous nerve block at mid-thigh"
• Rapidly replaced the FNB as the preferred block for total knee arthroplasty (TKA) in ERAS protocols

Exam Tip: The ACB is the motor-sparing alternative to femoral nerve block for TKA. Patients with ACB catheters ambulate further on day 1 post-TKA than patients with femoral block or no block — this is the primary evidence base.

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2. RELEVANT ANATOMY

Adductor Canal (Hunter's Canal)

ADDUCTOR CANAL (Hunter's Canal) BOUNDARIES:
─────────────────────────────────────────────
Superior:     SARTORIUS MUSCLE (roof)
Medial:       ADDUCTOR LONGUS and ADDUCTOR MAGNUS (floor/posterior)
Lateral:      VASTUS MEDIALIS MUSCLE
─────────────────────────────────────────────
Extends from: FEMORAL TRIANGLE (apex) → ADDUCTOR HIATUS
Length:       Middle third of thigh (approximately 15 cm)
─────────────────────────────────────────────
CONTENTS:
• Superficial Femoral Artery (SFA) — pulsatile
• Superficial Femoral Vein (SFV)
• SAPHENOUS NERVE ← primary target
• Nerve to Vastus Medialis (NVM) ← also blocked
• Posterior division of Obturator Nerve (PDON) ← also blocked (variable)
• Medial femoral cutaneous nerve (variable)
─────────────────────────────────────────────

Key Nerves Blocked in ACB

Viva Pearl: The ACB is NOT a pure saphenous nerve block — it also blocks NVM and PDON which innervate the knee capsule. This explains why ACB provides better knee analgesia than isolated saphenous block alone. However, it preserves quadriceps strength because the anterior femoral nerve (to rectus femoris and vastus lateralis) is NOT blocked.

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3. INDICATIONS

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4. ULTRASOUND-GUIDED TECHNIQUE

Patient Position

• Supine, knee slightly flexed (~10°), hip externally rotated

Probe

• High-frequency linear (15–6 MHz), transverse orientation

Probe Position

• Mid-thigh level — halfway between ASIS and superior patellar pole
• At this level the adductor canal is well-defined

Sonoanatomy

ADDUCTOR CANAL US (Transverse view, mid-thigh):
─────────────────────────────────────────────────
[Skin]
[SARTORIUS MUSCLE] ← triangular, superficial, hypoechoic
         ↓ (deep to sartorius)
[SFA (Superficial Femoral Artery)] ← pulsatile, anechoic, round
[SFV (Superficial Femoral Vein)] ← posterior/deep to SFA, compressible
[SAPHENOUS NERVE] ← hyperechoic, oval, ANTEROMEDIAL to SFA
                    (small, 2–3 mm, "shiny" appearance)
[VASTUS MEDIALIS] ← lateral
[ADDUCTOR MAGNUS / LONGUS] ← posteromedial (floor of canal)
─────────────────────────────────────────────────
NERVE POSITION: Saphenous nerve = anteromedial to SFA

Step-by-Step Technique

STEP 1: Probe transverse at mid-thigh
STEP 2: Identify SFA (pulsatile, anechoic) deep to sartorius
STEP 3: Locate saphenous nerve anteromedial to SFA —
         hyperechoic, small, honeycomb/oval
STEP 4: Apply Doppler — identify SFA and SFV
STEP 5: Insert 22G 50mm needle in-plane, lateral to medial
STEP 6: Advance needle THROUGH SARTORIUS, deep to its fascia
         into the adductor canal, anterior to SFA
STEP 7: Aspiration; inject 1 mL saline — confirm canal opening
STEP 8: Inject 15–20 mL LA; watch spread anterior to SFA
         (LA should surround the saphenous nerve — "donut sign")
STEP 9: For catheter: advance catheter 3–5 cm beyond needle tip

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5. DRUG DOSES

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6. ACB vs. FNB — THE KEY COMPARISON

Exam Tip (2025 Evidence): Gong et al. Meta-analysis (PLoS One 2024): Continuous ACB = Continuous FNB for pain scores at 24h but ACB group had significantly better quadriceps strength and earlier ambulation. ACB is now the standard of care for TKA in ERAS.

Viva Pearl (2025): Bai et al. BMC Anesthesiol 2025 — Femoral Triangle Block (FTB) vs ACB for TKA: FTB provides superior analgesia (as it covers more proximal femoral nerve branches) but at the cost of more motor block. ACB remains preferred for TKA when ERAS/early ambulation is priority.

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BLOCK 3: PERICAPSULAR NERVE GROUP (PENG) BLOCK

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1. DEFINITION

• An ultrasound-guided fascial plane block in which local anaesthetic is deposited in the musculofascial plane between the iliopsoas tendon and the pubic ramus, at the level of the anterior inferior iliac spine (AIIS) and iliopubic eminence (IPE), targeting the articular branches of the femoral, obturator, and accessory obturator nerves supplying the anterior hip capsule
• First described by Girón-Arango et al. (2018) — hence "PENG" = Pericapsular Nerve Group
• Key advantage: Motor-sparing — does not block the main trunk of the femoral nerve → no quadriceps weakness → no fall risk

Exam Tip: PENG block is specifically indicated for hip fracture analgesia and hip arthroplasty. It targets articular branches (sensory only) while sparing motor function — the gold standard motor-sparing hip block.

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2. ANATOMY OF THE PENG BLOCK

Hip Joint Innervation (Articular Branches)

HIP JOINT CAPSULE INNERVATION:
─────────────────────────────────────────────────────
ANTERIOR CAPSULE (primary PENG target):
  • Articular branches of FEMORAL NERVE (from posterior division L2–L4)
  • Articular branches of OBTURATOR NERVE (anterior branch)
  • Articular branches of ACCESSORY OBTURATOR NERVE (when present)

POSTERIOR/SUPERIOR CAPSULE:
  • Articular branches of nerve to QUADRATUS FEMORIS (L4–S1)
  • Superior gluteal nerve (L4–S1)
  → These are NOT blocked by PENG (require FICB, PVB, or sciatic components)
─────────────────────────────────────────────────────

PENG Injection Target

PENG BLOCK ANATOMICAL TARGET:
─────────────────────────────────────────────────────
AIIS (Anterior Inferior Iliac Spine)
         |
         ↓
Iliopubic Eminence (IPE) — junction of ilium and superior pubic ramus
         |
TARGET PLANE: Between ILIOPSOAS TENDON (superiorly) 
              and PUBIC RAMUS (anteriorly/inferiorly)
              → the articular branches run here before entering
                the anterior hip capsule
─────────────────────────────────────────────────────

Viva Pearl: The PENG injection plane sits between the iliopsoas tendon (posterior) and the superior pubic ramus (anterior). The articular branches course in this fascial cleft before entering the hip capsule. The femoral artery is the key medial landmark to avoid.

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3. INDICATIONS

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4. ULTRASOUND-GUIDED TECHNIQUE

Patient Position

• Supine, leg in neutral rotation

Probe

• Curvilinear or linear probe along inguinal crease direction (oblique — parallel to inguinal ligament)
• Probe orientation: Along the inguinal crease, rotated obliquely medially

Sonoanatomy

PENG BLOCK US VIEW (Oblique, inguinal crease):
─────────────────────────────────────────────────
[AIIS] ← hyperechoic bony prominence (lateral landmark)
[ILIOPUBIC EMINENCE (IPE)] ← rounded bony ridge (medial landmark)
   (junction of ilium + superior pubic ramus)
[FEMORAL ARTERY] ← pulsatile, medial to IPE (must avoid)
[ILIOPSOAS MUSCLE/TENDON] ← hypoechoic muscle, overlies IPE
[TARGET PLANE] ← between iliopsoas tendon and IPE
─────────────────────────────────────────────────
Needle path: In-plane, LATERAL to MEDIAL
Endpoint: Needle tip contacts pubic ramus lateral to psoas tendon

Step-by-Step Technique

STEP 1: Probe parallel to inguinal ligament/crease (oblique)
         medial to ASIS, covering AIIS → IPE
STEP 2: Identify AIIS (lateral) and IPE (medial) as bony landmarks
STEP 3: Identify femoral artery (pulsatile, medial to IPE) — AVOID
STEP 4: Identify iliopsoas muscle overlying the IPE
STEP 5: Insert 22G 80–100mm needle in-plane, LATERAL TO MEDIAL
STEP 6: Advance needle to contact PUBIC RAMUS lateral to psoas tendon
STEP 7: Aspirate; inject 1 mL saline — confirm plane opens between
         psoas tendon and pubic ramus
STEP 8: Inject 20 mL LA (ropivacaine 0.2–0.5%, up to 3 mg/kg, ≤ 20 mL)
STEP 9: Confirm LA spread in target plane; does NOT spread to femoral nerve trunk

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5. DRUG DOSES

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6. ADVANTAGES OVER FNB AND FICB

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7. RECENT EVIDENCE (2024–2026)

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BLOCK 4: OBTURATOR NERVE BLOCK (ONB)

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1. DEFINITION

• Block of the obturator nerve (L2–L4) in the medial thigh to provide analgesia/anaesthesia to the medial thigh, medial knee joint, and prevent adductor muscle contraction during transurethral bladder resection
• The obturator nerve splits into anterior and posterior divisions as it passes through the obturator canal; US-guided block targets both branches in the adductor muscle compartment

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2. ANATOMY OF THE OBTURATOR NERVE

Origin and Course

OBTURATOR NERVE PATHWAY:
─────────────────────────────────────────────────────
Origin: Lumbar plexus — posterior divisions of L2, L3, L4
         (medial to femoral nerve within psoas)
         ↓
Descends in psoas major → exits medial border at pelvic brim
         ↓
Crosses sacroiliac joint → enters OBTURATOR CANAL
(through obturator foramen with obturator vessels)
         ↓
Enters medial thigh → divides into:
  ANTERIOR DIVISION (between adductor longus and adductor brevis)
  POSTERIOR DIVISION (between adductor brevis and adductor magnus)
─────────────────────────────────────────────────────

Branches and Supply

Viva Pearl: The obturator nerve has highly variable cutaneous supply to the medial thigh — often minimal or absent. Its most clinically significant sensory contribution is the articular branch to the knee joint (posterior division) — which explains why ONB improves TKA analgesia when added to ACB.

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3. INDICATIONS

Exam Tip: The obturator reflex during TURBT is caused by electrostimulation of the obturator nerve by monopolar diathermy current → adductor muscle contraction → sudden hip adduction → risk of bladder perforation. ONB prevents this. Alternative: use bipolar diathermy (no obturator reflex) or spinal anaesthesia with muscular relaxation.

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4. ULTRASOUND-GUIDED TECHNIQUE

Patient Position

• Supine, thigh slightly abducted and externally rotated

Probe

• High-frequency linear (15–6 MHz), transverse orientation

Probe Position

• Medial thigh, 1–2 cm distal to the inguinal crease
• At the level of the adductor muscles

Sonoanatomy

MEDIAL THIGH US (Transverse, 1–2 cm distal to inguinal crease):
─────────────────────────────────────────────────────────────
[Skin]
[ADDUCTOR LONGUS] ← most superficial adductor (thin, triangular)
─── ANTERIOR OBTURATOR NERVE ← between AL and AB (hyperechoic fascicles)
[ADDUCTOR BREVIS] ← between AL and AM
─── POSTERIOR OBTURATOR NERVE ← between AB and AM
[ADDUCTOR MAGNUS] ← deepest
─────────────────────────────────────────────────────────────
FEMORAL ARTERY/VEIN visible medially — use Doppler

Step-by-Step Technique

STEP 1: Probe transverse at medial thigh, 1–2 cm below inguinal crease
STEP 2: Identify adductor longus (AL), brevis (AB), magnus (AM) —
         from superficial to deep
STEP 3: Locate anterior obturator nerve between AL and AB (hyperechoic, small)
STEP 4: Locate posterior obturator nerve between AB and AM
STEP 5: In-plane needle insertion (lateral to medial or medial to lateral)
STEP 6: Inject 8–10 mL LA between AL and AB (anterior ONB)
STEP 7: Re-position needle between AB and AM
STEP 8: Inject 8–10 mL LA (posterior ONB)
STEP 9: Total: 15–20 mL per nerve (8–10 mL per branch = 16–20 mL total)

Drug Doses

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5. NERVE STIMULATOR ENDPOINT

• Anterior division: Adductor longus contraction (hip adduction)
• Posterior division: Adductor magnus contraction (hip adduction + extension)
• Threshold: 0.2–0.5 mA

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6. COMPLICATIONS

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7. COMPARISON OF ALL FOUR LOWER LIMB BLOCKS

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8. CLINICAL PEARLS

1. FNB is being phased out for TKA in ERAS protocols — ACB is now standard of care due to motor preservation
2. ACB position: SFA → Saphenous nerve is ANTEROmedial to the SFA in the adductor canal
3. The "donut sign" (nerve surrounded by LA in cross-section) confirms successful circumneural injection in both FNB and ACB
4. PENG block is the motor-sparing block of choice for hip fractures — especially in elderly, frail patients at high fall risk (Vermazen et al. 2026)
5. Accessory obturator nerve (present in 29%) provides articular branch to hip — blocked by PENG but not by standard ONB
6. Obturator reflex in TURBT: ONB prevents adductor spasm during monopolar electrosurgery; bipolar diathermy is the non-block alternative
7. Continuous ACB catheter at mid-thigh provides superior TKA analgesia vs single-shot; distal catheter (near adductor hiatus) provides equivalent analgesia to proximal (Lombardi et al. Can J Anaesth 2024)
8. FNB + sciatic nerve block = complete anaesthesia for TKA surgery (surgical anaesthesia); ACB only provides postoperative analgesia
9. PENG block can be combined with FICB for even broader hip coverage: FICB covers the proximal femur + PENG covers the anterior capsule articular branches
10. ACB at proximal canal (upper third of thigh) = "femoral triangle block" — slightly more motor involvement but better pain scores; ACB at mid-canal = purer sensory block
11. For complete knee anaesthesia: FNB (or ACB) + Sciatic nerve block + Obturator nerve block — the "knee triad"
12. PENG block does NOT cover posterior hip capsule — add FICB or lumbar plexus block for complete THA coverage

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9. COMMON VIVA QUESTIONS

• ACB is predominantly sensory (saphenous + NVM + PDON) → minimal quadriceps weakness → preserved motor function → earlier ambulation → reduced fall risk → ACB preferred in ERAS protocols

• Hunter's canal — bounded by sartorius (roof), vastus medialis (lateral), adductor muscles (floor/posterior); contains SFA, SFV, saphenous nerve, NVM, PDON

• PENG = pericapsular nerve group block; LA deposited between iliopsoas tendon and pubic ramus at AIIS–IPE level; blocks articular branches of femoral + obturator + accessory obturator nerves; motor-sparing (does not block femoral nerve trunk) → no quadriceps weakness; ideal for hip fracture in elderly

• AIIS (lateral bony landmark), iliopubic eminence (IPE — medial), femoral artery (medial reference, must avoid), iliopsoas tendon (overlying IPE); needle from lateral to medial contacting pubic ramus lateral to psoas tendon

• Electrostimulation of obturator nerve during monopolar TURBT → adductor muscle contraction → sudden hip adduction → bladder wall perforation. Prevention: ONB before TURBT; alternatively use bipolar electrocautery or spinal anaesthesia + muscle relaxant

• Articular branches of: (1) femoral nerve posterior division, (2) obturator nerve anterior branch, (3) accessory obturator nerve (when present — 29%). Does NOT block the main femoral nerve trunk.

• From medial to lateral in the femoral triangle: N = femoral Nerve (most lateral), A = femoral Artery, V = femoral Vein, Y = empty/femoral canal (most medial). Note: Nerve is LATERAL to the artery.

• Dolstra et al. Am J Emerg Med 2025: PENG comparable to FICB for analgesia; less motor block; recommended as first-choice motor-sparing block in elderly NOF fracture patients. Vermazen et al. Arch Orthop Trauma Surg 2026: All three (FNB, FICB, PENG) effective for post-op analgesia; PENG has least motor impairment.

• FTB targets nerves at the proximal adductor canal/femoral triangle junction — captures more femoral nerve branches including more of the NVM; provides slightly better pain scores but marginally more quadriceps inhibition. Bai et al. 2025: FTB = superior analgesia vs ACB but with slightly more motor block.

• None — ONB alone is never sufficient for major surgery; it is used as an adjunct to: FNB/ACB for TKA, FICB/PENG for hip, or as a sole block for preventing obturator reflex during TURBT

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10. RAPID REVISION BOX

FNB + ACB + PENG + ONB — ONE PAGE REVISION
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
FEMORAL NERVE BLOCK:
  Nerve: L2–L4 | NAVY landmark (Nerve lateral to Artery)
  US: Below inguinal crease, transverse; FN lateral to FA, under fascia iliaca
  Volume: 15–20 mL ropivacaine 0.5%
  Motor block: FULL QUADRICEPS (fall risk)
  Best for: Hip fracture, femur, legacy TKA
  
ADDUCTOR CANAL BLOCK:
  Canal: Hunter's canal — Sartorius (roof), VM (lateral), Adductors (floor)
  Nerves: Saphenous N + NVM + PDON
  US: Transverse mid-thigh — SFA + Saphenous nerve ANTEROMEDIAL to SFA
  Volume: 15–20 mL | catheter 5–10 mL/h
  Motor: MINIMAL — MOTOR SPARING
  Best for: TKA (ERAS standard), ACL, knee arthroscopy
  Evidence: Gong 2024 = ACB equivalent to FNB analgesia + better ambulation
            Bai 2025 = FTB > ACB analgesia but more motor block

PENG BLOCK:
  Plane: Between iliopsoas tendon and pubic ramus (AIIS → IPE level)
  Nerves: Articular branches of FN + ON + Accessory ON
  US: Oblique along inguinal crease | AIIS (lat) + IPE (med) + FA (medial)
  Needle: Lateral → medial, contacts pubic ramus lateral to psoas tendon
  Volume: 20 mL ropivacaine 0.2–0.5% (max 3 mg/kg)
  Motor: NONE — fully motor sparing
  Best for: Hip fracture (elderly), THA, hip arthroscopy
  Evidence: Dolstra 2025 + Vermazen 2026 — PENG preferred over FNB in NOF
  First described: Girón-Arango et al. 2018

OBTURATOR NERVE BLOCK:
  Nerve: L2–L4 | Exits obturator foramen | splits into anterior + posterior
  US: Medial thigh transverse — Ant division (between AL and AB)
                               Post division (between AB and AM)
  Volume: 8–10 mL per branch (total 16–20 mL)
  Motor: ADDUCTORS
  KEY INDICATION: TURBT — prevents obturator reflex during monopolar
  As supplement: TKA (with ACB), hip blocks

MOTOR BLOCK COMPARISON:
  FNB = Full quadriceps (⬆ fall risk)
  ACB = Minimal (motor sparing) ✓ ERAS
  PENG = None ✓ Best for elderly
  ONB = Adductors only

KNEE TRIAD: FNB + Sciatic + ONB = complete knee surgical anaesthesia
HIP TRIAD: PENG + FICB + Sciatic = complete hip coverage
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