- Published on
Emergency And Acute Medicine – Poisoning, Toxidromes
A toxidrome is a recognizable constellation of signs and symptoms produced by a specific class of toxins. Identification of a toxidrome helps guide rapid diagnosis and empiric management when the exact substance is unknown. The clinical presentation depends on the toxin’s mechanism of action and receptor targets.
Several major toxidromes are commonly encountered in emergency practice: anticholinergic, cholinergic, sympathomimetic, hallucinogenic, opioid, sedative–hypnotic, withdrawal syndromes, serotonin syndrome, and neuroleptic malignant syndrome.
The anticholinergic toxidrome is classically remembered as “blind as a bat, mad as a hatter, red as a beet, hot as a hare, dry as a bone, the bowel and bladder lose their tone, and the heart runs alone.” Patients present with hyperthermia, dry flushed skin, mydriasis, delirium, tachycardia, hypertension, urinary retention, decreased bowel sounds, and possible seizures or somnolence.
The cholinergic toxidrome is summarized by the mnemonic DUMBELS for muscarinic effects: diarrhea and diaphoresis, urination, miosis, bradycardia with bronchorrhea and bronchospasm (the “killer Bs”), emesis, lacrimation, and salivation. Nicotinic findings include tachycardia, hypertension, weakness, fasciculations, and occasionally mydriasis.
The sympathomimetic toxidrome resembles anticholinergic toxicity but is distinguished by diaphoresis and increased bowel sounds. Patients exhibit tachycardia, hypertension, hyperthermia, mydriasis, agitation, seizures, and increased peristalsis.
Hallucinogenic toxicity may overlap with sympathomimetic features. Patients may present with disorientation, hallucinations, anxiety, panic, and seizures. Substances such as LSD, psilocybin, mescaline, and MDMA may produce these effects.
The opioid toxidrome is characterized by the classic triad of miosis, hypoventilation, and coma. Additional findings include bradycardia, hypotension, hypothermia, and decreased bowel sounds.
Sedative–hypnotic and alcohol toxicity present with sedation, confusion, slurred speech, ataxia, nystagmus, blurred vision, and delirium. In contrast, withdrawal from alcohol, benzodiazepines, or barbiturates produces tachycardia, hypertension, hyperthermia, tremor, diaphoresis, agitation, hallucinations, and seizures. Opioid withdrawal presents with mydriasis, piloerection, nausea, vomiting, diarrhea, abdominal cramps, tachycardia, lacrimation, salivation, yawning, and hypertension.
Neuroleptic malignant syndrome occurs after initiation or dose increase of antipsychotics and may develop hours to weeks after exposure. It presents with hyperthermia, muscular rigidity, diaphoresis, altered mental status, blood pressure instability, tremor, sialorrhea, leukocytosis, elevated creatine phosphokinase, and metabolic acidosis.
Serotonin syndrome typically develops shortly after an increase or addition of serotonergic agents. Common features include agitation, confusion, hyperthermia, diaphoresis, tachycardia, hypertension, mydriasis, tremor, hyperreflexia, clonus, myoclonus, muscle rigidity, and seizures.
Vital sign abnormalities may suggest specific toxin classes. Bradycardia may be seen with β-blockers, calcium channel blockers, clonidine, digoxin, cholinergics, and opioids. Tachycardia occurs with sympathomimetics, anticholinergics, tricyclic antidepressants, methylxanthines, and withdrawal states. Hyperthermia may result from anticholinergics, sympathomimetics, serotonin syndrome, neuroleptic malignant syndrome, salicylates, and withdrawal. Hypothermia is associated with opioids, ethanol, sedative–hypnotics, carbon monoxide, and α2-agonists. Hypertension is common with sympathomimetics, anticholinergics, nicotine, and phencyclidine. Hypotension may occur with β-blockers, calcium channel blockers, opioids, sedative–hypnotics, tricyclic antidepressants, and nitrates.
Pupillary changes are diagnostically useful. Miosis suggests opioids, cholinergics, clonidine, and certain antipsychotics. Mydriasis is seen with anticholinergics, sympathomimetics, and withdrawal states. Toxic seizures may be remembered by the mnemonic OTIS CAMPBELL, which includes organophosphates, tricyclic antidepressants, isoniazid, sympathomimetics, camphor, cocaine, amphetamines, methylxanthines, phencyclidine, benzodiazepine withdrawal, bupropion, ethanol withdrawal, lithium, lidocaine, and lead.
Dermatologic clues may assist diagnosis. Mees lines may suggest arsenic or thallium exposure. Bullae may be seen with barbiturates or carbon monoxide. Flushing can occur with anticholinergics, niacin, disulfiram reactions, scombroid poisoning, or vancomycin. Blue or cyanotic skin may indicate methemoglobinemia from nitrites, dapsone, aniline dyes, benzocaine, or chloroquine, whereas pseudocyanosis may occur with amiodarone, minocycline, silver, or gold.
Essential evaluation depends on the suspected toxin but commonly includes complete blood count, electrolytes, renal function, glucose, urinalysis, arterial or venous blood gas, carboxyhemoglobin and methemoglobin levels, toxicology screening, acetaminophen and salicylate levels, prothrombin time, and liver function tests.
An elevated anion gap metabolic acidosis may be remembered by the mnemonic A CAT MUD PILES, which includes alcohol ketoacidosis, carbon monoxide or cyanide, acetaminophen (late), toluene, methanol, uremia, diabetic ketoacidosis, paraldehyde or metformin, iron or isoniazid, lactic acidosis, ethylene glycol, and salicylates. An increased osmolar gap suggests methanol, ethylene glycol, isopropyl alcohol, ethanol, acetone, glycerol, mannitol, or glycine.
Initial management focuses on airway, breathing, and circulation. Further emergency department management depends on the identified or suspected toxidrome and may include antidotes, supportive care, and consultation with a poison control center or medical toxicologist.
Key clinical principles include recognizing characteristic patterns, obtaining appropriate laboratory studies early, and using toxidrome identification to guide timely and targeted therapy.
0 Comments
