Webster's New World Medical Dictionary

anesthesiology
The branch of medicine special-
izing in the use of drugs or other agents that cause
insensibility to pain.
anesthetic
A substance that causes lack of feeling
or awareness, dulling pain to permit surgery and
other painful procedures.
anesthetic, epidural
An anesthetic injected into
the epidural space surrounding the fluid-filled sac
(the dura) around the spinal cord. It partially
numbs the abdomen and legs and is most com-
monly used during childbirth.
anesthetic, general
An anesthetic that puts a
person to sleep rendering them unconscious.
anesthetic, local
An anesthetic that causes loss
of feeling in a limited part of the body.
anesthetist
A nurse or technician trained to
administer anesthetics.
aneuploidy
A condition in which a person has
one or a few chromosomes above or below the nor-
mal chromosome number. For example, three
copies of chromosome 21, which is characteristic
of Down syndrome, is a form of aneuploidy.
aneurysm
A localized widening (dilatation) of an
artery, a vein, or the heart. At the point of an
aneurysm, there is typically a bulge. The wall of the
blood vessel or organ is weakened and may rupture.
aneurysm, abdominal aortic
A balloon-like
swelling in the wall of the aorta within the abdomen.
This swelling weakens the aorta’s wall and, because
of the great volume of blood flowing under high
pressure in the aorta, it can rupture. An abdominal
aortic aneurysm is monitored by ultrasound.
Surgery is often recommended if the aneurysm is
more than 5.5 centimeters (2.2 inches) in diameter
or if a smaller aneurysm is enlarging with unusual
rapidity.
aneurysm, aortic
An aneurysm of the largest
artery in the body, the aorta, involving that vessel in
its course above the diaphragm (thoracic aortic
aneurysm) or, more commonly, below the
diaphragm (abdominal aortic aneurysm). Because
of the volume of blood flowing under relatively high
pressure within the aorta, a ruptured aneurysm of
the aorta is a catastrophe. See also 
aneurysm,
abdominal aortic; aneurysm, thoracic.