Local anaesthesia and sedation

About local anaesthesia and sedation

Local anaesthesia

The word ‘anaesthesia’ comes from a Greek word that means absence or loss of sensation. Anaesthesia is one of the most significant developments of modern medicine because it allows once unbearable medical procedures to be performed without discomfort. Local anaesthesia blocks pain by stopping pain signals being carried by nerves to your brain.

Local anaesthesia can be used in many types of procedures and operations, including dental surgery. It completely blocks pain from the area being treated and you will stay awake during the procedure. A different type of local anaesthesia called regional anaesthesia can also be used to completely block pain from a large part of your body, such as everything below your waist. Local and regional anaesthesia are also used to provide pain relief after an operation (postoperative pain relief), after you have had a general anaesthetic.

Local anaesthetic is available in the form of drops, sprays, ointments or injections. For regional anaesthesia, the anaesthetic is usually injected around your nerves, using the following injection techniques.

  • An epidural or spinal targets the space that surrounds your spinal cord.
  • A simple nerve block targets individual nerves in various locations.

Your anaesthetist, doctor or dentist can control how much feeling you will lose and how long the effect will last by varying the amount, strength and type of solutions he or she uses. Generally, the effects of a local anaesthetic last from around 30 minutes to four hours.


A sedative relieves anxiety and helps you to relax. You may be offered a sedative if you’re having a procedure under local or regional anaesthesia or a test that may cause anxiety, such as a colonoscopy or an MRI scan.

A sedative can be:

  • inhaled – as gas and air
  • swallowed – in tablet or liquid form
  • injected – using a fine plastic tube (cannula) into a vein on the back of your hand or in your arm

The type and dose of sedative you will have will depend on your procedure and how anxious you are about it.

What are the alternatives to local anaesthesia and sedation?

Instead of a local anaesthetic, you may be offered general anaesthesia. This means you will be asleep during the procedure.

Your anaesthetist will discuss with you which type of anaesthesia is most suitable for you.

Preparing for local anaesthesia and sedation

Your anaesthetist, doctor or dentist will explain how to prepare for your procedure. It’s important to tell him or her if you’re taking any medicines, particularly a type of medicine called blood thinning agents.

You may be asked to follow fasting instructions. This means not eating or drinking, typically for about six hours beforehand. However, it’s important to follow your anaesthetist, doctor or dentist’s advice. It’s also important not to drink any alcohol 24 hours before you have a local anaesthetic or sedative.

Your anaesthetist, doctor or dentist will discuss with you what will happen before, during and after your procedure, and any pain you might have. This is your opportunity to understand what will happen, and you can help yourself by preparing questions to ask about the risks, benefits and any alternatives to the procedure. This will help you to be informed, so you can give your consent for the procedure to go ahead, which you may be asked to do by signing a consent form.

What happens during local anaesthesia and sedation?

You will start to lose feeling in the treated area within minutes of having a local anaesthetic. Your procedure or operation won’t start until your doctor is absolutely sure that the area is numb. It’s important to realise that local anaesthesia takes away feelings of pain, but you may still feel pressure and movement during your operation.

You will start to feel calm and relaxed within minutes of having a sedative. Depending on the strength and type of sedative used, you may feel drowsy.

Sedatives can sometimes affect your breathing. While you’re sedated, your doctor will constantly monitor the amount of oxygen in your blood through a small device on your finger. You may be given extra oxygen through a mask or a plastic nasal tube.

What to expect afterwards

After a local anaesthetic, it may take several hours before the feeling comes back into the treated area. Take care not to bump or knock the area.

You may need pain relief to help with any discomfort as the anaesthetic wears off.

Depending on how deeply sedated you are and the type of sedative you have, you may remember very little about any treatment you have done under sedation.

You will usually be able to go home when you feel ready. If you had a sedative, you will need to arrange for someone to drive you home. Try to have a friend or relative stay with you for the first 24 hours after your procedure.

Sedation temporarily affects your co-ordination and reasoning skills, so you must not drive, drink alcohol, operate machinery or sign legal documents for 24 hours afterwards. If you’re in any doubt about driving, contact your motor insurer so that you’re aware of their recommendations, and always follow your doctor’s advice.

Recovering from local anaesthesia and sedation

It usually takes about 24 hours to make a full recovery from having a local anaesthetic and sedation, but this varies between individuals and on the type of anaesthetic you have, so it's important to follow your anaesthetist, doctor or dentist's advice.

If you need pain relief, you can take over-the-counter painkillers, such as paracetamol or ibuprofen. Always read the patient information that comes with your medicine and if you have any questions, ask your pharmacist for advice.

What are the risks?

There are some risks associated with having local anaesthesia and sedation but they are less than having a general anaesthetic.. We have not included the chance of these happening as they are specific to you and differ for every person. Ask your anaesthetist, doctor or dentist to explain how these risks apply to you.


Side-effects are the unwanted but mostly temporary effects you may get after having local anaesthesia or sedation.

Side-effects of local anaesthesia are very uncommon. Side-effects of sedation may include:

  • a headache
  • feeling or vomiting
  • dizziness
  • difficulty remembering what happened during the treatment


Complications are when problems occur during or after local anaesthesia or sedation.

Specific complications of local anaesthesia and sedation are uncommon but can include the following.

  • An allergic reaction. Signs of an allergic reaction include tingling lips, skin rash and difficulty breathing. Medicines are available to help treat this.
  • Difficulty breathing. Sedatives can sometimes affect your breathing. While you’re sedated, your doctor will constantly monitor the amount of oxygen in your blood and you will be given extra oxygen if required.
  • Very rarely, there may be some damage to your nerves.

Is local anaesthesia and sedation safe in pregnancy?


Local anaesthetic and sedation is safe to use if you’re pregnant. However, you will need to be closely monitored by a doctor or nurse while you’re under sedation.


Your doctor will only prescribe medicines when you’re pregnant if the expected benefit to you is thought to be greater than the risk to your baby. Local anaesthesia and sedation is only used in the smallest effective dose.

If you’re having a sedative, an experienced anaesthetist should give it to you.

Sedatives can sometimes affect your breathing. While you’re sedated, your anaesthetist will constantly monitor the amount of oxygen in your blood and will give you extra oxygen if you need it.

Is sedation safe in children?


Sedatives can have a greater effect on children. If your child needs a sedative, he or she will be closely monitored by an anaesthetist throughout the procedure.


If your child is having sedation, this should be given by an experienced anaesthetist in a hospital. Your anaesthetist will only suggest sedation if the expected benefit is thought to be greater than the risk to your child.

As with every procedure, there are some risks associated with having sedation. Children are at increased risk because sedatives can have a greater effect than they do in adults. Wherever possible, the anaesthetist may suggest alternatives to sedation such as distraction, parent involvement and play therapy. If your child is having a painful procedure, the anaesthetist may try behavioural techniques as well as local anaesthesia.

If your child is having sedation, he or she may be asked to follow fasting instructions. This means not eating or drinking, typically for about six hours beforehand. Ask your anaesthetist for specific advice about sedation.

While your child is sedated, the anaesthetist will constantly monitor the amount of oxygen in your child’s blood and may give extra oxygen if required.

If you have any questions about sedation, or would like more information about the alternatives, speak to your doctor or anaesthetist.

I have lots of allergies - will I react to the anaesthetic?


It's not possible to predict exactly who will have a reaction to an anaesthetic but some things such as food allergies or asthma make it more likely.


When you have an anaesthetic, you will be exposed to a number of substances that can cause an allergic reaction, but this is more common with a general anaesthetic than a local anaesthetic as fewer drugs are used. However, it’s possible you may have an allergic reaction to the drug used for your anaesthesia as well as other medicines or agents used during your procedure such as antibiotics, skin antiseptics and latex gloves.

All of these can cause an allergic reaction. Signs of a severe reaction (called anaphylaxis) include difficulty with breathing (wheezing), low blood pressure or swelling inside your throat. Medicines are available to help treat this – adrenaline is the most effective. Antihistamines, steroids and oxygen may also be used.

The exact reasons why you may develop a reaction to anaesthesia or sedation aren’t fully understood at present. However, you’re more likely to have a reaction to anaesthesia if you:

  • are a woman – severe allergic reactions seem to occur more in women than in men
  • have any existing allergies
  • have a history of asthma

If you suffer from allergies, tell your anaesthetist, doctor or dentist before you have an anaesthetic. He or she will choose which drugs to use based on your medical history and current health. All doctors and nurses are trained to recognise the signs of a serious reaction and how to deal with it.