Serious complications may occur with epidural anaesthesia.

  • Hypotension

Is the commonest side effect. It is common in labour and Caesarean Section. It is corrected promptly using fluid and medication to contract blood vessels wall. It presents often with nausea, which may occur before a change in blood pressure has even been detected.

  • Inadvertent high epidural block

An excessively large dose of local anaesthetic in the epidural space may present with hypotension, nausea, sensory loss or paraesthesia of high thoracic or even cervical nerve roots (arms), or difficulty breathing due to blockade of nerve supply to the intercostals ‘between ribs’ muscles. These symptoms can be very distressing to the patient and in the most severe cases may require induction of general anaesthesia with securing of the airway, while treating hypotension. If the patient has a clear airway and is breathing adequately they should be reassured and any hypotension immediately treated. Difficulty in talking (small tidal volumes due to phrenic nerve ‘diaphragm nerve’ block) and drowsiness are signs that the block is becoming excessively high and should be managed as an emergency - see total spinal.

  • Local anaesthetic toxicity

Can also occur as a result of 

  • Excessive local anaesthetic in the epidural space  
  • Inadvertent injection of local anaesthetic into an epidural vein

Symptoms usually follow a sequence of light-headedness, tinnitus, circumoral tingling or numbness and a feeling of anxiety or "impending doom", followed by confusion, tremor, convulsions, coma and cardio-respiratory arrest. It is important to recognise these symptoms early, and discontinue the further administration of local anaesthetic drugs. Treatment should be supportive, with the use of sedative/anticonvulsants when necessary, and cardiopulmonary resuscitation if required.

  • Total spinal

Is a rare complication occurring when the epidural needle, or epidural catheter, is advanced into the subarachnoid space without the operator's knowledge, and an "epidural dose" e.g. 10-20 ml of local anaesthetic is injected directly into the CSF. The result is profound hypotension, apnoea, unconsciousness and dilated pupils as a result of the action of local anaesthetic on the brainstem. The use of a test dose should prevent most cases of total spinal, but cases have been described where the epidural initially appeared to be correctly sited, but subsequent top-up doses caused the symptoms of total spinal. This has been ascribed to migration of the epidural catheter into the subarachnoid space, although the precise mechanism is uncertain.

Management of total spinal: Secure airway, Administer 100% oxygen - Ventilate by facemask and Intubate. Circulation - treat with i/v fluids and vasopressor e.g. ephedrine 3-6mg or metaraminol 2mg increments or 0.5-1ml adrenaline 1:10 000 as required Continue to ventilate until the block wears off (2 - 4 hours) As the block recedes the patient will begin recovering consciousness followed by breathing and then movement of the arms and finally legs. Consider some sedation (diazepam 5 - 10mg i/v) when the patient begins to recover consciousness but is still intubated and requiring ventilation.

  • Accidental dural puncture

Is usually easily recognised by the immediate loss of CSF through the epidural needle. This complication occurs in 1-2% of epidural blocks, although it is more common in inexperienced hands. It leads to a high incidence of post dural puncture headache, which is severe and associated with a number of characteristic features. The headache is typically frontal, exacerbated by movement or sitting upright, associated with photophobia, nausea and vomiting, and relieved when lying flat. Young patients, especially obstetric patients, are more susceptible than the elderly. The headache is thought to be due to the leakage of CSF through the puncture site. Basic measures, such as simple analgesics, caffeine, bed rest, fluid rehydration and reassurance are indicated in the first instance, and are often sufficient to treat the headache. Where the headache is severe, or unresponsive to conservative measures, an epidural blood patch may be used to treat the headache. This procedure is effective in treating approximately 90% of post dural puncture headaches. If unsuccessful, the blood patch may be repeated, and the success rate increases to 96% on the second attempt. The blood injected into the epidural space is thought to seal the hole in the dura.

 

Epidural blood patch

Indications: Clinical diagnosis of post dural puncture headache. Sufficiently severe so as to be incapacitating. Unrelieved by 2-3 days of conservative management.

Contraindications: 

Unexplained neurological symptoms 

Active neurological disease 

Localised sepsis in lumbar area 

Generalised sepsis 

Coagulopathy

 

  • Epidural haematoma

Is a rare ( 1in 170,000 epidural) but potentially catastrophic complication of epidural anaesthesia. The epidural space is filled with a rich network of venous plexuses, and puncture of these veins, with bleeding into the confined epidural space, may lead to the rapid development of a haematoma which may lead to compression of the spinal cord, and can have disastrous consequences for the patient including paraplegia. For this reason, coagulopathy or therapeutic anticoagulation with heparin or oral anticoagulants has long been an absolute contraindication to epidural blockade.

  • Infection

Is another rare ( 1 in 145,ooo epidural) but potentially serious complication. Meningitis has been described, as has epidural abscess. In addition to the symptoms of spinal cord compression described above, the patient may exhibit signs of infection such as pyrexia and a raised white cell count. 

 

Once again, a high index of suspicion is needed, and surgical decompression of an abscess should be performed without delay.

  • Persistent (more than one year) neurological injury

Occurred at a rate of about 1 in 240,000 women in larger, more recent studies. 

  • Transient (less than one year) neurological injury

Occurred at a rate of about 1 in 6,000 in larger, more recent studies. In individual studies the risk of transient neurological injury varied between about 1 in 100 to more than 1 in a million (Figure 1), though larger studies tended to be more consistent. 

  • Failure of Epidural Anaesthesia.

Can be due to:

Anaesthetist lacks experience 

The epidural catheter is inserted into an area other than the epidural space. 

Segmental sparing ‘patchy areas not anaesthetised’ 

Occurs occasionally ‘local anaesthetic fails to spread evenly throughout epidural space’  as a result of anatomic variation of the epidural space. The result is that some nerve roots are inadequately soaked with local anaesthetic, leaving the skin supplied with these nerve roots poorly anaesthetised. 

Unilateral ‘one side’ blockade occurs occasionally, and this is thought to be the result of a partitioned epidural space, with failure of the local anaesthetic solution to spread to one half of the epidural space. Positioning the patient on her side with the unblocked side down is sometimes successful in allowing spread of the local anaesthetic to the dependent side, giving bilateral anaesthesia. 

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