EM Toxicology 13 - Arsenic

Question 1

remarks on metalloids

Answer 1

chemical elements with properties intermediate to those of metals and nonmetals

tend to have 2 general properties:
1) semiconductors of electricity
2) form amphoteric oxides

Arsenic is the most clinically significant toxic metalloid

Question 2

remarks on Arsenic

Answer 2

nearly tasteless and odorless metalloid

used as a means for homicide and suicide

Question 3

pathophysiology of arsenic poisoning

Answer 3

Arsenic reversibly binds with sulfhydryl groups found in many tissues and enzyme systems

Acute exposure produces dilatation and increased permeability of small blood vessels, resulting in GI mucosal and submucosal inflammation and necrosis, cerebral edema and hemorrhage, myocardial tissue destruction, and fatty degeneration of the liver and kidneys

Question 4

acute toxicity of arsenic poisoning

Answer 4

10 mins to several hours
cholera-like diarrhea
hypotension
dysrhythmia (including torsades)
ARDS
renal failure
encephalopathy

Question 5

subacute toxicity of arsenic poisoning

Answer 5

1-3 weeks after acute exposure or with chronic exposure

headache, confusion
sensory aand motor neuropathy (stocking glove distribution)
ascending paralysis (mimicking GBS)
alopecia, Mees lines (1- to 2-mm wide transverse white lines in the nails)

Question 6

chronic toxicity of arsenic poisoning

Answer 6

hyperpigmentation
Bowen’s disease
squamous and basal cell CA of skin
DM
lung CA

Question 7

ECG manifestation of arsenic poisoning

Answer 7

prolonged QT interval, especially in subacute poisoning

Question 8

definitive diagnosis of acute arsenic poisoning

Answer 8

made by finding elevated arsenic levels in a 24-hour urine collection

all urinary measurements of metals should be collected in metal-free containers after a 5-day seafood-free diet

Due to rapid distribution of arsenic in tissues, blood arsenic levels are often unreliable

Question 9

most common cause of death in arsenic poisoning

Answer 9

hypotension and dysrhythmia

Question 10

what to do if abdominal radiographs reveal intestinal radioopaque materials consistent with arsenic?

Answer 10

whole-bowel irrigation

Question 11

Management strategies in acute arsenic poisoning

Answer 11

1) Volume replacement and vasopressor therapy as indicated
2) lidocaine, amiodarone, MgSO4, defib for dysrhythmia
3) gastric lavage / whole-bowel irrigation
4) chelation therapy with dimercaprol or succimer

Question 12

chelation therapy in arsenic poisoning

Answer 12

Dimercaprol
3-5 mg/kg deep IM every 4 h for 2 days, followed by
3-5 mg/kg IM every 6-12 h until able to switch to succimer, up to 10days total

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

Do not delay chelation therapy in severely ill patients until laboratory confirmation because chelation is most effective when given within minutes to hours of exposure

Dermatologic manifestations of chronic toxicity are unresponsive to chelation

Question 13

prognosis in arsenic poisoning

Answer 13

In patients with acute arsenic poisoning, prognosis may be influenced favorably by the rapid institution of dimercaprol therapy

Dimercaprol apperas to significantly shorten the duration of illness