Caudal Anaesthesia
Positions 1. Lateral position with hips and knees flexed (foetal position) 2. Prone position with the pelvis raised on a pillow and feet turned medially Drugs
15-20 ml (0.5% bupivacaine or 1.5% lignocaine or mixture) will fill the sacral canal of an adult, and provide a perinea! block. Increasing the volume further will push the fluid into the lumbar canal. Add fentanyl 50µg for quick onset, and better quality of block. Add morphine (preservative free) 2mg to provide post operative analgesia for 12-24h. Anatomy • The dural sac ends at S2 in adults and lower in children.
• The sacral hiatus is identified with the non dominant hand by moving the finger down along the midline of the sacrum till a give is felt which is usually just above the natal cleft and bordered by the two sacral comua. It forms an equilateral triangle with the posterior superior ilac spines. The sacral hiatus is covered by the sacro-coccygeal membrane.
Injection 1. Clean the area with antiseptic. Avoid spirits as it is irritant to the anus. 2. Infiltrate lignocaine and insert a short beveled (2") 20-21G needle at 90 °. 3. When the ligament is reached, lower the needle to 45° and pierce it. 4. When the loss of resistance is felt, check for absence of CSF. 5. Connect to syringe, and aspirate gently to check for blood. 6. Inject a test dose of 3-4 ml, followed by the rest if there are no signs of i.v. injection or CSF aspiration.
7. Check block by touching anus with a probe to assess relaxation of the sphincter
.COMPLICATIONS
• LA toxicity with i.v. injection (see page 19.23) • SAB with total spinal • Subdural block resulting in high sensory block • Urinary retention