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Peripheral nerve block and possible cryotherapy

If you are considering having a peripheral nerve block or have a procedure planned, it is important to know all you can about it. This includes:

why you need this procedure
what it will be like
how it will affect you
what risks are involved
any alternatives.

The information here is a guide to common medical practice. Each hospital and doctor will have slightly different ways of doing things, so you should follow their guidance where it is different from the information given here. Because all patients, conditions and treatments vary it cannot cover everything. Use this information when making your treatment choices with your doctors. You should mention any worries you have. Remember that you can ask for more information at any time.

What is the problem?

You have a painful condition in a small area of your body. This may be following an injury to the skin or deeper tissues in these areas. The pain may be due to damage to the nerves themselves. This can be caused by an infection, such as shingles. Nerves can also be damaged during accidental injury or when a cut (an incision) is made during an operation, perhaps after a hernia repair.

What is a peripheral nerve block?

Peripheral nerve block (PNB) injections are given to treat a number of different painful conditions. The injections are given into the skin around a single large nerve. The needle is inserted next to the nerve that supplies the area where your pain is coming from. Local anaesthetic and anti-inflammatory steroid drugs can be injected onto the nerve. By doing this painful conditions affecting the skin and underlying tissues can be treated.

If used, only a small amount of steroid is needed and it will not cause any of the side effects sometimes associated with taking steroid tablets. They are not the same kind of steroids that athletes may take.

What is a peripheral nerve?

There are many peripheral nerves throughout the body. A peripheral nerve supplies feeling to a small, well-recognised area of the skin and the underlying tissue. Each peripheral nerve has a name, based on the area of the body it supplies. For example, the genitofemoral nerve supplies feeling to the genitals and the top of the leg. A local anaesthetic block of this nerve can treat painful conditions in the area of the genitals and the top of the leg. There are many other peripheral nerves that can be blocked in the same way.

What has gone wrong?

There are many different things that could have gone wrong to require you to have a peripheral nerve block. Either the nerves to an area of the body or the area itself has been damaged. This is usually due to injury or disease. You now have pain in this area.

The aims

The aim of the procedure is to reduce the pain messages coming from the nerves around the painful area. It is hoped this will produce long lasting relief from your pain.

The benefits

Your pain should be reduced and you should be able to move around more easily. It should then be easier for you to perform your daily activities. You should need fewer painkilling tablets.

Are there any alternatives?

By the time that you consider having a peripheral nerve block you should have already tried other more simple treatments. These include rest, both painkilling and anti-inflammatory tablets, and physiotherapy.

You may also have tried a transcutaneous electrical nerve stimulation (TENS) machine for your pain. This works by sending soothing pulses across the surface of the skin and along the nerve fibres. The pulses prevent pain signals from reaching the brain. They also stimulate your body to produce higher levels of its own natural painkillers, called endorphins.

What if you do nothing?

If you do nothing there are several things that may happen:

With time and rest the pain may settle on its own
The pain and difficulty in moving around may remain the same
The pain may increase

Who should have it done?

The following patients should have the procedure done:

Patients who have consistent pain to a small area of their body

Who should not have it done?

Each patient has the final decision on whether to proceed or not. If you are unhappy about the procedure for any reason you should not continue.

There are specific medical situations when a peripheral nerve block should not be done and they are as follows:

When a patient is on medication (drugs) that prevents blood from clotting, such as warfarin. This would lead to more bleeding than normal. It may be possible to stop the medication a few days before the procedure. This will need to be discussed with your doctor
When a patient is suffering from an illness that prevents blood from clotting, such as haemophilia. This would also lead to more bleeding than normal
When there is infection of the skin over the site where the needle needs to be put in. This could lead to infection in the deeper tissues

Author: Dr Sean White FRCA. Consultant in pain and anaesthesia.