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Year 4 - Toxicology > Lecture 6 - Iron > Flashcards

Lecture 6 - Iron Flashcards

1
Q

Why are we only dealing with treatment of acute iron toxicity?

A

chronic toxicity usually doesn’t happen, we don’t absorb more than what we need unless you take a bunch at once (acute)

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2
Q

What is iron commonly used for?

A
  • anemia
  • prenatal supplement
  • daily nutritional supplement
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3
Q

Absorption of iron is an active process regulated by the level of body iron stores and demands for ________

A

erythropoiesis (production of red blood cells)

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4
Q

_____ iron is absorbed into the mucosal cell (duodenum and jejunum) and is oxidized to ferric iron

A

ferrous

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5
Q

____ iron is more available for absorption than inorganic forms of iron

A

heme

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6
Q

What is the daily intake or iron?

A

10-20mg

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7
Q

How much is actually absorbed from 10-20mg?

A

1-2 mg

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8
Q

In plasma, iron is bound to ______

A

transferrin

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9
Q

Transferrin system is normally ___ saturated

A

1/3

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10
Q

T or F: normally there is free iron present in serum

A

False: normally there is no free iron present in serum

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11
Q

In overdose, the acute corrosive effect of iron on the GIT mucosa ______ absorption and the transferrin system may become saturated.

A

enhances

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12
Q

In tissue, iron is stored as ______

A

ferritin

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13
Q

Is there a physiologic mechanism for iron excretion?

A

No

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14
Q

How will the body try and excrete iron?

A
  • sweat
  • bile
  • desquamation of the skin and mucosal surfaces (sort of like peeling)
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15
Q

What is the toxic dose of elemental iron?

A

10-20mg/kg of elemental iron

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16
Q

What are some direct corrosive effects of iron on the gastric and intestinal mucosa?

A

ulceration, severe edema, hemorrhage, infarction, venous thrombosis

which leads to:

vomiting, abdominal pain, diarrhea, ulceration, hematemesis, melena

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17
Q

hypovolemia = tissue perfusion = ______ _________

A

metabolic acidosis

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18
Q

What do high ferritin levels do?

A

cause tissue damage and release of vasoactive substances

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19
Q

Iron concentrates in the _______ which disrupts oxidative phosphorylation, free radical formation and lipid peroxidation which leads to cell death and tissue injury

A

mitochondria

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20
Q

What are acute corrosive effects of iron toxicity?

A

perforation and peritonitis - which may enhance iron absorption

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21
Q

How does iron cause hepatic toxicity?

A

Free iron concentrations in the hepatocyte during first absorptive pass will cause:

  • electron transport abnormalities
  • lactate production
  • glycogen depletion
  • enzymatic dysfunction
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22
Q

What type of acid base disorder comes from iron toxicity?

A

metabolic acidosis

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23
Q

How does iron toxicity affect blood sugar?

A

hyperglycemia

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24
Q

With acute iron poisoning, hepatocellular toxicity may be severe. What will this cause?

A
  • hyperbilirubinemia
  • aminotransferase abnormalities
  • coagulopathy
  • diffused tissue necrosis
  • disruption of normal metabolic pathways
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25
Q

How will free iron affect CV toxicity?

A
  • venodilation
  • CV compromise
  • shock
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26
Q

What does acute volume loss from GIT cause?

A
  • vomiting
  • diarrhea
  • hemorrhage
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27
Q

What will direct cytotoxic effects cause?

A
  • capillary leakage

- plasma loss

28
Q

What neurological effects will iron toxicity have?

A
  • lethargy and weakness are common in severe poisonings

- coma

29
Q

How long is the Stage 1 (initial period) after ingestion?

A

0.5-6 hours post-ingestion

30
Q

Describe symptoms of stage 1 toxicity (local toxicity)

A
  • n/v/d
  • gastroenteritis
  • hematemesis
  • ab pain
  • melena
  • lethargy
  • hypotension
  • tachycardia and tachypnea (may be present)
31
Q

How long is the Stage 2 (latent period) after ingestion?

A

6-24 hours

32
Q

What happens in Stage 2?

A

patient may recover or progress to stage 3

33
Q

How long is the Stage 3 (period of systemic toxicity?)

A

4-40 hours

34
Q

What happens in Stage 3?

A
  • pallor or cyanosis
  • lethargy
  • hypotension
  • disorientation
  • convulsions
  • coma
  • shock
  • coagulopathy
  • fever
  • leukocytosis
  • hyperglycemia
  • metabolic acidosis
35
Q

How long is stage 4 after ingestion?

A

2-4 days

36
Q

What happens in Stage 4?

A
  • jaundice
  • hypoglycemia
  • elevated transaminases
  • prolonged clotting times
  • thrombocytopenia
  • hemorrhage
  • renal failure
  • pulmonary edema
37
Q

How long is stage 5 (late complications) after ingestion?

A

2-8 weeks

38
Q

What happens in stage 5?

A
  • GI obstruction
  • pyloric stenosis secondary to scarring
  • gastric fibrosis
  • strictures
39
Q

Management:

What dose is usually asymptomatic?

A

< 20mg/kg

40
Q

Management:

What dose may produce self-limiting vomiting and diarrhea?

A

20-30 mg/kg

41
Q

Management:

What dose is potentially serious?

A

> 40mg/kg

42
Q

Management:

What dose is potentially lethal?

A

> 60mg/kg

43
Q

Management:

Refer children with a dose of ____ to an emergency facility

A

> 10 mg/kg

44
Q

What is the lowest reported lethal dose in a child?

A

600 mg

45
Q

Describe the diagnosis of iron toxicity

A
  • History of exposure
  • Presence of vomiting, diarrhea, hypotension
  • Laboratory involvement
  • Abdominal radiograph
46
Q

What is a normal Fe serum level?

A

80-180 mcg/dL

47
Q

Iron toxicity is associated with values > _____

A

350 mcg/dL

48
Q

What is the “action” level?

A

> 500 mcg/dL

49
Q

What interventions are appropriate for iron toxicity?

A
  • ABC
  • Basic life support
  • Gastric emptying (gastric lavage or whole-bowel irrigation)
  • Chelators
50
Q

Why is activated charcoal not useful?

A

metals are not really absorbed well by AC

51
Q

What is DFO (deferoxamine mesylate) ?

A

A specific iron-binding ligand

52
Q

What does DFO do?

A

chelates free iron and the iron of ferritin

*does not affect iron bound to hemoglobin or cytochromes!!

53
Q

What is Ferrioxamine?

A

iron/DFO complex

54
Q

Iron/DFO complex is _____

A

non-toxic

55
Q

Iron/DFO complex is excreted in the urine as what color?

A

orange, pink or brown

56
Q

How much DFO equals iron??

A

100mg DFO = 9mg iron

57
Q

How is DFO administered?

A

IV, IM or SC

*iv is recommended

58
Q

What is the dose of DFO?

A
  • Initial dose of 90mg/kg IM
  • Max 1 g in children, 2g in adults

-Subsequent IM dosing of 90mg/kg (to a max of 2g) at 4-12 hour intervals depending on serum iron levels and urine color

OR

-constant IV infusion at a rate up to 15mg/kg/h

59
Q

Why is IV therapy preferred to IM for DFO?

A

IV therapy removes several times more iron than IM

60
Q

When do you d/c DFO therapy?

A
  • Patient returns to an asymptomatic state after the presumed latent period has passed
  • Serum iron is < 150 ug/dL
  • Return to normal urine color
61
Q

With DFO, need to ensure proper _____

A

hydration

62
Q

Can DFO be used in pregnant patients?

A

yes

63
Q

What are the general side effects of DFO?

A
  • histamine release
  • DFO-iron complex, growth factor for Yersinia enterocolitica
  • Excessive intracellular chelation (oxidant damage)
64
Q

What are the acute side effects of DFO?

A
  • hypotension
  • infections
  • pulmonary toxicity
65
Q

What are the chronic side effects of DFO?

A
  • auditory/ocular toxicity
  • pulmonary toxicity
  • infections

Year 4 - Toxicology (24 decks)

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