Iron toxicity from an intentional or accidental ingestion is a common poisoning. Based on clinical findings, iron poisoning can be divided into 5 stages.
The first stage develops within the first few hours of ingestion. Direct irritative effects of iron on the gastrointestinal (GI) tract produce abdominal pain, vomiting, and diarrhea. Vomiting is the clinical sign most consistently associated with acute iron toxicity. The absence of these symptoms within 6 hours of ingestion essentially excludes a diagnosis of significant iron toxicity.
During the second stage, which may continue for up to 24 hours following ingestion, the patient's GI symptoms may resolve, providing a false sense of security despite toxic amounts of iron absorption. While patients may be asymptomatic, they often appear ill, and may have abnormal vital signs reflecting hypovolemia and metabolic acidosis.
The third stage may appear early or develop hours after the second stage as shock and a metabolic acidosis evolve. Iron-induced coagulopathy may cause bleeding and worsen hypovolemia. Hepatic dysfunction, cardiomyopathy, and renal failure may also develop.
The fourth stage develops 2 to 5 days after ingestion and is characterized by elevation of aminotransferase levels and possible progression to hepatic failure.
The fifth stage, which occurs 4 to 6 weeks after ingestion, reflects the corrosive affects of iron on the pyloric mucosa and may cause gastric outlet obstruction.
The diagnosis of iron poisoning is based on the clinical picture and the history provided by the patient, significant others, or EMS providers. When determining a patient's potential for toxicity, the total amount of elemental iron must be used in calculations. Table 110-1 reviews the predicted clinical effects based on the amount of iron ingested.
Table 110-1 Predicted Toxicity of Iron Ingestion |Favorite Table|Download (.pdf)
Table 110-1 Predicted Toxicity of Iron Ingestion
|Predicted Clinical Effects||Elemental Iron Dose*||Serum Iron Concentration†|
|Nontoxic or mild GI symptoms||<20 milligrams/kilogram||<300 micrograms/dL|
|Expected significant GI symptoms and potential for systemic toxicity||20 to 60 milligrams/kilogram||300 to 500 micrograms/dL|
|Moderate to severe systemic toxicity||>60 milligrams/kilogram||>500 micrograms/dL|
|Severe systemic toxicity and increased morbidity||—||>1000 micrograms/dL|
Laboratory evaluation includes serum electrolytes, renal studies, serum glucose, coagulation studies, complete blood count, hepatic enzymes, and a serum iron level. It is crucial to note that a single serum iron level does not reflect what iron levels have been previously, what direction they are going, or the degree of iron toxicity in tissues; a single low serum level does not exclude the diagnosis of iron poisoning since there are variable times to peak level following ingestion of different iron preparations. Serum iron levels have limited use in directing management since toxicity is primarily intracellular rather than in the blood. The ...