Nerve blocks for pain relief

What is a nerve block?

A nerve block is an injection of local anaesthetic next to the nerves that supply the part of your body being operated on. It numbs that area, which reduces pain during and after surgery and can reduce the need for strong pain medicines.

A nerve block is usually combined with a general anaesthetic, a spinal or sedation. For some operations on the arm or hand, a nerve block can be the main anaesthetic.

How it is done

• Dr Halvey uses an ultrasound machine to see the nerves and guide the needle.
• Blocks are often done before the operation, while you are awake or sedated, in the anaesthetic room. Some are done once you are asleep.
• The skin is cleaned and numbed with a small injection first. You may feel pressure, or a brief tingle down the limb. Tell Dr Halvey if you feel this.

Single injection or catheter

Single injection

The local anaesthetic is injected once and the needle is removed. The numbness lasts for a period of time and then wears off on its own. How long it lasts varies with the medicine, the type of block and the person.

Catheter and pump

A very thin plastic tube (catheter) is left next to the nerves and taped in place. It is connected to a small pump that gives a steady flow of local anaesthetic, which can extend the pain relief. The catheter is removed later. This is quick and does not usually hurt.

For knee replacement, Dr Halvey uses a nerve block that is either a single injection or a catheter. Which one depends on the operation and the surgeon. Your plan is agreed with you before surgery.

Looking after a numb limb

While the block is working you may not feel pain, heat, cold or pressure in that area, and the muscles may be weak.

• Do not put hot water bottles, heat packs or ice directly on the numb area. Check the skin for redness or pressure marks.
• Avoid resting the limb in one position for a long time, or against a hard edge.
• Leg blocks: your leg may give way. Do not stand or walk without a nurse or physiotherapist until they say it is safe, and use any walking aid or brace you are given.
• Arm blocks: keep your arm in the sling you are given and protect it from knocks.

As it wears off

Feeling usually comes back as tingling or pins and needles. Pain can return quite quickly once the block fades, and this can happen at night.

• Take your pain tablets as prescribed, on time, before the block wears off. Do not wait for the pain to start.
• Keep pain tablets and water within reach, especially overnight.
• If your pain is not controlled by your plan, contact the hospital or the rooms.

For pain relief at home, see the pain relief plans.

Going home with a catheter

Some people go home with a catheter and pump. If you do, you will be given written instructions on how to look after it, how and when it is removed, and who to call with questions. Keep the dressing clean and dry.

Risks

Most nerve blocks have no lasting effects. Possible problems include:

• The block does not work fully: you may need other pain relief, or the anaesthetic plan may be changed.
• Bruising or tenderness where the needle went in.
• Falls: a numb, weak leg can give way. This is why you need help to walk at first.
• Tingling or numb patches that last longer than expected: these are not unusual and nearly always settle with time.
• Permanent nerve damage: rare, about 2 to 5 in 10,000 (Royal College of Anaesthetists, UK).
• Infection at a catheter site: rare.
• A reaction to the local anaesthetic (if too much reaches the bloodstream), or an allergic reaction: very rare.

Some blocks have their own effects. For example, blocks for shoulder surgery can cause a hoarse voice, a droopy eyelid or a feeling of shortness of breath while they work. If a block like this is planned for you, Dr Halvey will explain it.