Salicylate Toxicity Summary

High-Risk Features

  • Age >70 years
  • Coma, convulsions, confusion
  • Pulmonary edema
  • Severe metabolic acidosis
  • Hyperpyrexia
  • Ventricular arrhythmias

Severity Classification

  • Mild: <300 mg/L - Tinnitus, nausea
  • Moderate: 300-700 mg/L - Hyperventilation, sweating
  • Severe: >700 mg/L - Pulmonary edema, coma

Emergency Management

  • Avoid intubation unless respiratory failure
  • Activated charcoal if <1 hour post-ingestion
  • Correct hypokalemia urgently
  • IV fluids for dehydration
  • Sodium bicarbonate for acidosis

Monitoring

  • Salicylate levels at 2h (symptomatic) or 4h (asymptomatic)
  • Repeat levels every 2h if symptomatic or >200 mg/L
  • Monitor urine pH hourly
  • Check K+ 1-2 hourly

Urine Alkalinization

  • Indications:
    • Adults: >500 mg/L
    • Children: >350 mg/L
  • Target urine pH: 7.5-8.5
  • Maintain K+ 4-4.5 mmol/L

Hemodialysis

  • Absolute indications:
    • >900 mg/L
    • >700 mg/L + acidosis
    • Coma due to salicylate
  • Consider: >700 mg/L

Discharge Criteria

  • Asymptomatic + normal acid-base
  • Observation for 6 hours
  • Salicylate <300 mg/L
  • Falling levels + improving symptoms

Salicylate Toxicity

Life-threatening poisoning requiring urgent recognition and management

Overview

Salicylates are highly toxic in large overdose. Patients are more likely to die if they are aged over 70 years, or if they develop coma, convulsions, confusion, agitation, pulmonary oedema, severe metabolic acidosis, or hyperpyrexia. Ventricular arrhythmias and asystole can occur, leading to fatalities.

Critical Warning: Avoid intubation unless there is evidence of respiratory failure. Loss of hyperventilatory drive can result in sudden decompensation and death.

Clinical Features by Severity

Mid Toxicity

Usually associated with peak salicylate concentration <300 mg/L (2.2 mmol/L)

  • Lethargy
  • Nausea
  • Vomiting
  • Tinnitus
  • Dizziness
  • Deafness

Moderate Toxicity

Usually associated with salicylate concentration 300-700 mg/L (2.2-5.1 mmol/L)

  • Dehydration
  • Restlessness
  • Sweating
  • Warm extremities with bounding pulses
  • Increased respiratory rate and hyperventilation
  • Respiratory alkalosis (may also be metabolic acidosis)

Severe Toxicity

Usually associated with peak salicylate concentration >700 mg/L (5.1 mmol/L)

  • Cardiac dysrhythmias
  • Acute non-cardiogenic pulmonary oedema
  • Cerebral oedema
  • Convulsions
  • Confusion
  • Coma
  • Hyperpyrexia
  • Heart failure
  • Renal failure
  • Worsening metabolic and lactic acidosis

Emergency Management

Initial Resuscitation
  1. Airway and ventilation: Maintain clear airway and ensure adequate ventilation. Avoid intubation unless evidence of respiratory failure (worsening respiratory acidosis, severe hypoxemia).
  2. Gastric decontamination: Consider activated charcoal (50g adults, 1g/kg children) if within 1 hour of ingestion of ≥125 mg/kg salicylate or any methyl salicylate.
  3. Gastric lavage: Consider within 1 hour of potentially life-threatening overdose (≥500 mg/kg) if expertise available and airway protected.

Laboratory Monitoring

  • Initial salicylate level: At least 2 hours (symptomatic) or 4 hours (asymptomatic) post-ingestion
  • Repeat monitoring: Every 2 hours in symptomatic patients or those with initial levels ≥200 mg/L until levels falling and clinical improvement
  • Additional monitoring: Electrolytes, ABG, renal function, glucose

Specific Treatment Measures

Fluid and Electrolyte Management

  • Treat hypokalaemia urgently - reduces risk of severe hypokalaemia with bicarbonate therapy
  • IV fluids with added potassium if necessary to replace substantial fluid losses
  • Monitor potassium 1-2 hourly during treatment

Acid-Base Management

  • Once serum potassium normal, correct metabolic acidosis with IV sodium bicarbonate 50-100 mmol over 30 minutes
  • Bicarbonate reduces transfer of salicylate into CNS, reducing toxicity
  • Monitor ABG regularly during therapy

Urine Alkalinization

Indications for urine alkalinization:

  • Plasma salicylate >500 mg/L (3.6 mmol/L) in adults
  • Plasma salicylate >350 mg/L (2.5 mmol/L) in children

Protocol:

  • Optimum urine pH: 7.5-8.5
  • Check urinary pH hourly
  • Monitor plasma sodium and potassium 1-2 hourly
  • Maintain plasma potassium around 4-4.5 mmol/L with IV replacement

Hemodialysis

Hemodialysis (or haemodiafiltration) is the treatment of choice for severe salicylate poisoning.

Indications for Hemodialysis

Category Indications
Absolute Indications
  • Salicylate concentration ≥900 mg/L (6.4 mmol/L)
  • Salicylate concentration >700 mg/L (5.1 mmol/L) with metabolic acidosis
  • Coma due to salicylate poisoning
Strongly Consider Plasma salicylate concentration >700 mg/L (5.1 mmol/L)
Additional Considerations
  • Severe acidosis
  • Renal failure
  • Congestive cardiac failure
  • Non-cardiogenic pulmonary oedema

Disposition and Follow-up

Discharge Criteria

Asymptomatic patients with normal acid-base status can be considered for discharge after:

  • Observation for 6 hours post-overdose
  • Plasma salicylate concentration <300 mg/L (2.2 mmol/L)
  • Falling salicylate levels with clinical improvement

Admission Criteria

Admit all patients with:

  • Symptomatic salicylate toxicity
  • Salicylate levels >300 mg/L
  • Abnormal acid-base status
  • Concerning clinical features regardless of levels
  • Requiring specific treatments (bicarbonate, dialysis)

Monitoring During Admission

Clinical Monitoring

  • Neurological status (GCS)
  • Respiratory rate and pattern
  • Vital signs including temperature
  • Fluid balance

Laboratory Monitoring

  • Serial salicylate levels until consistently falling
  • Electrolytes, especially potassium
  • Arterial blood gases
  • Renal function
  • Liver function tests