PERVERSION
PET SCANNING
P
cause vomiting. In infants, there is a
risk of temporary
apnoea
following a
coughing spasm. The illness may last
for a few weeks. The possible complica-
tions include nosebleeds,
dehydration,
pneumonia, pneumothorax, bronchiecta-
sis
(permanent widening of the airways),
and convulsions. Untreated, pertussis
may prove fatal.
Pertussis is usually diagnosed from the
symptoms. In the early stages,
erythro-
mycin
is often given to reduce the child's
infectivity. Treatment consists of keep-
ing the child warm, giving small, frequent
meals and plenty to drink, and protect-
ing him or her from stimuli, such as
smoke, that can provoke coughing. If
the child becomes blue or persistently
vomits after coughing, hospital admis-
sion is needed.
In developed countries, most infants
are vaccinated against pertussis in the
1st year of life. It is usually given as part
of the
DPT vaccination
at 2, 3, and 4
months of age. Possible complications
include a mild fever and fretfulness.
Very rarely, an infant may have a severe
reaction, with high-pitched screaming
or seizures.
perversion See
deviation, sexual.
pes cavus See
claw-foot.
pessary Any of a variety of devices placed
in the vagina. Some types are used to
correct the position of the uterus (see
uterus, prolapse of
); others are used as
contraceptive devices. The term pessary
is also used to refer to a medicated
vaginal suppository.
pesticides Poisonous chemicals used to
eradicate pests. Different types include
herbicides, insecticides, and fungicides.
Pesticide poisoning, particularly in chil-
dren, may result from swallowing an
insecticide or a garden herbicide (see
chlorate poisoning).
Poisoning may also
occur in agricultural workers, often as a
result of inhalation or absorption of the
chemical through the skin. Exposure to
pesticides can also occur indirectly,
through eating food in which chemicals
have accumulated as a result of crop
spraying. (See also
DDT; defoliant poi-
soning; lindane; paraquat; parathion.)
petechiae Red or purple, flat, pinhead
spots that occur in the skin or mucous
membranes. Petechiae are caused by
a localized
haemorrhage
from small
blood vessels. They occur in
purpura
and, sometimes, bacterial
endocarditis
.
pethidine A synthetic opioid
analgesic
drug
similar to, but less powerful than,
morphine.
Pethidine is used as a
pre-
medication
and to relieve severe pain
after operations, during childbirth, or in
terminal illness. As it may cause nausea
and vomiting, it is usually given with an
antiemetic drug
.
petit mal A type of seizure that occurs
in
epilepsy
. Petit mal attacks occur in
children and adolescents but rarely per-
sist into adulthood. There is momentary
loss of awareness, occasionally with
drooping eyelids. Treatment is with an
anticonvulsant drug
.
petroleum jelly A greasy substance
obtained from petroleum, also known
as petrolatum or soft paraffin. The jelly
is commonly used as an
ointment
base,
a protective dressing, and an
emollient.
PET
scanning The abbreviation for
positron emission tomography, a diag-
nostic technique based on the detection
of positrons (a type of subatomic parti-
cle) that are emitted by radioactively
labelled substances introduced into the
body. PET scanning produces 3-dimen-
sional images of the metabolic and
chemical activity of tissues.
Substances used in biochemical pro-
cesses in the body are labelled with
radioisotopes and then injected into the
PET SCAN OF NORMAL BRAIN
444
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