AS5.{1-3,5-6} | Regional Anaesthesia — Glossary

A lipid emulsion antidote for bupivacaine-induced cardiac arrest; acts as a 'lipid sink' sequestering free drug from cardiac tissue; dose: 1.5 mL/kg IV bolus then 0.25 mL/kg/min infusion.

Lipid emulsion used as antidote for LAST: 1.5 mL/kg IV bolus, then 0.25 mL/kg/min infusion; acts as lipid sink sequestering bupivacaine from cardiac tissue; must be available in every anaesthetic area.

A paediatric dosing formula for caudal block: 0.5 mL/kg (sacral block), 1.0 mL/kg (lumbo-sacral block), 1.25 mL/kg (lower thoracic block) of local anaesthetic — volume determines spread; dose in mg/kg must be independently verified.

Block of the terminal branches of the brachial plexus (median, ulnar, radial, musculocutaneous) in the axilla, with the axillary artery as the central ultrasound landmark; suitable for hand, forearm, and elbow surgery.

The density of a local anaesthetic solution relative to cerebrospinal fluid; hyperbaric solutions sink with gravity, hypobaric solutions rise, and isobaric solutions spread uniformly.

The neural network arising from C5–T1 anterior rami supplying the upper limb; organised as Roots → Trunks → Divisions → Cords → Terminal branches.

2 mg/kg — the most cardiotoxic LA; never give intravenously; adrenaline addition does NOT increase the safe dose.

2 mg/kg — identical to the adult maximum; must be calculated from the planned volume × concentration BEFORE injection to avoid inadvertent overdose from applying volume formulas alone.

The bundle of spinal nerve roots below the conus medullaris (L1–L2 in adults) that traverse the lumbar and sacral subarachnoid space; lumbar puncture below L1 avoids cord injury.

A neuraxial technique depositing local anaesthetic into the epidural space via the sacral hiatus, targeting sacral and low lumbar nerve roots; the most common regional technique in paediatric anaesthesia.

A technique combining the rapid dense onset of spinal block with the catheter-based flexibility of epidural, allowing top-ups for long cases and postoperative analgesia.

Sequential testing of temperature (earliest, sympathetic), pinprick (sensory), and motor power (latest) after block placement to determine completeness and predict adequacy for surgery.

The phenomenon where sympathetic fibres are blocked first, sensory fibres second, and motor fibres last — owing to fibre diameter and myelination differences; recovery is in reverse order.

The inferior end of the subarachnoid space; located at S2 in adults and at S3–S4 in neonates — a critical safety landmark governing maximum needle advance during caudal block.

A mixed alpha and beta adrenergic agonist vasopressor used for neuraxial hypotension; causes tachycardia, increases cardiac output; may reduce uteroplacental blood flow compared to phenylephrine in obstetrics.

A potential space between the ligamentum flavum and the dura mater, extending from the foramen magnum to the sacral hiatus; contains fat, veins, and lymphatics.

The triangle formed by the two posterior superior iliac spines and the sacral hiatus, used to locate the hiatus for caudal block; the hiatus sits at the apex inferior to the iliac spine line.

Volume-dependent block depositing LA in the fascia iliaca compartment to anaesthetise the femoral, lateral femoral cutaneous, and (partially) obturator nerves; widely used for hip fracture analgesia in emergency settings.

Block of the femoral nerve (L2–L4) just below the inguinal ligament, lateral to the femoral artery under the fascia iliaca; provides anterior thigh and knee analgesia; used for knee arthroplasty and femoral fractures.

In children under GA, block adequacy is inferred from the absence of tachycardia and hypertension in response to surgical stimulation — the analogue of verbal pain scoring in awake adults.

Needle approach where the entire needle shaft is visualised along its length on the ultrasound screen, allowing precise tip placement and continuous monitoring of needle-to-nerve distance.

In-plane: needle entered parallel to the ultrasound beam, entire shaft visible — safer, preferred. Out-of-plane: needle crosses the beam at 90 degrees, only the tip is visible as a bright dot — higher risk of inadvertent deep placement.

Block of the C5/C6/C7 roots between the anterior and middle scalene muscles; the standard block for shoulder surgery; universally causes ipsilateral phrenic nerve palsy.

Toxicity from inadvertent intravascular injection or excessive dose of LA; presents with CNS excitation (seizures) then cardiovascular collapse; treated with 20% intralipid and CPR.

A dense yellow elastic ligament connecting adjacent laminae; its characteristic resistance then sudden loss-of-resistance identifies epidural space entry.

3 mg/kg plain; 7 mg/kg with adrenaline — for infiltration and peripheral nerve blocks.

Expected transient inability to move the lower limbs after caudal bupivacaine in children; resolves as block regresses; must be communicated to recovery room nurses to prevent unnecessary alarm or investigation.

Terminal branch of the lateral cord (C5–C7) that exits the brachial plexus sheath proximally to enter coracobrachialis; supplies the lateral forearm (as the lateral cutaneous nerve of forearm); requires separate injection in axillary block.

Memory aid for femoral triangle contents from lateral to medial at the inguinal ligament: Nerve, Artery, Vein, Empty space, Lymphatics — critical for safe femoral nerve block placement.

Standard technique — one injection through the sacral hiatus without a catheter; provides 4–6 hours of postoperative analgesia with bupivacaine; extended analgesia possible with preservative-free caudal morphine (with monitoring).

A positional headache (worse standing, relieved lying) caused by CSF leak through the dural puncture, producing traction on meningeal structures; treated with bed rest, fluids, caffeine, or epidural blood patch.

Deposition of local anaesthetic adjacent to a specific peripheral nerve or plexus, producing reversible loss of sensation and motor function in the nerve's territory without affecting haemodynamics or airway.

A pure alpha-1 agonist vasopressor used to treat neuraxial hypotension, particularly in obstetrics, as it preserves uteroplacental blood flow better than ephedrine in most circumstances.

Paralysis of the ipsilateral hemidiaphragm due to block of the phrenic nerve (C3–C5) as an inevitable consequence of interscalene block; well tolerated in healthy patients but contraindicated if contralateral phrenic nerve is already compromised.

Air in the pleural space; a complication of supraclavicular and interscalene blocks due to proximity of the needle to the lung apex; may be delayed 30–60 minutes; diagnosed by absent lung sliding on ultrasound.

Prone is preferred in adults (better access to sacral cleft, especially in obese patients); lateral decubitus is preferred in children (easy to maintain GA with facemask or LMA without repositioning).

Reversible interruption of nerve conduction in a defined anatomical region using a local anaesthetic deposited near a nerve, plexus, or within the neuraxial spaces.

The continuation of the spinal canal within the sacrum; contains the terminal dural sac, sacral nerve roots, filum terminale, and caudal epidural venous plexus.

Paired bony prominences at the inferior tip of the sacrum, flanking the sacral hiatus; the primary palpable landmarks for identifying the caudal injection site.

A U- or V-shaped opening in the posterior wall of the sacral canal at S4–S5, formed by failure of the S4 laminae to fuse; covered by the sacrococcygeal membrane; the entry point for caudal epidural block.

A fibrous membrane covering the sacral hiatus posteriorly, analogous to the ligamentum flavum; penetrated by the caudal needle during caudal epidural block.

Block of the sciatic nerve in the popliteal fossa before it divides into the tibial and common peroneal nerves; covers the leg below the knee (excluding the medial saphenous strip); used for foot and ankle surgery.

The CSF-containing space between the arachnoid mater and pia mater; the target for spinal (subarachnoid) block; lies deep to the epidural space and dura.

The most common failure mode of caudal block: the needle fails to penetrate the sacrococcygeal membrane and LA deposits in the subcutaneous tissue, producing a visible sacral swelling and no block.

Block of the brachial plexus trunks/divisions in the supraclavicular fossa, targeting the compact cluster lateral to the subclavian artery on the first rib; known as the 'spinal of the arm' for reliable whole-limb coverage.

The functional abolition of sympathetic tone in a body region, caused by neuraxial block of preganglionic sympathetic fibres (T1–L2); leads to vasodilation, venous pooling, hypotension, and bradycardia if cardiac accelerators (T1–T4) are blocked.

Block depositing LA between the internal oblique and transversus abdominis muscles to anaesthetise the anterior rami of T10–L1; provides somatic anterior abdominal wall analgesia only — not visceral or peritoneal.

Injection of 3 mL of LA with 1:200,000 adrenaline before the full caudal dose; tachycardia (≥20 bpm) within 60 seconds indicates intravascular injection; dense rapid sacral block indicates subarachnoid placement.

An imaginary line connecting the top of the iliac crests, passing approximately through the L3/L4 interspace; used as a surface landmark for lumbar puncture needle insertion.

Real-time use of high-frequency ultrasound to visualise the target nerve, needle, and surrounding structures during block placement; increases success rates and reduces complication rates compared to landmark or nerve-stimulator techniques.

Real-time ultrasound of the sacral hiatus confirms needle entry into the sacral canal (absence of subcutaneous bulge, positive sacral canal fluid wave during injection); recommended in neonates, infants, and obese adults.

A confirmatory manoeuvre for caudal block: auscultation over the lower spine during injection of a small air bolus transmits a 'whoosh' sound if the needle is correctly placed in the sacral canal; not 100% reliable, now largely superseded by ultrasound confirmation.