Iron toxicity

Question 1

Describe the 5 stages of iron toxicity

Answer 1

I

GI (abdo pain, N/V/D, hematemesis, melena, lethargy, shock, met acidosis)

30m-6hrs

II

Quiescent phase (stop vomiting but developing acidosis)

6-24hrs

III

Met acidosis, renal failure, hepatotoxicity, GI symptoms, CNS dysfxnhypovolemic/distributive/cardiogenic shock

6-72hrs

IV

Fulminant hepatic failure: coma, coagulopathy, jaundice

12-96 days

V

GI strictures, gastric outlet obstruction, bowel obstruction

2-8wks

Question 2

What are the toxic levels of Fe

Answer 2

20-60 mg/kg toxic

more than 60 mg/kg serious toxicity

Question 3

what is the pathophys of iron toxicity

Answer 3

disrupts oxidative phosphorylation, decr ionotropy of myocardium, tnhibits thrombin

Question 4

what symptom indicates serious fe toxicity

Answer 4

vomiting, do not give antiemetics until they vomit

Question 5

indications for defuroxime

Answer 5

serum level 60-90umol/L and symptomatic
serum level more than 90
shock
metabolic acidosis
coma

Question 6

what can iron toxicity be treated with

Answer 6

defuroxime until the urine is rose coloured

Question 7

List common Fe preparations and their elemental Fe content

Answer 7

fummarate: 33%
sulfate20%
gluconate12%

Question 8

What causes the coagulation defects seen in iron poisoning?

Answer 8

• Early: Direct effects of vitamin K dependent clotting factors
  Late: Hepatic failure and decreased production of clotting factors

Question 9

List 5 occupations that increase risk of lead exposure.

Answer 9

• Lead smelting
• Battery manufacture
• Radiator repair
• Bridge and ship construction or demolition
• Smoldering or welding
• Cable or tin can production
• Stained glass manufacture
• Lead-crystal or crystal pottery making
• Glass production
• Firing range operation
• Lead based pain abatement

Question 10

Describe the anemia that is characteristic of lead poisoning?

Answer 10

• Inhibits heme synthesis
  
  • Normochromic or hypochromic
  • Severity of anemia correlates with lead BLL
  • smear shows basophilic stippling

Question 11

What diagnostic clue to chronic lead poisoning may be apparent of skeletal x-rays?

Answer 11

• “Lead band/lines” – Increased metaphyseal brightness seen with chronic exposures

Question 12

What are the indications for chelation therapy in lead poisoning?

Answer 12

• BLL >70 mcg/dL (3.38umol/L)
  
  • Protracted GI symptoms
    CNS symptoms from acute exposure

Question 13

In seriously lead poisoned patients what chelating agents are used?

Answer 13

• Dimercaptol (British antilewisite; BAL) first chelator

Calcium Disodium ethylenediaminetetraacetic acid (CaNa2-EDTA) given with second dose of BAL

Question 14

What is the pathophysiology of arsenic poisoning?

Answer 14

• Binds sulfhydryl groups, inhibiting critical enzymes in glycolysis
  
  • Disrupts oxidative phosphorylation by replacing phospohorous (arsenolysis)

Question 15

What strategies can limit or remove arsene?

Answer 15

• Exchange transfusions

- Urinary alkalinization

Question 16

List chronic effects of arsenic poisoning.

Answer 16

• Mees’ line on the nails
• Painful sensorimotor neuropathy
• Hyperkeratosis of the soled and palms
  Anemia (basophilic stippling), leukocytosis or penia, abn u/a, renal or lfts

Question 17

Which chelators are used in arsenic poisoning?

Answer 17

• Dimercaptol (IM)
  
  • DMSA orally
    D-penicillamine

Question 18

Which chelating agents are indicated for clinically significant inorganic mercury toxicity?

Answer 18

• BAL (dimercaptol) used for clinically significant inorganic mercury intox but contraindicated in pts with organomercurial poisoning (increases brain merc levels in pts with mentyl merc poisoning)
  
  • DMSA
  • D-penicillamine
  • Chelation therapy binds the sulfhydryl group that bind mercury after its absorption

Question 19

Outline your basic approach to heavy metal toxicities:

Answer 19

2. In acute exposures of large amounts:
   a. Draw levels, AXR à Fe, Pd, As, Hg are ALL radio-opaque
   b. AC not indicated, none bind adequately
   c. WBI in acute ingestion
   d. Manage ABCs
   e. Anticipate and manage CNX, renal, hepatic, toxicities
   f. Find the antidote à chelation