HealthInfo West Coast-Te Tai Poutini
Anaesthesia stops you feeling pain during surgery or other procedures. It uses medicines called anaesthetics.
Different anaesthetics may be used to relax you, numb an area of your body or make you unconscious during your procedure.
The effects are temporary and your awareness and feeling of pain return when the anaesthesia wears off.
Anaesthetics temporarily block the nerve signals from reaching your brain. This means procedures can be done without you feeling anything. After the anaesthetic wears off, the nerve signals reach your brain and feeling returns to the affected part of your body.
There are three main types of anaesthesia: local, regional and general.
The type of anaesthesia used depends on the type of procedure or surgery and the results of tests, such as blood tests or an electrocardiogram (ECG). It also depends on your general health. For example, whether you have heart disease or diabetes.
Local anaesthesia is used to numb a small part of your body while you are awake. It is used for minor procedures. You can be given the anaesthetic as an injection or as a spray, cream or gel that is put on the area.
Regional anaesthesia is used to numb a larger part of your body. This anaesthetic is given as an injection around specific nerves. Regional anaesthesia allows you to stay awake.
There are two types of regional anaesthesia:
General anaesthesia is used to keep you unconscious during surgery. You feel nothing and have no memory of what happens during your surgery. Your awareness returns when the effects of the anaesthesia wares off. General anaesthesia is given as a gas that you breathe into your lungs and as an injection through a vein.
While you are under a general anaesthetic, a breathing tube is put into your windpipe to help you breathe. The tube is removed as you wake up after surgery. General anaesthesia is used for many operations such as surgery on your heart, lungs and abdomen.
Sedation involves using small amounts of anaesthetic medication to make you relaxed and sleepy. But you are not unconscious. Many people having local or regional anaesthesia do not want to be awake for the surgery, so they choose to have sedation as well.
If you have sedation, you will remember little or nothing of the operation. It does not always mean you will have no memory of the operation. Only a general anaesthetic can do that.
Anaesthetists are doctors who have specialist training in anaesthesia. Before the procedure, your anaesthetist will discuss the best types of anaesthetic for your procedure. They will plan your anaesthetic and pain control with you, including any preferences you have.
Your anaesthetist will monitor you during your operation and make sure you wake up comfortably afterwards. They may also help with pain relief after the procedure.
Like all medicines, anaesthetics can cause side effects, but they do not last very long. Common side effects of general anaesthesia and some of regional anaesthesia include:
Usually, having anaesthesia is safe and major problems are rare. Your risk depends on the type of anaesthesia you get, your age, your health and how you respond to the medicines.
Some health problems, such as heart or lung disease, increase your chances of problems from anaesthesia. Being overweight or taking certain medicines can also increase your chance of problems. So can smoking and using illegal drugs. Your anaesthetist will talk with you about the best type of anaesthetic for you and will review the risks, benefits and other choices.
Possible complications include an allergic reaction, permanent nerve damage, heart attack, stroke and organ failure. Also, reawakening during a procedure and the risk of dying. Complications are more likely in the very young, the elderly and people with other health problems.
For a fit person under 60 years of age, the chance of dying due to an anaesthetic complication is approximately 1 in a million. The risk for people over the age of 60 can be higher depending on other health conditions.
Your doctor will let you know what to do the night before and on the day of the procedure. Here are some tips to help you prepare:
HealthInfo recommends the following videos
Information about preparing for your anaesthesia.
Information about what an anaesthetist does and how general anaesthesia works.
HealthInfo recommends the following pages
Information about having anaesthetics if you have asthma.
Information to help you feel more relaxed about having surgery under anaesthesia.
Information about general anaesthetics. Includes how they are given, possible side effects and risks and complications.
Adapted from Healthify He Puna Wairoa as part of a National Health Content Hub collaborative. Last reviewed June 2025.
Review key: HIHAA-98601