Updated: 5/2/2020

Salicylate/Aspirin Overdose

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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
  • Prognosis
    • depends on severity of toxicity
    • severe cases may be fatal
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

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