Snapshot A 30-year-old woman presents to the emergency room after an overdose of aspirin of an unknown amount. She has a history of depression. Her family reports that they found a bottle of aspirin next to her. An arterial blood gas reveals that she has a mixed respiratory alkalosis and metabolic acidosis. A serum salicylate level is obtained and she is immediately started on sodium bicarbonate and intravenous hydration. Introduction Clinical definition a constellation of symptoms resulting from toxicity or overdose from salicylates, most commonly aspirin Epidemiology Demographics patients taking chronic pain medications Etiology Intentional overdose Accidental overdose Pathogenesis salicylates have multiple effects on the body hyperventilation and early respiratory alkalosis aspirin directly stimulates the respiratory centers in the brainstem later metabolic acidosis, resulting metabolic metablic acidosis-respiratory alkalosis aspirin uncouples oxidative phosphorylation, which impairs the Kreb cycle this results in a lactic acidosis tinnitus aspirin is toxic to cranial nerve VIII acute respiratory distress syndrome aspirin is also toxic to the lungs renal insufficiency aspirin is toxic to the renal tubules increased bleeding time aspirin inhibits platelet aggregation Presentation Symptoms tinnitus nausea vomiting fever lethargy seizure or coma (in cases of severe poisoning) Physical exam tachypnea tachycardia hyperthermia paresthesias and spasms a sequelae of a low free calcium from the respiratory alkalosis early in presentation Studies Labs arterial blood gas to evaluate for acidosis or alkalosis respiratory alkalosis with a normal bicarbonate early in overdose respiratory alkalosis with an overwhelming metabolic acidosis late in overdose serum salicylate level to confirm diagnosis measure every 3 hours as toxicity can be delayed chemistry panel with liver function tests to assess renal and hepatic function Making the diagnosis based on clinical presentation and laboratory studies especially if patients present with tinnitus, anion gap metabolic acidosis, and elevated serum salicylate levels Differential Acetaminophen overdose distinguishing factors hepatic failure no tinnitus or acid-base derangement antidote is N-acetylcysteine Treatment Conservative supportive care indication for all patients modalities intravenous hydration Medical activated charcoal indications for patients with known salicylate ingestion within the past hour to block absorption sodium bicarbonate indications for patients in whom supportive care is not sufficient, or if patients are not good candidates for activated charcoal alkalinize urine to increase excretion of salicylates alkalinize serum to decrease central nervous system toxicity Non-operative dialysis indication for severe cases (salicylate concentration > 100 mg/dL) or if clinical features are severe Complications Renal failure Prognosis Depends on severity of toxicity Severe cases may be fatal