of the skin and affects only the epider-
mis, the top layer of the skin. A
2nd-degree burn damages the skin more
deeply, extending into the dermis and
causing blister formation. A 3rd-degree
burn destroys the full skin thickness
and may extend to the muscle layer
beneath the skin. Specialist treatment,
and possibly skin grafts, is necessary for
3rd-degree burns. Electrical burns can
cause extensive tissue damage with
minimal external skin damage. A 2nd-
or 3rd-degree burn that affects more
than 10 per cent of the body surface
causes shockdue to massive fluid loss.
A burn is covered with a non-stick
dressing to keep the area moist. If nec-
essary, analgesic drugsare given, and
antibiotic drugsare prescribed if there is
any sign of infection. For extensive 2nd-
degree burns, when there may be slow
healing or a fear of infection, a topical
antibacterialagent such as silver sul-
phadiazine is used. Skin graftsare used
early in treatment to minimize scarring.
3rd-degree burns always require skin
grafting. Extensive burns may require
repeated plastic surgery.
burpingAnother term for belching.
burr holeA hole made in the skull by a
special drill with a rounded tip (burr). A
hole is made to relieve the pressure on
the brain that often results from bleed-
ing inside the skull, usually following a
head injury. Burr holes may be made as
part of a craniotomyand may be life-
saving procedures.
bursaA fluid-filled sac that acts as a
cushion at a pressure point in the body,
often near a joint, where a tendon or
muscle crosses bone or other muscles.
The important bursae are around the
knee, elbow, and shoulder.
bursitisInflammation of a bursa, causing
pain and swelling. Bursitis may result
from pressure, friction, or slight injury
to the membrane surrounding the joint,
or to infection. For example, prepatellar
bursitis (“housemaid’s knee”) is caused
by prolonged kneeling on a hard surface.
Avoiding further pressure and taking
nonsteroidal anti-inflammatory drugsare
usually all the treatment needed. Occa-
sionally, antibiotic drugsmay be needed
if the bu rsa is infected.bypass operationsProcedures to by-
pass the blockage or narrowing of an
artery or vein or any part of the digestive
system. Arteries can become blocked or
narrowed in atherosclerosis.Obstructions
can be bypassed using sections of
healthy artery or vein from elsewhere in
the body or using synthetic tubing. Veins
are bypassed most often in patients with
diseases of the liver that cause portal
hypertension and bleeding oesophageal
varices. This kind of bypass is called a
shunt. Intestinal bypasses are employed
most commonly in patients with cancer
in which tumour growth is too extensive
to be removed. An obstructed bile duct
can be bypassed by constructing a new
opening into the digestive tract. (See
also coronary artery bypass.)
byssinosisA lung disease caused by an
unknown agent in the dust produced
during the processing of flax, cotton,
hemp, or sisal. Byssinosis produces a
feeling of tightness in the chest and
shortness of breath that may become
chronic if exposure continues. Broncho-
dilator drugsand other drugs used to
treat asthma may relieve symptoms,
but adequate ventilation and personal
protective equipment such as dust
masks will reduce the risk.BURPING BYSSINOSISB