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Pre-operative Information (Dental/ENT)

Changi General Hospital Logo | Preoperative Anaesthesia Assessment Clinic (PAAC)

Preoperative - Lower Body Surgery

Fasting Instructions

Favourites Remember to add this page to your Health Buddy ‘Favourites’ for easy access before your surgery. Simply click on the ‘star’ icon at the top right of Health Buddy app.

Before surgery

You will receive a phone call informing you of the time and location of your surgery.

Fasting instructions (VERY IMPORTANT)

Do not consume any food , juice, drinks with milk or carbonated drinks after midnight. This is to minimise the risk of aspiration, where food is regurgitated from the stomach and into the lungs. Water is the best option to keep yourself well hydrated.

  • No consumption of FOOD after midnight.
  • You are then only allowed to have WATER up to 6 am.
  • Ensure you drink 200ml of WATER at 6am.
  • No more WATER is allowed after 6am.


Patient Information Sheet


On the day of surgery

You will report to either the Day Surgery or the Same Day Admissions unit as instructed. After registration, you will be asked to change into the operating theatre (OT) gown and see a doctor before going into the OT reception area.

When you are in the OT, general anaesthesia (GA) will be administered and you will fall into a ‘deep’ sleep state during the operation.

General anaesthesia (GA)

  • General anaesthesia is a state of controlled unconsciousness during which you will feel nothing. It is almost like being in a ‘deep’ sleep.
  • Anaesthetic drugs will be injected into a soft plastic tube inserted into a vein in your hand. This is to induce the state of ‘deep’ sleep.
  • These drugs stop your brain from responding to sensory messages travelling from the nerves in your body.
  • You will be unaware of your surroundings, the surgery or pain.
  • You will be asleep for the entire duration of the surgery and woken up only after the surgery is completed.
  • You will have no memory of the procedure.
  • Your anaesthetist and anaesthetic team will be with you during the surgery.

Common risks associated with GA

This will affect 1 in 10 to 1 in 100 patients who undergo surgery with GA.

  • Nausea and vomiting – due to the side effects of the anaesthetic drugs and type of surgery.
  • Sore throat – due to the presence of the breathing tube we use when you are asleep.
  • Giddiness, headache or sleepiness – due to the remaining effect of the anaesthetic drugs.
  • Aches, pains and backache – due to your body posture during surgery.
  • Pain when drugs are injected – due to the side effects of the anaesthetic drugs.
  • Bruising and soreness – due to your body posture during surgery and side effects of the anaesthetic drugs.
  • Itch - due to the side effects of the anaesthetic drugs.

Uncommon risks associated with GA

This will affect 1 in 10,000 patients who undergo surgery with GA.

  • Eye abrasion causing pain and requiring treatment.
  • Damage to teeth and dental work, lips or tongue.
  • Injury to the skin, eyes, nerve due to prolonged positioning.

Rare risks associated with GA

This will affect 1 in 10,000 to 1 in 100,000 patients who undergo surgery with GA.

  • Awareness of activities in the operating room while still under anaesthesia.
  • Inherited muscle sensitivity to particular anaesthetic drugs (malignant hyperthermia). This can cause a rapid rise in body temperature, heart rate and breathing with high blood pressure and muscle rigidity.
  • Hoarseness of voice due to direct or indirect injury to the vocal cord.

Very rare risks associated with GA

  • Allergy to anaesthetic drugs causing wheezing, rash, swelling, and low blood pressure, and poor circulation in severe cases.
  • Heart attack (AMI - Acute Myocardial Infarction), stroke (CVA - Cerebrovascular Accident) and pneumonia. Brain damage or death.

Managing Pain after surgery

For more information regarding various pain medicines,


CGH Level 3

For appointments and enquires,
Please call the CGH Appointment Centre at
Tel: (65) 6850 3333

CGH Appointment Centre operating hours:
8.30 am to 8.00 pm (Monday to Friday)
8.30 am to 12.30 pm (Saturday & Sunday)
Closed on Public Holidays

For more information, please visit