Aspirin (Salicylate) Overdose

24 Apr

Absorption

Peak salicylate levels can occur within one hour when taken in standard forms at normal therapeutic doses

Enteric coated or delayed release tablets can take much longer to reach peak serum levels

-In an overdose, absorption can be delayed because of aspirin’s effect on gastric emptying, bezoar formation (coalescing of the aspirin into one large mass- Remember Harry Potter!) with peak levels taking up to 24 hours to be reached

-NOTE:  above normal therapeutic doses, protein binding decreases, the liver’s detoxification is saturated, and clearance becomes primarily dependent on renal excretion extending the half life of the drug

 

Effects of Aspirin

Cyclooxygenase inhibition leading to gastric irritation and platelet dysfunction

-Directly stimulates the medullary respiratory center in the CNS leading to increased respiratory rate

-Stimulation of the chemoreceptor trigger zone in the medulla causing nausea and vomiting

-Stimulates skeletal muscle metabolism leading to increased oxygen consumption and CO2 production

Oxidative phosphorylation uncoupling

-Increased lipolysis

-Reversible ototoxicity

-Mobilizes glycogen stores and inhibits gluconeogenesis

-Krebs Cycle inhibition

-Increased vascular permeability (Non-cardiogenic pulmonary edema)

 

Overdose

-Symptoms:  Nausea, vomiting, tinnitus/hearing loss, sweating, hyperventilation

Mixed acid base:  Respiratory alkalosis with metabolic acidosis

-Prognostic factors:  unconsciousness (can’t maintain hyperventilation!), fever, severe acidosis, seizures, dysrhythmias, older age. 

 

Testing:

-In moderate to severe poisonings, ASA level testing every 1-2 hours is recommending until concentrations begin to decline and the patient’s status improves

-Remember that depending on the type of pill taken (delayed absorption/enteric coated) and delayed gastric emptying, levels can continue to increase for up to 24 hours after ingestion

 

Treatment:

-The first goal is to minimize further absorption– charcoal, gastric lavage (less popular nowadays), and sorbitol can all be considered

-Replace fluid loss and electrolytes from vomiting/diarrhea with normal saline infusion

-Increasing systemic pH is the goal- Sodium Bicarbonate infusion is the primary treatment

Dialysis as last option:  intubated patients, clinical deteriorating patients, acute lung injury patients, altered mental status, renal failure/insufficiency, and severe acid/base disturbance

-NOTE:  If patient must be intubated/ventilated, hyperventilation MUST be continued

 

Submitted by J. Grover.

 

Sources: Tintinalli’s Emergency Medicine 7th Edition; Uptodate.  Salicylate poisoning in adults; picture 

 

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