ABEM Medical Tox flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Volume of distribution

Apparent volume relating drug dose to plasma concentration (Vd = dose/Cp). A Vd greater than about 1 L/kg suggests extensive tissue distribution and poor removal by hemodialysis.

First-order elimination half-life

Time for plasma concentration to fall by half; t½ = 0.693 × Vd/CL. Roughly five half-lives are needed to reach steady state or near-complete elimination.

Activated charcoal contraindications

Avoid in unprotected airway, gastrointestinal obstruction, caustic ingestion, and hydrocarbons with high aspiration risk. Give 1 g/kg, up to 50 g, ideally within one hour of ingestion.

Reference dose derivation

RfD = NOAEL or LOAEL divided by uncertainty factors, typically 10 each for animal-to-human and human variability. Used for noncancer risk assessment; hazard quotient = exposure/RfD.

Urine alkalinization indications

Weak acids such as salicylates and phenobarbital are ionized and trapped in alkaline urine. Target urine pH 7.5-8.5; monitor potassium and avoid in volume overload.

Toxidrome: cholinergic

SLUDGE plus DUMBELS: salivation, lacrimation, urination, diarrhea, GI upset, emesis, bradycardia, bronchorrhea, bronchospasm, miosis. Caused by organophosphates, carbamates, and some mushrooms.

Acetaminophen antidote

N-acetylcysteine replenishes glutathione and detoxifies NAPQI. Use the Rumack-Matthew nomogram from 4 hours post-ingestion; treat when the level is at or above the line.

Digoxin Fab fragments

Ovine antibody fragments bind digoxin and reverse toxicity. Indicated for life-threatening arrhythmia, significant hyperkalemia, or ingestion greater than 10 mg in adults.

High-dose insulin euglycemia

For calcium channel blocker or beta blocker overdose: regular insulin 0.5-1 U/kg/h with dextrose, monitoring glucose and potassium. Improves inotropy via carbohydrate metabolism.

Sodium bicarbonate for TCA

Indicated when QRS exceeds 100 ms, with seizures, or ventricular arrhythmia. Bolus 1-2 mEq/kg; target serum pH 7.45-7.55; avoid flumazenil and class IA/IC agents.

Lithium hemodialysis indications

Level above 4 mEq/L, or above 2.5 with symptoms, renal failure, or seizure. Lithium has a small volume of distribution, no protein binding, and is not bound by charcoal.

Iron poisoning antidote

Deferoxamine chelates free iron and is indicated for shock, acidosis, or serum iron above 500 µg/dL with symptoms. It may cause hypotension and vin rose urine.

Fomepizole mechanism

Potent alcohol dehydrogenase inhibitor that blocks formation of toxic metabolites from methanol and ethylene glycol. Dose 15 mg/kg loading, then 10 mg/kg every 12 hours; dialysis adjusts interval.

Ethylene glycol toxicity

Metabolites cause anion gap metabolic acidosis, hypocalcemia, and calcium oxalate crystalluria with renal failure. Fomepizole, thiamine, pyridoxine, bicarbonate, and hemodialysis are treatments.

Methanol toxicity features

Formic acid accumulation causes high anion gap metabolic acidosis, visual loss, and bilateral putaminal necrosis. Treat with fomepizole or ethanol, folinic acid, bicarbonate, and hemodialysis.

Cocaine-associated wide QRS

Sodium bicarbonate is used for cocaine-induced QRS widening from sodium channel blockade. Benzodiazepines treat agitation and hypertension; avoid pure beta blockade because of unopposed alpha stimulation.

Alcohol withdrawal treatment

Benzodiazepines are first line, symptom-triggered by CIWA score. Give thiamine before glucose to prevent Wernicke encephalopathy; monitor for complications such as seizures and delirium tremens.

Isopropanol ingestion

Produces ketosis without metabolic acidosis, hemorrhagic gastritis, and CNS depression. It is metabolized to acetone by alcohol dehydrogenase; treatment is supportive, and dialysis is rarely needed.

Lead toxicity mechanism

Inhibits aminolevulinic acid dehydratase and ferrochelatase, causing anemia with basophilic stippling. Chelation uses succimer or EDTA; encephalopathy requires dimercaprol (BAL) plus EDTA.

Methylmercury chelation caution

Dimercaprol is contraindicated in methylmercury poisoning because it redistributes mercury to the brain. DMPS or DMSA may be considered; treatment is otherwise supportive.

Carbon monoxide half-life

About 4-6 hours breathing room air, roughly 1 hour on 100% oxygen, and shorter with hyperbaric oxygen. COHb level does not reliably predict severity.

Methemoglobinemia treatment

Methylene blue 1-2 mg/kg IV reduces methemoglobin via NADPH. It is ineffective and potentially harmful in G6PD deficiency; use ascorbic acid or exchange transfusion instead.

Cadmium toxicity features

Inhalation causes pneumonitis and long-term emphysema; chronic oral exposure causes renal tubular proteinuria and osteomalacia. No chelator reliably improves outcomes; treatment is supportive.

Hydroxocobalamin for cyanide

Binds cyanide to form cyanocobalamin, excreted renally. Dose 5 g IV; it causes red discoloration of skin and urine and interferes with some colorimetric laboratory assays.

Nerve agent treatment

Atropine titrated to secretions, pralidoxime early to reactivate acetylcholinesterase, and benzodiazepines for seizures. Avoid succinylcholine because acetylcholinesterase is inhibited and paralysis is prolonged.

Sulfur mustard effects

Alkylating vesicant causing delayed erythema, blisters, airway injury, and bone marrow suppression after a latent period. There is no specific antidote; treatment is decontamination and supportive care.

Ricin mechanism

Ribosome-inactivating protein from castor beans that inhibits protein synthesis. Inhalation causes delayed pulmonary edema; ingestion causes hemorrhagic gastroenteritis. No antidote exists.

Botulism presentation

Descending flaccid paralysis with cranial nerve findings, respiratory failure, and no fever. Caused by preformed toxin; treat with antitoxin and supportive ventilation.

Hazmat Level A protection

Fully encapsulating vapor-protective suit with self-contained breathing apparatus, used for highest respiratory and skin hazard. Levels B, C, and D offer progressively less protection.

Phosgene exposure features

Causes delayed noncardiogenic pulmonary edema after a latent period, with minimal immediate irritation. Treatment is rest, oxygen, and observation; steroids and fluids are controversial.

Immunoassay false positives

Amphetamine screens can be positive after pseudoephedrine, bupropion, or ranitidine; opioid screens after poppy seeds; PCP screens after ketamine or dextromethorphan. Confirmatory GC-MS is required.

Osmolal gap formula

Measured osmolality minus calculated osmolality, where calculated = 2×Na + glucose/18 + BUN/2.8. A gap above 10 suggests unmeasured osmoles such as methanol, ethylene glycol, or isopropanol.