Bma Illustrated Medical Dictionary

pressure applied to stop any bleeding.
The procedure is not usually painful but
may cause some discomfort.
venereal diseasesSee sexually trans-
mitted infections.
venereologyThe medical discipline
concerned with the study and treatment
of sexually transmitted infections.
venesectionThe process of withdrawing
blood from a veinfor blood donationor
therapeutic bloodletting. Regular blood-
lettingis performed in the treatment of
polycythaemiaand haemochromatosis.
venlafaxineA serotonin and noradren-
aline reuptake inhibitor (SNRI) drug
used in the treatment of depression.
Venlafaxine combines the effects of sel-
ective serotonin reuptake inhibitorsand
tricyclic antidepressants to produce fewer
side effects than other types of anti-
depressant. Side effects may include
nausea, dry mouth, and constipation.
venographyA diagnostic procedurethat
enables veinsto be seen on an X-ray
film after they have been injected with a
substance opaque to X-rays. It is used
to detect abnormalities or diseases of
the veins, such as narrowing or blockage
from thrombosis.
venomous bites and stingsThe injec-
tion of venom by certain animals via
their mouthparts (bites) or other inject-
ing apparatus (stings). Venoms are often
carried to discourage predators, and are
sometimes used to kill or immobilize
prey. It is rare for a venomous animal to
attack a person unless it has been pro-
voked or disturbed. Specific antivenoms

are available to treat many, though not

all, types of animal venom. (See also

insect stings; jellyfish stings; scorpion

stings; snake bites; spider bites.)

ventilationThe use of a machine called a

ventilatorto take over or assist breathing.

Arrested or severely impaired breathing

may be due to head injury, brain dis-

ease, an overdose of opioid drugs, chest

injury, respiratory disease, a nerve or

muscle disorder, or major chest or ab-

dominal surgery. Ventilation may be

needed if a muscle relaxant has been

given during an operation as part of

general anaesthesia. Premature babies

with respiratory distress syndromemay

also need ventilation for a period until

their lungs develop sufficiently. Positive

pressure ventilation (continuous pump-

ing of air under high pressure) may be

used in the home in the treatment

of sleep apnoea.

ventilatorA device used for the artifi-

cial ventilationof a person who is

unable to breathe naturally. A ventilator

is an electrical pump connected to an

air supply that works like bellows. Air is

directed through a tube passed down

the windpipe to inflate the lungs. The air

is then expelled by the natural elasticity

of the lungs and ribcage. A valve on the

ventilator prevents the expelled air from

re-entering the lungs.

ventilatory failureA life-threatening

condition in which the amount of car-

bon dioxide in the blood rises, and the

amount of oxygen falls, due to disrup-

tion of the normal exchange of gases

VENEREAL DISEASES VENTILATORY FAILURE

V

VENEPUNCTURE

Skin

INSIDE THE VEIN

Fatty

tissue

Wall of vein

Needle

Vein

Muscle

Tourniquet

Syringe