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This is a clinician-written, evidence-based summary aligned to the USMLE Step 2 CK Content Outline. It is intended for medical students preparing for USMLE Step 2 CK. Management reflects current ACC/AHA, USPSTF, and APA guidelines. Always cross-reference with UpToDate, institutional protocols, and clinical judgment.
The Bottom Line
- Early salicylate toxicity causes respiratory alkalosis from direct respiratory center stimulation.
- Severe toxicity causes anion gap metabolic acidosis, hyperthermia, altered mental status, pulmonary edema, and cerebral edema.
- Classic symptoms: tinnitus, vomiting, tachypnea, diaphoresis, fever, confusion.
- Treat with activated charcoal when appropriate, IV sodium bicarbonate for serum/urine alkalinization, potassium repletion, and dialysis if severe.
- Avoid intubation if possible; if necessary, match pre-intubation minute ventilation to prevent sudden acidosis and CNS salicylate shift.
Overview
Aspirin/salicylate poisoning causing mixed respiratory alkalosis and metabolic acidosis, treated with alkalinization and hemodialysis when severe. Emergency management focuses on early recognition, stabilization, targeted investigation, and prompt definitive therapy while avoiding common pitfalls tested on USMLE Step 2 CK.
Epidemiology
This presentation is encountered in emergency and acute care settings. Risk varies by exposure, comorbidity, age, mechanism, and timeliness of treatment. Morbidity and mortality increase when recognition is delayed or when airway, breathing, circulation, antidotal therapy, or definitive source control is postponed.
Clinical Features
Symptoms
Tinnitus, hearing loss, vertigo, nausea, vomiting, and diaphoresis
Tachypnea or hyperventilation often precedes severe metabolic acidosis
Confusion, agitation, delirium, hallucinations, seizure, or coma
Fever or hyperthermia due to uncoupled oxidative phosphorylation
Dyspnea or frothy sputum suggesting noncardiogenic pulmonary edema
Signs
Tachypnea, respiratory alkalosis, dehydration, fever, tachycardia
Mixed acid-base disorder: respiratory alkalosis plus anion gap metabolic acidosis
Altered mental status or seizures indicate severe toxicity regardless of numeric level
Pulmonary edema, hypoxemia, or ARDS
Hypokalemia may prevent effective urine alkalinization
Investigations
First-line
Serial serum salicylate levelsRepeat every 2 hours until clearly declining and clinically improving; enteric-coated aspirin can peak late.
Blood gas and electrolytesLook for respiratory alkalosis, anion gap metabolic acidosis, bicarbonate depletion, and potassium abnormalities.
GlucoseCNS hypoglycemia can occur even with normal serum glucose; treat altered mental status with dextrose when appropriate.
Overdose screenAcetaminophen level, ethanol, pregnancy test, ECG, renal function, CK if severe.
Second-line
Chest X-rayIndicated for hypoxemia, dyspnea, or suspected pulmonary edema.
Urine pHTarget urine alkalinization pH 7.5-8.0 during bicarbonate therapy.
Serial clinical assessmentMental status, respiratory rate, temperature, urine output, and acid-base trend are more important than one level.
Specialist
Toxicology / nephrology consultationEarly for moderate-severe toxicity, rising levels, altered mental status, renal failure, pulmonary edema, or dialysis consideration.
1
Initial care and decontamination
- Assess airway, breathing, circulation, mental status, temperature, and co-ingestions.
- Activated charcoal if early presentation, large ingestion, or ongoing absorption and airway is protected.
- Multiple-dose activated charcoal may be considered for enteric-coated or bezoar-forming massive ingestion in consultation with toxicology.
- Treat hypoglycemia and seizures promptly with dextrose and benzodiazepines.
2
Alkalinization
- IV sodium bicarbonate bolus and infusion to alkalinize serum and urine.
- Target urine pH 7.5-8.0 and maintain serum pH in mildly alkalemic range when possible.
- Aggressively replete potassium because hypokalemia prevents urinary alkalinization.
- Avoid excessive fluids if pulmonary edema develops.
3
Airway caution
- Avoid intubation when possible because loss of compensatory hyperventilation can cause abrupt acidemia.
- If intubation is unavoidable, pre-oxygenate, give bicarbonate, and set high minute ventilation to match pre-intubation respiratory alkalosis.
4
Hemodialysis indications
- Altered mental status, seizure, cerebral edema, pulmonary edema, renal failure, refractory acidosis, severe electrolyte disturbance, or clinical deterioration.
- Very high salicylate levels, especially acute >100 mg/dL or chronic >60 mg/dL with symptoms, support dialysis consideration.
Complications
- Cerebral edema: Worsened by acidemia and increased CNS salicylate penetration
- Noncardiogenic pulmonary edema: Major cause of morbidity and dialysis indication
- Seizures/coma: Severe neurotoxicity requiring urgent escalation
- Hyperthermia: From uncoupled oxidative phosphorylation
- Renal failure: Reduces salicylate clearance and worsens acidosis
USMLE Step 2 CK Exam Tips
- 1Tinnitus + tachypnea + mixed respiratory alkalosis/metabolic acidosis = salicylate toxicity.
- 2Urine alkalinization requires potassium repletion.
- 3Enteric-coated aspirin can have delayed peak levels; trend serial salicylate levels.
- 4Avoid intubation if possible; if required, maintain high minute ventilation.
- 5Altered mental status or pulmonary edema = dialysis consideration regardless of exact level.
- 6Methyl salicylate oil is extremely concentrated and dangerous in children.
practicetest your knowledge on toxic ingestions — salicylateApply what you've learnt with USMLE Step 2 CK-style questions from the iatroX Q-Bank — emergency medicine and beyond.
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