Poisoning – Salicylates

Notes
  • Acute poisoning occurs after the ingestion of more than 150mg of salicylate/kg.
Symptoms
  • Nausea
  • Vomiting
  • Tinnitus
  • Confusion
  • Seizures
  • Hyperthermia
  • Hyperventilation and then hypoventilation
  • Respiratory alkalosis (at an earlier stage)
  • Metabolic acidosis (at a later stage)
  • Rhabdomyolysis
  • Multiple organ failure.
Diagnosis
  • Clinical
  • Arterial blood gas (ABG) test
  • Where possible determine salicylate plasma levels.
Management
  • Activated charcoal given orally or by nasogastric tube as a slurry in water: Initial dose in adults of 50-100g and maintenance dose of 50g every 4 hrs. In children less than13yrs: Initial dose of 10-25g and maintenance dose of 1-2 g/kg every 4 hrs. For teenagers 13-18yrs: Initial dose of 50-100g and maintenance dose of 50g every 4 hrs.
  • Catheterize to monitor urine output.
  • If possible the central venous pressure (CVP) should be measured during rehydration to reduce the risks of cerebral and pulmonary oedema.
  • Alkaline diuresis:

*Alkaline pH leads to the increase in the concentration of salicylate in the urine (up to 10 times when pH is increased from 7 to 8)

*It is indicated in moderate salicylate poisoning in absence of shock, heart failure and impaired renal function,

*It targets to achieve a urinary pH 8.0 -8.5.

*Plasma potassium deficit must be corrected to ensure that the alkalinity of urine is achieved without raising the plasma pH. This is achieved as follows:

      **Infuse the following in the 1st hr: 500 mL 5% dextrose to prevent hypoglycaemia, 500mL sodium bicarbonate 1.4%, 500 mL dextrose 5% and  Potassium chloride added (to maintain serum potassium of above 3.5 mmol/l).

      **The above is followed by 1.5-2.0L of i.v. fluids / hr for 3 hrs  and ensure the urine volume that is greater than 500mL/hr

      **Monitor urine pH at 30-minute interval to maintain the pH at 7.5 - 8.5.

      **Infuse at rate of 30mg/kg/hr in children

  • Vitamin K IV to correct hypothrombinaemia
  • Hemodialysis in severe cases
  • Intermittent positive pressure ventilation and pulmonary artery wedge pressure measurement
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