body during surgery. General anaesth-
esia is usually induced by intravenous
injection of a
maintained by inhalation of anaesthetic
gases such as
which may be
introduced into the lungs via an
During the anaesthetic,
the pulse, blood pressure, and other
vital signs are continuously monitored.
General anaesthetics have become
much safer, and serious complications
are rare. However, severe pre-existing
diseases such as lung or heart disorders
increase the risks. 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 during examinations,
diagnostic or treatment procedures, and
surgical operations. Local anaesthesia
is produced by the administration of
drugs that temporarily interrupt the
action of pain-carrying nerve fibres.
Local anaesthetics applied topically
before injections or blood tests include
sprays and skin creams and ointments.
These are often used for children. For
minor surgical procedures,
stitching of small wounds, local anaes-
thesia is usually produced by direct
injection into the area to be treated. To
anaesthetize a large area, or when local
injection would not penetrate deeply
enough into body tissues, a
may be used. Nerves can also be
blocked where they branch off from the
spinal cord, as in
which is widely used in childbirth, and
spinal anaesthesia, which is used for
surgery on the lower limbs and abdomen.
Serious reactions to local anaesthetics
are uncommon. Repeated use of topical
preparations may cause allergic rashes.
A term for the group of
drugs that produce
the medical discipline concerned with
A procedure for enlarg-
ing the anus. Anal dilatation is used to
treat conditions in which the anus be-
comes too tight, such as
. It is also used to treat
. Anal dilatation is usually
performed under general anaesthesia.
Reflex anal dilatation, in which the anus
dilates in response to local contact,
may occur in certain anal disorders or
after repeated anal penetration.
The loss of mucus, pus,
or blood from the anus.
( inflam -
mation of the rectum) can all cause
Drugs that stimulate
breathing. Replaced by
are seldom used now.
A common anal disorder
caused by an elongated ulcer or tear
that extends upwards into the anal
canal from the anal sphincter. A fissure
may be caused by the passage of hard,
dry faeces. There is usually pain during
defaecation and the muscles of the
anus may go into spasm. There may be
a small amount of bright red blood on
faeces or toilet paper.
The tear often heals naturally over a
few days. Treatment of recurrent or per-
sistent fissures is by
a high-fibre diet, which helps soften the
faeces. Surgery to remove the fissure is
An abnormal channel con-
necting the inside of the anal canal with
the skin surrounding the anus.
An anal fistula may be an indication of
Crohn's disease, colitis,
or cancer of the
colon or rectum (see
). In most cases, it
results from an
for unknown reasons in the anal wall.
The abscess discharges pus into the anus
and out on to the surrounding skin.
An anal fistula is treated surgically
by opening the abnormal channel and
removing the lining. The wound is then
left to heal naturally.
Loss or reduction of pain
sensation. Analgesia differs from
in that sensitivity to touch is still
preserved. (See also
Drugs used to relieve
pain. The 2 main types are nonopioid
(NSAIDs), are useful in the treatment of
mild to moderate pain (for example,
headache or toothache). Combinations