Aspirin (ASA) Toxicity

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Aspirin Toxicity and its Management in the Emergency Department
 
Mechanism and toxicity:

• Salicylates irreversible block the COX-1 pathway and modify the COX-2 pathway resulting in a decrease in inflammation and platelet aggregation
• Salicylate is conjugated in the liver and then excreted in the kidneys, which will be important in toxicity. 80-90% is protein bound, however, in acute toxicity, this decreases and more of the drug is in the non-ionized form. 
• This non-ionized form interferes with the Krebs cycle, uncouples oxidative phosphorylation and limits ATP production, increases fatty acid metabolism and causes accumulation of pyruvic and lactic acid

 
Effects of toxicity:

• Direct stimulation of the respiratory center causing hyperventilation
• Altered mental status and hypoglycemia in the CSF
• Cerebral edema 2/2 leakage of the BBB
• Metabolic acidosis and resp alkalosis causes hyperventilation which leads to dehydration, fluid losses and acute kidney injury
• Alters platelet function
• Affects cochlear blood flow and membrane permeability outer hair cell organ of corti leading to sensorineural alterations
• GI isrupts mucosal barrier that protects from acid, ulcers, bleeding 

 
ASA Level and Indications for Dialysis:

• 100mg/dL for acute ingestion
• 60mg/dL for chronic ingestion
• Tinnitus with levels as low as 30mg/dL
• Also, standard to obtain BMP, ABG, UA and CXR

 
Management in the ED:

• Start off with the ABCs like any acutely ill patient that presents to the ED
• Activated charcoal is indicated in acute ingestions
• Treat hypoglycemia and hypokalemia, quick bedside BMP/glucose testing will be very helpful
• Most importantly is combating the acidosis and elimination of the drug which includes aggressive use of NaHCO3 and HD when indicated
• Goal is to alkalize the urine and create ion trapping to assist elimination of the drug
• Goals for alkalization of urine are usually a pH of 7.5-8.5. The patient will need a foley and constant monitoring of UOP

 
Managing intubation?:

• Intubation should be avoided at all costs
• If you intubate, be sure to increase RR, if not, RR will drop causing worsening acidosis likely resulting in cardiac arrhythmias and possible death. 

 
Chronic ASA Toxicity:

• Patient history is key and we often misdiagnose these patients with sepsis, delirium, fever of unknown origin
• They may present with mixed acid base picture
• More common in elderly, which makes the diagnosis even more difficult. Indication for HD 60mg/dL as mentioned before.