There is an information leaflet available from Royal College of Anaesthetists.
The following is adapted from an addendum jointly prepared by the Singapore Society of Anaesthesiologists, Obstetrical Gynaecological Society of Singapore and College of Obstetricians and Gynaecologists Singapore.
What does General Anaesthesia involve?
An intravenous drip will be set up to administer medications. You will be given oxygen to breathe through a face mask. The anaesthetic will be put into your drip to induce sleep. At the same time, light pressure will be applied to your throat to prevent stomach fluids from getting into your lungs. The anaesthetic works very quickly to induce sleep.
When you are asleep, a breathing tube will be placed through your mouth to aid breathing. Pain relief in the form of morphine or similar painkillers will be administered during the operation.
At the end of the operation, anaesthesia will be reversed and the breathing tube removed when you are breathing well.
Risks from General Anaesthesia
Side effects and complications are sometimes unavoidable but generally temporary. They include, but are not limited to, the following:
Common temporary side-effects (e.g. 1 in 10): headache, dizziness, nausea, vomiting, pain or bruising at injection sites, drowsiness, shivering, blurred or double vision, sore throat.
Infrequent side-effects (e.g. 1 in 100): muscle aches and pains, weakness, mild allergic reactions like itching or rash.
Uncommon complications (e.g. 1 in 1000): awareness (i.e. having sensation / pain during the operation), damage to the teeth, dental prosthetics, lips or tongue, damage to vocal cords or larynx, allergic reactions and/or asthma, damage to the nerves or pressure areas, stomach fluids entering the lungs (i.e. aspiration pneumonia), blood clot in the legs or lungs, failure to place the breathing tube, worsening of existing conditions (e.g. kidney and liver problems, heart conditions and musculoskeletal injuries)
Extremely rare complications which may cause death (e.g. 1 in 10,000 to 1 in 100,000), especially in those with medical problems: severe allergy or shock, very high temperature (malignant hyperthermia), and stroke or heart attack.