Salicylate

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Mode of poisoning

• ingestion of aspirin (acetylsalicylic acid) most common
• ingestion of oil of wintergreen or methyl salicylate

Clinical features

Minor intoxication

• tinnitus
• vertigo
• diarrhoea

Significant intoxication

• acid-base disturbance
  • respiratory alkalosis
    • due to direct central stimulation
  • mixed elevated anion gap metabolic acidosis and respiratory alkalosis
    • acidosis due to uncoupling of oxidative phosphorylation
• non-cardiogenic pulmonary oedema
• altered mental status including coma
• fits
• GI bleeding
• liver failure
• renal failure
• hypoglycaemia

Treatment

• gastric lavage and activated charcoal useful for acute ingestion
• urinary alkalinization to decrease renal tubular back-diffusion and increase renal clearance
  • aim for plasma pH 7.45-7.5
  • avoid hypokalaemia which prevents excretion of alkaline urine
  • forced diuresis does not increase efficacy and may precipitate volume overload
• haemodialysis. Indications:
  • serum concentration >120 mg/dl acutely or >100 mg/dl 6 hours after ingestion
  • refractory acidosis
  • coma or fits
  • noncardiogenic pulmonary oedema
  • in chronic overdose haemodialysis may be necessary for symptomatic patient with serum concentration >60 mg/dl

Prognosis

• ICU mortality 15% following severe poisoning
• mortality correlates poorly with serum concentrations
• lethal dose 150 mg/kg

Further reading

Mokhlesi B et al. Adult toxicology in critical care. Part II: specific poisonings. Chest 2003; 897-922

©Charles Gomersall, October, 2009 unless otherwise stated. The author, editor and The Chinese University of Hong Kong take no responsibility for any adverse event resulting from the use of this webpage.
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