An epidural anaesthetic is an injection of medication(s) (administered by an
anaesthetist doctor), into the 'epidural space', usually into the lower (or 'lumbar') area of the spine. The epidural space is a 'potential' space that can be expanded up to about 4mm in width. The space surrounds the spinal cord and is located just outside a layer of tissue called the 'dura mater'. The dura mater tissue encases the spinal cord and spinal fluid. Large nerves that transmit pain, heat and touch sensations, enter and leave the spinal cord via the epidural space.
When using an epidural for a Caesarean birth, more concentrated (and often different mixtures) of medications are given, compared to an epidural used for pain relief in labour. If an epidural is already in place before the Caesarean is decided upon, then more medications will be added (or 'topped up') to make the epidural more effective for the operation.
The medications used for an epidural anaesthetic are usually a mixture of 'local' types of anaesthetics, such as lidocaine, bupivacaine and tetracaine, and narcotic types of drugs such as Fentanyl, Sufentanil and Morphine.
Epidurals are a form of what is called 'regional anaesthesia'. This means they are aimed at preventing pain sensations (and to a degree, touch and temperature sensations) from being felt in a 'region' of the body. An epidural affects the lower region of the body. The medications injected into the epidural space for a Caesarean birth are intended to prevent pain being felt by the woman during the operation. An epidural is often referred to as an 'epidural block' (or an 'EDB'), as they work by 'blocking' pain sensations.