Epidural anaesthesia and analgesia

What it is

Epidural anaesthesia places local anaesthetic, often with an opioid, into the epidural space, the fat- and vein-filled space between the ligamentum flavum and the dura. Because the drug must spread through this space and cross the dura and nerve root sleeves, onset is slower than a spinal and larger volumes are needed. A catheter is usually threaded through a blunt curved-tip needle and left in place, so the block can be extended, topped up or run as a continuous infusion for hours or days. The block is segmental: it spreads up and down from the level of insertion, so a thoracic catheter can cover the chest or upper abdomen while sparing the legs. The space is found by the loss-of-resistance technique: as the needle passes the dense ligamentum flavum, pressure on a syringe of saline or air suddenly gives way. Low concentrations give analgesia with little motor block, used in labour and after thoracic, abdominal and major orthopaedic surgery; higher concentrations give surgical anaesthesia. A test dose and incremental injection guard against the catheter lying in a vein or in the subarachnoid space.

Indications

• Labour analgesia, which can be extended to anaesthesia for caesarean section through the same catheter.
• Analgesia after thoracic and major upper abdominal surgery (thoracic epidural).
• Surgical anaesthesia for lower abdominal, pelvic or lower limb surgery, alone or with general anaesthesia.
• Combined spinal-epidural: fast spinal onset with the option to prolong it through the catheter.
• Patients with severe lung disease, where good analgesia improves coughing and breathing after surgery.

Contraindications and precautions

• Absolute: patient refusal, infection at the site, raised intracranial pressure, and severe uncorrected hypovolaemia.
• Coagulopathy, low platelets and anticoagulants: time insertion and catheter removal by each drug's rules.
• Fixed cardiac output lesions: a slow, titrated epidural is gentler than a single-shot spinal but still needs care.
• Sepsis, spinal deformity, previous spine surgery and pre-existing neurological deficits need individual judgement.
• A patient who cannot cooperate or stay still during insertion raises the risk of dural puncture and nerve injury.

Equipment and preparation

• Consent, intravenous access and standard monitoring; vasopressors and resuscitation equipment ready.
• Full sterile technique: antiseptic, drape, gown, gloves, mask and hat.
• Epidural needle with a blunt curved tip (for example 16- or 18-gauge) marked in centimetres, and a catheter with a filter.
• Loss-of-resistance syringe filled with saline or air.
• Local anaesthetic and opioid solutions labelled for epidural use only; an infusion pump with a dedicated, labelled line.

Step by step (and why)

1. Confirm consent, anticoagulant timing and platelets when relevant — a haematoma under the cord can cause paraplegia.
2. Start monitoring and secure intravenous access — hypotension or toxicity may need treatment within seconds.
3. Position sitting or lateral with the back flexed and choose the interspace for the surgery — the block spreads from that level.
4. Prepare the skin aseptically and infiltrate local anaesthetic — infection of the space is rare but serious.
5. Advance the needle with constant pressure on the syringe until resistance is suddenly lost — this marks the epidural space.
6. Thread the catheter a few centimetres into the space and remove the needle — too deep and it may exit a foramen or enter a vein.
7. Aspirate, then give a test dose and watch — blood, fluid, a rising heart rate or rapid leg block warn of a misplaced catheter.
8. Give the main dose in small increments and check the level — divided doses limit toxicity and hypotension.
9. Secure and label the catheter and the line — wrong-route injection of an intravenous drug or vice versa is a known error.
10. Assess the block, blood pressure and sedation regularly — catheters migrate and blocks wear off or spread.

Spinal compared with epidural

Complications

• Hypotension from sympathetic block, slower in onset than with a spinal.
• Failed, patchy or one-sided block, often from catheter position; it may need withdrawal or re-siting.
• Accidental dural puncture with post-dural puncture headache; injection through it can cause a high or total spinal block.
• Intravascular injection causing local anaesthetic systemic toxicity; respiratory depression and itching from opioids.
• Rare but serious: epidural haematoma or abscess with cord compression, and nerve injury.

Next step

• Record depth of the space, catheter length in the space, test dose result and block level.
• Hand over the epidural to the ward with a clear plan: monitoring, who to call, and when the catheter may be removed.
• Call a senior for signs of toxicity, a block spreading too high, or new leg weakness that does not fit the infusion.
• Stop the infusion and get an urgent scan and surgical review for back pain with new weakness, numbness or bladder change.
• Remove the catheter only when anticoagulant timing allows, and check the tip is intact.

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Elsewhere in DurgiPedia

• Patient-controlled and epidural analgesia: the nursing checks
• Clean and sterile technique: medical and surgical asepsis
• Pain and temperature: pathways and modulation
• Lumbar puncture

Connections

← 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: Epidural Anesthesia (StatPearls (NCBI Bookshelf), 2025).

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Representative model, for educational purposes only.