ANAESTHESIA, DENTAL
A
Two types of anaesthesia may be used:
local (see
anaesthesia, local)
and general
(see
anaesthesia
,
general
).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
localized area.
anaesthesia, dental
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
anaesthetic (see
anaesthesia, 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
nerve block).
For
more complicated procedures, such as
periodontal (gum) surgery and multiple
tooth extractions, general anaesthesia
(see
anaesthesia, general)
is carried out.
anaesthesia, epidural
See
epidural anaesthesia.
anaesthesia, general
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-
thetist,
who
gives
combinations
of
drugs by injection, inhalation, or both.
The anaesthetist is also responsible for
the
pre-anaesthetic
assessment
and
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
barbiturate
drug,
usually via a
cannula
(a blunt-
ended tube), which is left in place in
case further drugs need to be given.
Anaesthesia is maintained by the inhala-
tion
of
anaesthetic
gases
such
as
enflurane
or halothane, which may be
introduced into the lungs via a face
mask or an
endotracheal tube
(a flexible
tube passed into the
trachea
through the
nose or mouth). During the anaesthetic,
blood pressure, pulse, oxygen saturation
(see
oximeter
), and other vital signs are
monitored continuously. The principal
stages in administering, maintaining,
and reversing general anaesthesia are
shown in the illustrated box.
POSSIBLE COMPLICATIONS
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
antiemetic drugs.
anaesthesia, local
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
before
bronchoscopy
(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
gel before
cystoscopy
(examination of the
urethra and bladder using a rigid or flex-
ible viewing tube).
For minor surgical procedures, such
as stitching
of small
wounds, local
anaesthesia is usually produced by dir-
ect injection into the area to be treated.
To anaesthetize a large area, or when a
local
injection
would not
penetrate
deeply enough into body tissues, a
nerve
block
(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
epidural anaesthesia,
which is
used in childbirth or caudal block, and
spinal anaesthesia,
which is used for sur-
gery on the lower limbs and abdomen.
POSSIBLE COMPLICATIONS
Serious reactions are uncommon, but
repeated use
of topical preparations
may cause local allergic rashes.
LOCAL
ANAESTHETICS
Drug
Common uses
How taken
tetracaine (amethocaine)
Prior to taking a blood sample
or inserting a cannula
Gel
benzocaine
To treat painful conditions of
the mouth and throat, painful
anal conditions (e.g.
haemorrhoids), skin wounds
Lozenges,
suppositories, spray,
cream, ointment
bupivacaine
As nerve block (e.g.epidural
anaesthesia and caudal block)
Injection
cocaine
For surgery on the nose,
throat and larynx
Spray, liquid
lidocaine (lignocaine)
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,
cream, ointment,
liquid, eye-drops,
suppositories
prilocaine
As nerve block (e.g.
epidural anaesthesia
and caudal block)
Injection
42
previous page 41 BMA A Z Family Medical Encyclopedia   2004 read online next page 43 BMA A Z Family Medical Encyclopedia   2004 read online Home Toggle text on/off