What is the procedure for a caudal block?

Procedure for Caudal Block

The caudal block is a landmark-based regional anesthesia technique performed through the sacral hiatus to access the epidural space, particularly useful for infants and toddlers undergoing procedures below the umbilicus. 1

Patient Selection and Indications

• Caudal blocks are most appropriate for infants and toddlers, while lumbar epidural approaches are preferred for older children 1
• Primarily indicated for surgical procedures below the umbilicus 2
• Can be used as an alternative to general anesthesia in premature and high-risk infants 3

Anatomical Considerations

• The sacral hiatus is the entry point, located between the sacral cornua at the base of the sacrum 4
• Median depth of the caudal space at the hiatus is approximately 2.9 mm in children 5
• Patient positioning: lateral decubitus position is commonly used for ultrasound evaluation and needle placement 5

Procedural Technique

Equipment

• Appropriate needle size based on patient age/size
• Long-acting local anesthetic (with or without adjuncts)
• Ultrasound machine with high-frequency linear probe (if available) 1
• Sterile preparation materials

Step-by-Step Procedure

1. Position the patient in lateral decubitus or prone position 5
2. Identify the sacral hiatus by palpating the sacral cornua 4
3. Prepare the area with antiseptic solution
4. If using ultrasound (recommended):
   • Visualize the sacral hiatus and surrounding structures 1
   • Confirm appropriate depth and trajectory for needle insertion 5
5. Insert the needle at a 45° angle to the skin
6. Once through the sacrococcygeal membrane, decrease the angle to approximately 20-30° and advance slightly 4
7. Confirm proper needle placement:
   • No blood return on aspiration
   • No cerebrospinal fluid return
   • If available, use fluoroscopy or ultrasound to verify position 4, 6
8. Inject the calculated dose of long-acting local anesthetic (with or without adjuncts like clonidine) 1

Medication Selection and Dosing

• Long-acting local anesthetics are preferred, with optional adjuncts 1
• Common adjuncts include:
  • Clonidine (improves block quality and duration) 1
  • Morphine (for prolonged postoperative analgesia, if available) 1
• Dexamethasone or methylprednisolone may be considered to reduce postoperative swelling 1

Alternative Approaches

• S2-3 interspace approach can be used when the sacral hiatus is difficult to identify 5
  • Success rate at first puncture: 96.2% for S2-3 approach vs. 77.5% for hiatal approach 5
  • Particularly useful in children older than 36 months 5

Potential Complications and Prevention

• Overall complication rate is approximately 7/10,000, the lowest among central blocks 3
• Potential complications include:
  • Local anesthetic toxicity (use appropriate weight-based dosing) 3
  • Vascular penetration (always aspirate before injection) 3
  • Dural puncture (maintain proper angle and depth) 3
  • Intravascular injection (use test dose or imaging guidance) 4, 6
  • Infection or meningitis (maintain strict aseptic technique) 3

Success Rates and Considerations

• Success rate is approximately 99% in children under 7 years of age 3
• Failure rates increase with age, particularly in older children 3
• Fluoroscopy-guided needle placement with contrast confirmation improves success rates (failure rate reduced to approximately 17.7%) 6
• Ultrasound guidance has been demonstrated to be highly effective and comparable to fluoroscopy for accurate needle placement 4

Key Pitfalls to Avoid

• Incorrect identification of the sacral hiatus (use anatomical landmarks carefully) 4
• Advancing the needle too deeply (risk of dural puncture) 3
• Failing to confirm needle placement before injection (can lead to ineffective block or complications) 6
• Not recognizing anatomical variations (consider alternative approaches like S2-3 when needed) 5