Nerve blocks are often used to provide anaesthesia and postoperative pain relief for surgery on the shoulder, arm or hand. Nerve blocks can also be used for some surgeries on the leg.
What is a nerve block?
“Nerve block” is a general term for injections of local anaesthetic near nerves. Local anaesthetic drugs act to block signals transmitted by the nerve causing numbness (and weakness) of the arm.
For the nerves supplying the shoulder, arm or hand the block is normally done at the side of the neck, near the collarbone or armpit region depending on the exact type of surgery. The nerves supplying the shoulder, arm and hand are gathered together in a structure called the “Brachial Plexus” and so the common term for nerve blocks for shoulder, arm or hand surgery is a “Brachial Plexus Block”.
For leg, ankle or foot surgery the two main nerves supplying sensation to these areas are generally blocked separately, using two techniques - a “Femoral Nerve Block” and a “Sciatic Nerve Block”. These two injections can be done at various points between the groin and the lower leg.
All our nerve blocks are done using a sterile technique to prevent infection and under Ultrasound guidance for maximum accuracy and to minimise complications. Local anaesthetic is given to the skin first so the injections should be no more painful than having an intravenous cannula sited.
Why have a nerve block?
Surgery under nerve block can take place without the need for a general anaesthetic. This avoids the risks of general anaesthesia to the airway, breathing and circulation systems. The common side effects of general anaesthesia such as sore throat, nausea and vomiting and drowsiness are avoided.
For some patients, such as diabetics, the ability to eat and drink normally immediately afterwards is a big advantage and for patients requiring regular oral medication this can be taken afterwards normally.
The other big advantage of a nerve block is very good postoperative pain relief. For certain operations this pain relief can be extended to several days by inserting a catheter (a very narrow plastic tube) at the same time as the nerve block is performed. This can be very useful in certain operations where pain can significantly limit recovery (for example some types of shoulder and upper arm surgery).
In addition to using nerve blocks to provide anaesthesia for surgery it is also common to use nerve blocks in combination with general anaesthesia for operations where a nerve block alone might not provide adequate comfort during the surgery but can provide very good postoperative pain relief.
Can everyone have a nerve block?
Not everyone can have a nerve block. Some operations are not suitable for a nerve block because of where / how surgery is performed. Other operations require intact sensation afterwards. The surgeon and anaesthetist looking after you may judge that a general anaesthetic is more appropriate for you and your surgery. If so this will be explained to you.
A small number of patients have serious medical conditions which may make particular blocks less safe, for example a block for shoulder surgery in someone with significant lung disease. Your anaesthetist will discuss these important issues with you.
Can I decide not to have a nerve block?
Yes you can. If you prefer not to have a nerve block you will be offered a general anaesthetic if possible.
If you prefer not to be awake for your surgery most patients can safely be given some sedation to make you sleepy. The dose can be adjusted between feeling calm and slightly drowsy to being very sleepy, however this is not the same as a general anaesthetic - many patients drift in and out of sleep during the operation - but many patients having sedation have little or no memory of the surgery and are very satisfied with the experience.
What will happen when I have a nerve block?
Patients having nerve blocks for surgery or postoperative pain relief get the same level of care as any other patient having an anaesthetic. When you come to the operating theatre suite you will have safety and consent checks, monitoring will be attached and the anaesthetist will site an intravenous line.
Sometimes you will need to be lying in a particular position for the block, or you arm will need to be in a certain position. You will be told what to do and helped to get into the correct position.
The anaesthetist performing the block will clean the skin with a sterilising solution and wear sterile gloves. The ultrasound probe will be pressed firmly against the skin over the nerves and moved around until a good picture is obtained. A small local anaesthetic injection will be given to skin and then the block needle inserted.
Performance of the nerve block should not be painful. It is important that you tell the anaesthetist if you do feel any pain or discomfort - they will ask you in detail what you are feeling. Nerve blocks are performed in awake patients as what you, the patient, feels can add extra layer of safety to the procedure, minimising the risk of nerve injury.
For many nerve blocks the needle is moved around (under ultrasound control) and several small amounts of local anaesthetic mixture given. This is normal and, again, should not be painful.
Once the anaesthetist is happy with the placement of local anaesthetic around the nerves the needle is removed and the block is completed. If a nerve block catheter is being used it will be threaded along the needle before the needle is removed and secured using dressings.
Does the block work immediately?
Sometimes it can take up to 40 minutes after the injections for a block to fully establish and be suitable for surgery. During this time your blocked limb will become numb and can feel heavy. We will support and protect the limb to prevent injury.
Because a block normally takes some time to work, patients often have the block performed in a separate clinical area and are only brought to the operating theatre when the block is working well.
If you are having a block in addition to general anaesthesia, the block will be done first and the general anaesthetic given soon after.
What will I feel during the surgery?
Most patients feel nothing during their surgery. Commonly on surgery on the hand or foot a tight tourniquet is used on the upper arm or thigh. Many patients are aware of this and some will need sedation or extra pain relief. Some patients are aware of ‘something going on’ or movement during the surgery - this is not uncommon and generally not a problem.
Occasionally patients experience pain from the operation during their surgery. If this happens the surgeon can put in some more local anaesthetic or the anaesthetist can give extra pain relief. If necessary a general anaesthetic can be given - this is unusual.
It is important to stress that the anaesthetist will not allow surgery to start if the block is not working and that there are no circumstances where you can be left in pain during the operation with no-one helping you.
When will the block wear off?
The anaesthetist will choose the block technique which is best suited to your surgery. If your surgery is short and you are not likely to have much postoperative pain then the block may be designed to wear off in only 2-3 hours.
Conversely if you are having quite long surgery or the operation is likely to be painful afterwards the anaesthetist will choose to use drugs that last longer. Some blocks can continue to provide pain relief for up to 48 hours.
Catheter techniques are planned to give pain relief over many days, so last the longest.
Occasionally a block lasts much longer than expected. This can occur if a nerve is bruised during the block procedure but can also occur in patients with pre-existing nerve conditions, such as diabetic neuropathy. You will be told by your anaesthetist how long you should expect the numbness to last and be given instructions for who to contact if you are concerned.
As a block wears off it is common to have some tingling feelings as sensation returns. This is normal.
If you have been prescribed painkillers it is important to start taking these before the block fully wears off to remain comfortable.
What are the risks and complications of nerve blocks?
The most important risk to you is having a numb, weak arm or leg. You will be assisted to protect your blocked limb for as long as it stays numb, and given advice on discharge as to how you should do this. Most patients with a numb arm will use a sling. Patients with a numb leg will be kept on bed rest or mobilised only with trained assistance.
You should take care with moving around while your limb is numb or weak - there is a risk of serious injury if you try to do too much too soon and particularly if you try to do domestic chores or even to drive with a weak arm.
Nerve bruising or injury
When local anaesthetic is injected around or near nerves there is a small risk of bruising or damage to the nerve. This can be due to bleeding near the nerve or direct injury to the nerve with the needle. Anaesthetists are very aware of this small risk and our techniques and equipment are designed to minimise it by:
● Using Ultrasound to allow us to see the needle, nerves and blood vessels
● Performing blocks while patients are awake. If we are causing pain, we know to adjust needle position
● Using needles especially designed to minimise injury
It is also possible for nerve injury to happen as a complication of surgery, positioning or use of a tourniquet.
If you have numbness for more than a few days after a nerve block your surgeon or anaesthetist can refer you to a neurologist who may arrange special tests to identify if there is a nerve injury.
Depending on the duration and type of symptoms treatment generally involves exercise, physiotherapy and sometimes medications.
Short term numbness or tingling lasting more than 48 hours after a nerve block affects fewer than 10% (1 in 10) patients. Around 95% (19 in 20) of these patients will recover within 4-6 weeks. 99% (99 in 100) will be back to normal in one year.
Overall the risk of permanent nerve injury due to a nerve block is rare, thought to be approximately 1 in 10000.
Risk can vary between patients, as can benefit. Risk can also vary depending on the exact block used and the operation being performed. For this reason your anaesthetist will counsel you personally about the risks and benefits of a nerve block in your individual case.
Contributed by Department of Anaesthesia.