Two types of anaesthesia may be used:
).A patient given
a local anaesthetic remains conscious,
and sensation is abolished in only a spe-
cific part of the body. A patient under
general anaesthesia is rendered uncon-
scious and maintained in this state with
a combination of drugs that are either
injected into a vein or inhaled.
Damage to nerve tissues by injury or
disease can produce anaesthesia in a
Loss of sensation induced in a patient to
prevent pain during dental treatment.
Topical anaesthetics (usually using the
drug lidocaine (lignocaine) as a cream
or spray) are often used on the surface
of the gums before injection of a local
For minor procedures, a local anaes-
thetic is injected either into the gum at
the site being treated or around the
nerve a short distance away (a procedure
known as a peripheral
more complicated procedures, such as
periodontal (gum) surgery and multiple
tooth extractions, general anaesthesia
is carried out.
Loss of sensation and consciousness that
is induced to prevent the perception of
pain throughout the body during sur-
gery. General anaesthesia is also used to
abolish muscle tone and cardiovascular
reflexes in the patient.
The state of general anaesthesia is
produced and maintained by an anaes-
drugs by injection, inhalation, or both.
The anaesthetist is also responsible for
medication of patients, their safety dur-
ing surgery, and their recovery during
the post-anaesthetic period.
HOW IT IS DONE
General anaesthesia is usually induced
by intravenous injection of a
usually via a
ended tube), which is left in place in
case further drugs need to be given.
Anaesthesia is maintained by the inhala-
or halothane, which may be
introduced into the lungs via a face
mask or an
tube passed into the
nose or mouth). During the anaesthetic,
blood pressure, pulse, oxygen saturation
), and other vital signs are
monitored continuously. The principal
stages in administering, maintaining,
and reversing general anaesthesia are
shown in the illustrated box.
General anaesthetics have become much
safer and serious complications are now
rare. However, the presence of severe
pre-existing diseases, such as lung or
heart disorders, increase the risks of the
procedure. Minor after-effects, such as
nausea and vomiting, are usually con-
trolled effectively with
Loss of sensation induced in a limited
region of the body to prevent pain dur-
ing diagnostic or treatment procedures,
examinations, and surgery. Local anaes-
thesia is produced by administration of
drugs that temporarily interrupt the
action of pain-carrying nerve fibres.
HOW IT IS DONE
Local anaesthetics may be applied topi-
cally, before injections or blood tests, as
sprays, skin creams, and ointments. These
are often used for children. The throat,
larynx (voice-box), and respiratory pas-
sages can be sprayed with an anaesthetic
(examination of the
bronchi, the main airways of the lungs,
using a rigid or flexible viewing tube)
and the urethra can be numbed with a
(examination of the
urethra and bladder using a rigid or flex-
ible viewing tube).
For minor surgical procedures, such
anaesthesia is usually produced by dir-
ect injection into the area to be treated.
To anaesthetize a large area, or when a
deeply enough into body tissues, a
(in which the local anaesthetic is
injected around nerves at a point remote
from the area to be treated) may be used.
Nerve impulses can also be blocked
where they branch off from the spinal
cord, as in
used in childbirth or caudal block, and
which is used for sur-
gery on the lower limbs and abdomen.
Serious reactions are uncommon, but
of topical preparations
may cause local allergic rashes.
Prior to taking a blood sample
or inserting a cannula
To treat painful conditions of
the mouth and throat, painful
anal conditions (e.g.
haemorrhoids), skin wounds
As nerve block (e.g.epidural
anaesthesia and caudal block)
For surgery on the nose,
throat and larynx
For relief ofpain during
dental treatment; for spinal
anaesthesia, nerve blocks
(e.g. epidural anaesthesia),
eye surgery, and before
taking blood samples in
children; for urethra prior to
catheterization and larynx
prior to laryngoscopy
Injection, gel, spray,
As nerve block (e.g.
and caudal block)