What is a peripheral nerve block?
A peripheral nerve block is an injection of local anaesthetic around nerves, which makes the area of your body numb.
Your operation can be done with just a nerve block as your anaesthetic. A nerve block can be combined with a general anaesthetic to provide pain relief following your operation.
Sometimes we perform nerve blocks simply to relieve pain caused by injuries.
How is a nerve block performed?
As preparation for the nerve block, you will be instructed to fast as you would do for a general anaesthetic. You will be attached to routine monitors and a small tube (cannula) inserted into your vein. Nerve blocks are commonly performed while you are awake but light sedation can be given. An ultrasound machine or a nerve stimulator may be used to locate the nerves before injecting local anaesthetic via a small needle.
After the injection, the targeted area will feel warm and tingly, gradually becoming numb over 20 to 40 minutes. We confirm the block has worked before surgery starts.
Sometimes a fine tube is inserted next to the nerves so we can keep delivering local anaesthetic and provide long lasting pain relief after the operation – this is called a nerve catheter.
Why should I have a nerve block?
Nerve blocks have many benefits.
- Better pain relief after your operation
- You are more comfortable.
- You may mobilise and recover faster.
- You have less need for strong pain relief and their side effects e.g., nausea or drowsiness.
- Some patients, for example, those with severe heart or lung disease would pose a very high risk under general anaesthetic – nerve blocks are sometimes a lower risk option.
- These benefits may lead to a reduced stay in hospital.
Can I say ‘no’ to a nerve block?
Yes. Your anaesthetist will discuss your preferences, outline alternative methods of anaesthetic and pain relief, and together you can decide on the best plan. However, you may be advised to have a nerve block if this is a lower risk option.
What happens if the nerve block does not work?
Occasionally (less than 1 in 100) the block is unsuccessful. If this happens, we can give more local anaesthetic around the nerves or at the operation site to ensure complete numbness. If required, a general anaesthetic can be administered together with alternative pain-relieving medicines.
Are there any risks to having a nerve block?
Despite your anaesthetist’s experience, and use of ultrasound to guide the injection, risk cannot be removed completely. The anaesthetist will explain the risks specific to the proposed nerve block; these should be balanced against the risk of alternatives such as a general anaesthetic.
- All injections: can cause bleeding which usually resolves with a small amount of pressure.
- Injections around the neck: may cause a droopy eyelid, hoarse voice, blurry vision or mild breathlessness. These will resolve when the nerve block wears off.
- Injections around the neck, collarbone or chest wall: rarely (less than 1 in 1,000) involve damage to the covering of the lungs requiring further treatment.
- Infection: precautions are taken to minimise the risk of infection.
- Very rarely: these include allergic reaction, seizures (fits) or other life-threatening emergencies. Your anaesthetist is trained to manage these problems promptly.
- Nerve injury: this is failure of the nerves to function normally after the block should have worn off; this is experienced as numbness, tingling or very rarely weakness. Short-term nerve injury (longer than 48 hours) occurs in less than 1 in 10 (<10%) nerve blocks.
Risk varies between the different blocks. The vast majority of those affected (92–97%), recover within four to six weeks and 99% within a year.
Permanent nerve injury is rare with estimates between 1 in 2000 and 1 in 5000 as precise numbers are not available. You should note that the risk of nerve damage is present in any operation regardless of the type of anaesthetic. This can be due to the operation itself, positioning for the operation or the use of the tourniquet.
What happens during the operation?
An operating theatre is a busy place with between five and eight people in theatre looking after you.
If you are awake, a screen is used, so you do not need to see the operation being done. A member of staff sits with you so if you had a problem, they would immediately help you. Your anaesthetist remains close by.
What happens after the operation?
The nerve block can last from 2 to 36 hours depending on the injection site and type of local anaesthetic used. During this time, you may feel the following: numbness, tingling, weakness or inability to move your arm or leg. Usually, the weakness wears off first followed by return of sensation.
Until normal sensation has returned:
Protect your limb from excessive heat or cold and avoid placing it in abnormal positions.
Keep your leg or arm well supported, avoiding excessive pressure.
Do not mobilise without support if your nerve block involves the foot or leg.
Avoid doing things for example, using machinery which could injure you while you cannot feel your limb.
If your pain is not controlled by the pain relief given, please seek medical help or visit your nearest A&E.
If your nerve block injection was performed near your collar bone, neck or chest wall and you experience severe breathlessness, please contact emergency services, or visit your nearest Accident and Emergency (A&E) department.
You may be contacted by hospital staff after your discharge to check on your wellbeing. If you have not been contacted but you continue to have numbness or weakness in your limb after 36 hours, please contact the hospital switchboard on 01642 850850 and ask for the anaesthetics registrar on call.
Further information about nerve blocks and anaesthesia in general is available at
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This service is based at The James Cook University Hospital but also covers the Friarage Hospital in Northallerton, our community hospitals and community health services.