Updated: 12/31/2021

Salicylate/Aspirin Overdose

Review Topic
  • Snapshot
    • A 30-year-old woman presents to the emergency room after an overdose of aspirin of an unknown amount. She has a history of depression. Her family reports that they found a bottle of aspirin next to her. An arterial blood gas reveals that she has a mixed respiratory alkalosis and metabolic acidosis. A serum salicylate level is obtained and she is immediately started on sodium bicarbonate and intravenous hydration.
  • Introduction
    • Clinical definition
      • a constellation of symptoms resulting from toxicity or overdose from salicylates, most commonly aspirin
  • Epidemiology
    • Demographics
      • patients taking chronic pain medications
  • Etiology
    • Intentional overdose
    • Accidental overdose
    • Pathogenesis
      • salicylates have multiple effects on the body
        • hyperventilation and early respiratory alkalosis
          • aspirin directly stimulates the respiratory centers in the brainstem
        • later metabolic acidosis, resulting metabolic metablic acidosis-respiratory alkalosis
          • aspirin uncouples oxidative phosphorylation, which impairs the Kreb cycle
            • this results in a lactic acidosis
        • tinnitus
          • aspirin is toxic to cranial nerve VIII
        • acute respiratory distress syndrome
          • aspirin is also toxic to the lungs
        • renal insufficiency
          • aspirin is toxic to the renal tubules
        • increased bleeding time
          • aspirin inhibits platelet aggregation
  • Presentation
    • Symptoms
      • tinnitus
      • nausea
      • vomiting
      • fever
      • lethargy
      • seizure or coma (in cases of severe poisoning)
    • Physical exam
      • tachypnea
      • tachycardia
      • hyperthermia
      • paresthesias and spasms
        • a sequelae of a low free calcium from the respiratory alkalosis early in presentation
  • Studies
    • Labs
      • arterial blood gas to evaluate for acidosis or alkalosis
        • respiratory alkalosis with a normal bicarbonate early in overdose
        • respiratory alkalosis with an overwhelming metabolic acidosis late in overdose
      • serum salicylate level
        • to confirm diagnosis
        • measure every 3 hours as toxicity can be delayed
      • chemistry panel with liver function tests
        • to assess renal and hepatic function
    • Making the diagnosis
      • based on clinical presentation and laboratory studies
        • especially if patients present with tinnitus, anion gap metabolic acidosis, and elevated serum salicylate levels
  • Differential
    • Acetaminophen overdose
      • distinguishing factors
        • hepatic failure
        • no tinnitus or acid-base derangement
        • antidote is N-acetylcysteine
  • Treatment
    • Conservative
      • supportive care
        • indication
          • for all patients
        • modalities
          • intravenous hydration
    • Medical
      • activated charcoal
        • indications
          • for patients with known salicylate ingestion within the past hour
          • to block absorption
      • sodium bicarbonate
        • indications
          • for patients in whom supportive care is not sufficient, or if patients are not good candidates for activated charcoal
          • alkalinize urine to increase excretion of salicylates
          • alkalinize serum to decrease central nervous system toxicity
    • Non-operative
      • dialysis
        • indication
          • for severe cases (salicylate concentration > 100 mg/dL) or if clinical features are severe
  • Complications
    • Renal failure
  • Prognosis
    • Depends on severity of toxicity
    • Severe cases may be fatal

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