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    Anaesthesia

    Overview
    Types of Anaesthesia
    Complications of Anaesthesia
    Preparing for Surgery
    Post-Surgery Care
    Contributed by:
    SingHealth Duke-NUS Anaesthesiology & Perioperative Sciences Academic Clinical Programme

    Overview


    Anaesthesia: What is it?

    Anaesthesia means "loss of sensation''. Anaesthesia stops a patient from feeling pain and other sensations. Medications that cause anaesthesia are called anaesthetics. These medications work by blocking the signals that pass along the nerves in the body to the brain, so that a patient does not feel pain, move during the surgery or remember the surgery or procedure. When the anaesthetics wear off, the patient will start to feel normal sensations again.

    During surgery, an anaesthesia specialist doctor (also known as an anaesthetist) will ensure that the patient is safe and comfortable throughout the anaesthesia and also direct the patient’s care immediately after the surgery.

    Types of Anaesthesia

    The type of anaesthesia a patient will receive depends on the type of surgery, medical conditions the patient may have and the length of the operation. The anaesthetist will discuss with the patient the various options.

    Sometimes the anaesthetist will use a combination of anaesthetics. It depends on what is best for the patient.

    Types of Anaesthesia include:

    • General Anaesthesia
    • Regional Anaesthesia
      • Epidural Anaesthesia
      • Spinal Anaesthesia
      • Nerve Blocks
    • Monitored Anaesthesia Care with or without Sedation

    General Anaesthesia

    General anaesthesia is a medically induced, reversible state of unconsciousness. This is achieved using a combination of drugs which include pain-killers. Drugs are injected into a vein and/or breathed in as gases into the lungs. A breathing tube will be inserted into the windpipe to help the patient breathe while under the anaesthetic. The tube is removed when the patient wakes up after surgery.

    Regional Anaesthesia

    Regional anaesthesia numbs one region of the body. Patients are usually sedated for the procedure itself and throughout surgery. Sometimes, regional anaesthesia is combined with a general anaesthetic. Regional anaesthesia may be performed as a single shot or with a continuous catheter through which medication is given over a prolonged period.

    • Epidural Anaesthesia
      Local anaesthetic medicine and other pain medicines are given using an epidural catheter (a small tube or line) that is inserted into the back to block pain during surgery and/or after operation. Epidural anaesthesia is commonly used to help labour pain. This catheter may be left in place up to several days after surgery. This allows for continued post-operative pain relief.
    • Spinal Anaesthesia
      Local anaesthetics and other pain medicines are injected directly into the spinal canal to block pain during surgery. Generally during spinal anaesthesia, the patient is numb from the chest or abdomen down to the legs for 1-4 hours.
    • Nerve Blocks
      Local anaesthetics and other pain medicines are injected near a nerve or a group of nerves supplying sensation to the intended surgical site, hence numbing the region and blocking pain during surgery. A single injection lasts 8-16 hours, although in about 2% of people they can last for a few days. Blocks lasting longer than this are extremely rare. A catheter may also be left near the nerves to administer medication for post-operative pain relief.

    Monitored Anaesthesia Care with or without Sedation

    The anaesthetist monitors the vital functions such as heart rate, heart rhythm, blood pressure and breathing to ensure that patients are safe and comfortable during a procedure. Medication may be administered to make patients relaxed and drowsy.

    Complications of Anaesthesia

    General Anaesthesia

    General anaesthesia is remarkably safe today, even for a young child. In general, anaesthetic risks depend on the patient’s medical condition as well as the type of surgery. Side effects are sometimes unavoidable but generally transient.

    Common temporary side effects
    - Headache, dizziness
    - Nausea and vomiting
    - Pain or bruising at injection sites
    - Sore throat
    - Drowsiness, short-term memory loss
    - Shivering or teeth-chattering
    - Emergence Delirium: a restless and irritable recovery process
    - Skin redness or rash from tapes/medication

    Uncommon complications
    - Awareness
    - Damage to teeth, dental prosthetics, lip or tongue
    - Damage to vocal cords or larynx
    - Allergic reactions
    - Injury to nerves or vulnerable pressure areas
    - Pressure sores (especially if the surgery is long and involves cardiopulmonary bypass)
    - Corneal injuries

    Extremely rare and serious complications
    - Severe allergy (anaphylaxis) or shock
    - Very high temperature (malignant hyperthermia)
    - Aspiration resulting in lung complications

    Regional Anaesthesia

    It may take several hours for the effects of regional anaesthesia to wear off. As the anaesthetized site is numb, extra care should be taken to avoid accidental injury.

    Common side effects (usually temporary) of regional anaesthesia
    - Numbness or tingling sensation in area where the anaesthetic is working
    - Weakness of muscle over numbed areas
    - Inadequate pain relief
    - Prolonged nerve block

    Common side effects (usually temporary) of epidural and spinal anaesthesia
    - Shivering
    - Backache and bruising over injection site
    - Inability to pass urine
    - Dizziness, headache
    - Drop in blood pressure

    Serious but rare side effects of regional anaesthesia
    - Trauma to surrounding structures
    - Nerve damage
    - Blood clot (Haematoma)
    - Seizures
    - Breathing difficulties
    - Infection, abscess formation
    - Cardiac arrest

    Preparing for Surgery

    Before Operation

    The anaesthetist will meet the patient before the operation to check on their health, perform relevant examinations and discuss the patient’s anaesthetic in detail. They may also send the patient for blood or other tests. The anaesthetist would need to know:

    1. If the patient has a history of high blood pressure, heart problems, thyroid problems, diabetes, asthma, history of reflux or heartburn, or any other medical conditions.
    2. The past operations the patient has had and if there were any problems with anaesthesia.
    3. If the patient has had any abnormal reactions to any drugs or if he/she has any allergies.
    4. If the patient is currently taking any medications, traditional medicines or health supplements. If he/she is taking aspirin, non-steroidal anti-inflammatory agents or other blood thinning drugs, the patient should consult his/her surgeon or anaesthetist on whether he/she should stop taking them before surgery. This also applies to traditional medicines and health supplements.
    5. If the patient has any loose or capped teeth, crowns, or wear dentures.
    6. If the patient smokes. Giving up smoking for several weeks before the operation reduces the risks of breathing problems. If the patient is unable to stop smoking, cutting down on smoking will help.

    On the Day of Operation

    Nil by mouth = Nothing to eat or drink

    The doctors or nurses will advise the patient how long to fast. It is important to follow these instructions. Food or fluid in the stomach may enter the lungs while the patient is unconscious. If the patient does not follow this rule of fasting, the operation may be postponed in the interests of his/her safety. If the patient is taking medications, the patient should continue to take them, e.g. high blood pressure or asthmatic medications, unless the anaesthetist or surgeon tells the patient not to.

    If the patient feels unwell on the day that he/she is coming into the hospital for an elective operation, the doctor should be informed.

    Post-Surgery Care

    Immediately after surgery, the patient will be observed after surgery to ensure recovery is as smooth and trouble-free as possible. The anaesthetist, assisted by the recovery room staff, will continue to monitor the patient’s condition carefully.

    The patient will feel drowsy for a little while after he/she wakes up from the anaesthetic. He/she may have a sore or dry throat, feel sick or have a headache. These are temporary and he/she will recover from them soon.

    To help the recovery process, the patient may be given oxygen to breathe, usually by a clear plastic facemask, and encouraged to take deep breaths and to cough.

    Only when the patient is fully awake and comfortable will he/she be transferred back to the room/ward or waiting area before returning home.

    The patient may also experience some dizziness, blurred vision or short-term memory loss, but these will pass quickly. If he/she experiences any worrying after effects, he/she should contact his/her anaesthetist.

    Going Home
    If the patient is having "day surgery", make sure there is someone to accompany him/her home. For the next 24 hours, the patient must not:

    • Drive a car/motorcycle
    • Make important decisions
    • Use any dangerous equipment or tools
    • Sign any legal documents
    • Drink alcohol or take sedatives
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