ABEM Toxicology, Environmental & Infectious Diseases 3 — Questions and Answers
Question 1: A child ingests iron tablets and presents 6 hours later with vomiting, abdominal pain, and bloody diarrhea. Which laboratory finding best indicates systemic iron toxicity?
- Serum iron level > 350 µg/dL
- Anion gap metabolic acidosis (Correct answer)
- Leukocytosis > 15,000/µL
- Hyperglycemia
Correct answer: Anion gap metabolic acidosis
An anion gap metabolic acidosis reflects mitochondrial dysfunction from free radical damage and is a marker of systemic iron toxicity requiring deferoxamine.
Question 2: A patient develops diffuse muscle pain, dark urine, and AKI after a severe rattlesnake envenomation. Which complication is most directly responsible for the renal injury?
- Direct nephrotoxin in venom
- Myoglobinuria from venom-induced rhabdomyolysis (Correct answer)
- Disseminated intravascular coagulation
- Hypotension-related ischemia
Correct answer: Myoglobinuria from venom-induced rhabdomyolysis
Crotalid venom causes myonecrosis and rhabdomyolysis; the resulting myoglobinuria precipitates in renal tubules and causes acute tubular necrosis.
Question 3: Which of the following is the MOST appropriate management of severe hypothermia (core temp 25°C) with ventricular fibrillation refractory to three defibrillation attempts?
- Continue CPR and withhold further shocks until rewarmed to ≥30°C (Correct answer)
- Initiate extracorporeal membrane oxygenation (ECMO) rewarming
- Administer amiodarone 300 mg IV and shock every 2 minutes
- Perform urgent cardiopulmonary bypass in the ED
Correct answer: Continue CPR and withhold further shocks until rewarmed to ≥30°C
In severe hypothermia, pharmacologic and electrical therapies are largely ineffective below 30°C; CPR should be maintained and rewarming prioritized before repeating defibrillation.
Question 4: A patient with HIV and CD4 count of 60/µL presents with headache, fever, and altered mentation. India ink stain of the CSF is positive. What is the first-line induction therapy?
- Fluconazole 400 mg PO daily
- Amphotericin B deoxycholate + flucytosine (Correct answer)
- Voriconazole IV
- Micafungin IV
Correct answer: Amphotericin B deoxycholate + flucytosine
Cryptococcal meningitis induction therapy requires amphotericin B plus flucytosine for at least 2 weeks to achieve fungal clearance before consolidation with fluconazole.
Question 5: After a house fire, a victim presents with confusion, cherry-red skin, and carboxyhemoglobin of 28%. What is the half-life of COHb with 100% normobaric oxygen?
- ~5 hours
- ~60–90 minutes (Correct answer)
- ~30 minutes
- ~4–5 hours without oxygen treatment
Correct answer: ~60–90 minutes
100% normobaric oxygen reduces the carboxyhemoglobin half-life from ~5 hours on room air to approximately 60–90 minutes.
Question 6: A patient is found unconscious with empty bottles of amitriptyline and alcohol. ECG shows a QRS of 140 ms and right axis deviation of the terminal 40 ms. What is the most appropriate initial treatment?
- Physostigmine 2 mg IV
- Sodium bicarbonate 1–2 mEq/kg IV bolus (Correct answer)
- Magnesium sulfate 2 g IV
- Overdrive pacing
Correct answer: Sodium bicarbonate 1–2 mEq/kg IV bolus
Sodium bicarbonate narrows the QRS in tricyclic antidepressant overdose by increasing serum sodium and alkalinizing the blood, reversing sodium channel blockade.
Question 7: Which of the following presentations is MOST consistent with black widow spider envenomation rather than brown recluse envenomation?
- Expanding necrotic wound with blue-gray halo at the bite site
- Diffuse muscle cramping, diaphoresis, and severe abdominal rigidity (Correct answer)
- Painless local erythema with central eschar formation
- Local urticaria and angioedema within 30 minutes of the bite
Correct answer: Diffuse muscle cramping, diaphoresis, and severe abdominal rigidity
Latrodectus (black widow) venom causes alpha-latrotoxin-induced neurotransmitter release, producing the classic latrodectism: painful muscle cramping, diaphoresis, and autonomic instability.
ABEM Toxicology, Environmental & Infectious Diseases 3
A child ingests iron tablets and presents 6 hours later with vomiting, abdominal pain, and bloody diarrhea.
Which laboratory finding best indicates systemic iron toxicity?