What is an epidural?
An epidural is a spinal procedure that delivers anaesthetic or painkilling drugs to the nerves that convey pain.
It is often used while women are in labour to ease the pain of childbirth. It is also commonly used to numb women while they have a Caesarean section.
The name ‘epidural’ comes from its place of delivery into the body, the spine. The spinal cord is surrounded by cerebrospinal fluid which helps protect and cushion the brain and spinal cord from damage. The fluid is held within a tough sheath called the dura, which means ‘hard’ or ‘tough’. However, the spinal cord and the dura do not run all the way down the entire length of the spinal canal: they come to an end at the first lumbar vertebra (one of the bones of the back).
An epidural is delivered to the area of the spinal canal that is not protected by the dura, known as the epidural space. This space contains the spinal nerves which then pass up the spinal cord to the brain. Epidural literally means ‘above the dura’, so some doctors prefer to call it an ‘extradural’ or ‘peridural’ which mean ‘outside the dura’.
A skilled anaesthetist can control the amount of pain relief or numbness you receive, while still allowing you to retain some sensation and some movement.
This is because the nerve fibres that transmit pain are relatively thin, compared with the nerve fibres that allow movement of the skeletal muscles or the sensation of touch, which means the ‘pain’ nerve fibres are affected by the anaesthetic more quickly. In addition, the anaesthetist can adjust the strength of the anaesthetic to offer a fine balance between pain relief and the ability to move.
What happens when you have an epidural?
Before your epidural, you will usually need to have an intravenous ‘drip’ inserted into your arm so that you can be given fluids. This is just a safety precaution.
The anaesthetist will ask you to sit hunched forward over a pillow or curled on your side. This is to allow the spaces between the bones of your spine to open up as much as possible so that the anaesthetist can find the epidural space more easily. It is vital not to move throughout the procedure.
After cleaning the skin with antiseptic, the anaesthetist will inject some local anaesthetic into your back (which may cause a slight stinging or burning sensation) before inserting an epidural needle into the gap between two of your vertebrae (bones) of the spine to reach the epidural space. When the epidural needle is inserted you may feel a pushing sensation, but it will not hurt.
A catheter is then inserted through the needle before the needle is taken out. The catheter, which is taped to the skin, then allows the anaesthetist to deliver the anaesthetic and top it up, if required, to keep you numb.
The exact procedure for an epidural may vary from hospital to hospital. An epidural may take up to about half an hour to be administered and take effect, depending on the strength of the anaesthetic delivered. You are still conscious but cannot feel any pain.
The effects of an epidural anaesthetic do wear off, but how long they last depends on the strength of the anaesthetic delivered and how much of it you were given: it takes several hours for an anaesthetic to be eliminated from the body.
What are the advantages of an epidural?
If you are having a Caesarean, having an epidural means you can avoid the side effects of a general anaesthetic: you won't have a sore throat or need to cough up any fluids, and you won't feel groggy or hazy afterwards.
It also means that you can be awake throughout the surgery, so you can experience your child's birth as fully as possible. And the epidural can remain in place to deliver painkilling drugs such as morphine or pethidine after the surgery, although different hospitals may have different policies about offering this as an option.
Opinions vary about the use of epidurals in conventional delivery. However, for some women in the throes of labour, an epidural can provide welcome pain relief and allow them to relax enough to enjoy giving birth. It is usually possible to still feel that contractions are occurring, and to feel the urge to push.
You can usually choose whether to have an epidural or not, and when to have one during labour, but be aware that it does take up to about half an hour to be administered and to take effect. While an epidural can be given at any stage during labour, they are usually not performed once the baby has entered the birth canal (stage 2 of labour) because the baby is usually born very soon after this occurs.
What are the disadvantages of an epidural?
If you are in labour, trying to give birth vaginally, an epidural may slow down your labour or numb you so much that you don't have enough muscle control to push your baby out. This means that there is an increased risk of having a forceps or vacuum-assisted delivery when an epidural is used.
Having an epidural means that you'll need to have a drip inserted in your arm, and your baby may also need more frequent monitoring.
Among the side effects of epidural anaesthetic is that your blood pressure may drop, which could affect how much blood, and therefore oxygen, is delivered to your baby via the placenta. And because an epidural can affect your body's temperature control system, some women feel shivery.
It is also possible, though rare, that the epidural may be delivered to the wrong place in your spine, resulting in a painful so-called ‘spinal headache’ afterwards. These headaches are worse when you stand up, so if this happens you usually need to remain lying down for a day or 2.
Last Reviewed: 03/07/2009
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