What is an inhalational general anaesthetic?
An inhalational anaesthetic is a way of sending you off to sleep for an operation. This is where gases are used to put you to sleep instead of using an injection.
We simply hold a mask over your face and you breathe (inhale) the anaesthetic gases; hence the name ‘inhalational’. The gases are absorbed through the lungs into the blood stream and reach your brain. As long as you are breathing the anaesthetic gases you will remain asleep. This way you will be unaware of anything during your surgical procedure.
This is one way of giving a general anaesthetic (GA). The other is to give special medications into a drip to make you fall asleep. Either way, you are unaware of what is happening and hence feel no pain during your operation.
The aim of the inhalational GA is to allow you to have a pain free operation. Being asleep with an inhalational anaesthetic may be the best and safest way to do this.
There are several benefits. The main benefit of any general anaesthetic is that it allows you to have your operation in comfort. The general anaesthetic also enables the surgeon to perform your operation with greater ease and safety.
The inhalational method is good for people with a fear of needles. It may be possible to allow you to breathe gases until you are asleep; the drip can be put in afterwards.
The most important benefit is that you can be put to sleep in the safest way possible. You may need an inhalational anaesthetic for reasons outlined above i.e. if you have a short neck or restricted neck movement. If this is so, then drugs into a drip may not be safe for you. Drugs into a drip can stop you breathing. This is not a problem when it is planned and can be controlled by the anaesthetist.
If you continue breathing as you go off to sleep, this is very safe. Once asleep the anaesthetist will decide whether it is safe to continue. S/he will then be able to put the breathing tube through your mouth and into your lungs as usual. If not you will be woken up and other anaesthetics will be used (see below).
Are there any alternatives?
There are several alternatives to an inhalational general anaesthetic.
Awake fibreoptic intubation
You can still have a general anaesthetic, with different ways to get the plastic tube down into your lungs. This can be done with an awake fibreoptic intubation.
An awake fibreoptic intubation (AFI) is a very specialised procedure that is used to place the breathing tube into your windpipe (intubation) while you are awake. This can be done either through your nose or mouth.
Local anaesthetic is used to numb from your lips, or nose to your windpipe (trachea). This is done under a sedative, where you are made to feel sleepy and relaxed. Once comfortable and numb in your mouth and throat, the breathing tube is gently slid into your windpipe. This is done with the help of a fibreoptic camera, so that the anaesthetist can see down to your voice box and into your windpipe. As soon as the breathing tube is safely secured you will be put off to sleep in the normal way for your operation.
It may be possible to perform an epidural where the lower part of the body goes numb and is pain free. This involves placing a plastic tube next to the nerves in the spine, so that drugs can be injected, making the nerves stop working temporarily. This would avoid the need for a general anaesthetic at all.
Alternatively a single injection, like an epidural, but without putting the plastic tube in, can be used. This single injection is called a spinal. It does not last as long as an epidural. This would also avoid the need for a general anaesthetic.
Another method is to make individual nerves go numb temporarily. This could be your whole arm or leg. This makes a small region of the body numb, hence the name ‘regional anaesthetic’. This would also avoid the need for a general anaesthetic.
Sometimes, if the surgery is minor, local anaesthetic injections can be used to numb the operation area.
More recently, some patients have used hypnosis to help them during an operation. Very few people can tolerate operations with hypnosis alone, but it may assist with the relief of anxiety, when used with other nerve blocking methods.
Whether any of these alternatives are suitable, depends on the part of the body to be operated on. The length of the procedure is also important. All of these injection methods can be used with sedation into a vein to help relieve anxiety.
If you are to have one of these procedures there is another information leaflet that will tell you more about it.
Who should have it done?
General reasons for having an inhalational anaesthetic are listed below:
Small children. It may be best to use the inhalational anaesthetic if they are afraid of injections. It would cause them less distress. It may also be difficult to put a needle in very small veins. Sometimes there is a medical reason not to have an inhalational anaesthetic. It may be that the child has the risk of a full stomach. This could be after an accident for instance. If so a drip must be placed in a vein first and the child put off to sleep quickly. This stops vomit getting into the lungs.
Adults that are scared of needles (needle phobic). If there is no medical reason not to an inhalational anaesthetic can be used. Again it may be that you have the risk of a full stomach. This may be due to urgent, unplanned surgery. As with the children, you will be put off to sleep quickly with drugs into a drip instead of an inhalational anaesthetic. This will stop vomit getting into your lungs.
When it is expected that it may be difficult putting a tube from your mouth to your lungs (as described previously).
Who should not have it done?
If you are unwilling to have a general anaesthetic you should not have one. If an epidural, or other method where you can stay awake is safe, then a general anaesthetic need not be performed.
Patients with the medical conditions listed, should not have a general anaesthetic:
The most common reason for not having a general anaesthetic is a throat or chest infection. During the general anaesthetic a tube is passed through the throat to the lungs. Infection can be passed from the throat to the lungs. This will make you ill after the operation and delay your recovery. If there is already infection in the lungs, it can be made much worse by the general anaesthetic. This is a serious problem. The right thing to do is to cancel the operation until the infection has gone. This may require antibiotics. If you have a sore throat or a cough producing phlegm, then tell your anaesthetist.
Previous allergy to general anaesthetic drugs. There is a relatively rare, but serious condition called malignant hyperpyrexia. This condition runs in families. Anaesthetic gases and other drugs used in a general anaesthetic can cause a severe rise in temperature in patients who suffer from this condition.
Where you have had problems with your windpipe or trachea in the past. It may be narrowed or have had previous surgery. It is not impossible to have a general anaesthetic, but other methods may be simpler and safer. Again an epidural may be suitable.
All patients can have a general anaesthetic if absolutely necessary. There are MANY situations too numerous to mention in this leaflet, where it is preferable to avoid a general anaesthetic if possible. The risks and benefits should be discussed with your anaesthetic doctor.
Author: Dr Sean White FRCA. Consultant in pain and anaesthesia
© Dumas Ltd 2006