Toxicological Emergencies

Overview – Toxicological Emergencies

Toxicological emergencies represent a critical component of acute and emergency medicine, often requiring fast, structured, and targeted intervention. Toxic exposures may arise from overdose, accidental ingestion, envenomation, or withdrawal. This article explores the key toxidromes, antidotes, and assessment strategies for managing toxicological emergencies, with a focus on high-yield clinical features and management principles crucial for final-year medical students.

Definition

A toxicological emergency is any acute medical presentation resulting from exposure to a toxic substance—whether through ingestion, inhalation, injection, or dermal contact—that threatens life, organ function, or long-term health. Management hinges on early recognition, systematic assessment, and tailored decontamination and antidote strategies.

Aetiology

Common Causes

• Accidental Poisoning: Most often seen in children (household toxins) or occupational exposure (acute or chronic).
• Intentional Overdose:
  • Recreational drug use
  • Parasuicidal gestures
  • Suicide attempts
• Inappropriate Medication Use: Incorrect dosing or interactions.
• Withdrawal Syndromes: Particularly following abrupt cessation of alcohol, benzodiazepines, or opioids.
• Envenomation: Snake or insect bites, marine stings.

Clinical Features

General Red Flags

• As little as 2 tablets of some drugs can kill a 10kg child.
• Key to early management: recognise “nice vs nasty” drugs (i.e. those with high lethality or no known antidote).
• Always consult the Poisons Information Centre for guidance.

Key Toxidromes

• Paracetamol: Asymptomatic early; hepatotoxicity due to NAPQI metabolite.
• Cholinergic (Organophosphates): “SLUDGE” – Salivation, Lacrimation, Urination, Defecation, GI upset, Emesis.
• Anticholinergic (Tricyclic antidepressants, antihistamines): Dry mouth, urinary retention, constipation, widened QRS on ECG.
• Extrapyramidal (Antipsychotics): Tremor, rigidity, abnormal posture (opisthotonos), dysphagia.
• Opioid: Coma, respiratory depression, pinpoint pupils (miosis).
• Sedative/Hypnotic (Benzodiazepines): Coma, respiratory depression, airway compromise.
• Sympathomimetic (Cocaine, amphetamines): Agitation, hallucinations, hypertension, tachycardia.
• Serotonergic (SSRI overdose): Confusion, tremor, fever, diarrhoea, hyperreflexia.
• Withdrawal syndromes: Restlessness, hallucinations, sympathetic overactivity, seizures.

Investigations

Primary

• ECG: Look for QRS widening, arrhythmias
• Blood Sugar Level (BSL)
• Basic bloods: Electrolytes, liver function tests, full blood examination
• Arterial blood gas (ABG)
• Toxicology screen
• Paracetamol level
• Blood alcohol level

Management

1) Primary Survey

• ABCD Approach:
  • Airway: Watch for aspiration, coma, swelling
  • Breathing: Tachypnea or apnoea
  • Circulation: Bradycardia, tachycardia, hypo/hypertension
  • Disability: Assess conscious state; gather “what/when/how much” history
• Initial Decontamination & Antidotes:
  • Activated Charcoal (within 1 hr) – Binds many drugs but not small ions/heavy metals/alcohols
  • Gastric Lavage – Rarely used; only within 1 hour
  • Whole Bowel Irrigation – Polyethylene glycol
  • Skin decontamination – Especially organophosphates
  • Antidotes:
    • Paracetamol → N-Acetylcysteine
    • Opiates → Naloxone
    • Benzodiazepines → Flumazenil (rarely used)
    • Calcium Channel Blockers → Insulin + Glucose
  • Other techniques: Dialysis, urinary pH manipulation, chelation
• Differential Diagnosis – SMASHED:
  • S – Sepsis/Substrate (glucose, O₂)
  • M – Meningitis/Mental illness
  • A – Alcohol/Accident (CVA, trauma)
  • S – Seizures/Stimulants
  • H – Hypo/Hyper-[everything]
  • E – Electrolytes/Encephalopathy/Envenomation
  • D – Drugs

2) Secondary Survey

• History: Who, What, Where, When, Why, How
• Exam: Identify toxidromes and complications
• Focused Investigations (as above)

3) Definitive Care

• ICU: If serious or life-threatening
• Observation: For milder cases
• Psychiatric Review: For self-harm or intentional overdose
  • Use tools like the SAD PERSONS score
  • Explore underlying mental health or psychosocial triggers

Summary – Toxicological Emergencies

Toxicological emergencies require rapid assessment, identification of toxidromes, and targeted treatment using the ABCD framework. High-yield toxidromes such as cholinergic, anticholinergic, opioid, and serotonin syndromes must be recognised early to initiate life-saving antidotes. Always consider both physical and psychiatric aspects of poisoning. For a broader context, see our Pharmacology & Toxicology Overview page.