Sub-topics

Sedatives
Painkillers
Antacids
Antiemetics
Antibiotics

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.

Sedatives

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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.

Painkillers

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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’.)

Antacids

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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 you are so unfortunate as to suffer this complication, 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 (fat), then you might be given all three types of drugs. (People who are very fat tend to have large volumes of very acid fluid in the stomach.

Antiemetics

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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.

Antibiotics

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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.