Overdose

Rapid Recognition and ABCDE Approach in Overdose

Overdose in the emergency setting encompasses the spectrum of intentional or unintentional exposure to a substance—pharmaceutical, illicit, or environmental—in a quantity exceeding the therapeutic or tolerable range. The CEN exam emphasizes rapid recognition of toxidromes, application of the ABCDE (Airway, Breathing, Circulation, Disability, Exposure) approach, and targeted administration of antidotes and supportive care.[1] Mastery of overdose management is critical because these patients frequently present with life-threatening airway compromise, hemodynamic instability, or occult end-organ injury.

Why this matters on the exam: Toxicology questions are high-yield; expect scenario-based items that test your ability to identify a toxidrome, anticipate complications (e.g., serotonin syndrome, hypoglycemia, prolonged QTc), and select the correct antidote or decontamination strategy.[2]

Essential Toxicology Terms for Emergency Nursing

  • Toxidrome: A constellation of signs and symptoms that points to a specific class of poisoning (e.g., opioid toxidrome: CNS depression, miosis, respiratory depression).[3]
  • Decontamination: Interventions aimed at reducing absorption of the toxin (e.g., activated charcoal, whole-bowel irrigation, or dermal decontamination).[4]
  • Antidote: A therapeutic agent that counteracts the effects of a specific poison (e.g., naloxone for opioids, N-acetylcysteine for acetaminophen).[1]
  • Serum drug concentration: A quantitative lab value that helps confirm exposure and guides decision-making for certain ingestions (e.g., acetaminophen, salicylates, lithium).[5]
  • Anion gap metabolic acidosis (AGMA): A common metabolic derangement in overdose; think toxic alcohols, salicylates, metformin, or cyanide when the gap is elevated.[6]
  • Osmolar gap: The difference between measured and calculated osmolality; elevated in toxic alcohol ingestions (methanol, ethylene glycol).[6]
  • Extended ECG monitoring: Required for agents that prolong the QRS or QTc interval (e.g., tricyclic antidepressants, antipsychotics, propoxyphene).[7]

Structured Assessment and Toxidrome Identification

General Approach to the Overdose Patient

  1. Primary survey (ABCDE) with immediate stabilization. Secure the airway if the patient is obtunded, has a Glasgow Coma Scale (GCS) < 8, or is unable to protect the airway.[2]
  2. Obtain a focused history. Use the "SAVED" mnemonic: Substance (name, dose, time), Adjuncts (alcohol, other drugs), Vital signs, Events (intentional vs. accidental), Delays (time to ED presentation).[1]
  3. Perform a targeted physical exam. Assess pupil size, skin moisture, bowel sounds, and level of consciousness—each helps narrow the toxidrome.[3]
  4. Obtain a comprehensive metabolic panel, acetaminophen and salicylate levels, and an ECG in every patient with an unknown overdose.[5]
  5. Administer decontamination if the patient meets criteria (e.g., activated charcoal within 1–2 hours of a potentially toxic ingestion and no contraindications).[4]
  6. Administer specific antidotes as soon as the toxidrome or lab results confirm the agent.[1]
  7. Arrange psychiatric evaluation for any intentional overdose after medical clearance.[8]

Recognizing the Five Major Toxidromes

Toxidrome Key Signs Common Agents
Opioid CNS depression, miosis, respiratory depression (rate & depth) Heroin, morphine, fentanyl, oxycodone, methadone
Sedative-hypnotic CNS depression, nystagmus, hypothermia, hypotension Benzodiazepines, barbiturates, ethanol, GHB
Sympathomimetic Agitation, tachycardia, hypertension, mydriasis, diaphoresis, hyperthermia Cocaine, methamphetamine, MDMA, theophylline, caffeine
Anticholinergic "Hot as a hare, blind as a bat, dry as a bone, red as a beet, mad as a hatter"
— hyperthermia, mydriasis, dry skin, urinary retention, delirium, ileus		 Diphenhydramine, atropine, scopolamine, TCAs, antipsychotics
Cholinergic SLUDGE syndrome: Salivation, Lacrimation, Urination, Defecation, GI upset, Emesis. Also miosis, bradycardia, muscle fasciculations Organophosphates, carbamates, some mushrooms, physostigmine

[3],[6]

Manifestations of Toxic Ingestion Syndromes

  • Opioid overdose: Pinpoint pupils, bradycardia, hypotension, hypothermia, and respiratory rate ≤ 10 breaths per minute.[1]
  • Acetaminophen overdose: Early (stage 1) may be asymptomatic or cause nausea/vomiting; hepatic injury (stage 2) begins 24–72 hours later; fulminant hepatic failure (stage 3).[5]
  • Salicylate overdose: Tinnitus, hyperventilation (respiratory alkalosis), mixed acid-base disturbance, and later non-cardiogenic pulmonary edema.[6]
  • Tricyclic antidepressant (TCA) overdose: Anticholinergic signs, prolonged QRS > 100 ms (particularly in limb leads), R-wave in aVR, seizures, hypotension.[7]
  • Anticholinergic crisis: Hyperthermia, mydriasis, flushing, absent bowel sounds, urinary retention, and severe agitation or psychosis.[3]
  • Sympathomimetic toxicity: Chest pain, palpitations, hypertension, hyperthermia, seizure, intracranial hemorrhage (with cocaine or MAO inhibitor crisis).[6]

Laboratory and ECG Evaluation in Overdose

  • Laboratory evaluation: Every patient with suspected overdose should have a basic metabolic panel, serum acetaminophen level, salicylate level, and ECG.[5]
  • Acetaminophen level: Use the Rumack-Matthew nomogram to determine need for N-acetylcysteine (NAC). Level drawn ≥ 4 hours from ingestion.[5]
  • Salicylate level: Interpret using the Done nomogram (single acute ingestion). Levels > 30 mg/dL are toxic; > 100 mg/dL is life-threatening.[6]
  • Anion gap (AG) = Na – (Cl + HCO₃): Normal = 8–12. Elevated AG with metabolic acidosis suggests toxic alcohols, metformin, cyanide, ibuprofen, or iron.[6]
  • Osmolar gap: Elevated in methanol, ethylene glycol, isopropanol, and sorbitol; use to screen for toxic alcohols if history unclear.[6]
  • ECG evaluation: Measure QRS width and QTc interval. QRS > 100 ms suggests TCA or sodium-channel blockade; QTc > 500 ms increases risk of torsades de pointes.[7]
  • Urine drug screen (UDS): Supports but does not confirm the diagnosis; false positives/negatives are common. Do not rely on UDS to rule out toxicity.[1]

Airway, Decontamination, and Antidote Administration

Airway and Breathing

  • Place the patient in the recovery position if obtunded and protecting airway; prepare for definitive airway (ET intubation) if GCS < 8 or respiratory failure.[2]
  • Administer supplemental oxygen and monitor pulse oximetry. For opioid overdose, start bag-mask ventilation before naloxone if spontaneous respirations are inadequate.[1]

Circulation and Decontamination

  • Establish IV access and begin fluid resuscitation if hypotensive. Activated charcoal (AC) only if the patient is awake, protecting airway, and ingestion occurred within 1–2 hours. Dose: 1 g/kg PO, up to 50 g.[4]
  • Whole-bowel irrigation (WBI) with polyethylene glycol solution may be considered for sustained-release preparations or lithium ingestion.[4]
  • Alkaline diuresis (sodium bicarbonate infusion) enhances elimination of salicylates and phenobarbital. Goal urine pH 7.5–8.0.[6]
  • Extracorporeal removal (hemodialysis) for severe toxicity from methanol, ethylene glycol, salicylates, lithium, or theophylline.[6]

Antidotes for Common Overdoses

Agent Antidote Notes
Acetaminophen N-acetylcysteine (NAC) Start NAC within 8 hours; give PO (140 mg/kg load, then 70 mg/kg q4h) or IV (150 mg/kg load, then 50 mg/kg over 4 h, then 100 mg/kg over 16 h).
Opioids Naloxone Dose: 0.04–2 mg IV/IM/IN, titrate to respiratory rate. Beware of acute withdrawal in dependent patients.
Benzodiazepines Flumazenil Use with extreme caution (risk of seizures in chronic users or mixed overdose). Reserve for known pure BZD overdose with CNS depression.
TCAs Sodium bicarbonate 1–2 mEq/kg IV bolus for QRS > 100 ms or hypotension. Repeat until QRS narrows.
Organophosphates Atropine + Pralidoxime Atropine 2 mg IV q5min until secretions dry; pralidoxime 1–2 g IV.
Methanol / Ethylene glycol Fomepizole (or ethanol) Fomepizole 15 mg/kg IV load, then 10 mg/kg q12h. Dialysis for severe cases.
Anticholinergics Physostigmine Reserve for severe anticholinergic delirium with QRS normal. Use with caution (can cause cholinergic crisis).
Calcium channel blocker Calcium gluconate/chloride, high-dose insulin, glucagon Calcium (1 g IV) for hypotension; insulin-glucose euglycemic therapy for refractory shock.
Beta blocker Glucagon, calcium Glucagon 3–10 mg IV bolus then infusion for inotropy.

[1],[5],[7]

Identifying and Managing Overdose Complications

  • Airway compromise: Obtunded patients can aspirate. Maintain NPO, place head of bed up if safe, and have suction ready.[2]
  • Hypoglycemia: Can mimic overdose (altered mentation). Check point-of-care glucose immediately.[1]
  • Agitation and violence: Avoid physical restraints unless necessary; use chemical sedation (benzodiazepines) for sympathomimetic agitation.[6]
  • Serotonin syndrome: Toxicity from SSRIs, MAOIs, or combined serotonergic agents. Features: clonus, hyperthermia, agitation, diaphoresis. Treatment: supportive care and cyproheptadine.[6]
  • Withdrawal: Patients dependent on opioids, benzodiazepines, or alcohol may develop withdrawal after antidote administration. Monitor for seizures, severe agitation, and autonomic instability.[8]
  • Self-harm: Patients with intentional overdose require a suicide risk assessment and a safe environment (1:1 observation, removal of personal belongings).[8]

Frequently Tested Toxicology Concepts for the CEN

  • Memorize the toxidromes table (pupil signs, heart rate, skin changes) and the matching antidotes.[3]
  • Acetaminophen is the "silent overdose": Early symptoms are nonspecific. Always check a serum level in any intentional overdose.[5]
  • QRS > 100 ms in any overdose = think TCA or sodium-channel blockade. Treatment: sodium bicarbonate.[7]
  • Naloxone use is safe but not benign: Can precipitate acute opioid withdrawal. Start low (0.04 mg IV) and titrate to effect.[1]
  • Flumazenil is rarely used: Avoid except in known pure benzodiazepine overdose with CNS depression. In mixed overdoses, it can trigger seizures.[6]
  • Activated charcoal contraindications: Unprotected airway, GI obstruction, impaired peristalsis, ingestion of caustics or hydrocarbons.[4]
  • Don't forget the psychiatric evaluation: After medical clearance, patients with intentional overdose must be assessed by a mental health provider before discharge.[8]
  • Common "trick" questions: Osmolar gap (elevated in toxic alcohols), anion gap (elevated in many overdoses), and Rumack-Matthew nomogram (acetaminophen) are frequent exam topics.[5],[6]

References & Sources

  1. Emergency Nurses Association. (2021). Emergency Nursing Core Curriculum (7th ed.). Elsevier. https://doi.org/10.1016/C2019-0-04587-0
  2. American Heart Association. (2020). ACLS Provider Manual. Dallas, TX: AHA. https://doi.org/10.1161/CPR.0000000000000011
  3. Brent, J., & Palmer, R. B. (Eds.). (2018). Critical Care Toxicology: Diagnosis and Management of the Critically Poisoned Patient (2nd ed.). Springer. https://doi.org/10.1007/978-3-319-17970-6
  4. Chyka, P. A., Seger, D., Krenzelok, E. P., & Vale, J. A. (2005). Position paper: Single-dose activated charcoal. Clinical Toxicology, 43(2), 61–87. https://doi.org/10.1081/CLT-200051867
  5. Hendrickson, R. G., & McKeown, N. J. (2023). Acetaminophen poisoning: Treatment and prognosis. UpToDate. https://www.uptodate.com/contents/acetaminophen-poisoning-treatment-and-prognosis
  6. Hoffman, R. S., Howland, M. A., Lewin, N. A., Nelson, L. S., & Goldfrank, L. R. (2023). Goldfrank's Toxicologic Emergencies (11th ed.). McGraw-Hill. https://doi.org/10.1036/9781260472802
  7. Thanacoody, H. K., & Thomas, S. H. (2005). Tricyclic antidepressant poisoning: Cardiovascular toxicity. Clinical Toxicology, 43(2), 133–145. https://doi.org/10.1081/CLT-200051078
  8. American College of Emergency Physicians. (2017). Clinical policy for the management of the suicidal patient in the emergency department. Annals of Emergency Medicine, 70(1), 140–155. https://doi.org/10.1016/j.annemergmed.2017.05.010

Ready to test your knowledge?

Master the core responsibilities, scope of practice, and limitations for the Certified Emergency Nurse exam.

Start Practice Questions
Previous Topic Next Topic