only during periods of REM (rapid eye
movement) sleep, which last for about
20 minutes and occur 4–5 times a night.
Compared to other phases, the REM
phase of sleep is active. Blood flow and
brain temperature increase, and there
are sudden changes in heart-rate and
blood pressure.
Dreams usually closely mirror the
day’s preoccupations. Dreaming can be
seen as a process in which the mental
impressions, feelings, and ideas are
sorted out. People roused during REM
sleep report especially vivid dreams.
dressings Protective coverings for wounds
that are used to control bleeding, abs-
orb secretions, prevent contamination,
or retain moisture.
Dressler’s syndromeAn uncommon
disorder, also known as postinfarction
syndrome, that may occur after a myo-
cardial infarction (heart attack) or heart
surgery. It is characterized by fever,
chest pain, pericarditis, and pleurisy.
Treatment is with aspirinor, in severe
cases, with corticosteroid drugs.
dribblingInvoluntary leakage of urine
(see incontinence, urinary) or of saliva
from the mouth (also known as drool-
ing). Dribbling of saliva is normal in
infants. In adults, it may be due to
poorly fitting dentures or may be the
result of facial paralysis, dementia, or
another disorder of the nervous system,
most commonly Parkinson’s disease.
Dribbling of saliva may also be caused
by obstruction to swallowing.
dripSee intravenous infusion.
drop attackA brief disturbance affecting
the nervous system, causing a person to
fall suddenly to the ground without warn-
ing. Unlike in fainting, the person may
not lose consciousness, but injuries can
occur. Elderly women are the most com-
monly affected. The causes are not fully
understood, but they may be a form of
transient ischaemic attack(TIA) in which
there is a fall in blood flow to nerve cen-
tres in the brainstem. Elderly men may
have a drop attack while passing urine or
while standing, possibly due to low
blood pressure or an abrupt alteration
in heart rhythm. Akinetic seizures (a rare
form of epilepsy) are also sometimes
described as drop attacks.There is no treatment for drop attacks
in the elderly. Akinetic seizures respond
to anticonvulsant drugs.
dropsyAn outmoded term for general-
ized oedema(fluid collection in body
tissues). It is not a disease in itself, but
a sign of disease, especially congestive
heart failure or kidney disease.
drowningDeath caused by suffocation
and hypoxia(lack of oxygen) associated
with immersion in a fluid. Most often,
the person inhales liquid into the lungs;
sometimes, no liquid enters the lungs, a
condition called dry drowning (see
drowning, dry). People who are resusci-
tated after prolonged immersion are
said to be victims of “near drowning”.
Initially, automatic contraction of a
muscle at the entrance to the windpipe,
a mechanism called the laryngeal reflex,
prevents water from entering the lungs;
instead it enters the oesophagus and
stomach. However, the laryngeal reflex
impairs breathing and can quickly lead
to hypoxia and to loss of conscious-
ness. If the person is buoyant at this
point and floats face-up, his or her
chances of survival are reasonable
because the laryngeal reflex begins to
relax and normal breathing may resume.
An ambulance should be called and the
person’s medical condition assessed. If
breathing and/or the pulse is absent,
resuscitative measures should bestarted
(see artificial respiration; cardiopulmonary
resuscitation) and continued until an am-
bulance or doctor arrives. Victims can
sometimes be resuscitated, despite a
long period immersed in very cold water
(which reduces the body’s oxygen needs)
and the initial appearance of being dead.
In all cases of successful resuscitation,
the person should be sent to a hospital.
drowning, dryA form of drowningin
which no fluid enters the lungs. Some
fatal drowning cases are “dry”. Victims
have a particularly strong laryngeal reflex,
which diverts water into the stomach
but at the same time impairs breathing.
drowsinessA state of consciousness
between full wakefulness and sleepor
unconsciousness. Drowsiness is medically
significant if a person fails to awaken
after being shaken, pinched, and shouted
at, or wakes but relapses into drowsiness.DRESSINGS DROWSINESSD