What is a nerve block?

Nerve block, also known as regional anaesthetic, is an injection of local anaesthetic by your anaesthetist to “block” the nerve or a group of nerves that supply the area of your body where your operation will be.

How is a nerve block used?

Nerve blocks for shoulder, arm and hand surgery can be made to last up to 24 hours. The nerve block may be part of your general anaesthetic to give you pain relief after your operation.

Some operations can be done under nerve blocks alone. Sedation can be given with this to make you feel relaxed and comfortable.

Certain drugs or medical conditions may make blocks unsuitable for you. Your anaesthetist will discuss these with you on the day of your operation.

What nerves are blocked?

In the case of shoulder, arm or hand surgery, a group of nerves known as the “brachial plexus” will be blocked. These nerves run between your neck and armpit. For some surgery, the nerves further down in your elbow or forearm can be blocked. Where the block injection is will depend on the site of your operation and will be explained by your anaesthetist.

What are the benefits of having a nerve block?

These include:

  • Better pain relief. You are less likely to need strong pain killers after your operation, avoiding their side effects like nausea or sleepiness and confusion.
  • If your operation can be done under a block alone, you can avoid the risks and side effects of a general anaesthetic.
  • You are more likely to go home on the same day after your operation if your pain is well-controlled after a block.

How are blocks performed?

You should prepare for your operation by following the instructions in the letter from your surgeon. This includes following the fasting guidelines.

The nerve block is usually performed in the anaesthetic room. Your heart rate, blood pressure and breathing will be monitored and a cannula (“a drip”) placed into a vein before the block. Medicine is usually given before the block injection to help you relax.

Depending on where the block injection is, an assistant will help you to get into the correct position. This may involve adjusting your pillow, turning your head or raising your arm. Some blocks may be done when you are under general anaesthetic; your anaesthetist will discuss this with you on the day.

The skin will be cleaned and the area numbed before the injection. The nerves are located using an ultrasound machine or a very small machine that makes your arm muscle twitch. A very fine block needle is used to give the local anaesthetic to block the nerves.

For most patients, the injection is no more painful than having the cannula in your vein or bloods taken. Once the injection is done, your arm may start to feel warm, tingly or numb but it can take 20 to 40 minutes for the block to work fully.

What are the risks and side effects of having a block?

Block injections are generally very safe but there are still risks to be aware of. Common side effects including bruising or discomfort around the injection site are usually short-lived.

Other side effects are related to the spread of local anaesthetic around the injection site or the placement of the block needle. Bleeding may occur if a blood vessel is damaged but can usually be treated by putting pressure on the injection site.

More specific side effects to be aware of:

For injection at the side of your neck or behind your collar bone: hoarse voice, droopy eyelid or difficulty in breathing (the nerve that supplies your diaphragm may be affected by the block). These usually get better as the block wears off. In very rare cases, breathing difficulty may become persistent or permanent (See Nerve injury below). There is a small risk (less than 1 in a thousand) of damage to the lining of the lung. This may require treatment but is rare.

Very rare: life-threatening reactions such as a fit or seizure in reaction to the local anaesthetic are very rare. These require emergency treatments. Your anaesthetist can discuss these with you if you wish to know more.

Nerve injury: nerves can be damaged during surgery, general anaesthetic or a block. It is estimated to happen between 1 in 700 to 1 in 5000 cases where a block is performed. There may be a persistent patch of numbness or tingling after the operation. Uncommonly, there may be weakness in one or more muscles and persistent pain.

These symptoms go away within 4 to 6 weeks in most cases (95%) and within a year in majority (99%). Swelling after the operation or conditions such as diabetes can make nerve damage more likely.

What happens after the operation?

Your arm may be numb for between 4 to 24 hours after your block. It is likely that you will be going home with the arm still numb.

Therefore, it is important to avoid injury by taking precautions whilst the block is still working.

  • Keep your arm in a sling as instructed.
  • Do not drive for at least 48 hours to allow your block to wear off completely. Your surgeon will give you instructions if there are further restrictions on driving depending on the type of surgery.
  • Do not handle sharp instruments or very hot or cold objects until the numbness has worn off to avoid cuts, burns or scalding.
  • Do not put your blocked arm near a radiator, stove or oven.

What happens if a block is not done?

It is perfectly acceptable if you do not want a block for your operation. Occasionally, the block may not work as well as planned. In some cases, it may not be a suitable option.

Your anaesthetist and surgeon can discuss other options with you. These include local anaesthetic injected by the surgeon (but not a nerve block) around the operation site during the operation or different types of pain killers available.

What to do with pain killers?

As the block wears off, you may experience some pins and needles sensation in your arm.

It is important to begin taking regular pain killers as instructed so that they can start to work before the block wears off completely.

This will help reduce the intensity of pain when the block has worn off.

Further information

Information on blocks
Information on nerve damage
Patient information on nerve blocks for leg, foot or ankle surgery