A to Z of medical terms (glossary)

A to Z of medical terms (glossary)

The following are words or medical terms you may hear or read in information about anaesthesia and what they mean. We welcome suggestions to improve this list so please let us know if you think there are additional words that should be included. You can contact us via: patientinformation@rcoa.ac.uk.

A–Z of medical terms (glossary)

Amnesia: Loss of memory you have for an event.

Anaesthesia: General anaesthesia: medication that gives a deep sleep-like state. It is essential for some operations and procedures. You are unconscious and feel nothing.

Anaesthesia Associate: A healthcare professional who works as part of the anaesthetic team under the supervision of a consultant anaesthetist. Previously known as Physicians’ Assistant (Anaesthesia) [PA(A)].

Anaesthetist: A doctor trained to give anaesthetics.

Analgesia: Pain relief.

Anaphylaxis: A serious allergic reaction to a drug or substance.

Anticoagulant: Medicines to stop your blood clotting.

Antiemetic: A drug to help prevent or treat sickness.

Anti-inflammatory drug: A drug to stop or reduce swelling and pain.

Arterial line: A cannula put into an artery (often at your wrist). This measures your blood pressure continuously. Your anaesthetist can also take blood samples from it to measure your oxygen levels.

Artery: A blood vessel that takes blood rich in oxygen from your heart to another part of your body.

Awareness: Unintentionally becoming conscious during a general anaesthetic and being able to remember some of this time. It is rare for this to happen.

Blood clots: Blood can form clots in your veins, usually when you are less mobile. If this happens in your legs it is also called a deep vein thrombosis (DVT). If the clots break off and go to your lungs, it is called a pulmonary embolus (PE), which can be life-threatening.

Blood group: The type of blood you have in your body. There are four main types: A, B, AB, and O. If you have a blood transfusion, you need blood of the correct group so you don’t have a serious reaction.

Blood pressure: The pressure of blood in your arteries. Usually you see it as two numbers eg 120/80. The top number is your systolic pressure. This is measured when your heart contracts (pumps). The lower number is your diastolic pressure. This is the pressure when you heart relaxes.

Body Mass Index: A calculation often used to work out your weight compared to your height. You can calculate this by dividing your weight (in kg) by your height (in metres squared). The ideal number is between 19 and 25, which shows your weight is normal. Over 30 means you have obesity.


Cannula: A thin plastic tube that goes into a blood vessel. It used to give drugs. 

Cardiac arrhythmia: A group of conditions in which your heartbeat is irregular, too fast, or too slow.

Cardiopulmonary bypass (CPB): A technique that temporarily takes over the function of your heart and lungs during surgery, usually on the heart. It pumps blood round your body and adds oxygen. The CPB pump is often called a heart–lung machine.

Complications: Problems that may develop after your operation, treatment or illness.

Compression boots: A soft “boot” that inflates and deflates around your legs to help blood keep moving in your veins during an operation. This helps to stop blood clots forming.

Consent form: A form a doctor will ask you to sign after they tell you all the benefits and risks of an operation or procedure. This shows you agree to go ahead.

Cornea: The membrane that covers the front of your eye.

CPX testing (Cardiopulmonary Exercise Testing): A method used to find out how well you your heart and lungs work at rest and during exercise.

CPR (Cardiopulmonary resuscitation): A way to support and maintain your breathing and circulation if you ever stop breathing (respiratory arrest) and/or if your heart stops (cardiac arrest).

Combined spinal and epidural (CSE): A type of regional anaesthetic placed in your back that uses both a spinal and an epidural injection together. This allows your anaesthetist to quickly numb the nerves in your lower body with the spinal injection but to also have the epidural to use if it is likely the operation will take a little longer. The epidural part can also provide help with pain relief afterwards if needed.

Cross match: A test before a blood transfusion to make sure that you are given blood of the right group. This check means that you will have a very low chance of having any reaction to the blood given.

CVP line: Central Venous Pressure Line (‘central line’): A soft tube that your anaesthetist puts into a vein (often in your neck) that ends up in the large vein taking blood to your heart. It is used to measure pressure in these veins and to give you medicines, fluids or food.

Day case: An operation after which it is expected you will be well enough to leave hospital the same day.

Deep Vein thrombosis (DVT): A blood clot that forms in a deep vein in your leg or abdomen.

Defibrillator: A machine that uses an electric current to stop any irregular and dangerous activity of your heart.

Diabetes: A disease which results in high levels of sugar (glucose) in your blood. Usually this is controlled by a hormone called insulin, but in diabetes you may not have enough.

Drip: Fluids put into a vein. These can have different minerals or drugs added.

Dural puncture (‘dural tap’): Can occasionally happen when an anaesthetist puts in an epidural. The epidural needle accidentally goes through the dura, which is a membrane surrounding your spinal cord. This causes a leak of cerebrospinal fluid and often leads to a headache.

Dural puncture headache: A complication of a dural puncture. The headache is caused by a leak of cerebrospinal fluid through a small hole left by the needle. It is an uncommon side effect of spinal anaesthesia, lumbar puncture and epidural anaesthesia.

ECG (electrocardiogram): A tracing of the electrical activity made when your heart beats.

Echo (echocardiogram): A test that uses ultrasound waves to create a picture of your heart and shows how it moves.

Enhanced recovery: The name given to a programme that aims to get patients back to their normal health as quickly as possible after a major operation. Hospital staff look at all the evidence of what they and patients can do before, during and after surgery to help give the best quality recovery.

Endotracheal tube: A small plastic tube that your anaesthetist may put into your windpipe (trachea) during an anaesthetic. This delivers oxygen and anaesthetic gas to your lungs.

Epidural: A type of regional anaesthetic placed in your back. A needle is used to place a very fine tube (epidural catheter) in your back. ‘Top-up’ local anaesthetic is given for pain relief through the catheter, which can make the numbness last many hours or even days. This is commonly used for pain relief in childbirth or to reduce pain in your abdomen or pelvis after surgery.

Family history: Health information about you and your blood relatives

Fast/Fasting: Time when you should not eat or drink before a surgical operation or procedure.

Full blood count: A test that measures all the cells in your blood. (red blood cells, white blood cells and platelets)

Gas: Anaesthetic drugs that you breathe into your lungs.

Gastric tube (nasogastric tube): Soft tube that passes in through your nostril and into your stomach. This can drain liquid out of your stomach. Liquids, foods or medicines can go down it and into your stomach.

Group and Save: A blood sample to check which blood group you have in case you need a blood transfusion. It also looks at whether you have any other antibodies that need to be matched to stop you reacting to blood you are given.

Guedel airway: A curved plastic device put into your mouth when you are unconscious. This keeps the tongue from blocking your airway so allows you to breathe more easily.

Haemorrhage: Bleeding.

High dependency Unit (HDU): A ward for people who need more intensive observation, treatment and nursing care than is possible in a general ward, but slightly less than that given in intensive care.

Hypertension: High blood pressure

Hyperglycaemia: High blood sugar level

Hypotension: Low blood pressure

Hypoglycaemia (‘hypo’): Low blood sugar level

Identity bracelet: A soft plastic bracelet you wear on your wrist or ankle that shows your name, your date of birth and your hospital number. Before anyone gives you medicines or treatment, they will look at your bracelet to check that all your records match.

Inpatient: A patient who is staying in hospital having treatment.

ICU (or ITU) Intensive Care Unit: Specialist hospital ward that provides treatment and high level monitoring for people who are very ill.

Intravenous drip (or infusion): Fluids put into your vein through a cannula. These may contain drugs.

Intubation: Placing a tube into your windpipe (trachea) when you’re anaesthetised to allow oxygen and anaesthetic gasses to pass easily to your lungs.



Labour ward: A ward in a hospital where women deliver their babies.

Laparoscopy (keyhole surgery): A modern type of surgery that allows a surgeon to operate inside your abdomen (tummy) and pelvis using cameras and small instruments. This means you have only small cuts in your skin, so you recover more quickly.

Laryngeal Mask Airway (LMA): A piece of anaesthetic equipment. This lets oxygen and anaesthetic gas pass easily to your lungs without needing to put an endotracheal tube into your trachea.

Laryngoscope: Equipment with a light for examining your larynx (voice box) so your anaesthetist can see where to put an endotracheal tube.

Mask: Equipment, usually made of clear soft plastic, which sits over your mouth and nose. Your anaesthetist can give you extra oxygen to breathe through this before your anaesthetic or when you wake up in the recovery room.

Mobilise: To get out of your bed and move around.

Muscle relaxant: A drug that reduces your muscle contractions by blocking nerve impulses.

Nausea: This is an unpleasant sensation, usually felt in your stomach area, which can also be described as ‘feeling queasy’ or ‘feeling sick’. You often feel it when you want to vomit.

Neonatal Intensive Care Unit (NICU) [sometimes called Special Care Baby Unit (SCBU)]: specialist hospital ward that provides treatment and high level monitoring for babies who are very ill.

Nasotrachael tube: an endotracheal tube that delivers oxygen and anaesthetic gas when having surgery in the mouth. Rather than putting in through the mouth, this small plastic tube is put in through the nose so as to allow surgeons to work in the mouth more easily.

Operating Department Practitioner (ODP): A skilled member of staff who works in the operating theatre.

Oesophagus (gullet): Tube your food passes down when it goes from the back of your mouth down into your stomach.

Outpatient: A patient who comes into hospital to see a specialist or have treatment or tests, but stays at home.

Paediatric: Refers to a child – usually less than 16 years old.

Palpitations: The sensation that your heart has skipped a beat or added an extra beat. It may feel like your heart is racing, pounding, or fluttering.

Patient Controlled Analgesia (PCA) pump: An electronically controlled pump that gives a dose of a painkiller into your vein when you press a button. This allows you to decide how much you need.

Peribulbar block: A type of regional anaesthetic block that can numb your eye for surgery.

Peripheral nerve: A nerve that is not part of  your brain or spinal cord.

Peripheral nerve block : A nerve block that can numb a part of your body. This can be used instead of a general anaesthetic or it can be used with a general anaesthetic to reduce pain after surgery. Usually  ultrasound is used to guide to the nerve.

Perioperative care: Describes the care of patients from the moment surgery is considered until they are fully recovered to ensure they receive the most efficient care and best outcomes. Many healthcare professionals from different specialties will work together to achieve this and will keep the patient at the centre of decision making throughout. 

Physicians’ Assistant (Anaesthesia) [PA(A)] – see Anaesthesia Associate.

Paediatric Intensive Care Unit (PICU): Specialist hospital ward that provides treatment and high level monitoring for children who are very ill.

Platelets: Small parts of cells in your blood that are needed for blood to clot.

Postoperative nausea and vomiting (PONV): Postoperative means that it happens after the operation.

Preoperative assessment (clinic): A nurse or doctor assesses your health to see if you are fit enough to have your surgery. They will also arrange any tests you might need and give you information about what to expect before, during and after your stay in hospital.

Premed (or premedication): Medicine that you may have before an operation or other treatment.

Pulmonary embolus (PE): Part of a blood clot in your leg or abdomen (DVT) which breaks off and blocks veins in your lung.

Pulmonary Function Tests (lung function tests): Breathing tests that measure how well your lungs take in and breathe out air. They also measure how well they transfer oxygen into your blood.

Pulse oximeter: A probe (a peg) that fits on your finger, toe or ear lobe and measures how much oxygen your blood is carrying.


Recovery room [also called post-anaesthesia care unit (PACU)]: An area close to an operating theatre where a patient goes after surgery to safely regain consciousness from anaesthesia. You receive care there until you are well enough to return to the ward or go home.

Regional anaesthesia: An injection of local anaesthetic near a large nerve or collection of nerves which makes an area of your body numb.

Resuscitation: The process of treating someone who is very unwell and needs life saving treatment.

Risk: The chance that something will cause harm. The higher the risk, the more likely it is to happen.

Scrub suit: Loose fitting top and trousers worn by surgeons and theatre staff while working in the operating theatre.

Sedation: Giving drugs to reduce anxiety and make you feel relaxed and calm.

Sensory messages: Some nerves take messages from the skin or other organs to your spinal cord or brain. These messages can be called sensory messages.

Spinal: Relating to your spine.

Spinal anaesthetic: A type of regional anaesthetic placed in your back. A fine needle is used to inject a local anaesthetic mixture to numb the nerves in your lower body. This starts to work quickly but only lasts one to two hours. This is commonly used for caesarean sections and some orthopaedic, bladder and gynaecology surgery.

Sputum (phlegm): A mixture of saliva (spit) and mucus coughed up from your lungs.

Starvation time (fasting time): Period of time before an operation or procedure when you should not eat or drink. This is usually six hours for food and two hours for clear fluids.

Suction: A machine that sucks up liquids and secretions.

Suppository: Small, solid pill containing a drug that can be put inside your anus (back passage), where it dissolves. This can be a useful way to give pain relief or drugs to treat sickness.

Surgical stockings: Elastic support stocking to reduce your risk of getting blood clots (a DVT) in your legs.

Sutures: Stitches.

Tachycardia: A rapid heartbeat.

Transverse Abdominis Plane (TAP) block: A nerve block that can help numb an area of your abdomen to reduce pain after surgery. Usually put in using ultrasound to guide.

Temperature probe: Equipment to measure the temperature inside your body

Theatre: A large room in a hospital where surgical operations are performed

Thromboprophylaxis: Any method of trying to stop blood clotting in your veins. This may use drugs (anticoagulants) and / or methods to compress your veins such as surgical stockings.

Topical: On the surface. This usually means when a local anaesthetic is dropped onto an area such as your eye, to numb it.

Tourniquet: a band for stopping the flow of blood – usually used when taking a blood sample or during surgery to reduce bleeding.

Trachea (windpipe): The tube that carries air from the back of your mouth down to your lungs.

Ultrasound: High-frequency sound waves used to show the tissues and organs in the body. Commonly used to see pictures of your baby developing in the womb.

Urea and electrolytes (U and E’s): A blood test looking at your kidney function and amount of minerals in your blood.

Urine: Fluid excreted by your kidneys containing waste products of your body.

Urometer: A plastic collecting container that connects to a urinary catheter, which is a tube that drains urine from your bladder. It has markings on to accurately measure how much urine you make each hour.

Valve: Tissue in your body that controls the flow of blood. Valves in your heart allow your heart to pump blood the correct direction around the chambers of your heart and out to your body. There are also small valves in your veins to help blood travel back to your heart.

Vein: A blood vessel that takes blood back to your heart. They are darker in colour than arteries as the blood cells are carrying less oxygen.

Ventilator: A machine that blows oxygen and anaesthetic gases into your lungs and removes carbon dioxide if you are not breathing for yourself.

Vomiting: This means being sick. It is when you forcefully empty your stomach, or ‘throw up’.

Wean: When a patient in ICU starts breathing again for themselves. As your breathing gets stronger, you need less help from the ventilator, until you no longer need it at all.

White cells: Cells in the blood which fight infection. They are part of your body’s immune system.

World Health Organization (WHO) checklist or surgical checklist: A list of checks carried out by the whole theatre team. This checks that everything is correct and information is shared before the start of your operation and also as it ends. This is routinely done for all operations in the UK to increase safety.