AS5.5 | Caudal Epidural Technique in Adults and Children — Summary & Reflection

KEY TAKEAWAYS

Caudal epidural block enters the epidural space via the sacral hiatus — a gap at S4–S5 covered by the sacrococcygeal membrane. In children, it is the most common regional technique, performed under GA as an adjunct for any surgery below the umbilicus. The equilateral triangle landmark (posterior superior iliac spines + sacral hiatus) identifies the injection site. The Armitage formula determines volume: 0.5 mL/kg (sacral), 1.0 mL/kg (lumbo-sacral), 1.25 mL/kg (lower thoracic) — always verify mg/kg dose against the maximum of 2 mg/kg for bupivacaine. In neonates the dural sac ends at S3–S4 (vs S2 in adults) — never advance the needle more than 1–2 mm past the membrane in infants. In adults, caudal block is used for perineal surgery, sacral pain syndromes, and failed lumbar epidural. Confirmation: aspiration (no blood/CSF) + test dose + ultrasound. Subcutaneous injection (sacral swelling) is the most common failure mode — do not re-inject immediately. LAST management: 20% intralipid 1.5 mL/kg.

REFLECT

Consider the difference between performing a caudal block in a 6-month-old versus a 45-year-old obese adult. In the infant, the anatomy is consistent, the hiatus is readily palpable, the skin-to-sacrococcygeal membrane distance is only a few millimetres, and the dural sac is worryingly close. In the adult, the anatomy is variable, the hiatus may be impalpable, and ultrasound guidance may be the only way to confirm placement — yet the dural sac is 2 cm away, giving more margin. What would you prepare differently for each case? Think about positioning, needle gauge, volume, concentration, confirmation method, and the rescue drugs you would want immediately available. Preparing these answers now — before you stand beside the anaesthetist — transforms your observation into a participatory learning experience.