EMQs in Clinical Medicine.pdf - Peshawar Medical College

Treatment of poisoning and overdose – answers 235
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A 20-year-old woman presents to A&E with confusion, sweating and
blurred vision after taking some ecstasy. She has a rectal temperature
of 40.5°C. Creatine kinase (CK) is 4000 U/l.
The patient is hyperthermic and should be immediately transferred to
intensive care for active cooling and fluid replacement (via central line).
A 32-year-old woman presents 6 hours after a paracetamol overdose.
The paracetamol level is above the treatment line.
The metabolism of paracetamol involves the conversion to the toxic
metabolite N-acetyl-p-benzoquinonimine (NAPQI), which covalently
binds with sulphydryl groups on liver cell membranes, leading to liver
cell necrosis. NAPQI generated by safe doses of paracetamol is normally
inactivated by reduction with glutathione. However, large doses of
paracetamol deplete glutathione stores, leading to toxic levels of NAPQI
and hence hepatocellular damage.
N-Acetylcysteine and oral methionine are sulphydryl donors that act
as precursors to glutathione, and hence help to replenish depleted
glutathione stores.
A 7-year-old boy presents to A&E with constricted pupils, sweating
and increased salivation after drinking a bottle of insecticide lying in
the garden.
Organophosphate insecticides are cholinesterase inhibitors and therefore
poisoning results in an accumulation of acetylcholine (muscarinic and
nicotinic acetylcholine receptor activation). Any contaminated skin
should be washed (wear gloves during all contact with the patient, e.g.
removing patient’s clothes). Medical first-line treatment involves intravenous
atropine until full atropinization (i.e. patient has dilated pupils,
flushed dry skin, heart rate normalized). Pralidoxime mesilate
(cholinesterase activator) by slow intravenous injection is used as
an adjunct to atropine.
A 54-year-old painter requires treatment for lead poisoning.
Chronic lead poisoning was more common when water pipes were made
of lead. Lead poisoning is now more commonly occupational, e.g. exposure
to lead-based paints, metal workers. Lead poisoning affects many
organs as a result of its interference with enzyme systems and so presentation
can involve many non-specific symptoms/signs. These include
nausea, vomiting, abdominal pain, anaemia, constipation and sleep
disturbance. There are no pathognomonic signs but a characteristic sign
in children is the appearance of dense metaphyseal bands indicating
arrested growth on a radiograph. These are known as lead lines.
Calcium EDTA and D-penicillamine have also been used in the treatment
of lead poisoning by acting as chelators. Incidentally, dimercaprol is also
used to treat other types of heavy metal poisoning, e.g. arsenic, mercury.