Aspirin Overdose

Question 1

Definition

Answer 1

Excessive ingestion of aspirin causing toxicity

Question 2

Aetiology

Answer 2

· It can be a result of deliberate self-harm, suicidal intent or by accident

· 10-20 g can cause moderate-severe toxicity in adults

Question 3

Pathophysiology

Answer 3

o Increases respiratory rate and depth by stimulating the respiratory centre

o This hyperventilation –> respiratory alkalosis (in the early stage)

o The body compensates by increasing urinary bicarbonate and K+ excretion

o This leads to dehydration and hypokalaemia

o Loss of bicarbonate, uncoupling of mitochondrial oxidative phosphorylation and the build up of lactic acid can lead to metabolic acidosis

o In SEVERE cases, CNS depression and respiratory failure can occur

Question 4

Epidemiology

Answer 4

One of the most common drug overdoses

Question 5

Urgent questions

Answer 5

o How much aspirin was taken?

o When was it taken?

o Were any other drugs taken?

o Have you had any alcohol?

Question 6

Presenting symptoms (early)

Answer 6

Patient may initially be asymptomatic

o Flushed
o Fever
o Sweating
o Hyperventilation
o Dizziness
o Tinnitus
o Deafness

Question 7

Presenting symptoms (late)

Answer 7

o Lethargy
o Confusion
o Convulsions
o Drowsiness
o Respiratory depression
o Coma

Question 8

Signs on physical examination

Answer 8

· Fever
· Tachycardia
· Hyperventilation
· Epigastric tenderness

Question 9

Investigations

Answer 9

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

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