Caudal Anaesthesia

Question 1

A 2-year-old male patient is undergoing hypospadias repair surgery. You are
asked to review him prior to his procedure.

What are the key aspects in the preoperative assessment for this patient?

Answer 1

History:
* This is a young child, so the history will be taken from the parent/ guardian. It is important to engage the child and put them at their ease.

• Birth history, vaccinations and a family history of anaesthetic problems should be emphasised.
• Infections are common in children and a reason to delay surgery. Ask
  about coryzal symptoms, fevers and contact with unwell individuals.

Examination:
* Examinations may need to be pragmatic depending on the cooperation of the child.

• Airway assessment.
• Review observations, in particular the child’s temperature.
• Check that the patient has been recently weighed.

Investigations:
* No specific investigations should be required unless indicated by the patient’s medical history.

Question 2

What are the benefits of caudal anaesthesia?

Answer 2

• Excellent analgesia during the perioperative period.
• Safe and straightforward procedure.
• Avoidance of side effects of opioid-based analgesia.
• Caudal catheters can be used for prolonged blockade if appropriate.
• Minimal haemodynamic instability.

Question 3

How would you perform a caudal block in this patient?

Answer 3

• Ensure access to a checked anaesthetic machine, trained assistant and full resuscitative capabilities.

Prior to the procedure:
* Obtain consent from the parents.
* Apply AAGBI monitoring.
* Perform a general anaesthetic.
* Position the patient: left lateral with knees flexed to chest.
* Full asepsis using a hat, mask, sterile gloves, sterile drapes and
chlorhexidine 0.5% spray.
* Calculate the correct dose/volume of local anaesthesia based on
the patient’s weight and the Armitage formula (0.5 mL/kg 0.25% bupivacaine for a sacro-lumbar block).

Question 4

How would you perform a caudal block in this patient?

Answer 4

During the procedure:
* Identify the sacral hiatus – forms an equilateral triangle with the posterior superior iliac spines.
* Insert a 22G cannula in a cranial direction through the sacral hiatus until a “click” is felt to indicate passage through the sacrococcygeal membrane.
* Advance the cannula and remove the needle.
* Allow the cannula to drain under gravity looking for blood or CSF drips.
* Aspirate the cannula again looking for blood or CSF.
* If no blood or CSF is seen, inject the local anaesthetic solution.
* Palpate the skin over the sacrum during injection. This will detect a
cannula incorrectly positioned in the subcutaneous tissue.

Postoperative:
* Warn the nurses and parents that the patient may have weak/numb legs and an unsteady gait.

Question 5

How can the duration of the block be prolonged?

Answer 5

• Higher concentration or volume of local anaesthetic (ensuring the maximum safe dose is not exceeded).
• Use of a caudal catheter to enable additional local anaesthesia to be administered.
• Many different drugs have been added to the local anaesthetic in caudal blocks, including fentanyl, clonidine and ketamine. The ketamine must be a preservative free preparation to avoid neurotoxicity.

Question 6

What are the complications associated with caudal analgesia?

Answer 6

• Block failure.
• Leg weakness.
• Urinary retention (although unlikely to be an issue as the patient
  would be catheterised intraoperatively).
• Intravenous injection and local anaesthetic toxicity.
• Dural puncture/intrathecal injection.
• Epidural haematoma/abscess.