Durgical
EN
Open the app

Caudal block in children

  • Technique

Numbing medicine injected through a small gap at the bottom of the spine, usually after the child is asleep, to give pain relief below the belly button.

Updated

What it is

A caudal block is an epidural injection given through the sacral hiatus, the gap at the lower end of the sacrum formed by the unfused laminae of the fifth sacral vertebra. The hiatus lies between the two sacral cornua and is covered by the sacrococcygeal ligament. It is the most common regional technique in children and is usually performed after induction of general anaesthesia, as a single injection, to give analgesia during and after surgery below the umbilicus: inguinal hernia repair, circumcision, hypospadias repair, orchidopexy and lower limb operations. In infants and young children the landmarks are easy to feel, the epidural fat is loose and the solution spreads well, and blood pressure usually stays stable because their sympathetic tone is low. The anatomy changes with age: in newborns the spinal cord and the dural sac end lower than in adults, so a needle advanced too far can enter the dural sac. Ultrasound can show the hiatus, the needle and the spread. A single injection lasts several hours; additives can prolong it, and catheters can be threaded higher in small infants. Children are vulnerable to toxicity: neonates have less of the plasma protein that binds local anaesthetics and immature liver metabolism, so the maximum safe dose by weight must be respected, and under general anaesthesia toxicity may first show as arrhythmia rather than symptoms.

Indications

  • Inguinal and umbilical hernia repair and orchidopexy.
  • Circumcision and hypospadias repair.
  • Lower limb, perineal and anal surgery in infants and young children.
  • Opioid-sparing analgesia in infants, including former preterm babies at risk of postoperative apnoea.
  • Caudal catheters for longer analgesia after selected major abdominal surgery in small infants.

Contraindications and precautions

  • Parental refusal, or refusal by a child old enough to decide, after explanation.
  • Infection or skin lesions over the sacrum, including a pilonidal sinus.
  • Coagulopathy or anticoagulant therapy, judged as for other neuraxial blocks.
  • Sacral or spinal anomalies, such as spina bifida, a tethered cord or abnormal sacral skin signs: image or avoid.
  • Raised intracranial pressure, uncorrected hypovolaemia and allergy to the local anaesthetic class.

Equipment and preparation

  • General anaesthesia established, standard monitoring with continuous ECG, and intravenous access in place.
  • Resuscitation drugs and lipid emulsion available, with doses calculated by weight on the chart.
  • Sterile skin preparation, gloves, a short-bevel needle or cannula of suitable size, and ultrasound if available.
  • The local anaesthetic, with any additive, calculated by weight below the maximum safe dose and clearly labelled.
  • Consent from the parents or guardians, with the child's assent when appropriate.

Step by step (and why)

  1. Place the child in the lateral position with hips and knees flexed, or prone — this opens the hiatus and makes landmarks easier to feel.
  2. Feel the coccyx and slide upwards to the sacral cornua; the hiatus lies between them — accurate landmarks prevent misplacement.
  3. Clean the skin widely with antiseptic and let it dry — the site is near the anus and contamination is a real risk.
  4. Insert the needle at a steep angle until a «pop» through the sacrococcygeal ligament — the pop marks entry into the caudal space.
  5. Flatten the angle and advance only slightly — going further risks the dural sac, which ends low in neonates.
  6. Aspirate gently for blood or cerebrospinal fluid — either means the needle is in a vessel or the dural sac.
  7. Inject slowly in increments, watching the ECG and the skin over the sacrum — ECG changes suggest intravascular injection; swelling, a misplaced needle.
  8. Feel for easy injection with no resistance and, if available, confirm spread with ultrasound — free flow suggests correct placement.

Complications

  • Failed block from misplacement under the skin or into the sacrum.
  • Intravascular injection with local anaesthetic systemic toxicity, often first seen as ECG changes or arrhythmia.
  • Dural puncture with a high or total spinal block, causing apnoea and bradycardia.
  • Intraosseous injection into the soft sacrum of infants, which behaves like an intravenous injection.
  • Motor weakness of the legs, urinary retention and, rarely, infection or haematoma.

Next step

  • Hand over the block, the drugs and the time of injection to recovery staff so they know when it will wear off.
  • Warn parents that the legs may feel weak or numb for a few hours and plan simple oral analgesia before the block fades.
  • Check that the child passes urine before discharge after day surgery, according to local policy.
  • Call a senior for prolonged leg weakness, apnoea, persistent bradycardia or any sign of toxicity.
  • Ask about fever, back pain or redness at the site at follow-up; these may suggest infection.

Test yourself

Think of the answer, then tap the question to see it.

What forms the sacral hiatus and what covers it?

The unfused laminae of the fifth sacral vertebra form the hiatus, between the sacral cornua; the sacrococcygeal ligament covers it.

Why must the needle not be advanced far into the caudal canal in a newborn?

In neonates the dural sac and spinal cord end lower than in adults, so the needle can enter the dural sac and cause a total spinal block.

How is toxicity usually first detected when a caudal block is given under general anaesthesia?

As ECG changes during injection, such as T-wave or ST changes, tachycardia or arrhythmia, because the child cannot report symptoms.

Why are neonates more vulnerable to local anaesthetic toxicity than older children?

They have less plasma protein to bind the drug, so more is free, and their liver metabolism of amide local anaesthetics is immature.

Add to my cards (4)

Elsewhere in DurgiPedia

Connections

In Pharmacology5

← All of anaesthesia

Educational content; it does not replace supervised training, your institution's protocols or the anaesthetist's or intensivist's decision. It contains no doses and no ventilator or infusion settings.

Sources: Caudal Anesthesia (StatPearls (NCBI Bookshelf), 2025); Local Anesthetics in Children (StatPearls (NCBI Bookshelf), 2026).

Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake

Representative model, for educational purposes only.