Salicylate poisoning

Salicylate poisoning is a serious complication of aspirin overdose and is characterized by mixed respiratory alkalosis and increased anion gap metabolic acidosis.

Pathophysiology

Early mixed respiratory alkalosis → ↑ anion gap metabolic acidosis
1. Salicylates directly stimulate the respiratory center of the brain → hyperventilation → CO2 washout → primary respiratory alkalosis
2. Disruption of mitochondrial oxidative phosphorylation → inhibition of TCA cycle and ATP production → accumulation of lactic acid and ketones → ↑ anion gap metabolic acidosis
3. Fatigue impairs the ability to compensate for acidosis (via hyperventilation) → hemodynamic instability and end-organ damage
↑ Pulmonary capillary permeability → ARDS with pulmonary edema.

Clinical features

Early symptoms: tinnitus, nausea, vomiting, tachypnea, hyperpnea
Late symptoms: hyperthermia, agitation, delirium, seizures, noncardiogenic pulmonary edema

Diagnostics

Differential diagnostics

Feature	Salicylate (ASA) Poisoning	Acetaminophen (APAP) Poisoning	Reye Syndrome
Classic Hx	Overdose (intentional/accidental)	Intentional OD; chronic EtOH use	Child after viral illness + ASA use
Pathophysiology	Uncouples ox-phos; Resp center stim; Direct ototoxicity	Glutathione depletion -> toxic metabolite (NAPQI) -> liver necrosis	Mitochondrial dysfunction -> fatty liver & encephalopathy
Presentation	Tinnitus, fever, hyperventilation, AMS	Asymptomatic initially -> RUQ pain -> fulminant liver failure	Profuse vomiting, delirium/coma, NO jaundice
Key Lab Finding	Mixed resp. alkalosis + metabolic acidosis	Massive AST/ALT elevation (>1000s)	Hyperammonemia, elevated LFTs, hypoglycemia
Antidote / Tx	IV Sodium Bicarbonate, Hemodialysis	N-acetylcysteine (NAC)	Supportive care (manage ICP, hypoglycemia)
Buzzword	"Mixed acid-base disorder"	"Rumack-Matthew nomogram"	"Child + virus + aspirin"

Treatment

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