Bma Illustrated Medical Dictionary

body during surgery. General anaesth-

esia is usually induced by intravenous

injection of a barbiturate drug and

maintained by inhalation of anaesthetic

gases such as halothane, which may be

introduced into the lungs via an endo-

tracheal tube. 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 antiemetic drugs.

anaesthesia, localLoss 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, such as

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 nerve block

may be used. Nerves can also be

blocked where they branch off from the

spinal cord, as in epidural anaesthesia,

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.

anaestheticsA term for the group of

drugs that produce anaesthesiaand for

the medical discipline concerned with

their administration.

anal dilatationA procedure for enlarg-

ing the anus. Anal dilatation is used to

treat conditions in which the anus be-

comes too tight, such as anal stenosis

and anal fissure. It is also used to treat

haemorrhoids. 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.

anal dischargeThe loss of mucus, pus,

or blood from the anus. Haemorrhoids,

anal fissures, and proctitis (inflam-

mation of the rectum) can all cause

anal discharge.

analeptic drugsDrugs that stimulate

breathing. Replaced by ventilation, they

are seldom used now.

anal fissureA common anal disorder

caused by an elongated ulcer or tear

that extends upwards into the anal

canal from the anal sphincter. A fissure

may becaused 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 anal dilatationand

a high-fibre diet, which helps soften the

faeces. Surgery to remove the fissure is

occasionally necessary.

anal fistulaAn 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 colon,cancer of;

rectum,cancer of). In most cases, it

results from an abscessthat develops

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.

analgesiaLoss or reduction of pain

sensation. Analgesia differs from anaes-

thesiain that sensitivity to touch is still

preserved. (See also analgesic drugs.)

analgesic drugsDrugs used to relieve

pain.The 2 main types are nonopioid

and opioid. Nonopioid analgesics,

which include aspirin, paracetamol, and

nonsteroidal anti-inflammatory drugs

(NSAIDs), are useful in the treatment of

mild to moderate pain (for example,

headache or toothache). Combinations

ANAESTHESIA, LOCAL ANALGESIC DRUGS

A