Preparing for your anaesthetic

Home Preparing for your anaesthetic

Here’s what you need to know as you prepare for anaesthetic.

This guide covers important aspects, from meeting your anaesthetist to fasting and medications.

What to Expect on the Day of Your Surgery

Almost all patients are now admitted to hospital on the same day as their operation. Depending on the hospital’s requirements, you may be waiting for some hours.

  • Make sure that you leave plenty of time to get to the hospital and the admissions area prior to your designated arrival time.
  • There can often be a considerable waiting period at hospitals, so bring something to read or listen to and try to remain relaxed – as difficult as this may be! Your anaesthetist and the hospital staff are there to look after you.
  • There will normally only be limited time available for you to talk to your anaesthetist before your procedure. If you are having a major procedure, or have concerns about your health or anaesthesia, it is beneficial to consult with your anaesthetist at a separate visit before the day of your surgery.

Remember, if you have any concerns or questions please contact your anaesthetist prior to coming to hospital.

Telling your anaesthetist..

…exactly what tablets and medications you are taking is one of the most important things you can do.

This includes both prescription and non-prescription drugs, including alcohol and nicotine.

 You should also mention if you are taking any herbal preparations and vitamins.

Meeting your anaesthetist

You may meet your anaesthetist in a preoperative Assessment Clinic. Otherwise, you will meet shortly before you enter the Operating Room. This meeting may take place on a ward, in an admissions unit, or in a holding area outside the Operating Room.

Your anaesthetist will review information contained in your hospital record or chart, such as the results of any tests you have undergone. He or she will ask you some additional questions, such as your, or your relatives’, experience with anaesthetics. Your anaesthetist will talk to you about possible choices of anaesthetic, such as between general and regional or local anaesthesia, and about any specific problems or concerns you have. In addition, your anaesthetist will discuss with you the different choices for postoperative pain management.

After this, your anaesthetist will examine you, by looking at your mouth, your teeth, and the veins of your hands, arms, and neck, and may listen to your chest. If you are to have a regional or local anaesthetic, your anaesthetist may also look at the area of your body where the anaesthetic is to be injected, such as the small of your back.

As the last part of pre-anaesthetic assessment, the anaesthetist makes an overall evaluation of you and assigns a numerical classification. This is known as the ASA Class, where ASA stands for American Society of Anesthesiologists. Although it was developed in the United States, the ASA Class is now used worldwide as a way of classifying patients according to how well or ill they are. This classification refers only to your physical condition at the time of assessment. The higher the score, the less well you are. An ‘E’ after the appropriate classification designates that you are to undergo an emergency operation.

  • ASA Class I: A normal healthy patient

  • ASA Class II: A patient with mild systemic disease

  • ASA Class III: A patient with severe systemic disease limiting activity but not incapacitating

  • ASA Class IV: A patient with incapacitating systemic disease that is a constant threat to life

  • ASA Class V: An extremely ill patient who is not expected to live 24 hours with or without an operation.

The ASA classification is not a score of how risky the anaesthetic might be for you. However, the ASA Class has been shown to correlate with the risk of complications occurring after the operation, particularly the risk of dying. This risk is related to the operation performed and how well or ill a patient was before the procedure (or a patient’s preoperative physical condition). In general, there is very little contribution from the anaesthetic to the chance of a patient dying after a procedure.


Ask questions...

This is your opportunity to ask about your anaesthetic.

Even though you may think that the time for questions is short, you should ask whatever you want and make sure that all your questions are answered.

If you had an operation in the past, then chances are that you were admitted to hospital one to two days beforehand. During this period you underwent all the steps necessary for preparation for anaesthesia and surgery, being examined by various doctors, undergoing tests, and meeting with your anaesthetist the evening before surgery.

In many parts of the world, patients are no longer admitted to hospital the night before the operation. Instead, they are admitted on the day of the procedure for all elective surgery. This is known by such terms as ‘Admit Day of Procedure’ (ADOP) or ‘Day of Surgery Admission’. Patients arrive at the hospital for admission as little as one to two hours before the operation. This shortened period of hospital stay is more efficient, allowing more patients to be treated in a hospital than previously.

Because you probably will not be admitted to the hospital until a few hours before the operation, all the tests and preparation that would once have been done when you were in the hospital are done in the days or weeks before. You may be asked to attend an anaesthetic assessment clinic or preadmission clinic, where you will be evaluated.

However, if you require an emergency operation, your anaesthetist needs to assess you quickly. If time permits, you are assessed in the Accident & Emergency Unit or on the ward; otherwise the assessment takes place when you arrive in the Operating Room. In life-threatening emergencies, the opportunity for your anaesthetist to assess you is obviously very limited. Often your anaesthetist only has the opportunity to ask you a few specific questions, such as “Do you have any allergies?”, “Do you take any medication?”, “Have you had any problems with anaesthesia in the past?” These questions might be asked as your anaesthetist starts  intravenous lines and attaches monitors. Frequently, your anaesthetist must rely on your surgeon and other doctors or paramedical staff to provide an overall summary of your previous health and your current condition. In addition, anaesthetists rely on their own observational skills. In extreme emergencies, there may be no opportunity for your anaesthetist to discuss with you the options or risks of anaesthetic care.

Anaesthetists recommend that you do not have anything alcoholic to drink on the day before and the day of the operation. In general, patients who drink alcohol every day need higher doses of anaesthetic drugs than those patients who do not consume any alcohol. So it is also important to tell your anaesthetist exactly how much alcohol you drink and how often.

Why is fasting important?
If you vomit when you are awake, or even when you are asleep at night (and not anaesthetised), your reflexes prevent any of that vomit being sucked into your lungs. You cough and splutter to clear the area around the back of your throat and larynx. Then you can breathe again.

When anaesthetised (or very drunk, or affected by an overdose of sedatives or certain street drugs), you may be able to vomit but some of your protective reflexes do not work. There is therefore a possibility that fluid from the stomach will regurgitate – that is, run up your oesophagus and into the back of your throat. Should this happen when your level of consciousness is decreased, then you cannot protect yourself by swallowing and coughing. The fluid may then pass into your windpipe or trachea and down into your lungs. This is known as aspiration. Should you inhale some stomach contents, then there is the risk of suffocation, particularly if undigested food is present. The acid in your lungs may also cause severe wheezing and a lack of oxygen. Later, pneumonia may develop. This pneumonia is a particularly severe form because of the effect of the acid on the delicate tissue of the lungs.

How long do patients go without food or drink?
Until about ten years ago, it was common for patients scheduled for elective surgery to fast from midnight on the night before surgery. If the operation was scheduled in the afternoon, patients had to fast for periods of up to 16–18 hours. In the late 1980s, a number of scientific studies were carried out that questioned the validity of this fasting policy. In some countries, professional organisations have changed their recommendations to allow shorter hours of fasting. For example, the Canadian Anesthesiologists’ Society produced a revision to the Guidelines to the Practice of Anesthesia in 1996. These new guidelines stated that fasting policies should take into account the age of the patient, as well as any medical problems that the patient might have. The guidelines also recommended that a patient should not eat any solid foods on the day of surgery, but could drink clear fluids up to three hours before the operation. Despite increasing amounts of scientific evidence about the safety of following guidelines such as these, standard textbooks of anaesthesia still recommend that patients be ‘NPO’ (‘Nil per os’ or ‘nothing by mouth’) for six to eight hours before anaesthesia and surgery. It is likely that such statements will change in the future, although anaesthetists still recommend in general that patients do not eat any solid food after midnight before the scheduled operation.

Emergency surgery
If you have been in an accident, are in pain, or have been given an injection of a painkiller, the speed at which food leaves your stomach and passes downwards is slowed. This results in you having what anaesthetists term a ‘ full stomach’, which increases the possibility of stomach contents being regurgitated back up the throat. Theoretically, your operation could be delayed until your stomach has emptied, although this is not always appropriate. There are ways of minimising the possibility of regurgitation of gastric contents. Some patients may need to have a nasogastric inserted through the nose, down the oesophagus, and into the stomach. The fluid in the stomach can then be suctioned out through the tube, although removing solids is still a problem. This technique is important in patients who have an obstruction of the bowel. Unfortunately, suctioning cannot ensure that the stomach is empty, but only one that is ‘less full’. Drugs that are currently used to lessen the risk of regurgitation include those to neutralise stomach acid, those to decrease acid production, and those to increase the downward emptying of the stomach.

Many patients now take herbal and other over the counter (OTC) medications and supplements. Some of these medications may interact with anaesthetic drugs, as well as those used to relieve pain in the  postoperative period. For example, St John’s Wort is a herbal preparation commonly used by patients who are feeling ‘blue’ or a little depressed. This herb is known to affect the length of time that certain prescription drugs last, as well as some anaesthetic agents.

Other non-prescription items of importance are antacids, such as Mylanta, Maalox, or Pepto-Bismul. These antacids come either as a thick creamy liquid or as tablets. You should not take any of these after midnight the day before your operation. If inhaled into your lungs, these antacids can cause damage from the tiny particles from which they are made.

You should therefore give your anaesthetist a complete list of every herbal, vitamin, and supplement you are taking, in addition to your prescription medication. Some anaesthetists actually prefer that you bring to the hospital or clinic all of the medications, herbals, supplements and vitamins that you actually take, even if it means bringing them in a ‘shopping bag’. That way, your anaesthetist can read the labels of each of the containers. This is particularly important if you are taking unusual supplements or those that contain more than one ingredient.

There are two types of medication which you might be asked to take before your anaesthetic. The first group is the regular medications or tablets that you are already taking. The second group is additional medications that your doctors might prescribe before your anaesthesia and operation or procedure.

Take them or stop them?
You may be taking several different regular medications, particularly if you are older, or have a chronic condition such as high blood pressure, heart disease, asthma, or diabetes. In the past, anaesthetists often asked their patients to stop taking some of these tablets before anaesthesia. However, anaesthetists now prefer that their patients continue to take almost all their medications, right up to the time of surgery.

There are three major exceptions to this recommendation: some antidepressants, anticoagulants including aspirin, and diabetic drugs.

Antidepressants – monoamine oxidase inhibitors or MAOIs
There is a specific class of drugs used to treat depression, known as monoamine oxidase inhibitors or MAOIs. There is a probability of a serious drug interaction between the MAOI drug and adrenaline (epinephrine) or pethidine (meperidine), producing an over-excitation of the brain and a potentially fatal rise in blood pressure. The same reaction can occur if you are taking an MAOI drug and eat mouldy cheese or drink red wine. If you are taking this type of drug and you need to have an anaesthetic, then you and your GP or psychiatrist should arrange for the drug to be stopped before your anaesthetic. However, if you need to have an emergency operation or have not stopped taking the drug, tell your anaesthetist so he or she can avoid giving you any of the drugs which may interact.

Anticoagulants and aspirin
These drugs are used to thin the blood and reduce clotting. If you are taking warfarin or coumadin, then you must check with both your anaesthetist and surgeon for specific instructions on when and how to taper the dose of these drugs. If you have had a stroke or been threatened with one, you may be taking a type of drug known as an anti-platelet agent, or one of the non-steroidal anti-inflammatory drugs such as aspirin. You may also be taking aspirin because of heart problems or arthritis. Again, you should check with your anaesthetist and surgeon. These drugs have an effect on how certain cells in the blood stream (platelets) stick to each other when blood clots. Because the cells are no longer so sticky, there can be more bleeding during and after the operation. The effect of these drugs on blood clotting may last for as long as 14 days. Some patients can stop taking these drugs without any problems before anaesthesia and surgery. However, other patients should not stop them, including those with chronic heart disease or a past stroke. Also, patients who rely on these drugs for pain relief and other symptoms for their arthritis may find that their joints are much more painful if they stop the tablets. Again, it is vital that you ask the doctor who normally looks after you, as well as your anaesthetist and surgeon.

Diabetic drugs and insulin
If you normally take tablets for the control of blood sugar for diabetes, you should not do so on the day you are to have your anaesthetic. If you do so and then go without eating (fasting), your blood sugar might drop to a low level while you are under the anaesthetic, when you cannot complain of the symptoms of low blood sugar or hypoglycemia. In addition, one of these drugs, metformin, has been associated with the development of a severe condition where acid builds up in the blood stream. The probability of this developing is more likely in patients who undergo certain procedures, such as heart operations where the heart-lung machine is used.

On the other hand, if you are taking insulin for control of diabetes, you will want to discuss how best to manage your insulin. Ideally, patients with diabetes should be scheduled to undergo their procedures as the first case of the day. This will allow them more time during the day to recover and perhaps be able to start back on a reasonably normal diet. Some diabetics will be asked to take less than their normal dose of insulin. A few diabetics might even omit taking any insulin until the procedure is over and they are capable of eating or drinking again. All diabetic patients should have their blood sugar tested immediately before the operation and again when they arrive in the recovery room. Some patients also have their blood sugar tested during the procedure by their anaesthetist.

In general, you should be as well as possible before undergoing any anaesthetic or surgery. Sometimes, of course, surgery is necessary and there may even be some degree of urgency to have the operation. Your surgeon, perhaps together with your anaesthetist, can weigh up your need for the operation and how urgent it is, against any illness or condition you have. If you are scheduled for elective surgery, it is usual to delay the operation if you become unwell. In most cases, an optimal time will be suggested.

The final decision as to whether or not to delay your operation rests with your anaesthetist and your surgeon. It is best to contact them if you become unwell in the days leading up to your appointment. You may also wish to contact your family doctor for advice and possible treatment.

If you have a cold or the flu, it is likely that your anaesthetic and operation will be postponed. If you have a sore throat with no other symptoms, then your anaesthetist may consider that you can proceed, although your throat may be very sore afterwards. If the sore throat is an early sign of the development of a cold or the flu (and it isn’t always), then the resulting illness may be hastened and you may feel extremely unwell after the operation. Again, the decision to proceed rests with your anaesthetist and your surgeon, although if you decide not to proceed your wishes will be respected.

There is an increased probability of respiratory complications when anaesthesia is administered to a patient with an established cold or influenza. Your anaesthetist, however, is aware of the potential for complications and of the means for managing them safely. Diarrhoea is not a contraindication to anaesthesia or surgery unless it is part of a more generalised illness. One of the benefits of the developments in anaesthetic drugs and techniques is that anaesthesia is now relatively safe, even in patients who are severely ill.

Many people think of the ‘premed’ as being a tablet or injection given to produce a state of calmness. In fact, the term premedication refers to the prescribing of all drugs before anaesthesia and surgery.

These drugs may be prescribed to make you less anxious, to relieve pain, to lessen the possibility of your inhaling stomach acid into your lungs, and to lessen the possibility of your having any postoperative nausea and vomiting. In addition, you may also be given antibiotics to reduce the potential for infection. In the past, many of these drugs were given by injection. However, anaesthetic practice has changed and now almost all of these drugs can be given in tablet or liquid form.

If you are extremely anxious, ask your anaesthetist or your surgeon for something to calm you. In the past, many different drugs were used to help patients feel less anxious before anaesthesia. These drugs included barbiturates and antihistamines. Currently, you might receive one of a class of drugs known as benzodiazepines, such as midazolam, temazepam or diazepam. You may be given a single tablet or a prescription for something to take at home the night before the operation. Or you may be given a tablet, or less often, an injection, once you arrive at the hospital. However, many patients are not admitted to hospital until shortly before the operation. Because of this, you might not receive any form of sedative premed.

You may prefer not to receive any form of sedation, as this will enable you to remain in control for as long as possible before your anaesthetic and operation. Another reason is that studies have shown that patients who do not receive any sedation recover from the effects of the anaesthetic more quickly than those who were sedated beforehand. Older patients tend to remain sleepy for longer and may also have some problems with memory when sedated to reduce preoperative anxiety.

In the past, patients were often given an injection of a painkiller, such as pethidine. This injection was designed to help reduce anxiety and also to supplement the drugs given at the time of the anaesthetic. Some patients, such as those undergoing open-heart surgery, may be given an injection of a sedative and a painkiller. This helps to ensure that they are calm before the operation and that the heart is not stressed. Many anaesthetists no longer give pain-relieving drugs until the patient is actually in the Operating Room, unless the patient is already in pain.

If you are taking painkillers, such as narcotics, it is important to continue taking them so that your pain does not get out of control. But your anaesthetist needs to know about them in order to plan which drugs to give you both during and after the operation. (See also ‘Postoperative pain relief’.)

Another group of drugs that you might be given are those that lessen any chance that you might inhale some of the acid contents of your stomach into your lungs, either during or after anaesthesia. If this complication were to occur, there is an immediate possibility of suffocation by any large pieces of partially digested food that are present in your stomach. There is also a later risk of severe pneumonia from the acid contacting delicate lung tissue. This complication is known as pulmonary aspiration of gastric acid and is potentially lethal.

Three types of drugs can be used to lessen the chances of this occurring in patients who are considered at risk.

A drug that will decreases the production of acid, such as cimetidine or ranitidine, which are know as histamine2 (H-2) receptor-blocking agents.
A drug to help neutralise acid in your stomach, such as the antacid sodium citrate. Taken by mouth, sodium citrate makes your stomach contents less acid (by increasing the pH). Unlike other antacids, sodium citrate is a clear liquid and does not contain any small particles that could damage your lungs if you inhale any stomach contents.
A drug to increase the rate at which your stomach empties into the small intestine, thus decreasing the volume of fluid in your stomach. One drug used for this purpose is metoclopramide.
There are no set rules or strict guidelines for the use of any of these drugs. If you were to undergo a caesarean section, you might be given some sodium citrate. Some anaesthetists use H-2 receptor blockers in patients who have a hiatus hernia or heartburn. If you are extremely obese, then you might be given all three types of drugs. People who are obese tend to have large volumes of very acid fluid in the stomach.

Antiemetics are now commonly administered routinely, especially if you have suffered from nausea and vomiting after a previous procedure. There are a variety of antiemetics, which may be given by various routes, however, they are usually administered intravenously after the start of the anaesthetic. Some, like ondansetron, may be taken orally.

In addition, your surgeon may ask that you be given a dose of antibiotics before the procedure, because the prophylactic use of antibiotics has been shown to reduce the possibility of infection. You are most likely to be given ‘prophylactic’ antibiotics if you are to undergo almost any type of major operation, such as a hip replacement, and even some more minor ones, such as a simple hernia repair. Your surgeon may also order antibiotics if you are having a device, such as a pacemaker, implanted. Generally, your anaesthetist is not responsible for ordering antibiotics for this purpose, although he or she might order ‘prophylactic’ antibiotics if you have problems with your heart valves. Another doctor, such as a heart specialist or surgeon, may also take responsibility for ordering them.

Sometimes these antibiotics are given in the hour before the operation. In other cases your anaesthetist administers them, usually at the start of the anaesthetic. This ensures that the amount of antibiotic in your blood is as high as possible at the time of the operation.

Ideally, you should stop smoking six months before the operation. If you do quit, you may notice that you have a cough and are bringing up some phlegm. This is usually a sign that your lungs are starting to recover from the effects of the nicotine and the smoke. However, you may not have that much time to quit before the operation, or you may be unable to quit entirely. In either case, decreasing the number of cigarettes and the amount smoked of each cigarette will help. Using nicotine gum or a nicotine patch may make it easier, although neither should be used on the day you have your anaesthetic.

It is vital for your anaesthetist to know what drugs you have used in the past and when. Street or ‘recreational’ drugs, such as heroin, LSD and cocaine, can strongly influence the anaesthetic. Cocaine and ecstasy are two drugs that excite the nervous system. They may excite your heart, producing dangerous swings in blood pressure and heart rate, both during and after the operation. Drugs such as LSD can produce hallucinations, which may cause flashbacks in the  postoperative period. As a general rule, it is safer not to use any of these drugs for at least one week before your anaesthetic and operation.

Find out more


During your anaesthetic



After your anaesthetic



Advice according to procedure type