EM Toxicology 10 - Iron Flashcards
Symptomatology of iron toxicity
GI toxicity (vomiting, abd pain, mucosal ulceration and bleeding)
Multifactorial acidosis
Hepatotoxicity
Coagulopathy (inhibition of thrombin formation and the effect of thrombin on fibrinogen)
Myocardial and vascular dysfunction
toxic levels of iron
moderate toxicity: 20 to 60 mg/kg of elemental iron
severe toxicity: >60 mg/kg of elemental iron
ferrous sulfate has how many elemental iron?
20%
therefore a 325-mg tablet contains 65 of elemental iron
and approx 20 tablets would be expected to produce moderate toxicity after an acute ingestion in an average-size (65-kg) adult
stage 1 of iron toxicity
vomiting, abdominal pain, diarrhea
vomiting is the clinical sign most consistently associated with acute iron toxicity
the absence of GI symptoms within 6 hours of ingestion essentially excludes a significant iron ingestion
stage 2 of iron toxicity
“the latent stage”
6- to 24- hour interval following ingestion
in severe poisonings, the latent stage is marked by ongoing clinical illness and progressive systemic deterioration secondary to volume loss and worsening metabolic acidosis
stage 3 of iron toxicity
shock and lactic acidosis
iron-induced coagulopathy may worsen bleeding and hypovolemia
- biphasic; initial coagulopathy appears to be reversible with chelation therapy
- subsequent coagulopathy is due to iron-induced hepatic injury
stage 4 of iron toxicity
“the hepatic stage”
develops 2-5 days following ingestion
manifests as elevation of aminotransferase levels and may progress to acute fulminant hepatic failure
stage 5 of iron toxicity
refers to delayed sequelae, including gastric outlet obstruction secondary to the corrosive effects of iron on the pyloric mucosa
rare and occur 4-6 weeks after ingestion
remarks on iron toxicity
iron toxicity is largely a clinical diagnosis
patients who develop GI effects that resolve and who continue to look well clinically and have near normal laboratory findings will not develop significant systemic toxicity
what are the MUDPILES
Methanol
Uremia
DKA
P**ropylene glycol, **Paraldehyde
*Iron, Isoniazid
Lactic acidosis
Ethanol, Ethylene glycol
Salicilates
remarks on imaging in iron toxicity
standard ferrous sulfate tablets and reduced iron are radioopaque and frequently visible on routine radiographs, and this may help guide GI decontamination when present
absence of radioopaque material on radiographs does not exclude iron ingestion
remarks on treatment of iron toxicity
signs and symptoms consistent with iron poisoning should guide treatment, rather than serum iron concentrations alone
patients who vomit once or twice from the gastric irritant effects of iron but are are otherwise asymptomatic, hemodynamically stable, and without metabolic acidosis can also be observed and may require no specific treatment
chelation therapy is with deferoxamine
antiemetics such as metoclopramide or ondansetron should be used for repetitive vomiting
coagulopathy whould be traeted with parenteral Vitamin K1 and/or FFP, as indicated
GI decontamination in iron toxicity
whole-bowel irrigation with a polyethylene glycol solution may be effective in patietns with large iron gestions
administration of 250-500 mL/hour in children or 2 L/hour in adults by NGT may clear the GI tract of iron pills before absorption can occur
remarks on deferoxamine
derived from Streptomyces pilosus
Upon binding iron, it forms the complex ferrioxamine, which is renally excreted
although deferoxamine binds only a small amount of iron (9 mg of elemental iron for each 100 mg of deferoxamine) and thus chelates only a small fraction of the total amount of iron ingested, this generally proves clinically effective in restoring cellular function
indications of deferoxamine
systemic/progressive toxicity
persistent emesis
metabolic acidosis
serum iron level predictive of moderate to severe toxicity
mod: 300-500 mcg/dL
(54-90 mcmol/L)
sev: >500 mcg/dL
(>90 mcmol/L)
administration of deferoxamine
initial adult dose of 1000 mg (children 50mg/kg) IV
begin infusion slowly, starting at 5 mg/kg per hour to avoid producing a rate-related hypotension
hypotension is not a contraindication to IV deferoxamine
the infusion rate can be titrated to 15 mg/kg per hour as tolerated
the recommended amount od deferoxamine for an acute iron overdose is a total of 360 mg/kg or 6 grams in adult during the first 24 hours
- typically ordered as 500 mg infusions over 4-8 hours after the initial 1000-mg dose (?)
complications of deferoxamine therapy
renal insufficiency or failure
pulmonary toxicity
occurs when larger that recommended amounts are given or when administered longer than 24 hours
as ferrioxamine is excreted, the urine color changes to what is classically called
vin rose
but is more typically a brown or rusty hue
the disappearance of the “vin rose” color suggests there is no more free iron available to be complexed with deferoxamine and excreted
most important factor guiding the decision to terminate deferoxamine therapy
clinical recovery of the patient is the most imptorant factor guiding the decision to terminate deferoxamine therapy
because measured iron levels are articifically depressed by the presence of deferoxamine and urine color change can be unreliable
continue deferoxamine therapy in patients who continue to exhibit severe iron toxicity after 24 hours of treatment, using a decreased rate to avoid associated risks mentioned (renal/pulmonary)
other therapies is iron toxicity
hemodialysis and hemofiltration may be necessary to remove the deferoxamine-iron complex in patients with renal failure
severe iron poisoning can be treated with exchange transfusion in addition to deferoxamine therapy
liver transplantation
who can be discharged?
1) patients who have not ingested a potentially toxic amount of iron
2) who remain asymptomatic (other than transient vomiting from the gastric irritant effects of iron)
3) and who have normal findings on PE and laboratory evaluation
4) for a period of 4-6 hours
when to take serum iron
4-6 hours post-ingestion
