FACEM Toxicology and Poisoning 2 — Questions and Answers
Question 1: A hiker in Australia is bitten by an unknown snake and develops local pain and systemic symptoms. Which first aid measure is MOST important?
- Apply a tourniquet proximal to the bite site
- Apply pressure immobilization bandaging to the entire bitten limb (Correct answer)
- Incise the bite site and suction out venom
- Wash the bite site thoroughly with soap and water
Correct answer: Apply pressure immobilization bandaging to the entire bitten limb
Pressure immobilization bandaging slows lymphatic spread of venom and is the recommended first aid for Australian elapid snake envenomation; tourniquets and incision/suction are contraindicated.
Question 2: A patient with respiratory depression after benzodiazepine overdose is considered for flumazenil. What is the most important contraindication to its use?
- History of asthma
- Suspected co-ingestion of opioids
- Physical dependence on benzodiazepines (Correct answer)
- Advanced age with renal impairment
Correct answer: Physical dependence on benzodiazepines
Flumazenil can precipitate acute benzodiazepine withdrawal seizures in physically dependent patients, making it dangerous without clear knowledge of the patient's benzodiazepine use history.
Question 3: A patient presents with visual disturbances, high anion gap metabolic acidosis, and osmolar gap after suspected methanol ingestion. What is the mechanism of methanol toxicity?
- Direct methanol-induced retinal ischemia
- Accumulation of formaldehyde and formic acid via alcohol dehydrogenase metabolism (Correct answer)
- Competitive inhibition of cytochrome P450 3A4
- Methemoglobin formation impairing oxygen delivery
Correct answer: Accumulation of formaldehyde and formic acid via alcohol dehydrogenase metabolism
Methanol is metabolized by alcohol dehydrogenase to formaldehyde and then to formic acid, which inhibits cytochrome oxidase in the optic nerve and causes high anion gap metabolic acidosis.
Question 4: A patient with beta-blocker overdose has a heart rate of 32 bpm and BP of 70/40 mmHg, refractory to atropine 3mg IV. What is the next most appropriate treatment?
- High-dose insulin euglycemic therapy (HIET)
- Glucagon 3–5mg IV bolus (Correct answer)
- Calcium gluconate 1g IV
- Norepinephrine infusion at 0.1 mcg/kg/min
Correct answer: Glucagon 3–5mg IV bolus
Glucagon bypasses the blocked beta-adrenergic receptor to activate adenylyl cyclase via its own receptor, increasing intracellular cAMP and improving heart rate and contractility.
Question 5: A patient develops hyperthermia (39.8°C), clonus, hyperreflexia, mydriasis, and diaphoresis after starting tramadol and sertraline concurrently. What is the most likely diagnosis?
- Neuroleptic malignant syndrome
- Malignant hyperthermia
- Serotonin syndrome (Correct answer)
- Anticholinergic toxidrome
Correct answer: Serotonin syndrome
Serotonin syndrome presents with the triad of altered mental status, autonomic instability, and neuromuscular features including clonus and hyperreflexia, distinguishing it from neuroleptic malignant syndrome which features rigidity and bradyreflexia.
Question 6: A patient with severe calcium channel blocker overdose develops cardiogenic shock unresponsive to calcium, vasopressors, and atropine. Which treatment has the most evidence for this scenario?
- High-dose insulin euglycemic therapy (HIET) with dextrose (Correct answer)
- Sodium bicarbonate 2 mEq/kg IV bolus
- Magnesium sulfate 4g IV infusion
- Phenylephrine infusion at 2 mcg/kg/min
Correct answer: High-dose insulin euglycemic therapy (HIET) with dextrose
High-dose insulin euglycemic therapy (HIET) improves myocardial carbohydrate utilization and cardiac contractility in calcium channel blocker toxicity and is supported by case series and animal data.
Question 7: A firefighter is removed from a structure fire with severe lactic acidosis, refractory cardiovascular collapse, and a bitter almond odor. Which antidote is the current preferred treatment for suspected cyanide poisoning?
- Sodium thiosulfate 12.5g IV alone
- Hydroxocobalamin 5g IV (Correct answer)
- Dicobalt edetate 300mg IV
- Amyl nitrite inhalation followed by sodium nitrite IV
Correct answer: Hydroxocobalamin 5g IV
Hydroxocobalamin (Cyanokit) is the preferred antidote for cyanide poisoning, binding cyanide to form cyanocobalamin which is renally excreted; it does not cause methemoglobinemia and is safe in co-existing carbon monoxide poisoning.
FACEM Toxicology and Poisoning 2
A hiker in Australia is bitten by an unknown snake and develops local pain and systemic symptoms.
Which first aid measure is MOST important?