Epidurals for surgery and pain relief

Published by Bupa's Health Information Team, June 2010.

This factsheet is for people who are having an epidural to provide anaesthesia for surgery, and/or to control pain afterwards, or who would like information about it.

An epidural is an injection of local anaesthetic or other pain-relieving medicines into the epidural space that surrounds the spinal cord, temporarily numbing the nerves.

You will meet the anaesthetist carrying out your epidural to discuss your care. It may differ from what is described here as it will be designed to meet your individual needs.

About epidurals for surgery and pain relief

Epidural anaesthesia (also called regional anaesthesia) stops you feeling pain without putting you to sleep.

Epidural anaesthesia is often used as an alternative to general anaesthesia for surgery in your pelvic area or legs. Advantages include being awake and responsive during the operation, less nausea and vomiting, and a quicker recovery afterwards. There may also be a lower risk of you developing a blood clot in a vein in your leg (deep vein thrombosis).

Alternatively, you may be given an epidural at the end of an operation that has been done under general anaesthesia to help control any post-operative pain. It may be left in for a few days to provide you with continuing pain relief after the operation.

An epidural is unlikely to be suitable for you if you have a blood-clotting problem or have had a previous operation on your back. You must tell your anaesthetist if you're taking blood-thinning medicines such as aspirin, warfarin or clopidogrel.

How does an epidural work?

Your spinal cord runs through a channel formed by your vertebrae (irregular-shaped bones in your spine) and is surrounded by three protective layers of tissue called the meninges. A protective layer of fluid lies between two of these tissue layers (this is known as the cerebrospinal fluid or CSF). The area just outside all these layers is called the epidural space.

Your spinal cord carries signals, in the form of electrical impulses, between your brain and the network of nerves that branch outwards from your spine to all parts of your body. At each level of your spine, nerves leave your spinal cord to go to specific parts of your body. For example, nerves from the lower part of your body join your spinal cord in your lower back.

Injecting local anaesthetic into the epidural space in your lower back temporarily blocks the nerves in your spine that lead to the lower part of your body and therefore blocks feeling in your pelvic area and legs. Your anaesthetist can control how much feeling is lost, depending on the amount, strength and type of solutions used.

Injections and infusions

A single injection into your epidural space can be used for short-term pain relief. The local anaesthetic wears off within a few hours and feeling in the affected area returns.

Alternatively, a continuous flow of pain-relief medicines can be given through a fine plastic tube (cannula) placed in your lower back and attached to a pump. This is known as an epidural infusion and is useful for longer operations or for providing pain relief over several days.

After some operations, you may be allowed to control the infusion yourself by pressing a button on an epidural pump. This is called patient-controlled analgesia or PCA.

What are the alternatives?

Alternatives to epidural anaesthesia during surgery include spinal anaesthesia and general anaesthesia. Spinal anaesthesia involves your anaesthetist injecting local anaesthetic into the fluid that surrounds the nerves in your lower back. Spinal anaesthesia lasts around two hours and can't be topped up. General anaesthesia means you're asleep during the operation.

Painkilling medicines such as diamorphine or morphine can be used instead of an epidural to provide pain relief immediately after surgery. You may be given painkilling medicines into a vein through a drip. This method can also be patient controlled.

Preparing for an epidural

Your anaesthetist will discuss with you what will happen before, during and after your procedure, and any pain you might have. This is your opportunity to understand what will happen, and you can help yourself by preparing questions to ask about the risks, benefits and any alternatives to the procedure. This will help you to be informed, so you can give your consent for the procedure to go ahead, which you may be asked to do by signing a consent form.

You will stay awake during the procedure, but you may be offered a sedative (calming medicine) to help you relax.

What happens during an epidural

You will be asked either to lie on your side, with your knees drawn up to your tummy and your chin tucked in, or to sit up on the bed and lean forward. Both positions open up the space between your vertebrae.

Your anaesthetist will carefully select a point to inject by feeling for specific bones in your spine and hips. He or she will inject a small amount of local anaesthetic into your skin.

When your skin is numb, your anaesthetist will pass a larger epidural needle into the epidural space. When the needle reaches the correct spot, he or she will insert a cannula through the centre of the needle. Your anaesthetist will remove the needle and the cannula will be left in place running from the epidural space to the outside of your body.

Where the epidural is positioned

Your anaesthetist uses the cannula to inject local anaesthetic and/or other pain-relieving medicines directly into the epidural space. Your anaesthetist may attach a pump to the cannula to give a continuous infusion of medicines.

It's very important to stay still while your anaesthetist is preparing the site for the epidural injection and especially while the epidural needle is being inserted.

When you no longer need any pain relief, the cannula is carefully withdrawn and the area covered with a plaster.

What to expect afterwards

After an epidural you will need to rest until the effects of the anaesthetic have passed. You may not be able to feel or move your legs for several hours. However, you won't experience the drowsiness that usually follows a general anaesthetic.

What are the risks?

Epidurals are commonly performed and generally safe. However, in order to make an informed decision and give your consent, you need to be aware of the possible side-effects and the risk of complications of the procedure.

Side-effects

These are the unwanted, but mostly temporary effects of a successful procedure. Common side-effects are listed here.

• Inability to pass urine because of the numbing of nerves to your bladder. You may have a temporary catheter fitted until the effects of the epidural pass. This is a thin tube used to drain urine from your bladder into a bag outside your body.
• Nausea and vomiting. However, this is less common than with general anaesthesia.
• Backache. This usually only occurs in people who already had a back problem.
• A drop in blood pressure. Your blood pressure will be checked regularly. If it drops, you may be given medicines to correct it.
• Loss of strength or control of your muscles. You may not be able to move your legs or arms, depending on the location of the epidural. This wears off with the anaesthetic.
• Imbalance in pain relief. Sometimes the medicine doesn't spread equally around your spinal cord, meaning that one half of your body is more anaesthetised that the other. A top-up dose can usually correct this.
• Itchy skin. This is an allergic reaction and your anaesthetist will change the medicine to deal with this.

Complications

This is when problems occur during or after the procedure. Most people aren't affected. With any procedure involving anaesthesia there is a very small risk of an unexpected reaction to the anaesthetic. Complications specific to an epidural are uncommon but can include the following.

• Headache. The epidural injection may puncture the membrane covering your spinal cord and fluid can leak out. This puts pressure on the surrounding nerves causing headaches. Headaches can last up to a week and sometimes longer, but can be treated.
• Infection. This is rare because your skin is cleaned before the (sterile) needle is inserted. If you develop an infection, you may need to have the infected area drained and you may also need to take antibiotics.
• Long-term numbness. You may have temporary patches of numbness. Permanent damage, such as paralysis (complete loss of sensation and movement), is extremely rare.

The exact risks are specific to you and differ for every person, so we have not included statistics here. Ask your anaesthetist to explain how these risks apply to you.

For answers to frequently asked questions on this topic, see Common questions.

For sources and links to further information, see Resources.