Iron toxicity: Difference between revisions
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==Background== | ==Background== | ||
* | *Toxicity determined by mg/kg of elemental iron | ||
*Total amount of elemental iron ingested can calculated by multiplying the estimated number of tablets by the percentages of iron in the tablet preparation | |||
*Clinical severity is based approximated by elemental dose per kilograms:<ref name="ironoverview">Robotham JL, Lietman PS: Acute iron poisoning. A review. Am J Dis Child 1980; 134:875-879.</ref> | |||
{| {{table}} | {| {{table}} | ||
| align="center" style="background:*f0f0f0;"|'''Mild:''' | | align="center" style="background:*f0f0f0;"|'''Mild:''' | ||
Revision as of 14:22, 25 August 2015
Background
- Toxicity determined by mg/kg of elemental iron
- Total amount of elemental iron ingested can calculated by multiplying the estimated number of tablets by the percentages of iron in the tablet preparation
- Clinical severity is based approximated by elemental dose per kilograms:[1]
| Mild: | 10-20mg/kg |
| Moderate | 20-60mg/kg |
| Severe | >60mg/kg |
- Absence of GI symptoms w/in 6hr of ingestion excludes significant iron ingestion
- Significant iron toxicity can result in a severe lactic acidosis from hypopefusion due to volume loss, vasodilation and negative inotropin effects.
Elemental Iron Percentages
Elemental Iron Percentages
| Iron Preparation | % of Elemental Iron |
| Ferrous Fumarate | 33% |
| Ferrous Sulfate | 20% |
| Ferrous Gluconate | 12% |
| Ferric pyrophosphate | 30% |
| Ferroglycine sulfate | 16% |
| Ferrous carbonate (anhydrous) | 38% |
Pathophysiology
- Direct caustic injury to gastric mucosa[2]
- Causing vomitting, diarrhea, abdominal pain, and bleeding
- Impaired cellular metabolism
- Inhibiting the electron transport chain causes lactic acidosis
- Direct hepatic, CNS, and cardiac toxicity
- Cell membrane injury from lipid peroxidation[3]
- Increased capillary permeability
- Hypotension
- Venodilation
- Portal vein iron delivery to liver
- Hepatotoxicity
- Thrombin formation inhibition
- Coagulopathy - direct effect on vitamin K clotting factors
Clinical Features
| Stage | Clinical Effect | Time Frame |
|---|---|---|
| Stage 1 | GI irritation: n/v, abd pain, diarrhea | 30-60 mins |
| Stage 2: latent | reduced GI symptoms | 6-24 hours |
| Stage 3: shock and metabolic acidosis | metabolic acidosis, lactic acidosis, dehydration, coags, renal failure | 6-72 hours |
| Stage 4: hepatotox | hepatic failure | 12-96 hours |
| Stage 5: bowel obstruction | GI bowel scarring/healing | 2-8 weeks |
Diagnosis
Work-Up
- CBC
- Chemistry
- Anion gap metabolic acidosis
- Hyperglycemia
- Coags
- LFTs
- Iron levels
- UA
- Used to follow efficacy of Fe chelation (urine changes from rusty color to clear)
- Type and Screen
- In ambiguous cases consider abd xray as most Fe tabs are radioopague
Serum Iron Concentration
Serum Iron concentration can guide treatment but are not absolute in predicting or excluding toxicity: Peak serum iron level:
- <300 mcg/dL: nontoxic or mild
- 300-500 mcg/dL: Significant GI symptoms and potential for systemic toxicity
- >500 mcg/dL: Moderate to severe systemic toxicity
- >1000 mcg/dL: severe systemic toxicity and increased morbidity
If unable to obtain a serum iron level a glucose > 150 mg/dL and leukocyte count above 15000 is 100% specific and 50% sensitive in predicint=g levels > 300mcg/mL[4]
Management
Observation x 6 hrs
- Patients with asymptomatic ingestion of <20mg/kg only require observation x 6hr
- Volume resuscitation
GI decontamination
- Consider only for large overdose with visible pills in the stomach on x-ray
- Whole-bowel irrigation (polyethylene glycol) will promote increased gastric emptying and avoid large bezoar formation[5]
Polyethylene glycol dosing
Can be given orally or by NG tube
- 20-40 mL/kg/hr in young children
- 2L/hr in adults
Continue irrigation until the rectal effluent is clear
Deferoxamine
Deferoxamine chelates iron and creates a water-soluble compound ferrioxamine that is renally excreted and can be dialyzed.[1]
Indications
- Systemic toxicity and iron level > 350 mcg/dL
- Metabolic acidosis
- Progressive symptoms
- Serum iron level >500 mcg/dL
Dosing
- 1000mg IV; start at 5mg/kg/hr, increase up to 15mg/kg/hr as tolerated for up to 24hrs
- Subsequent doses are 500mg increments guided by clinical status of pt / urine color
- Recommended amount during first 24hr is 360mg/kg not to exceed 6g.
Adverse effects
- Hypotension (pre-existing hypotension is NOT a contraindication to therapy)
- ARDS
- Yersinia enterocolitica sepsis[6]
- Can see "vin rose" colored urine from chelated iron extretion
Contraindications
- Renal failure patients not on hemodialysis
Hemodialysis
- Not effective in removing iron due to large volumes of distribution
- Dialysis can removes deferoxamine-iron complex in renal failure patients
Exchange Transfusion
- Minimal evidence but has been described in larger overdoses[7]
Orogastric lavage
- Does not remove large numbers of pills and may have serious adverse events
Activated charcoal
- Does not bind iron
Disposition
- Discharge after 6hr obs for asymptomatic (or only vomited 1-2x) AND ingestion <20mg/kg
- Admit to ICU if deferoxamine required
- Psychiatric evaluation if intentional ingestion
See Also
References
- ↑ 1.0 1.1 Robotham JL, Lietman PS: Acute iron poisoning. A review. Am J Dis Child 1980; 134:875-879.
- ↑ Robotham JL, Lietman PS. Acute iron poisoning. A review. Am J Dis Child 1980; 134:875-879.
- ↑ Aisen P et al. Iron toxicosis. Int Rev Exp Pathol 1990. 31:1-46.
- ↑ Lacouture PG et al. Emergency assessment of severity in iron overdose by clinical and laboratory methods. J Pediatr 1981; 99:89-91.
- ↑ Position paper: Whole bowel irrigation. J Toxicol Clin Toxicol 2004; 42:843-854.
- ↑ Mazzoleni G. et al. Yersinia enterocolitica infection with ileal perforation associated with iron overload and deferoxamine therapy. Dig Dis Sci 1991; 36:1154-1160.
- ↑ Movassaghi N. et al. Comparison of exchange transfusion and deferoxamine in the treatment of acute iron poisoning. J Pediatr 1969; 75:604-608.