Sciatic nerve block
Find out more about this type of anaesthetic before your surgery.
What is a nerve block?
It’s an injection of local anaesthetic near the nerves which supply a region of your body. A nerve block numbs the region of your body that we’ll operate on.
It means that we can conduct the operation while you’re awake (similar to an injection at the dentist). Whilst you maybe aware of movement, there is no pain. We sometimes use a nerve block in combination with a general anaesthetic to give you good pain relief after your operation.
What is the sciatic nerve?
It’s a nerve passing through the buttock to supply the hip joint, back of the thigh, and the knee joint with sensation. It runs down into the lower leg to also give sensation to the lower leg and foot.
Why should I have a sciatic nerve block?
Surgery to the leg especially hip, knee and ankle joints cause considerable pain in the first 24 hours after the operation. A sciatic nerve block can relieve this pain.
The benefits include:
- a pain free / less painful experience in the first 4 to 24 hours after surgery which can mean a shorter recovery period
- reduced common side effects associated with stronger pain killers – drowsiness, nausea and vomiting.
What should I do before my operation?
As for a general anaesthetic, we’ll ask you not to eat for 6 hours or drink 2 hours before your operation. This is really important if you’re having a general anaesthetic as well, or if you need one unexpectedly. Your anaesthetist will assess you before your operation and answer any questions you may have.
If your surgery is in the morning
- Do not eat food after midnight
- Drink water only until 6am
If your surgery is in the afternoon
- Do not eat food after 7.30am
- Drink water only until 11am
What’s the preparation for the procedure?
When you arrive in the anaesthetic room, we’ll connect you to routine monitoring equipment. This will include:
- a blood pressure cuff
- a probe on your finger to monitor oxygen levels in the blood
- 3 stickers on your chest to monitor your heart rate (an ‘ECG’).
Your anaesthetist will also use a needle to place a cannula (a thin plastic tube) in a vein in the back of your hand.
We’ll then put your leg in the best position to perform the block using a sterile solution to clean the area. Your anaesthetist will then perform the sciatic nerve block, which may take between 5 to 10 minutes.
If you have a nerve block and a general anaesthetic, your anaesthetist may either do the nerve block while you’re awake or sedated or under a general anaesthetic.
What happens during the procedure?
We’ll numb the skin at the site of the block with an injection of local anaesthetic. We’ll then introduce a needle through this numb area. If you”re awake or sedated, you may be aware of some movement in the area. You may get pins and needles, or discomfort in the buttock as the needle approaches the nerves.
If you have the nerve block under general anaesthetic, you won’t feel any of these sensations.
To make sure the needle is in the right plac,e the anaesthetist may use either a nerve stimulator or an ultrasound machine. The nerve stimulator delivers a tiny electric current to stimulate the nerve. The ultrasound enables the direct visualisation of the nerves and the needle. Your anaesthetist may either use both the techniques together or either one of the techniques.
After confirming the position of the needle, we inject local anaesthetic around the nerves. If you’re awake, your anaesthetist will ask you to report any of these sensations.
Initially your leg will feel warm and tingly but within 30 minutes, it will feel numb and heavy.
Why might I be awake even though I’m also having a general anaesthetic?
There are no studies to show that having a block while you’re awake is safer than having it done when unconscious. However, some experts believe that the information you can give the anaesthetist during the procedure may help to avoid complications.
What problems can occur following a sciatic nerve block?
Your anaesthetist is fully trained in the procedure to minimise the risks of harm and can discuss this with you.
With a popliteal nerve block, you may experience the most frequent (but still uncommon) complication of an altered sensation in the thigh or leg. This may persist after the main block has worn off. The symptoms include tingling and / or numbness in the thigh more than 48 hours after the block procedure.
This occurs in around 1 in 20 patients and usually resolves on its own, within 3 weeks or occasionally up to 3 months after the procedure. It’s very rare for symptoms to last longer than this.
99% of problems will have resolved at 12 months.
The risk of long term complications from a femoral nerve block can be compared to the 1 in 15000 risk of dying in a road traffic accident in the UK. This comparison gives you an idea of the rarity of a serious problem occurring.
What if the nerve block does not work?
Occasionally, the nerve block may not provide enough pain relief. If this happens, we will offer you an alternative form of pain relief afterwards.
What happens when the block wears off?
The effects of the local anaesthetic will last between 4 and 24 hours (on average about 10 to 12 hours). As the block starts to wear off, you may feel pins and needles in your leg. These will gradually disappear as the sensation comes back. You must start taking regular painkillers by mouth before the sensation returns so that you’ll feel comfortable once the block has worn off. You may need additional help to stand up and walk until the block wears off completely.
Please follow any additional instructions from the surgeons and physiotherapists.