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The term salicylate refers to any group of chemicals that are derived from salicylic acid.

Acetylsalicylic acid or aspirin is metabolized to salicylic acid after ingestion.

• Aspirin is well absorbed from stomach and delayed by the presence of food . Entric coated aspirin will have slow absorption.

PATHOPHYSIOLOGY

• Local gastric irritation:

  It may cause vomiting and nausea as a result of local gastric irritation & stimulation of the chemoreceptor trigger.

• Stimulation of medullary respiratory center:

  Salicylate increases respiratory rate through a direct stimulatory effect on medullary respiratory center in CNS but very high dose of salicylate conc. depress respiration .

• Stimulates skeletal muscle metabolism:

  skeletal muscle metabolism leads to increase in oxygen consumption and carbondioxide production. Initially respiratory center stimulation and the increase in carbondioxide production cause an increased respiratory rate resulting in respiratory alkalosis. but if respiratory center fails it will lead to respiratory acidosis.

• Uncoupling of oxidative phosphorylation , enhances lipolysis and inhibits various kreb cycle enzyme. Leading to

  1) increased catabolism and increased CO2.

  2)increased heat production

  3)increased glycolysis and peripheral demand of glucose

  4)Production of metabolic intermediate that contribute to metabolic acidosis. (organic acid, lactate,pyruvate & ketoacids).

• Acute lung injury & proteinuria

• Glucose metabolism : Although salicylate causes mobilisation of glycogen stores it causes inhibition of gluconeogenesis so it can produce hypo,hyper or normoglycemia.

• Reversible ototoxicity : It is thought to be a secondary to interference with chloride channels in the cochlear hair cells that transmit sound waves.

PRESENTATION

• Typically occurs when serum salicylate level is > 30mg/dl.

• Nausea, vomiting

• tinnitus, hearing loss, sweating

• Hyperventilation

• Patients with mixed ingestion that include aspirin may have a normal anion gap acidosis.

• Most patients with acute aspirin overdose have a mixed acid base disturbance of respiratory alkalosis and metabolic acidosis.

• Uncommon features include acute lung injury , cardiac dysarrythmia, hypoglycemia, fever, neurological dysfunction.

• Chronic salicylate intoxication hyperventilation, pappiledema, tremors, agitation, paranoia, bizarre behavior, memory deficit, confusion.

Done nomogram

• The aspirin normogram was developed by Done in 1960. Data from pediatric patients who ingested a one time dose of aspirin were plotted over time to create an instrument to predict toxicity.

• It has very limited applicability and its routine use is not presently recommended.

MANAGEMENT

• ABC

• GI DECONTAMINATION :

  Gastric lavage : salicylates can induce pylorospasm and form gastric bezoars so that lavage may be beneficial even when performed more than 1 hr from ingested overdose.

  Activated charcoal : It effectively reduces the absorption. Single dose of activated charcoal 1 to 2gm/kg should be administrated.

  Whole bowel irrigation: There are evidence that they are more effective than activated charcoal.

• IV FLUIDS

  • Fluid replacement with NS intially

  • After initial bolus the fluid should contain 5% dextrose for target urine output of 1-2ml/kg/h.

  • 5% Dextrose is used to prevent hypoglycemia.

• Urine alkanisation:

  It is an effective in elimination.

  NaHCo3 bolus of 1-2mEq/kg is given followed by continuous infusion.

• Extracoporeal elimination techniques : hemodialysis, hemofiltration, hemodiafiltration.

• Dialysis is indicated in

  • Severe acidosis or hypotension refractory to optimal supportive care (regardless of absolute serum aspirin concentration)

  • Evidence of end organ injury (Seizures, rhabdomyolysis, pulmonary edema)

  • Renal failure

  • High serum aspirin concentration >100mg/dl

• ALI : Salicylate induced lung injury is managed similarly to other ALI.

Signs & Symptoms following acute ingestion

Updated on 16/3/2013.

Reference :

• Tintinalli

• ED mangement of the salicylate poisoned patient ; By Ferald F. O malley ; Emergency medicine clinics of north America.