Differential Diagnosis for Unresponsive 4-year-old Boy Following Unknown Ingestion
Single Most Likely Diagnosis
- Aspirin (Salicylate) Overdose: The patient's arterial blood gas results show a mixed acid-base disturbance with a low pH (acidosis), low PaCO2 (indicating respiratory alkalosis), and low bicarbonate (indicating metabolic acidosis). This combination is classic for salicylate toxicity, which can cause both a respiratory alkalosis (due to central stimulation of respiration) and a metabolic acidosis.
Other Likely Diagnoses
- Ethylene Glycol Poisoning: This can cause a metabolic acidosis with an elevated anion gap, similar to what might be seen in this patient. However, the presence of respiratory alkalosis (low PaCO2) is less typical for ethylene glycol poisoning.
- Methanol Poisoning: Similar to ethylene glycol, methanol poisoning can lead to metabolic acidosis but typically does not cause the significant respiratory alkalosis seen here.
Do Not Miss Diagnoses
- Cyanide Poisoning: Although less common, cyanide poisoning can cause severe metabolic acidosis and is potentially lethal. It might not be the first consideration but should be ruled out due to its high mortality rate if untreated.
- Severe Sepsis or Septic Shock: While the context suggests an ingestion, severe infections can cause similar laboratory abnormalities and must be considered, especially in an unresponsive child.
Rare Diagnoses
- Formaldehyde or Formic Acid Poisoning: These can cause metabolic acidosis but are less common and typically associated with specific exposures (e.g., industrial or laboratory settings).
- Pyroglutamic Acidosis (5-Oxoprolinuria): A rare condition that can cause metabolic acidosis, often seen in the context of certain medications (e.g., acetaminophen) or malnutrition, but it would be an unusual cause of acute presentation like this, especially with respiratory alkalosis.