|The word 'anaesthesia' is
derived from a Greek word, meaning absence or loss of sensation.
Anaesthesia is one of the most significant developments of modern
medicine because it allows once-unbearable medical procedures
to be performed while the patient is relaxed and asleep.
Anaesthetists are medical doctors with further training in the
specialised field of anaesthesia. They also have expertise in
intensive care medicine and pain relief, and are responsible for
pain control and anaesthesia for women in labour. However, most
of the work of an anaesthetist is in preparing hospital patients
for surgery, then caring for them during the operation.
There are 3 principle types of anaesthesia:
- General anaesthetic - putting people to sleep,
and keeping them asleep for surgery or other medical procedures
- Regional anaesthetic - numbing an area of the
- Local anaesthetic - numbing a small part of the
Often a combination of the above techniques is used to ensure
that the minimum doses of drugs are used to ensure successful
anaesthesia and a quick recovery.
|Thanks to development of
new, safer anaesthetic drugs and sophisticated monitoring equipment,
modern anaesthesia is now very safe. Several million general anaesthetics
are successfully performed each year. A recent study showed that
deaths due to an anaesthetic problem occurred in only 5 per million
|What happens during a general
|The anaesthetist is responsible
for the general welfare of the person having surgery. He or she
gives a variety of drugs that have different effects with the
overall aim of ensuring you are soundly unconscious, will have
no memory of the operation (amnesia) and suffers no pain (analgesia).
Anaesthesia usually begins when the anaesthetist injects a drug
through a fine plastic tube (cannula) inserted into a vein in
the back of the hand. Within a few seconds, this sends you quickly
and smoothly to sleep. It's known as the 'induction' of anaesthesia.
It is also possible to induce anaesthesia with anaesthetic gases,
breathed through a mask.
To maintain this unconsciousness, the anaesthetist gives a mixture
of oxygen and anaesthetic gases to breathe. This makes sure you
are unconscious throughout the operation and will not remember
anything about it. This element of anaesthesia is known as 'maintenance'.
It is sometimes necessary to have muscle-relaxing drugs. This
is often to allow the surgeon to perform the operation by relaxing
the body's natural muscle tone, which is present even when asleep.
When a muscle relaxant is used, the anaesthetist also has to control
breathing for the patient. To do this, a plastic tube is inserted
into the windpipe (trachea) and a machine called a ventilator
inflates and deflates the lungs in a highly accurate and controlled
A general anaesthetic can interfere with the body's natural cough
reflex, which normally helps prevent anything but air entering
the breathing system. When this protection for the airway is affected,
the contents of the stomach could seep back into the throat during
an operation and be inhaled, causing damage to delicate lung tissues.
This helps to explain why you are obliged to have 'nil by mouth'
for about six hours before an operation.
The anaesthetist will also use strong painkilling drugs to control
pain during and after surgery.
|Monitoring the patient
|The anaesthetist is able
to monitor precisely your condition. For example, the rate and
electrical activity of the heart, blood pressure and the amount
of oxygen in the blood are measured continuously. It's also possible
to measure the exact composition of the gases breathed in and
out. This helps to ensure the correct acid/alkaline balance of
the blood and the correct dose of anaesthetic gases.
|When the anaesthetic gases
are stopped, you begin to 'emerge' or 'recover' quite quickly.
A drug is given to reverse the effects of any muscle relaxant
used and, for all but very major operations, such as open heart
surgery, you will be breathing normally soon after the operation
|Most people have no problems
following their operation and anaesthetic. Indeed, many operations
are now planned as 'day cases', with no overnight stay in hospital.
Serious complications of an anaesthetic are very rare. However,
some people experience minor temporary side-effects. These depend
on a number of factors including the general health of the patient
and the type and length of the operation.
A little drowsiness is common but this usually wears off quickly,
particularly if the operation was short. Some patients can experience
some discomfort after their operation, but this can be relieved
by giving painkilling drugs as injection(s) or tablets.
As a result of modern anaesthetic drugs, nausea after an operation
is less common than it was. Anti-sickness medicine may also be
given if the operation itself, or the painkillers used, are known
to be common causes of nausea.
|A general anaesthetic is
not always necessary or advisable. Depending on the type of operation,
it's possible for the anaesthetist to use techniques to completely
'numb' specific parts of the body. This is known as 'regional
anaesthesia' and is used increasingly frequently to avoid the
possible side-effects of general anaesthesia. Regional anaesthesia
can also be useful in people who are too frail to undergo a general
An injection of a small amount of a local anaesthetic drug is
given near to the nerves that supply a part of the body. The local
anaesthetic temporarily prevents nerves from sending any messages
to the brain - where pain is registered - so the part of the body
is completely insensitive to pain.
A spinal anaesthetic is one of the most common types of regional
anaesthesia. It involves an injection of local anaesthetic into
the fluid that surrounds the nerves in lower part of the spine
and is used for operations below the waist or in the pelvic region.
The patient will be completely numb from the waist down for a
couple of hours or so.
An 'epidural' anaesthetic is a related technique, where a narrow
plastic cannula is left in position near to the nerves in the
back. This means that the anaesthetist can give repeated doses
of local anaesthetics (and painkillers), without further injections.
This makes it useful for longer operations. By being able to increase
the dose as required, a lower overall dose of medication can be
given so that pain is controlled without complete loss of feeling.
As the cannula can be left in place for up to several days, an
epidural can be useful for postoperative pain relief and for labour
Similar techniques are used to numb other parts of the body. For
example, the arm can be numbed with an injection into the upper
arm or armpit to allow a broken wrist to be treated.
|For operations on a small
area of the body, it is possible to simply inject local anaesthetic
at the site of the operation. This technique is often performed
by the surgeon or GP in minor surgery units, and is usually only
used for short, simple operations such as stitching a wound or
removing a mole, or other skin lesion.
|The Association of Anaesthetists
American Society of Anesthesiologists
|Healthwise (Health Information Resource
Tel : (852) 2849 2400
Fax : (852) 2849 2900
Email : email@example.com
Homepage : http://www.healthwise.org.hk/
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