Aspirin OD

Question 1

What is the chemical name for aspirin?

Answer 1

acetylsalicylic acid,

Question 2

Define aspirin overdose

Answer 2

• Salicylate poisoning is the result of ingestion of, or (rarely) topical exposure to:
  
  • chemicals metabolised to salicylate
• poisoning can be due to acute or chronic aspirin exposure
• characterised by:
  
  • acid-base disturbances
  • electrolyte abnormalities
  • CNS effects

Question 3

Summarise the metabolism of aspirin

Answer 3

acetylsalicylic acid rapidly hydrolysed –> salicylate in the:

• GI tract
• liver
• bloodstream

Question 4

When can

• acute
• chronic

poisoning occur (doses)

Answer 4

• acute = single dose of aspirin or equivalent of >150 mg/kg or >6.5 g
• chronic = repeated exposure to high-dose aspirin or equivalent (150 mg/kg/day)
  
  • particularly in pts with renal insufficiency

Question 5

What is the aetiology of aspirin OD?

Answer 5

poisoning can be due to:

• accidental ingestion
• self-harm
• attempted suicide
• Incorrect salicylate dosing (children & older people)
• cutaneous absorption - rare

Question 6

Other than prescribed aspirin, with OTC medications/therapies contain salicyclic acid?

Answer 6

• Alka-Seltzer XS
• Anadin and Anadin Extra
• Askit powders
• Aspro Clear
• Beechams powders
• Codis 500
• Disprin
• Many cold and influenza preparations

Question 7

What is bismuth subsalicylate & where is it found?

Answer 7

• 50% aspirin equivalent
• found in some non-prescription antidiarrheal medications (Pepto-Bismol, Maalox Total Stomach Relief, and some formulations of Kaopectate

Question 8

What are the risk factors for aspirin OD?

Answer 8

• age:
  
  • young (<3yrs)
  • old (>70yrs)
• Hx of self-harm or suicide attempts
• ingestion of >recommended dose of aspirin, bismuth salicyclate, oil of wintergreen

Question 9

Summarise the epidemiology of aspirin OD

Answer 9

• In the UK, deaths by suicidal overdose of analgesics, including salicylates, were reduced by 22% in the 1999
  
  • (after the introduction in 1998 of legislation limiting the pack size of analgesics that could be purchased)
• all age groups

Question 10

What are the presenting symptoms of aspirin OD?

Answer 10

• CNS symptoms
  
  • abnormal behaviour
  • Tinnitus/deafness
    
    • ​is reversible
  • malaise
    
    • early sign
  • dizziness
    
    • ​early sign
  • movement disorders, asterixis
    
    • ​depth correlates with level of poisoning
  • seizures
• GI symptoms:
  
  • nausea
  • vomiting
  • epigastric pain
• profuse sweating
  
  • due to impaired production of energy and its release as heat
• respiratory signs
  
  • SOB
    
    • MAY BE THE ONLY PRESENTING SYMPTOM
    • due to underlying metabolic acidosis and/or respiratory alkalosis
  • tachypnoea
  • hyperpnoea
  • Kussmaul’s respirations
    
    • Salicylates directly stimulate the respiratory centre and cause tachypnoea. Respiratory alkalosis

Question 11

What are the signs of aspirin OD O/E?

Answer 11

• CNS signs
  
  • coma, papilloedema
  • confusion, delirium
  • abnormal behaviour
• GI signs
  
  • haematemesis
• Fever
  
  • ​due to impaired production of energy and its release as heat ​
• Respiratory symptoms
  
  • tachypnoea
  • hyperpnoea
  • Kussmaul’s respirations
  • Salicylates directly stimulate the respiratory centre and cause tachypnoea. Respiratory alkalosis

Question 12

What are some uncommon signs of aspirin OD & what do they imply?

Answer 12

• rales + low O2 sats
  
  • Indicates life-threatening non-cardiogenic pulmonary oedema
  • which can develop in both subacute and chronic poisoning
  • with additional risk at high altitude

Question 13

What are the primary investigations for aspirin OD?

Answer 13

Question 14

wWhat would the results of these primary investigations be in the case of aspirin OD?

Answer 14

• ABG
  
  • initially respiratory alkalosis;
  • later concomitant metabolic acidosis
  • (more prominent in children as they have less capacity to compensate with hyperventilation than adults)
  • potentially with wide anion gap

BLOODS

• serum electrolyte panel
  
  • hypokalaemia, hypocalcaemia, and/or hypomagnesaemia
• serum salicyclate
  
  • ​Salicylate levels should be followed every 2-4 hours until they peak.
  • Tx decisions are driven by clinical presentation rather than salicylate level
  • but salicylate levels can help to determine whether the patient is still absorbing salicylate and so assist in decision-making.
• urea & creatinine
  
  • ​may show renal insufficiency (rare complication)
• ketones
  
  • ​may be positive (mainly in children) or negative
• blood glucose
  
  • ​may show hyperglycaemia due to derangement of carbohydrate metabolism
• FBC
  
  • WBC count may be elevated (but non-specific)
• LFTs
  • ​Direct hepatotoxicity can occur and is usually reversible
  • However, most patients develop asymptomatic elevation of transaminases (AST. + ALT)
• PT, activated PTT, INR
  
  • ​coagulopathy may be present due to hepatoxicitity, but do not usually clinically manifest in the picture
• toxicology screen (bloods + urine for drugs of abuse)​

IMAGING

• CXR
  
  • ​to exclude non-cardiogenic pulmonary oedema
  • requires urgent haemodialysis
• ECG
  
  • ​to exclude prolonged corrected QT interval (associated with severe ventricular dysrhythmias)
  • may be life-threatening

Question 15

What are some secondary investigations for aspirin OD?

Answer 15