Monday, 25 October 2010

MRCP revision battle 34.5: Salicylate overdose

Patients who have taken a salicylate overdose are potentially more interesting than those who have taken a paracetamol overdose as salicylate poisoning actually has early clinical features you can look out for,  such as:
  • sweating
  • tinnitus
  • dizziness
  • pyrexia
  • hyperventilation

A blood gas should show a mixed respiratory alkalosis and metabolic acidosis, and potentially a low potassium.

The sweating and pyrexia are due to uncoupling of oxidative phosphorylation.

The effects of salicylate are dose related:
  • 150mg/kg: mild
  • 250mg/kg: moderate
  • >500mg/kg: severe

Later features of salicylate poisoning include:
  • renal failure
  • hypo or hyperglycaemia
  • seizures
  • acidosis

  • activated charcoal if within 1 hr
  • correct acidosis with 1.26% sodium bicarb
  • haemodialysis if:
    • conc >700mg/l
    • metabolic acidosis resistant to treatment
    • acute renal failure
    • pulmonary oedema
    • seizures
  • urinary alkalinization is rarely used and is contra-indicated in cerebral or pulmonary oedema

Lets move on to consider use of haemodialysis in overdoses in general...