EM Toxicology 12 - Mercury and other metals

Question 1

Form of mercury that’s more toxic to humans

Answer 1

the short-chained alkyls, such as methyl mercury and ethyl mercury

with dimethyl mercury being lethal in small amounts

Question 2

pathophysiology of mercury poisoning

Answer 2

Mercury binds with sulfhydryl groups, affecting a diverse number of enzyme and protein systems

Question 3

organs systems predominantly affected in mercury poisoning

Answer 3

neurologic
GI
renal

Question 4

remarks on elemental mercury

Answer 4

quicksilver

absorbed primarily by vapor inhalation or transdermally

absorption by the GI tract is usually negligible so that swallowing elemental mercury contained in a glass thermometer does not produce adverse effects unless the mucosa is damaged

Question 5

remark on inorganic mercury

Answer 5

such as mercurous (Hg+) (such as calomel or mercurous chloride)
and mercuric (Hg2+) (such as cinnabar or mercuric chloride)

absorbed primarily through the GI tract

Mercury salts do not enter the CNS in consequential amounts nor do they cross the placenta

Question 6

remarks on organic mercury

Answer 6

the short-chained alklyls are highly lipid soluble and are excreted primarily in the bile, where they undergo significant enterohepatic circulation

Question 7

clinical features of elemental mercury poisoning

Answer 7

in severe cases, patients may develop ARDS

Question 8

clinical features of inorganic mercury poisoning

Answer 8

Mercury salts are highly irritating and an acute ingestion produces a severe hemorrhagic gastroenteritis with abdominal pain often associated with a characteristic graying of the oral mucosa and metallic taste

shock and cardiovascular collapse may rapidly ensue

Question 9

hallmarks of chronic neurologic toxicity in inorganic mercury poisoning

Answer 9

tremor
neurasthenia (fatigue, depression, headaches, and difficulty concentrating)
erethism (behavioral changes characterized by shyness, emotional lability, irritability, insomnia, and delirium)

Question 10

an immune-mediated reaction to mercury characterized by generalized rash; edema and erythema of the palms, soles, and face; excessive sweating; fever; irritability; splenomegaly; and generalized hypotonia

Answer 10

Acrodynia
“Pink disease” in small children
Hypotonia - particular weakness of the pelvic and pectoral muscles

Question 11

[form of mercury] with the most devastating effects on the CNS

Answer 11

the short-chained alkyl compounds, methyl, dimethyl, and ethyl mercury

Question 12

remarks on mercuric chloride

Answer 12

ingestion of mercuric chloride can produce a rapidly fatal course and should be considered in a patient presenting with a corrosive gastroenteritis

found in
- cosmetic products
- manufacture of FIVE (Fireworks, Ink, Vinyl chloride, Explosives)

Question 13

specimen of choice in determining mercury levels

Answer 13

all forms except short-chained alkyls:
24-hour urine after a 5-day seafood-free diet

short-chained alkyl mercury compounds:
whole-blood

Although elevated blood or urine values are necessary to confirm the diagnosis, levels correlate poorly with toxicity and do not distinguish asymptomatic exposure from merucry poisoning

Levels are most useful in confirming exposure and in following the effects of chelation therapy

Question 14

general therapeutic measures in mercury poisoning

Answer 14

elemental mercury: may require endotracheal intubation and positive-pressure ventilation
chelation therapy

inorganic mercury salts:
treat with aggressive IV hydration and GI decontamination, including gastric lavage if the patient has not had significant emesis, and consider activated charcoal unless contraindicated (e.g., bleeding)
chelation therapy

organic merucry:
gastric decontamination, supportive care, chelation therapy

Question 15

chelation therapy in severe acute poisoning of elemental and inorganic mercury

Answer 15

Dimercaprol
75 mg/m2 (5mg/kg) IM every 4 h for 2 days, ff’d by
2.5 mg/kg IM every 6 h for 2 days, ff’d by
2.5 mg/kg IM every 12-24 h until clinical improvement or until able to switch to succimer thearpy, for up to 10 days total

Question 16

cheleation therapy in severe acute poisoning of organic mercury

Answer 16

Succimer
10 mg/kg PO every 8 h for 5 days, then
every 12 hours for 14 days

Dimercaprol is contraindicated in methyl mercury poisoning due to the potential for exacerbation of central neurologic symptoms

Question 17

in mercury poisoning, death can occur in

Answer 17

severe cases of mercuric chloride poisoning and with
dimethyl mercury exposure

Question 18

metal fume fever

Answer 18

clinical syndrome of fever, chills, body ache, headache, and fatigue resulting from inhalation of dust or fumes containing zinc, aluminum, magnesium oxide, or copper

Question 19

ouch-ouch disease

Answer 19

“itai-itai disease”
from chronic cadmium poisoning

Question 20

metal lung disease

Answer 20

chronic cobalt poisoning

Question 21

resembles iron poisoning

Answer 21

acute poisoning of copper and zinc

Question 22

may cause childhood cirrhosis

Answer 22

chronic copper poisoning

Question 23

may cause permanent skin discoloration

Answer 23

chronic silver poisoning
“Argyria”
- permanent skin discoloration due to silver deposition and melanocyte stimulation

Question 24

remarks on thallium poisoning

Answer 24

most poisonings are related to homicide

may cause painful ascending neuropathy, cardiac dysrhythmias, AMS

tx:
MDAC
Prussian blue, 125 mg/kg PO every 12 hours (usually disoovled in 50 mL of 15% mannitol)