Salicylates

Mechanism of toxicity
Toxic dose
Symptoms and signs of poisoning
Special investigations
Management
Urine alkanisation
Symptomatic and supportive
Monitoring

Mechanism of toxicity

Direct CNS stimulation and acid-base balance derangement.

Toxic dose

150 mg/kg (acute ingestion) or 100 mg/kg/day over > 2days (accumulation).

Symptoms and signs of poisoning

• General: restlessness, hyperventilation, tachycardia, sweating, hyperthermia, dehydration.
• Gastro-intestinal: nausea, vomiting (GIT bleeding is not common).
• Neurological: tinnitus, deafness, stupor, coma.
• Other: pulmonary oedema, acute renal failure, hypokalaemia, hypoglycaemia and hypoprothrombinaemia with prolonged INR and bleeding.

Special investigations

• Arterial blood gas: children more likely to develop acidosis while adults develop respiratory alkalosis.
• Renal function and electrolytes: acute renal failure and hypokalaemia / hyperkalaemia.
• Salicylate concentrations: severe poisoning: > 5.1 mmol/L (> 700 microgram/mL).

Management

Note general principles of acute poisoning.

Urine alkalinisation

• Adult dose: 225 mmol sodium bicarbonate (225 mL of 8.4% solution) IV over 1 hour.
• Paediatric dose: 25-30 mmol (25 mL of 8.4% solution) IV over 1 hour.
• Monitor: urine pH every 10 – 30 minutes (aim for pH 7.5-8.5) and potassium hourly (hypokalaemia most common complication).
• Caution: Correct hypokalaemia before administering sodium bicarbonate.

Symptomatic and supportive

• Electrolytes, glucose and fluid status: correct dehydration, acidosis, hypoglycaemia and electrolyte disturbances.
• Hyperthermia: external cooling.

Monitoring

• Renal function, acid-base, potassium and fluid status.