Differential Diagnosis for Poisoning with Dilation of Pupils and Severe Metabolic Acidosis

• Single Most Likely Diagnosis
  • Cyanide Poisoning: Cyanide is known to cause severe metabolic acidosis due to its inhibition of cellular respiration, leading to lactic acidosis. It can also cause dilation of pupils due to its effect on the nervous system. The combination of these symptoms makes cyanide a prime suspect.
• Other Likely Diagnoses
  • Ethylene Glycol Poisoning: Ethylene glycol, found in antifreeze, can cause severe metabolic acidosis due to its metabolites, including glycolic acid and oxalic acid. It may also cause neurological symptoms, including alterations in mental status that could be associated with pupillary changes.
  • Methanol Poisoning: Similar to ethylene glycol, methanol poisoning leads to metabolic acidosis through its toxic metabolites, formic acid, and can cause visual disturbances and neurological effects, potentially including pupillary dilation.
  • Salicylate Poisoning: Aspirin overdose can lead to severe metabolic acidosis and respiratory alkalosis. While pupillary changes are not the most common symptom, salicylates can cause neurological effects, and in severe cases, alterations in mental status might be associated with pupillary changes.
• Do Not Miss Diagnoses
  • Carbon Monoxide Poisoning: Although carbon monoxide primarily causes tissue hypoxia without directly leading to metabolic acidosis, severe cases can result in lactic acidosis due to tissue hypoxia. Pupillary changes might not be a primary symptom, but given the potential for severe and delayed neurological effects, it's crucial not to miss this diagnosis.
  • Strychnine Poisoning: Strychnine causes muscle convulsions and can lead to metabolic acidosis due to the intense muscular activity. It also affects the nervous system, potentially causing pupillary dilation. The severity of its symptoms makes it a critical diagnosis not to overlook.
• Rare Diagnoses
  • Amanita Mushroom Poisoning: Certain mushrooms, like Amanita species, can cause severe gastrointestinal symptoms, liver failure, and in some cases, metabolic acidosis. Neurological symptoms, including alterations in mental status, could potentially lead to pupillary changes, although this is less common.
  • Hyoscyamus (Henbane) Poisoning: Hyoscyamus contains scopolamine and hyoscyamine, which can cause anticholinergic effects, including dilated pupils. In severe cases, it might lead to metabolic disturbances, although this is less typical. The primary concern would be the anticholinergic toxidrome.