ABEM Medical Tox common mistakes
ABEM Medical Tox · Understand the traps and how to avoid them.
Draws a serum acetaminophen level before 4 hours post-ingestion and plots it on the Rumack-Matthew nomogram, then discharges or withholds N-acetylcysteine based on that single early value.
Early concentrations reflect incomplete absorption and are falsely reassuring; the nomogram is validated only for a single acute ingestion at ≥4 hours, and candidates anchor on the first available laboratory result.
What to do instead
Confirm the ingestion time, start N-acetylcysteine if the timing is unknown or the level is detectable/uncertain, and apply the nomogram only to a single acute ingestion with a level drawn ≥4 hours after ingestion; repeat the level and use the 150-line treatment threshold.
Administers activated charcoal to a drowsy patient without a protected airway, or after a caustic or hydrocarbon ingestion.
A decontamination reflex equates charcoal with universal benefit, and candidates underestimate aspiration pneumonitis and the specific contraindications.
What to do instead
Restrict charcoal to an alert, cooperative patient or one with a protected airway, ideally within 1–2 hours, and avoid it in caustic, hydrocarbon, or altered-mental-status patients unless the airway is secured.
Gives flumazenil to a patient with depressed consciousness after an unknown or mixed overdose.
Reversing a benzodiazepine feels like a safe targeted antidote, so candidates discount the risk of seizures from co-ingested tricyclics or chronic benzodiazepine use.
What to do instead
Reserve flumazenil for a known isolated benzodiazepine overdose in a patient with no seizure history, no tricyclic co-ingestion, and no chronic benzodiazepine use; otherwise support airway and ventilation.
Treats sulfonylurea-induced hypoglycemia with dextrose alone and discharges the patient after a single normal glucose reading.
Glucose corrects immediately with dextrose, so candidates overlook the drug's long duration of action and the high rate of recurrent hypoglycemia.
What to do instead
Give octreotide, admit for serial glucose monitoring, and observe for recurrence; never discharge based on one response to dextrose.
Excludes ethylene glycol or methanol poisoning because the osmolal gap is normal or only mildly elevated.
The osmolal gap falls as the parent alcohol is metabolized to acid while the anion gap rises, and candidates treat a single osmolal gap as a rule-out test.
What to do instead
Calculate both osmolal and anion gaps and interpret them as time-dependent; if suspicion exists, give fomepizole and obtain specific alcohol levels rather than relying on a normal osmolal gap.
Treats a child with lead encephalopathy using oral dimercaptosuccinic acid (succimer) alone.
Succimer is familiar and oral, and candidates extrapolate from outpatient chelation of lower-level lead poisoning.
What to do instead
Use parenteral BAL plus CaNa2EDTA for lead encephalopathy or a blood lead >70 mcg/dL with symptoms, and reserve succimer for lower levels or after parenteral therapy.
Gives 2 mg IV atropine, sees no response, and stops or escalates slowly in organophosphate poisoning with copious secretions.
Candidates apply standard ACLS atropine dosing as a fixed dose instead of titrating to effect in cholinergic crisis.
What to do instead
Rapidly double the atropine dose (2, 4, 8 mg, and so on) until secretions dry and ventilation improves; there is no fixed maximum dose, and pralidoxime should be given early.
Makes a diagnosis or disposition decision based on an unconfirmed urine immunoassay screen, such as a positive amphetamine, PCP, or opiate result.
Screens are immunoassays prone to cross-reactivity, and candidates treat a positive screen as a confirmed result.
What to do instead
Confirm positive or unexpected screens with GC-MS or LC-MS, interpret them in clinical context, and never base a forensic or disposition decision on an immunoassay alone.
Uses lidocaine or phenytoin for tricyclic-induced wide-complex dysrhythmia or a QRS >100 ms.
Antiarrhythmic familiarity and hesitation about bicarbonate lead candidates to miss that tricyclic cardiotoxicity is sodium-channel blockade.
What to do instead
Give sodium bicarbonate boluses (1–2 mEq/kg) to narrow the QRS and alkalinize serum, and avoid class IA/IC agents and phenytoin.
Attributes a fatal drug concentration drawn from a central postmortem blood sample to antemortem toxicity.
Postmortem redistribution from liver and lung can raise central levels, and candidates treat an autopsy level like an antemortem level.
What to do instead
Use femoral or peripheral blood, vitreous, and the clinical circumstances; account for postmortem redistribution and do not equate a central blood level with the antemortem concentration.