Bma Illustrated Medical Dictionary

cause vomiting. In infants, there is a

risk of temporary apnoeafollowing 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-

mycinis 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 vaccinationat 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.

perversionSeedeviation, sexual.

pes cavusSee claw-foot.

pessaryAny 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.

pesticidesPoisonous 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.)

petechiaeRed 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.

pethidineA synthetic opioid analgesic

drugsimilar to, but less powerful than,

morphine. Pethidine is used as a pre-

medicationand 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 malA 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 jellyA greasy substance

obtained from petroleum, also known

as petrolatum or soft paraffin. The jelly

is commonly used as an ointmentbase,

a protective dressing, and an emollient.

PET scanningThe abbreviation for

positron emission tomography, a diag-

nostictechnique 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

PERVERSION PET SCANNING

P

PET SCANNING

Area of low

brain activity

Area of high

brain activity

PET SCAN OF NORMAL BRAIN