Caudal block

Background knowledge:

Anatomy

Sacral hiatus:

· Triangular gap between sacrum and coccyx

· Two cornua at the base, median crest at the apex

· Covered by sacrococcygeal ligament (= ligamentum flavum)

Neuraxis:

· Epidural space is underneath the ligament

· Epidural-spinal distance is 1cm in neonates, 3cm in adults

· N.B. injectate leaks out to bathe sacral nerves; hence long duration

Landmarks:

· Imaginary south-pointing equilateral triangle

· Two PSIS at the base

· Sacral hiatus at the apex

Boundaries of caudal space:

· Anterior/medial/lateral: bone

· Posterior: sacrococcygeal membrane

· Inferior: sacrum/rectum/anus (needle damage if hiatus misidentified)

· Superior: dural sac S2/3, spinal cord L1/2

Contraindications

Practical:

· Child >20kg (carry limit)

Medical:

· Coagulopathy

· Localised infection

· Spinal malformation

· Neurological disorder

Complications

Needle:

· Too shallow: failure

· Too deep: dural puncture, high spinal

· Too far south: rectal perforation

· In nerve: catastrophic damage

· In vessel: LAST, epidural haematoma

· In marrow: LAST

Block:

· Urinary retention

· Respiratory depression (if opioid)

· High block

Equipment	· Sterile regional kit · Sterile gloves · 0.5% Chlorhexidine / 70% alcohol lollipop · 0.5% bupivacaine · 20mL syringe · 21g needle
Monitoring	· Sat probe · NIBP · ECG (risk of LAST)
Positioning	· Left lateral decubitus · Spine, hips, knees flexed
Mechanics	· Palpate cornua with thumb of other hand · Pierce skin at 60 degrees · Flatten out to 30 degrees · Advance until ‘pop’ · Aspirate for blood · Inject
Dose	Bupivacaine: · 0.5mL/kg circumcision · 0.75mL/kg herniorraphy · 1mL/kg orchidopexy – go to dose Additives: · Clonidine 1-2mcg/kg