Aspirin Overdose

Question 1

Define Aspirin Overdose

Answer 1

Excessive ingestion of aspirin causing toxicity

Question 2

What is the aetiology of Aspirin Overdose?

Answer 2

• Can be deliberate self-harm, suicidal intent or by accident
• 10-20g can be moderate-severe toxicity adults
  Pathophysiology:
  
  • increases respiratory rate and depth by stimulating the respiratory centre
  • hyperventilation => respiratory alkalosis (early stages)
  • the body compensations by increasing urinary bicarbonate and K+ excretion
  • leads to dehydration and hypokalaemia
  • loss of bicarbonate, uncoupling of mitochondrial oxiditative phosphorylation and the build up of lactic acid can lead to metabolic acidosis
  • in severe cases, CNS depression and respiratory failure can occur

Question 3

What is the epidemiology of Aspirin Overdose?

Answer 3

Most common drug overdose

Question 4

What are the presenting Symptoms?

Answer 4

- Initially may be asymptomatic
Early Symptoms:
- Flushed
- Fever
- Sweating
- Hyperventilation
- Dizziness
- Tinnitus
- Deafness
Later Symptoms:
- Lethargy 
- Confusion
- Convulsions
- Drowsiness
- Respiratory depression
- Coma

Question 5

What are the Important questions to ask?

Answer 5

• How much aspirin was taken?
• When was it taken?
• Were any other drugs taken?
• Was alcohol consumed?

Question 6

What are the signs of Aspirin overdose on Physical examination?

Answer 6

• Fever
• Tachycardia
• Hyperventilation
• Epigastric tenderness

Question 7

What are the Investigations for Aspirin Overdose?

Answer 7

Blood:

• Salicylate levels
• FBC
• U&Es - check for hypokalaemia
• LFTs - high AST/ALT
• Clotting screen - high PT
• Other drug levels (e.g. paracetamol)
• ABG - may show mixed metabolic acidosis and respiratory alkalosis

ECG:
- signs of hypokalaemia: flattened/inverted T-waves, U waves, prolonged PR interval, ST depression