Anaesthesia explained: what to expect

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For a lot of people, the anaesthetic is the part of the process they think about most. It is very common to feel more nervous about going to sleep than about the procedure itself, and it is one of the questions our team is asked more than almost any other.

This page explains what anaesthesia is, the types used, who looks after you, how to prepare, what happens on the day, how recovery works and what the risks are, so that you go into your pre-procedure conversation already knowing the basics.

What anaesthesia is and the types used

Anaesthesia is medication used to stop you feeling pain during a procedure. Depending on the type used, it may also send you to sleep, or numb one part of your body while you stay awake.

Your anaesthetist decides on the most appropriate approach with you, based on the procedure, your medical history, any previous experience of anaesthesia, your medication and your own preference.

Type

What it is

What to expect

General anaesthetic

A carefully controlled state of unconsciousness. You are unaware of the surgery and will not remember it.

It is started through a cannula in your hand or arm, or with gas through a mask. You go to sleep in the anaesthetic room and wake up in recovery.

Regional anaesthetic

Injections, such as a spinal or a nerve block, that numb a larger area of the body, for example an arm or a leg.

You stay awake. Light sedation can be added so that you feel relaxed or doze.

Local anaesthetic

A numbing injection into the skin and tissue around the area where the surgeon is operating.

Used for shorter treatments. You stay fully awake and aware. You may feel pressure or movement but should not feel pain.

Sedation, sometimes called twilight sedation

Medication that makes you very relaxed and drowsy, usually combined with a local anaesthetic.

You drift in and out and remember little or nothing. You are not fully unconscious and can respond if spoken to.

Who looks after you

Your anaesthetic is given by a consultant anaesthetist. Anaesthetists are fully qualified doctors who complete several years of specialist training in anaesthesia before practising independently. Every anaesthetist working with us is registered with the General Medical Council (GMC).

Your anaesthetist stays with you for the entire procedure, continuously monitoring your breathing, heart rate, blood pressure and oxygen levels. After surgery you are cared for in a recovery unit by specially trained nurses until you are stable.

Your anaesthetic, step by step

Knowing the order of events helps many people feel less anxious. This is what happens on the day.

  1. Meeting your anaesthetist. On the morning of your procedure your consultant anaesthetist meets you in your room to review your health records, talk through your anaesthetic options, check your fasting times and answer your questions.
  2. The anaesthetic room. You are taken to the anaesthetic room, where monitoring equipment is attached: ECG pads for your heart rhythm, a clip on your finger for oxygen levels and a cuff on your arm for blood pressure. None of these involve needles.
  3. Going to sleep. A cannula, which is a small plastic tube, is placed in a vein in your hand or arm. For a general anaesthetic you breathe oxygen through a face mask while the anaesthetic is given through the cannula. Most people are asleep in under a minute.
  4. Waking up in recovery. When the surgery is finished the anaesthetic is stopped and you wake in the recovery unit, with a nurse beside you monitoring your vital signs.

Pain control and preventing sickness

We use several kinds of pain relief together, known as multimodal pain management.

  • Pain relief before you wake. Pain relief is given through your cannula while you are asleep, so it is already working when you wake up.
  • Combining medicines. Regular non-opioid pain relief, such as paracetamol and anti-inflammatories, is used alongside local anaesthetic or nerve blocks. This reduces the need for stronger medicines that cause drowsiness.
  • Care in recovery. Recovery nurses ask you to score your pain and can give fast-acting top-ups through your cannula if you need them.

Feeling sick. Feeling sick after an anaesthetic is common. Before your procedure ends we routinely give anti-sickness medication, known as anti-emetics, through your cannula to reduce the chance of it.

Preparing for your anaesthetic

Your pre-operative assessment. We review your medical history, medication, allergies and general health. Be completely open, including about smoking, alcohol, recreational drugs, herbal supplements and weight. Your team needs an accurate picture to plan your care, and nothing you say is used to judge you.

Eating, drinking and medication. Follow your fasting instructions exactly. Having food or drink in your stomach when you have an anaesthetic carries real risks, and your procedure may be postponed if the instructions have not been followed. Continue or stop medicines only as your team tells you.

Getting home. You cannot drive yourself home after a general anaesthetic or sedation. You must arrange for a responsible adult to collect you and stay with you for the first 24 hours.

Recovery: the first 24 hours

The main effects wear off within a few hours, but your judgement, coordination and memory can be affected for longer. For the first 24 hours you should not drive, operate machinery, drink alcohol, sign legal documents, make important decisions or look after children or dependants on your own.

Common after-effects. Feeling sick, a sore or dry throat, drowsiness, dizziness, shivering, headache, aching around the cannula site and difficulty concentrating. These usually settle on their own within a few days.

Risks and side effects

Anaesthesia is closely monitored, but like all medical treatment it carries risks. Your own level of risk depends on your health, your age and the procedure you are having.

Side effects and complications are grouped by how often they happen.

How often

What this includes

Very common and common: between 1 in 10 and 1 in 100 people

Feeling sick, sore throat, shivering and minor bruising around the cannula site. These are short-lived and treatable. Serious risks do not fall into this group.

Uncommon and rare: between 1 in 1,000 and 1 in 10,000 people

Minor damage to lips or teeth, an existing medical condition flaring up for a short time, temporary breathing difficulties on waking, serious allergic reaction, temporary nerve damage from positioning or nerve blocks, and strain on the heart or lungs.

Very rare: between 1 in 10,000 and 1 in 100,000 people, or fewer

Permanent nerve damage, accidental awareness during a general anaesthetic, and severe, life-threatening complications.

What you can do to reduce your risk. Be completely honest at your pre-operative assessment, follow your fasting and medication instructions exactly, and stop smoking beforehand if you can. Stopping even a few weeks before your procedure helps reduce breathing complications.

Common questions

Will I wake up during my procedure?

Accidental awareness during a general anaesthetic is rare. Your anaesthetist monitors your level of anaesthesia continuously and adjusts it throughout.

You should not feel pain during your procedure. Pain relief for afterwards is planned in advance, and medication is provided in recovery and to take home.

Most people describe a cold sensation moving up the arm, sometimes a taste or smell, then nothing. It usually takes under a minute.

Tell your anaesthetist. This is very common, and there are several options to make the process more comfortable for you.

Usually yes. Smoking and weight can affect breathing and how medication is dosed, so they form part of your assessment and your anaesthetic is planned around them.

This is one of the most common and understandable worries. Most people say nothing at all going to sleep or waking up, and anything that is said is treated in strict confidence by staff who hear it routinely.

The main effects wear off within a few hours, but your judgement, coordination and memory can be affected for up to 24 hours, and tiredness can last for several days.

Tell us at your pre-operative assessment and bring any details you have. Previous reactions directly change how your anaesthetic is planned and managed.

Not after a general anaesthetic or sedation. You must arrange for a responsible adult to collect you and stay with you afterwards.

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