General Anaesthesia

General anaesthesia is a medically controlled state of deep, reversible unconsciousness that allows doctors to perform surgery or other painful procedures without the patient feeling any pain or being aware of what is happening.

An anaesthesiologist (a doctor who specialises in anaesthesia and pain control) gives you a combination of drugs that work on your brain and nervous system. These drugs switch off your awareness, block pain signals, and relax your muscles. Your breathing is carefully supported throughout — usually with a breathing tube or mask connected to a ventilator (a machine that breathes for you). The anaesthesiologist monitors your heart, blood pressure, oxygen levels, and depth of unconsciousness the entire time, adjusting the drug levels as needed.

General anaesthesia is used whenever a procedure is too painful, too long, or too distressing for the patient to tolerate while awake, or when the patient needs to be completely still and their muscles fully relaxed.

• Major surgery on the abdomen (stomach, bowel, liver, kidneys, or other internal organs)
• Heart surgery and major blood vessel surgery
• Brain and spinal surgery
• Long or complex orthopaedic (bone and joint) surgery such as joint replacement
• Thoracic (chest and lung) surgery
• Major head and neck surgery, including some ear, nose, and throat operations
• Procedures in children who cannot cooperate with sedation (light sleep) alone
• Emergency surgery where there is no time for another approach
• Procedures where the patient has a strong preference to be fully unconscious

General anaesthesia may not be the first choice — or may require special planning — in certain situations:

• Patients with severe heart or lung disease that makes controlled unconsciousness high-risk
• Patients with a known history of malignant hyperthermia (a rare, dangerous reaction to some anaesthetic drugs)
• Patients with a difficult airway (such as a very small mouth, short neck, or certain jaw conditions) that makes inserting a breathing tube challenging
• Patients who have eaten or drunk recently and have not fasted as instructed, raising the risk of inhaling stomach contents
• Patients on certain medications that interact with anaesthetic drugs — your anaesthesiologist will review all medicines beforehand

General anaesthesia is given to millions of people safely each year, but like all medical procedures it carries recognised risks, and your anaesthesiologist will discuss these with you beforehand.

• Nausea and vomiting after waking up — the most common side effect, especially in the first few hours
• Sore throat or hoarseness — caused by the breathing tube and usually settles within a day or two
• Shivering and feeling cold when waking up
• Confusion or disorientation on waking, particularly in older patients; this usually clears within hours
• Headache or muscle aches in the hours after waking
• Temporary memory lapses, especially in the elderly
• Dental injury — teeth, especially crowns or loose teeth, can be chipped or dislodged when the breathing tube is inserted
• Breathing difficulties or airway complications during or just after the procedure
• Allergic reaction (hypersensitivity) to one of the anaesthetic drugs — this is uncommon
• Aspiration pneumonia (lung infection) — if stomach contents are accidentally inhaled; this is why fasting rules are strict
• Awareness under anaesthesia — waking or having memories of the procedure; this is rare but is monitored for actively
• Malignant hyperthermia (a sudden dangerous rise in body temperature and muscle breakdown) — rare but life-threatening; anaesthetic teams are trained to respond to it
• Serious heart or breathing complications — uncommon and more likely in patients with pre-existing conditions

Preparation for general anaesthesia begins days before your procedure and covers what you eat and drink, which medicines you take, and your lifestyle habits.

Fasting is essential. The stomach must be empty to prevent stomach contents from entering the lungs during anaesthesia. In most hospitals, adult patients are asked to stop eating solid food for a period of hours before the procedure, and to stop drinking clear liquids a shorter time before. Your surgical team will give you exact fasting times — follow these instructions precisely, because ignoring them can lead to your surgery being cancelled or to a serious complication.

Medicines and substances to review with your doctor include:

• Blood thinners (anticoagulants) — these are often paused before surgery to reduce bleeding risk; your doctor decides when and whether to stop them
• Diabetes medicines, including insulin — dosing usually changes on the day of surgery because you are fasting
• Herbal supplements and traditional medicines — some interact with anaesthetic drugs or affect bleeding; tell your anaesthesiologist about all supplements
• Smoking — smokers have more airway secretions and a higher risk of breathing complications; doctors usually advise stopping smoking several weeks before surgery
• Alcohol — heavy regular drinking affects how anaesthetic drugs are processed; inform your team honestly

Tests that are commonly arranged before general anaesthesia include:

• Blood tests — to check for anaemia (low red blood cell count), kidney and liver function, electrolytes (blood salts), and clotting ability
• EKG (electrocardiogram, a heart tracing) — to check heart rhythm and detect any silent heart conditions
• Chest X-ray — to assess the lungs and heart size, especially in older patients or those with lung disease
• Lung function tests — in patients with asthma, chronic obstructive pulmonary disease (COPD, a long-term lung condition), or other breathing problems
• Echocardiogram (an ultrasound scan of the heart) — if a heart condition is suspected or known

On the day of the procedure, here is what typically happens step by step — though the exact sequence varies between hospitals:

• You arrive at the hospital and are admitted to a pre-operative (pre-surgery) area where nurses check your identity, confirm your fasting status, and record your vital signs.
• The anaesthesiologist visits you to review your medical history, allergies, and test results, and to answer any last questions.
• You change into a hospital gown and remove jewellery, contact lenses, nail polish, and hearing aids.
• A small intravenous (IV) cannula (a thin plastic tube) is placed into a vein, usually in the back of your hand or arm, to allow drugs and fluids to be given.
• You are taken to the operating room (or anaesthetic induction room in some hospitals).
• Monitoring equipment is attached: sticky pads on the chest to trace the heart (EKG), a cuff on the arm for blood pressure, and a small clip on a finger to measure blood oxygen levels.
• The anaesthesiologist gives the induction drugs (the drugs that bring on unconsciousness) through the IV line. You typically fall asleep within a few seconds.
• Once you are fully unconscious, the team secures your airway — usually by placing a laryngeal mask (a soft mask that sits in the throat) or an endotracheal tube (a firm tube passed into the windpipe). The choice depends on the surgery.
• Anaesthetic gas and/or ongoing IV drugs are given to keep you unconscious throughout the operation.
• At the end of surgery, the anaesthetic is stopped. The team waits for you to begin breathing on your own, then removes the airway device and wakes you gently.

After surgery you are moved to the post-anaesthetic care unit (PACU), sometimes called the recovery room, where nurses monitor your breathing, blood pressure, heart rate, pain level, and level of consciousness until you are fully awake and stable. How long this takes varies — it may be less than an hour or considerably longer, depending on the type of surgery and how your body responds to the anaesthetic.

• Monitoring in recovery: nurses check your oxygen levels continuously and give oxygen through a mask or nasal prongs if needed until you are breathing well on your own.
• Pain relief: the team will manage your pain as you wake; tell the nurse if you are uncomfortable — pain is easier to control when treated early.
• Nausea: anti-nausea medicines are usually available in the recovery room; ask for them if you feel sick.
• Eating and drinking: most patients start with small sips of water once they are fully awake and not nauseated, then progress to light food as tolerated — your team will advise the right timing.
• Activity restrictions: for the first 24 hours after general anaesthesia, patients are typically advised not to drive, operate machinery, sign legal documents, or make important decisions, because reaction time and judgment may still be impaired.
• Companion at home: most hospitals require that an adult companion take you home and stay with you overnight after a day-surgery procedure.
• Wound care: follow the specific instructions given for your surgical wound — these come from your surgical team, not from the anaesthesia team.
• Medications at home: the team will prescribe pain relief and any other necessary medicines for you to take after discharge; take them as directed.
• Sore throat: if you had a breathing tube, mild throat soreness usually resolves on its own within a day or two; cold drinks or throat lozenges (pastilles) may help.
• Follow-up appointments: you will usually have at least one follow-up visit to check your recovery from surgery; any ongoing concerns about the anaesthetic itself should be raised with your anaesthesiologist.
• When to seek urgent help: go to the nearest emergency department or contact your medical team immediately if you develop severe difficulty breathing, chest pain, a high fever, unusual swelling, heavy bleeding from the wound, or if you are unable to wake someone properly after they have returned home.