What is anaesthesia?
General anaesthesia (from Greek “without sensation”) is a reversible state of controlled, temporary loss of sensation or awareness which cannot be interrupted by stimulation.
By Dr Paul Williams and Dr Andrea Santoro
An anaesthetist is a specialist doctor trained in all aspects of anaesthesia, who, after obtaining their medical degree, has spent at least two years working in the hospital system before completing a further five years of training in anaesthesia.
Clinical anaesthesia is built on the knowledge of physiology (how the body works) and pharmacology (how medications work in the body). Anaesthetists have an extensive knowledge of medicine and surgery and understanding of the basic sciences. They know how the body responds to anaesthesia and surgery, and how a patient’s health affects these responses.
Note: the information provided below is not a substitute for a direct and individualised discussion with & assessment by your treating specialist anaesthetist, that will occur prior to surgery.
Australia is one of the safest countries in the world to have an anaesthetic due to rigorous training, continual professional development and continuing medical education that is required of anaesthetists within Australia to maintain registration. A tailored discussion of risk associated with anaesthesia for surgery will occur with your anaesthetist prior to surgery. This is an opportunity to ask any additional questions you may have.
Allergy under anaesthesia is rare occurring 1 in 5,000 to 1 in 10,000 anaesthetics. Most of the people who experience severe allergy or anaphylaxis do well with the appropriate emergency treatment from the anaesthetic team. Allergy to anaesthesia medications or serious reactions to them is exceedingly rare.
Be aware that false eyelashes may be damaged or removed by anaesthesia gels and tapes. We suggest not getting these placed close to the surgery.
Nail polish may interfere with anaesthesia monitoring of circulation and oxygen levels in your blood. Ideally nail polish should be removed prior to surgery. At least one nail (finger or toe) should be polish free. At least one nail on each side should be free for acrylic nails.
Do not wear makeup or apply moisturiser to your face on the day of surgery. It interferes with anaesthesia monitoring and application of tapes.
Beards may interfere with anaesthesia. If your beard is not important to you it is suggested, but not essential, to shave prior to anaesthesia.
Jewellery can cause pressure sores on the skin (as you don’t move under anaesthesia- like you would in normal sleep) and can also conduct electricity from surgical instruments causing burns so it is best not to wear any. If you are unable to remove jewellery you must inform the nurse who admits you to hospital. Precautions can be made to reduce these risks.
In the weeks prior to elective surgery and anaesthesia regular cardiovascular exercise is recommended as it has been shown to assist in your recovery, even as little as a 4-6 weeks regular exercise prior to surgery will reduce your risk.
Exercise may be restricted following surgery, typically for 2-4 weeks depending on the surgery.
Smoking is harmful and can impact on your surgery and anaesthesia. Ideally smoking should be stopped 6-8 weeks prior to elective surgery, with increasing benefit with up to 6 months cessation. Smoking cessation for this period of time removes the irritant effects of smoking, decreasing your associated risks while improving your capacity to heal from surgery. Stopping smoking is difficult and if stopping is not possible, a period of abstinence of greater than 12-24 hours is also useful to remove nicotine from your bloodstream and allow more oxygen into your bloodstream during anaesthesia and recovery.
Alcohol in the 24 hours before and after surgery should be avoided as it can interact with sedatives and analgesics (pain medicines) received during anaesthesia. Alcohol should not be ingested while on strong pain medicines, such as endone, codeine (panadeine forte), tramadol & tapentadol, as they interact and may cause you harm.
Recreational drugs should not be taken prior to or after your anaesthesia. If you take recreational drugs you should let your anaesthetist know as this may impact on the amount of anaesthesia required OR your tolerance to analgesics (pain medicine) depending on the type of drug & regularity of use. Abstinence from recreational drugs for one week prior to anaesthesia is recommended.
Fasting? (not eating and drinking)
The hospital will contact you prior to surgery, usually the day before surgery & prior to 7pm to tell you when to arrive at hospital and when to start fasting. Different hospitals have slightly different policies. In general, you will be requested to stop eating and drinking at least 6 hours prior to the estimated surgical start time. Drinking water will be allowed for up to 2 hours prior to the planned surgical start time. Fasting is mandatory in elective surgery to avoid the rare but serious complication of ‘aspiration’ (stomach contents entering the lungs) which can rarely occur, as anaesthesia is not the same as normal sleep.
Bring all your regular medicines to hospital so that the drugs, doses and timing of drugs can be confirmed as required. Continue all your medicines unless instructed by your surgeon or anaesthetist to stop. Once fasting you can take your normal tablets with a sip of water OR enough to get them down.
Blood thinners: if you are on drugs that thin your blood (anticoagulants) notify your surgeon and anaesthetist who will let you know to continue, stop or adjust these medicines around surgery.
- Diabetic tablets are not taken on the day of surgery.
- Newer diabetic tablets (SGLT-2 inhibitors OR ‘Gliflozines’) need to be stopped 3 days prior to surgery
Diabetics on insulin need a plan for insulin and blood sugar management during fasting. Insulin management should be directed by your endocrinologist, surgeon or anaesthetist. Type 1 diabetes have an absolute requirement for insulin and so some form of insulin at a safe level is required even while starving.
Scans: bring all scans (CT, MRI, X-ray) that are relevant to your surgery or anaesthesia. They will be required to perform the surgery safely.
Pre-medication with sedatives is not normally required with modern anaesthesia. If you feel you require a sedative or normally take these medications you must inform your anaesthetist and they can make a plan with you as sedatives may interact with anaesthetic medicines.
A mild cold usually has little impact on anaesthesia for a healthy person. Your anaesthetist is best able to assess you and if you are suffering from a significant illness (Fevers over 38 degrees and/or a lower chest infection) elective surgery may be postponed to minimise the risks associated with being unwell at the time of surgery. Your safety will be the most important consideration when this decision is made.
Anaesthesia time is commonly experienced as ‘lost time’ as anaesthesia is not the same as normal sleep. Some people do report dreaming during anaesthesia. This is more likely to occur during periods of lighter anaesthesia such as when you are going to sleep (induction) or during waking (emergence).
Memory of events during surgery are referred to as awareness and fortunately this is rare. There are different types of awareness referred to as implicit or explicit awareness. Implicit awareness occurs when specific events are not remembered but you may have a ‘feeling’ you remember something, similar to waking after a night’s sleep knowing you had a dream without remembering what the dream was about.
Explicit awareness is when a patient remembers specific events like music, conversations or even surgery itself- these explicit awareness events are very rare.
All types of awareness combined are fortunately rare, occurring in about 1 in 1000 patients. This estimated rate includes high risk patients such as emergency & trauma surgery, obstetrics (mothers having a baby under general anaesthesia), open heart surgery & very unwell patients. The estimated rate of awareness in healthy elective surgery patients in reality is much lower.
A patient continuously receives anaesthetic medicine while ‘asleep’. In general, once ceased it takes 10-30minutes to wake from anaesthesia. This is dependent on a patients age, type and duration of anaesthesia and underlying health. It takes up to 24 hours for anaesthesia to be cleared from your body.
Nausea & vomiting are common following anaesthesia, occurring in 1 in 3 anaesthetics. The risk of nausea & vomiting is related to the type of surgery, the age and gender of the patient (higher in females and children), type of anaesthesia, patients previous experience as well as other factors. Your anaesthetist routinely makes a risk assessment of nausea and vomiting and alters or adds medicines administered as part of your anaesthetic to minimise this side effect.
Confusion following anaesthesia is referred to as delirium or post-operative cognitive decline and is related to the anaesthesia, patients age, and pre-surgical brain function. In children, brief confusion (delirium) is seen in approximately 10% and usually settles by itself within 30 minutes. Confusion in adults is uncommon, being more likely in the elderly and those with pre-existing cognitive (thinking) impairment. It is rare to have significant persistent confusion following anaesthesia in low risk patients.
A breathing tube is commonly placed during general anaesthesia for safety reasons. Your throat is very sensitive and the placement of a breathing tube can cause some irritation. Generally speaking, the rates of sore throat range from 1 - 3 people in 10 or up to 30%. A sore throat caused by the breathing tube OR anaesthesia generally settles spontaneously (by itself) over one to two days.
You legally MUST NOT drive, operate machinery, sign documents or make important decisions for at least 24 hours following anaesthesia. There may be surgical reasons that extend your inability to drive beyond 24 hours.
Following day surgery (going home the same day as your anaesthesia) you MUST be discharged from hospital into the care of a RESPONSIBLE ADULT who may care for you on the first post-operative night, for your safety. If this is not possible you should stay the first night in hospital.
If you are not required to stay in hospital and wish to go home but have no-one to take you another option is utilising home nursing services that are able to take you home and care for you on the first night. These services need to be organised and paid for in advance.
Yes. It is essential that you have a responsible adult to care for you for at least the first 24 hours including during your transfer from hospital to home if you are discharged the same day as your surgery/ anaesthesia.
Death as a direct cause of anaesthesia is very rare. The incidence in Australia is estimated at 1 in 50,000 to 1 in 80,000 anaesthetics. To put this number into perspective the rate of road related deaths in Australia is between 1 in 10,000 to 1 in 15,000 per year.
Children are frequently unwell with minor coughs and colds, most often surgery can proceed safely.
Children with a significant lower chest infection or fever may be at increased risk of anaesthetic complications. The risk is higher in younger children, when they have a moderate to high fever, asthma, or when there is a smoker in their household.
If your child is unwell inform the surgeon, anaesthetist and/or hospital on the day prior to surgery. Your anaesthetist will decide whether it is safe to proceed or to postpone surgery. Sometimes this decision is not able to be made over the phone, and in this case an assessment will be done on the day of surgery when a consultation and examination of your child can be performed by your anaesthetist.
The decision to postpone surgery is not taken lightly and is only done in the interest of your child’s safety.
The approach taken to anaesthetising a child differs from that in adults. Every effort is made to make the experience of ‘going to sleep’ as pleasant as possible. On most occasions, children will be able to go to sleep breathing through a mask rather than having an injection or needle. A parent or guardian can be with their child as they go to sleep. Young children can sit on their parents lap or lie on the bed while they go to sleep. Your anaesthetist will try their best to engage your child in an open and friendly manner, to put your child at ease. Children can bring a soft toy, comforter or device into the operating room until they fall asleep. After surgery, you will re-join your child in the recovery room as they start to wake.
Malignant hyperthermia is a rare life-threatening disease that can occur under anaesthesia. It is a reaction that occurs when specific anaesthetic medicines trigger a process within the bodies muscles that result in uncontrolled heating. When untreated MH will most often result in death. Anaesthetists are trained to detect and treat this illness and as a result the survival rate in Australia is very high.
Thankfully, this illness is rare and usually (but not always) hereditary. The risk of genetic susceptibility (the likelihood of having genes that predispose) to Malignant hyperthermia is 1:5000. The likelihood of MH occurring is much less at 1:50000.
If someone in your family or extended family has had Malignant Hyperthermia or has been diagnosed as susceptible, you MUST inform your surgeon and anaesthetist when booking surgery so a plan for a safe ‘trigger free’ anaesthetic, in a suitable location, can be made in advance. When medicines that ‘trigger’ Malignant Hyperthermia are not used the MH reaction is NOT triggered and anaesthesia can proceed safely.