A 4-year-old boy is brought to the emergency department by his father due to nausea, vomiting, diarrhea, and abdominal pain over the past 4 hours. Their home bathroom is being repainted due to peeling paint, and prior to the onset of symptoms the patient's father noticed that several pill bottles were open. Temperature is 37.2 C (99 F), blood pressure is 76/38 mm Hg, pulse is 160/min, and respirations are 34/min. On physical examination, the patient appears tired and is responsive only to painful stimuli. The oropharynx is clear but appears dry. Peripheral pulses are weak, and capillary refill is 4 seconds. Not long after examination, the boy develops hematemesis. Laboratory results are as follows:
| Complete blood count | |
| Hemoglobin | 13.5 g/dL |
| Platelets | 300,000/mm3 |
| Leukocytes | 6,800/mm3 |
| Serum chemistry | |
| Sodium | 143 mEq/L |
| Potassium | 4.8 mEq/L |
| Chloride | 102 mEq/L |
| Bicarbonate | 14 mEq/L |
| Blood urea nitrogen | 31 mg/dL |
| Creatinine | 1.1 mg/dL |
| Glucose | 118 mg/dL |
| Arterial blood gas | |
| pH | 7.30 |
| PaO2 | 90 mm Hg |
| PaCO2 | 30 mm Hg |
Chest and abdominal x-rays reveal several small opacities in the stomach and duodenum. Which of the following was most likely ingested by this patient?
Anion gap metabolic acidosis | |
Calculation | Anion gap = sodium – (chloride + bicarbonate) (normal: 10-14 mEq/L) |
Common causes Mnemonic: MUDPILES |
|
Acute iron poisoning classically presents in children age <6 due to unintentional ingestion of prenatal vitamins or concentrated ferrous sulfate tablets. Iron causes direct mucosal damage to the intestinal tract, leading to abdominal pain, vomiting, diarrhea, and bleeding (hematemesis, melena), as seen in this case. Due to these gastrointestinal losses, patients may develop hypovolemic shock within hours of ingestion, as suggested by this patient's hypotension, tachycardia, and prerenal azotemia.
Laboratory evaluation reveals an anion gap (AG) metabolic acidosis, as seen in this patient with an AG of 27. Acidosis results from hydrogen ion production during iron absorption and increased lactic acid production in shock. Imaging may reveal small opacities in the stomach and intestines because some formulations of iron tablets are radiopaque. Diagnosis is confirmed with elevated serum iron levels, and treatment includes intravenous deferoxamine chelation therapy.
(Choice A) Acute acetaminophen overdose can cause nausea and vomiting. However, AG metabolic acidosis and gastrointestinal bleeding would not be expected.
(Choice B) Salicylate (eg, aspirin) poisoning presents with nausea, vomiting, and a metabolic acidosis with respiratory compensation. However, tinnitus is a common early sign, and aspirin tablets are not visualized on x-ray.
(Choice D) Patients with acute lead poisoning have abdominal pain, vomiting, and altered mental status/seizures. Radiopaque tablets on x-ray may be seen; however, lead is not corrosive to gastric mucosa and does not cause hematemesis. In addition, metabolic acidosis would not be seen.
(Choice E) Patients with a narcotic overdose (eg, oxycodone) typically have central nervous system and respiratory depression. This patient's respiratory rate is high.
(Choice F) Warfarin poisoning can present with bleeding secondary to coagulopathy (eg, hematuria, hematemesis, intracranial hemorrhage). Metabolic acidosis does not occur.
Educational objective:
Patients with acute iron poisoning have abdominal pain, diarrhea, and hematemesis; in addition, they may develop hypovolemic shock within a few hours due to gastrointestinal losses. Laboratory evaluation reveals an anion gap metabolic acidosis, and x-ray may show radiopaque tablets.