Epidurals for surgery and pain relief

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. This factsheet doesn’t include information about epidural for childbirth, or for the relief of chronic back pain and sciatica.

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

Your anaesthetist will discuss your care with you before your procedure, including what the epidural involves. There may be some differences from what is described here depending on your individual needs and particular operation.

About epidurals for surgery and pain relief

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

Epidural anaesthesia can be used alone as an alternative to general anaesthesia for some forms of surgery, usually in your pelvic area or legs. This means you won’t have the risks and side-effects of general anaesthesia, such as feeling sick and vomiting, or dental damage. Also, you will be able to stay awake during the operation and are more likely to recover faster.

Alternatively, an epidural may be combined with general anaesthesia for major upper abdominal surgery and can be left in for a few days to provide you with continuing pain relief after the operation.

An epidural may not be suitable for you if you have had previous back surgery or have a blood-clotting problem. For this reason, 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 is the main nerve pathway of your body and runs through a protective channel within your vertebrae (the bones in your spine). It’s surrounded by three layers of tissue called the meninges. The cerebrospinal fluid (CSF) lies between the inner two of these tissue layers, cushioning your spinal cord. Just outside the third tissue layer (or dura) lies the epidural space, which is very close to the nerves.

Your spinal cord carries signals, in the form of electrical messages, between your brain and 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 stops the messages in your spinal nerves that cause sensation in the lower part of your body, therefore blocking the feelings in your pelvic area and legs. Your anaesthetist can control how much feeling is lost, depending on the amount, strength and type of medicines used.

Injections and infusions

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

More often, a continuous flow of pain-relief medicines is given through a fine plastic tube (catheter) placed into the epidural space through 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 given control of the infusion by pressing a button on an epidural pump. This is called patient-controlled epidural analgesia (PCEA).

What are the alternatives?

Alternatives to epidural anaesthesia that are used for surgery include spinal anaesthesia and general anaesthesia. Spinal anaesthesia is related to epidural anaesthesia and involves your anaesthetist injecting local anaesthetic directly into the CSF that surrounds the spinal nerves in your lower back. General anaesthesia means you're asleep during the operation.

Instead of having epidural pain relief, you can be given other painkilling medicines, such as morphine, immediately after surgery. You may be given morphine into a vein through an intravenous (IV) drip. This method can also be controlled by you and then it’s called patient controlled analgesia (PCA).

Preparing for an epidural

Your anaesthetist will discuss with you what will happen before, during and after your procedure, including any pain relief you may need. 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.

If you’re having an epidural without general anaesthesia, you can stay awake during the procedure, but you may be offered a sedative 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 abdomen and your chin tucked in, or to sit up on the bed and lean forward. Both positions open up the space between your vertebrae making it easier and quicker for your anaesthetist to place the epidural.

Your anaesthetist will carefully select a point to inject by feeling for specific bones in your spine and hips. Your anaesthetist will clean the skin on your back with a sterilising solution and give you an injection of local anaesthetic to numb the tissues in this area. He or she will also cover your back in a sterile drape, with a square hole around the site of the epidural.

When your skin is numb, your anaesthetist will pass a larger, hollow epidural needle into the epidural space. When the needle reaches the correct spot, he or she will insert a catheter through the needle. Your anaesthetist will then remove the needle and the catheter will be left in place running from the epidural space to the outside of your body. It will be held in place with adhesive tape.
 

Where the epidural is positioned

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

It's very important to stay still while the epidural needle is being inserted, but you must say if it’s hurting you, particularly if this is in your legs because this helps your anaesthetist to carry out the procedure safely.

When you no longer need any pain relief, the catheter 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 properly for several hours and you mustn’t try to stand until your doctor or nurse says you can, as you may fall and injure yourself. However, you won't experience the drowsiness that usually follows general anaesthesia.

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 inserted until the effects of the epidural wear off. This is a thin tube used to drain urine from your bladder into a bag outside your body.
• Feeling sick and vomiting. However, this is less common than with general anaesthesia.
• A drop in blood pressure. Your blood pressure will be checked regularly. If it drops, you may be given medicines to raise it up to normal.
• 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 after your operation.
• 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.
• A bruise on your skin where the epidural needle was placed.

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 CSF can leak out. This means there is less fluid around your brain, causing headaches. You may have headaches for up to a week or sometimes longer, but this 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.
• Bleeding. Very rarely blood clots can form in the epidural space, which if not detected can cause permanent injury. You will be monitored to reduce this risk to a minimum.
• Long-term numbness. You may have temporary patches of numbness. Permanent damage, such as paralysis (complete loss of sensation and movement), is extremely rare.

As with every procedure, there are some risks associated with an epidural. We have not included the chance of these happening as they are specific to you and differ for every person. Ask your surgeon or anaesthetist to explain how these risks apply to you.

Produced by Louise Abbott, Bupa Health Information Team, April 2012. 

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

For sources and links to further information, see Resources.