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Emergency And Acute Medicine – Poisoning
Poisoning may be intentional or unintentional. Any patient presenting with an unexplained change in mental status should be evaluated for possible intoxication or overdose. Intentional poisoning may be related to depression, suicide attempts, homicide, or recreational drug abuse. Unintentional poisoning commonly occurs in children and may result from accidental ingestion, therapeutic errors such as double dosing, or recreational experimentation. In pediatric patients, most accidental ingestions occur in children aged 1–5 years. A history that is inconsistent or suspicious should raise concern for possible child abuse.
Clinical presentation varies depending on the substance involved. Neurologic findings may include lethargy, agitation, coma, hallucinations, or seizures. Respiratory effects may range from tachypnea to bradypnea or apnea, with possible inability to protect the airway. Cardiovascular manifestations include dysrhythmias and conduction abnormalities. Vital sign abnormalities may include hyperthermia or hypothermia, tachycardia or bradycardia, and hypertension or hypotension.
Recognition of toxidromes can guide management. Anticholinergic toxicity presents with altered mental status, dry skin and mucous membranes, fixed dilated pupils, tachycardia, hyperthermia, flushing, and urinary retention. Cholinergic toxicity presents with excessive secretions including salivation, lacrimation, urination, diaphoresis, miosis, bronchospasm, and wheezing. Opiate toxicity is characterized by central nervous system and respiratory depression with miosis. Sympathomimetic toxicity presents with CNS excitation, seizures, tachycardia, hypertension, and diaphoresis.
Initial evaluation requires complete vital signs including core temperature and a thorough physical examination, paying attention to pupils, skin findings, and unusual odors. Laboratory testing typically includes electrolytes, BUN, creatinine, and glucose. Calculation of the anion gap (normal 8–12) is essential when metabolic acidosis is suspected. Elevated anion gap metabolic acidosis can be remembered using the mnemonic “A CAT MUD PILES,” which includes causes such as alcoholic ketoacidosis, cyanide, carbon monoxide, salicylates, methanol, uremia, diabetic ketoacidosis, iron, lactic acidosis, and ethylene glycol. Serum osmol gap should be calculated when toxic alcohol ingestion is suspected. The calculated osmolality is 2(Na⁺) + glucose/18 + BUN/2.8 + ethanol/4.6 (if ethanol in mg/dL). An osmol gap greater than 10 suggests substances remembered by the mnemonic “ME DIE A”: methanol, ethanol, diuretics (mannitol, glycerin, sorbitol), isopropyl alcohol, ethylene glycol, and acetone. A normal osmol gap does not completely exclude toxic alcohol ingestion. Additional testing may include pregnancy testing, acetaminophen level in suicidal ingestions, toxicology screening, ECG for conduction abnormalities or QRS/QT prolongation, head CT for unexplained altered mental status, and chest radiograph if aspiration is suspected.
The differential diagnosis for altered mental status includes intracranial mass or hemorrhage, infection or sepsis, endocrine abnormalities, hypothermia, hypoxia, metabolic disturbances, and psychogenic causes. These must always be considered alongside toxicologic causes.
Pre-hospital management includes searching the scene for clues such as pill bottles or drug paraphernalia and transporting all medications for identification. Uncooperative patients may require restraint for safety. Comorbid trauma, medical illness, or environmental exposures should be considered. Activated charcoal may be administered pre-hospital in selected cases if transport time is prolonged.
Initial stabilization in the emergency department follows standard ABC principles. Endotracheal intubation is performed as needed for airway protection, oxygenation, and ventilation. Supplemental oxygen, pulse oximetry, cardiac monitoring, and IV access are established. Hypotension is treated with intravenous 0.9% normal saline boluses and vasopressors if persistent. Bradycardia may require atropine or pacing. In patients with altered mental status, administration of thiamine, dextrose (after checking glucose), and naloxone is appropriate.
Decontamination strategies depend on the timing and substance ingested. Orogastric lavage may be considered within one hour of potentially lethal ingestion without a known antidote, provided the airway is protected. Activated charcoal is most effective within a few hours of ingestion and is contraindicated in caustic ingestions, unprotected airways, or bowel obstruction. Charcoal does not effectively bind metals (iron, lithium), alcohols, or potassium. Whole-bowel irrigation with polyethylene glycol solution may be used for sustained-release preparations, iron or lithium ingestion, and body packers, but is contraindicated in bowel obstruction, perforation, or hypotension.
Enhanced elimination techniques include multiple-dose activated charcoal for drugs such as theophylline, carbamazepine, and phenobarbital. Urinary alkalinization is used for salicylates and phenobarbital. Hemodialysis is indicated for lithium, salicylates, theophylline, toxic alcohols, and valproate in selected cases. Seizures are treated initially with benzodiazepines such as diazepam or lorazepam. Persistent seizures may require phenobarbital. Phenytoin is generally not effective for toxicologic seizures unless related to epilepsy or status epilepticus of other etiology.
Specific antidotes are used when appropriate. Examples include N-acetylcysteine for acetaminophen toxicity, physostigmine for severe anticholinergic toxicity, flumazenil for selected benzodiazepine overdoses, glucagon for β-blocker toxicity, calcium and insulin for calcium-channel blocker overdose, oxygen or hyperbaric oxygen for carbon monoxide, vitamin K for warfarin toxicity, hydroxocobalamin or cyanide antidote kit for cyanide, digoxin-specific antibody fragments for digoxin toxicity, fomepizole or ethanol for methanol and ethylene glycol, deferoxamine for iron, pyridoxine for isoniazid, methylene blue for methemoglobinemia, naloxone for opioid toxicity, atropine and pralidoxime for organophosphates, and sodium bicarbonate for tricyclic antidepressant toxicity.
Admission is required for patients with altered mental status, cardiopulmonary instability, suicidal intent, significant laboratory abnormalities, or risk of delayed decompensation. Discharge may be considered for patients who are psychiatrically cleared, detoxified, hemodynamically stable, and medically safe. Accidental poisonings require prevention counseling, while intentional poisonings require psychiatric evaluation. Substance abuse referral should be considered when appropriate. In pregnancy, treatment of the mother is generally the best treatment for the fetus.
Clinicians must avoid overlooking non-toxicologic causes of altered mental status and should not rely solely on urine drug screens, as these test for a limited number of substances and may produce false-positive or false-negative results.
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