6 - Iron Flashcards
What is the leading cause of fatal poisonings in children?
Iron toxicity
Rate the 3 types of iron based on % of elemental iron
Gluconate < sulfate < fumarate
Describe iron absorption
- Active process regulated by level of body iron stores and demands of erythropoiesis
- Ferrous iron absorbed into mucosal cell (duodenum and jejunum), oxidized to ferric iron
Which form of iron is most available for absorption?
Heme iron (instead of inorganic forms)
What is the daily intake of iron and how much is absorbed?
- Daily intake = 10-20 mg
- Amount absorbed = 1-2 mg
Describe distribution of iron
- In plasma, iron is bound to transferrin (transferrin system normally 1/3 saturated, normally no free iron present in serum)
- In OD, acute corrosive effect of iron on GI tract mucosa enhances absorption (transferrin system may become saturated)
- In tissue, iron is stored as ferritin
Describe iron elimination
- No physiologic mechanism for iron excretion
- Sweat, bile, desquamation of skin and mucosal surfaces
What is a toxic dose of iron?
10-20 mg/kg of elemental iron
What are the effects of iron toxicity?
- Direct corrosive effects on gastric and intestinal mucosa (vomiting, abdominal pain, diarrhea, ulceration, hematemesis, melena)
- Hypovolemia = tissue hypoperfusion = metabolic acidosis
- High ferritin levels cause tissue damage and release of vasoactive substances
- Iron concentrates in mitochondria disrupting oxidative phosphorylation, free radical formation, lipid peroxidation = cell death and tissue injury
Describe the effects of iron toxicity in the GI tract
- Clinically correlates to -> N/V, abdominal pain, hematemesis, diarrhea, melena
- Acute corrosive effects = perforation and peritonitis, which may enhance iron absorption
What causes hepatic effects of iron toxicity?
Direct result of free iron concentrations in hepatocyte during first absorptive pass
Acute manifestations of hepatic effects of iron toxicity
- Electron transport abnormalities
- Lactate production
- Glycogen depletion
- Enzymatic dysfunction (metabolic acidosis and hyperglycemia)
Severe manifestations of hepatic effects of acute iron toxicity
- Hyperbilirubinemia
- Aminotransferase abnormalities
- Coagulopathy
- Diffused tissue necrosis
- Disruption of normal metabolic pathways
CV effects of iron toxicity
- Free Fe -> venodilation, CV compromise, shock
- Acute volume loss from GI tract -> vomiting, diarrhea, hemorrhage
- Direct cytotoxic effects -> capillary leakage, plasma loss
Neurological effects of iron toxicity
- Lethargy and weakness common in severe poisonings
- Coma
Describe the initial period of iron toxicity (stage 1)
- 0.5 - 6 hours after ingestion
- Considered local toxicity
- N/V, severe gastroenteritis, abdominal pain, diarrhea, hypotension, lethargy; may proceed rapidly to stage 3
Describe the latent period of iron toxicity (stage 2)
- 6 - 24 hours after ingestion
- Pt may recover or progress to stage 3 (depends on dose)
Describe the period of systemic iron toxicity (stage 3)
- 4 - 40 hours after ingestion –> pallor or cyanosis, lethargy, hypotension, disorientation, coma, shock, convulsions, fever, hyperglycemia, leukocytosis, metabolic acidosis
- 2-4 days after ingestion –> jaundice, hypoglycemia, elevated transaminases, prolonged clotting times, thrombocytopenia, hemorrhage, renal failure, pulmonary edema
Describe late complication of iron toxicity
- 2-8 weeks after ingestion
- GI obstruction, pyloric stenosis secondary to scarring, gastric fibrosis, strictures
What do the different doses of iron ingestion correlate to?
- < 20 mg/kg = usually asymptomatic
- 20 – 30 mg/kg = may produce self-limiting vomiting and diarrhea
- > 40 mg/kg = potentially serious
- > 60 mg/kg = potentially lethal
Diagnosis of iron toxicity
- Hx of exposure
- Presence of vomiting, diarrhea, hypotension
- Lab involvement (Fe serum level)
- Abdominal radiograph
What does the Fe serum level correlate to?
- Normal Fe serum level = 80-180 mcg/dL
- Toxicity associated w/ values > 350 mcg/dL
- “Action” level > 500 mcg/dL
Interventions for iron toxicity
- ABC, basic life support
- Gastric emptying (gastric lavage, whole-bowel irrigation) -> must be careful especially in px w/ GI tract injuries as this procedures can lead to perforation
- Chelators
Is activated charcoal used for iron toxicity?
- Not effective and dangerous
- Iron not really absorbed by AC
