What is a nerve block?

An injection of local anaesthetic that numbs the nerves that supply feeling to the site in your arm or hand that you are having surgery on. Your arm and hand will go numb, and the strength of feeling will be reduced.

How is it done?

Having a nerve block is not very painful. It can be performed while you are fully awake, or your anaesthetist can give you some sedation to help you to relax.

The procedure is usually performed in the anaesthetic room where you will be connected to equipment that monitors your heart rate, blood pressure and oxygen levels. Your anaesthetist will place a cannula (a thin plastic tube) in a vein on the back of your hand or in your arm. You will be lying on a bed.

Once cleaned, a small amount of local anaesthetic will be used to numb the skin where the rest of the nerve block will be performed.

Your anaesthetist will use an ultrasound machine to see the nerves they want to numb. They will then inject local anaesthetic around the nerves. You might feel pressure during this injection. Initially your arm will feel warm and tingly. Within 20 minutes, it will become numb and feel heavy.

What are the advantages of having nerve block?

Nerve blocks are very low risk procedures that provide numbness during surgery. In most cases, surgery will be performed while you are awake. In some cases, surgery is performed with some sedation or a general anaesthetic in addition to the nerve block. Your anaesthetists will discuss these options with you prior to surgery.

Having a nerve block means you do not have to have a general anaesthetic and you can avoid the risks and side effects associated with one, for example, feeling sleepy or sick after your surgery. This also means that you are likely to go home much sooner after the surgery and can get on with your normal, everyday life more quickly.

You are also unlikely to need strong painkillers and should only need over-the-counter medications such as paracetamol and ibuprofen. This means that you can avoid the side effects of stronger painkillers (for example, nausea, constipation and feeling woozy).

You may want to bring a music player, so that you can listen to music while you are having the block and during surgery.

Nerve block side-effects

Nerve blocks are routine and very safe procedures. Side-effects are extremely rare but include:


It is possible to insert the injection needle into a blood vessel and cause some localised bleeding (like when you have a blood test). Applying pressure to the site of the blood vessel usually stops it.

Failure of the nerve block

The numbness of your arm will be checked before starting surgery. Very occasionally the block does not work fully. This may be due to the operation affecting a larger area than expected or due to technical difficulty. Your anaesthetist will be with you throughout the operation. If at any time you are uncomfortable or unhappy in any way, then please tell them.

There are lots of options available to help in this situation, including:

  • Injection of more local anaesthetic
  • Extra painkillers
  • Sedation

If none of these work adequately, or are not appropriate, then a general anaesthetic may be considered.


Antiseptic will be used to clean your skin first. All the equipment used by your anaesthetist to carry out the nerve block will be sterile to avoid causing any infection.

Nerve damage

About 1 in 10 patients notice a patch of numbness or tingling in their arm after the nerve block has worn off.  This usually lasts between a few hours and a few days. 

In somewhere between 1 in 1000 and 1 in 5000 people these sensations last longer. Studies have shown that in 95% of cases everything has gone back to normal within four to six weeks, and in 99% within a year.

The risk of long-term nerve damage caused by a nerve block is difficult to measure. Your nerve may have been damaged in the injury that you have suffered. Surgery itself can result in nerve damage as well (the risk of this is something that your surgeon can discuss with you).

Allergic reaction to local anaesthetics (extremely rare)

Allergies to local anaesthetics are incredibly rare. Your anaesthetist has been trained to deal with such events and will manage them promptly if they occur.

On the day of surgery

You will be advised to stop eating and drinking just as you would for a general anaesthetic. This is important in case of any complications or if a general anaesthetic is unexpectedly needed.

Can I have anything to eat on the day of surgery?

If you have been told to attend the hospital at any time before 11.30am then you cannot eat anything from midnight before the surgery.

If you have been told to come in at any time after 11.30am then you can have a light breakfast (such as toast, cereal, fruit, or yoghurt) if you have finished eating it by 6.30am.

Can I have anything to drink?

You can and should drink clear fluids until the time you leave your home to come to the hospital. It is better for you to keep hydrated and, if you follow these instructions, your surgery will not be delayed because you have had a drink.

What are the clear fluids that I can drink?

Examples of clear fluids that you can drink before your procedure:

  • Water.
  • Black coffee or black tea (including herbal tea).
  • Cordial or “squash”.

You should not drink any of the following on the day of your surgery:

  • Fruit juice.
  • Milk.
  • Coffee or tea with milk.


After the surgery, you will go to the recovery room if you had a general anaesthetic or sedation. If you did not, then you can go straight back to the ward. You won't be able to move or feel your arm and hand. Some people find this a bit strange but get used to it. They are usually pleased to feel little or no pain.

Management of your “numb” arm

The effects of the local anaesthetic will last between four and 24 hours. You will be given a sling to wear. You should keep your “numb” arm in the sling until normal feeling and power return in your arm. Your arm should be protected from heat and pressure, and you should avoid extremes of movement.

You should take care not to come into contact with extremely hot or cold items because you will not be able to protect your arm from injuries of extremes of temperature. You may be required to wear the sling for a longer period if the surgeons request this.

What to do when the block wears off

You will be given pain medication to take home with you. You should start taking these regularly as directed before the block starts to wear off. As the block wears off it is normal to experience tingling in your arm or hand as movement and sensation returns.

Further information

Not all anaesthetists perform nerve blocks. Your anaesthetist on the day will decide what is the most suitable form of anaesthetic.

If you have any questions, please ask your anaesthetist, your surgeon, or your nurses. Your anaesthetist will see you on the day of your operation and will be able to answer your questions. It might be useful to note them down in advance.