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.

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.

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.

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

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.

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.

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

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.