Anaesthesia

Anaesthetics temporarily block 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 will return to the affected part of your body.

Video: How does anesthesia work? 

(Steven Zheng, TedEd, 2015)

There are 3 main types of anaesthesia – local, regional and general. Sedation (see below) is sometimes used with local and regional anaesthesia to help relax you or make you feel sleepy.

The type of anaesthesia used will depend on the type of procedure or surgery, your health (eg, whether you have heart disease or diabetes) and the results of tests, such as blood tests or an electrocardiogram (ECG).

1. Local anaesthesia

Local anaesthesia is used to numb a small part of your body while you're awake. It's used for minor procedures like getting stitches for a cut. This anaesthetic can be given as an injection or as a spray, cream or gel that's put on the area. Read more about numbing creams and gels. 

Video: Numb and numb-er – A child’s guide to local anaesthetics

(Swansea Bay NHS TV, UK, 2020) 

2. Regional anaesthesia

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 2 types of regional anaesthesia:

• peripheral nerve block which is often used for procedures on your hands, arms, feet, legs, or face. They are also useful for pain relief after your operation, as the area will stay numb for a few hours.
• epidural and spinal anaesthesia is given near your spinal cord and the nerves that connect to it. It blocks pain from an entire region of your body, such as your belly, hips, or legs. It can be used for pain relief during labour and childbirth, bladder operations and hip replacement surgery. 

3. General anaesthesia 

General anaesthesia is used to keep you unconscious during surgery, so you will feel nothing and have no memory of what happens during your surgery. Your awareness will return when the effects of the anaesthesia wares off. General anaesthesia is given as both a gas that you breathe into your lungs (inhalational anaesthesia) and as an injection through a vein (intravenous anaesthesia). It's used for many operations such as surgery on your heart, lungs, and abdomen (tummy).

What is sedation?

Sedation involves using small amounts of intravenous anaesthetic medicine to make you relaxed and sleepy, but not unconscious. Many people having local or regional anaesthesia don't 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 doesn't always mean you will have no memory of the operation. Only a general anaesthetic can do that.

Some types of inhaled anaesthetic medicine are used for pain relief but don't make you fully unconscious. They're used for dental procedures, emergencies or when you're in labour, eg, nitrous oxide (laughing gas) and methoxyflurane.

Anaesthetists are doctors who have specialist training in anaesthesia. Before the procedure, your anaesthetist will discuss the best types of anaesthetic. They'll plan your anaesthetic and pain control with you, and will consider any preferences you have. Your anaesthetist will carefully monitor you during your operation and make sure you wake up comfortably afterwards. They may also help with pain relief after the procedure.

An anaesthetist is the only kind of doctor trained to use general anaesthetics. Anaesthetists work with anaesthetic technicians and nurses as a team during operations. Anaesthetists also specialise in chronic pain management, and work in pain clinics. They often care for patients in intensive care units and during resuscitation in hospitals.

Healthcare providers such as GPs, emergency department and orthopaedic doctors and nurses, nurse practitioners and paramedics use local and regional anaesthetics and sedation too.

Once surgery is offered, the hospital will ask you to fill out a health questionnaire. It will ask about:

• other medical conditions
• previous anaesthetics
• any problems or concerns you have about anaesthesia
• what medicines you're taking
• your home and whānau and friends who may be involved with your care around the time of surgery.

You may have a phone call or be invited for a face-to-face preoperative assessment. The healthcare team will use this information to give you the best and safest anaesthetic and plan for your post-operative care including going home and what happens afterwards. This is a good opportunity to discuss your concerns.

All this information is used to advise you about preparing for surgery including stopping smoking, what medicines to take and when to stop eating and drinking. 

Video: Preparing for your anaesthesia 

(ANZCA, 2019)

Like all medicines, anaesthetics can cause side effects, but they don't last very long. Common side effects of general anaesthesia and some of regional anaesthesia include:

• feeling sick (nausea) or vomiting
• headache
• sore throat and dry lips
• dizziness and feeling faint
• feeling cold or shivering
• itchiness
• pain and bruising at the injection site
• difficulty passing urine (pee)
• aches and pains.

Having an anaesthetic is usually 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, taking certain medicines, smoking and using recreational drugs can also increase your chance of problems. Your anaesthetist will talk with you about the best type for you and will review risks, benefits and other choices.

Possible complications include allergic reaction, permanent nerve damage, heart attack, stroke, organ failure, reawakening during a procedure and the risk of dying. Complications are more likely for people who are very young, older or have other health problems. For a fit person under 60 years of age, the chance of dying due to an anaesthetic complication is very low.

• It's best to talk about your concerns with the anaesthetist and other members of your healthcare team before your procedure.
• Ask about the possible risks and complications that apply to you because of your specific circumstances, eg, your age, other health conditions and the procedure you're having. 
• You can take a support person with you to be a second pair of eyes and ears during the pre-op assessment.