Poisoning

Scope and Clinical Importance of Poisoning Emergencies

Poisoning is a leading cause of emergency department visits and a high-yield topic for the Certified Emergency Nurse (CEN) exam^[1]. It encompasses intentional overdoses, accidental ingestions, occupational exposures, and envenomations. The CEN must rapidly recognize toxidromes, initiate decontamination, administer antidotes, and provide supportive care. Mastery of poisoning principles directly impacts patient survival and is frequently tested on the exam^[2].

Essential Terminology for Toxicologic Assessment

• Toxidrome – A constellation of signs and symptoms suggestive of a particular poison class (e.g., cholinergic, anticholinergic, opioid).
• Decontamination – Techniques to reduce absorption (e.g., activated charcoal, whole bowel irrigation).
• Antidote – A specific agent that counteracts the effect of a toxin (e.g., naloxone for opioids).
• Elimination enhancement – Methods to increase poison removal (e.g., hemodialysis, multiple-dose activated charcoal).
• Lethal dose – The amount of a substance likely to cause death (e.g., LD50).

Systematic Approach to Acute Poisoning Care

1. Stabilization and Assessment

1. Airway, Breathing, Circulation (ABCs) – Secure airway if the patient is unconscious or has a depressed gag reflex; provide oxygen and intravenous access^[3].
2. Check vital signs, pulse oximetry, and capnography – Identify hypotension, bradycardia/tachycardia, hypoxia, or hyperthermia.
3. Obtain point-of-care glucose – Hypoglycemia can mimic poisoning.
4. Administer naloxone – If opioid overdose is suspected (respiratory depression, miosis).

2. Decontamination

• Activated charcoal (AC) – Most effective within 1 hour of ingestion; dose 1 g/kg (max 50 g). Contraindicated in compromised airway, ileus, or caustic ingestion^[4].
• Gastric lavage – Reserved for life-threatening ingestions within 1 hour; only after airway protection.
• Whole bowel irrigation – For sustained-release preparations or drug packets; use polyethylene glycol solution.
• Skin decontamination – Remove contaminated clothing, wash with soap and water for chemical exposures.

3. Antidote Administration & Enhanced Elimination

• Common antidotes:
  • Naloxone – Opioids; N-acetylcysteine (NAC) – Acetaminophen; Flumazenil – Benzodiazepines (use cautiously in combined overdoses); Fomepizole – Ethylene glycol/methanol; Atropine + Pralidoxime – Organophosphates.^[5]
• Multiple-dose activated charcoal (MDAC) – Enhances elimination of certain drugs (e.g., carbamazepine, theophylline, phenobarbital).
• Hemodialysis – For lithium, methanol, ethylene glycol, salicylates in severe cases.

Recognizing Toxidromes: A Guide to Poison Classes

Diagnostic Evaluation for Suspected Overdose

• History – Obtain time, amount, substance (pill count, bottle), intent, co-ingestants (alcohol, drugs).
• Physical exam – Focus on pupil size, skin moisture, bowel sounds, vital sign patterns, mental status.
• Laboratory tests:
  • Acetaminophen and salicylate levels – Routine for all unknown overdoses.
  • Serum electrolytes, creatinine, BUN – Assess for metabolic acidosis, renal injury.
  • Urine drug screen – Limited utility; confirmatory testing rarely changes acute management.
  • ABG – Evaluate for acidosis, respiratory compensation.
  • Serum osmolality & osmolar gap – Screens for methanol, ethylene glycol, isopropanol.
• ECG – Assess QRS duration (tricyclics), QT prolongation (antipsychotics, methadone), dysrhythmias.

Therapeutic Strategies and Antidote Administration

General Supportive Care

• Maintain airway and ventilation; administer oxygen.
• Correct hypotension with IV crystalloid boluses; consider vasopressors (norepinephrine) if refractory.
• Treat seizures with benzodiazepines; avoid phenytoin in toxin-induced seizures.
• Control hyperthermia with aggressive cooling (ice packs, cold IVF, sedation/paralysis).
• Monitor for rhabdomyolysis and acute kidney injury.

Specific Antidote Protocols (High-Yield)

• Acetaminophen poisoning – Administer NAC (oral or IV) if serum level is above Rumack-Matthew nomogram line; start within 8 hours for full efficacy^[6].
• Opioid overdose – Naloxone 0.04–2 mg IV (titrate to respiratory rate); may require continuous infusion for long-acting opioids.
• Organophosphate poisoning – Atropine 2 mg IV (double every 5 min until drying of secretions), pralidoxime 1–2 g IV over 15–30 min.
• Ethylene glycol/Methanol – Fomepizole (15 mg/kg IV loading) plus hemodialysis if acidosis or vision changes.
• Benzodiazepine overdose – Flumazenil 0.2 mg IV over 30 sec (use only if no seizure risk or mixed overdose).

Managing Risks and Adverse Events in Poisoning Cases

• Airway – Rapid sequence intubation may be needed for severe CNS depression; avoid succinylcholine in organophosphate poisoning because of prolonged paralysis.
• Cardiac monitoring – Continuous ECG for tricyclic antidepressants, antiarrhythmics, or any prolonged QRS/QT.
• Aspiration – Decontamination (charcoal, lavage) can cause vomiting; protect airway first.
• Delayed effects – Some toxins (e.g., acetaminophen, methanol, hepatotoxic mushrooms) have latent presentations; reassess at 4–6 hours.
• Violent behavior – Chemical restraints (benzodiazepines, antipsychotics) may be needed for agitation (e.g., sympathomimetic toxidrome). Ensure staff safety.
• Antidote errors – Avoid unnecessary flumazenil in benzodiazepine-dependent patients (risk of withdrawal seizures). Naloxone can precipitate acute withdrawal in opioid-dependent patients—use small titrated doses.

Frequently Tested Scenarios and Clinical Pearls

• Memorize the Rumack-Matthew nomogram for acetaminophen – only valid for single acute ingestion with known time.
• Know that activated charcoal is most effective within 1 hour; "golden hour" concept applies.
• Remember "ABCs before antidotes" – stabilize airway, breathing, and circulation first.
• Common exam scenario: A patient with miosis, bradycardia, and respiratory depression = opioid toxidrome → administer naloxone.
• Patients with tachycardia, mydriasis, and hyperthermia often have anticholinergic or sympathomimetic poisoning – treat symptomatically.
• For serotonin syndrome, administer cyproheptadine (not a routine emergency drug, but tested).
• Always obtain an ECG in tricyclic antidepressant overdose – widened QRS (>100 ms) is a marker of cardiotoxicity and indication for sodium bicarbonate.
• For methanol/ethylene glycol, the key lab is elevated osmolar gap; antidote is fomepizole or ethanol (rarely used now).
• The CEN exam often includes calculation of anion gap and osmolar gap – practice these formulas.

References

1. Tintinalli JE, Ma OJ, Yealy DM, et al. Tintinalli’s Emergency Medicine: A Comprehensive Study Guide. 9th ed. McGraw-Hill; 2020. https://accessemergencymedicine.mhmedical.com/book.aspx?bookid=2914
2. Board of Certification for Emergency Nursing. CEN Review Manual. 5th ed. BCEN; 2021. https://bcen.org/cen-review-manual/
3. Marx JA, Hockberger RS, Walls RM, et al. Rosen’s Emergency Medicine: Concepts and Clinical Practice. 9th ed. Elsevier; 2018. https://doi.org/10.1016/C2015-1-04425-6
4. American Academy of Clinical Toxicology; European Association of Poisons Centres and Clinical Toxicologists. Position statement and practice guidelines on the use of multi-dose activated charcoal in the treatment of acute poisoning. Clin Toxicol. 2019;57(5):295-331. https://doi.org/10.1080/15563650.2019.1573951
5. Goldfrank LR, Flomenbaum NE, Lewin NA, et al. Goldfrank’s Toxicologic Emergencies. 11th ed. McGraw-Hill; 2019. https://accessemergencymedicine.mhmedical.com/book.aspx?bookid=2513
6. Lewis SM, Dirksen SR, Heitkemper MM, Bucher L. Medical-Surgical Nursing: Assessment and Management of Clinical Problems. 11th ed. Elsevier; 2021. https://evolve.elsevier.com/cs/product/9780323551496