Salicylates
Salicylates include aspirin and Oil of Wintergreen. The Oil has ↑↑ toxic potential due to ↑ drug concentration.
Salicylate overdose classically causes:
- Triad of:
- Nausea
- Vomiting
- Tinnitus
- An initial primary respiratory alkalosis
Direct respiratory centre stimulation. - Secondary metabolic acidosis
Late sign indicating imminent demise. Produces a HAGMA due to:- Salicylate anion production
- Uncoupled oxidative phosphorylation
Nausea and vomiting occur due to irritation of both gut mucosa and the medullary chemoreceptor trigger zone.
Epidemiology and Risk Factors
Pathophysiology
Aetiology
Clinical Features
Initial:
- Tinnitus
- Nausea, vomiting
- Abdominal pain
Severe:
- Pulmonary oedema
- ARDS
- Seizures
- Coma
- Acidaemia
- Hyper or hypoglycaemia
- Hypokalaemia
Assessment
History:
- Dose
Risk assessment:- <150mg/kg: Minimal
- 150-300mg/kg: Mild-moderate
Recommend activated charcoal. - >300mg/kg: Severe intoxication, metabolic acidosis and neurological features expected
- >500mg/kg: Potentially lethal
Consider gastric lavage.
Exam:
Investigations
Many bedside ABG machines mistake salicylate for chloride and incorrectly report a hyperchloraemic NAGMA.
Bedside:
- ABG
- Respiratory alkalosis
- HAGMA
Laboratory:
- Blood
- Salicylate level
Correlate poorly with toxicity but can be used to identify trend of absorption. - UEC
- Monitor for hypokalaemia
- Paracetamol level
- BSL
- Salicylate level
Imaging:
Other:
Diagnostic Approach and DDx
Management
- Activated charcoal
- Treat seizures
- Urinary alkalinisation or RRT
Resuscitation:
- Pulmonary oedema
- CPAP
NIV or intubation, depending on conscious state.
- CPAP
- C
- Fluid resuscitation
GIT and insensible losses.
- Fluid resuscitation
- D
- Seizures
- Benzodiazepines
- Seizures
Specific therapy:
Activated charcoal and urinary alkalinisation are covered in detail under Poisoning.
- Pharmacological
- Activated charcoal
Up to 8 hours following overdose. - Alkalinisation
- ↑ Urine pH traps salicylate ions in urine, ↑ elimination
- ↑ Blood pH prevents salicylate movement into CSF
- Activated charcoal
- Procedural
- RRT
- ↑ Clearance
- Allows control of volume when bicarbonate is ↑
- RRT
- Physical
Supportive care:
- B
- Hyperventilation
To aid alkalinisation.
- Hyperventilation
- F
- Correct hypokalaemia
Hypokalaemia will ↑ DCT K+/H+ exchange, acidifying urine.
- Correct hypokalaemia
Disposition:
Preventative:
Marginal and Ineffective Therapies
Anaesthetic Considerations
Complications
Prognosis
Key Studies
References
- Bersten, A. D., & Handy, J. M. (2018). Oh’s Intensive Care Manual. Elsevier Gezondheidszorg.