Toxicology (main)

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Background

Epidemiology

  • In 2014, ~2.2million human exposures reported to US poison control centers
  • Top 5 substance classes:
    • analgesics (11%)
    • cosmetics/personal care products (8%)
    • household cleaning substances (8%)
    • sedatives/hypnotics/antipsychotics (6%)
    • antidepressants (4%)
  • 1,835 human exposures resulted in death

Autonomic Nervous System

  • Parasympathetic - ACh is transm
    • Muscarinic
      • receptors in heart, eye, lung, GI, skin and sweat glands
      • Bradycardia
      • Miosis
      • Bronchorrhea / Bronchospasm
      • Hyperperistalsis (SLUDGE)
      • Sweating
      • Vasodilation
    • Nicotinic
      • receptors in both sympathetic and parasympathetic nervous systems
      • fasciculations, flaccid paralysis
      • ?Mild bradycardia, hypotension
  • Sympathetic
    • ALPHA EFFECTS - vessels, eye, skin
      • Mydriasis, hypertension, Sweating
    • BETA EFFECTS - heart, lungs
      • Tachycardia, Bronchodilation

Clinical Features

Toxidrome Chart

Finding Cholinergic Anticholinergic Sympathomimetic Sympatholytic^ Sedative/Hypnotic
Example Organophosphates TCAs Cocaine Clonidine ETOH
Temp Nl Nl / ↑ Nl / ↑ Nl / ↓ Nl / ↓
RR Variable Nl / ↓ Variable Nl / ↓ Nl / ↓
HR Variable ↑ (sig) Nl / ↓ Nl / ↓
BP Nl / ↓ Nl / ↓
LOC Nl / Lethargic Nl, agitated, psychotic, comatose Nl, agitated, psychotic Nl, Lethargic, or Comatose Nl, Lethargic, or Comatose
Pupils Varriable Mydriatic Mydriatic Nl / Miotic
Motor Fasciculations, Flacid Paralysis  Nl Nl / Agitated Nl
Skin Sweating (sig) Hot, dry Sweating Dry
Lungs Bronchospasm / rhinorrhea Nl Nl Nl
Bowel Sounds Hyperactive (SLUDGE) ↓ / Absent Nl / ↓ Nl / ↓
^Consider Sympatholytic when looking at Sedative OD or someone who doesn't respond to Narcan
Withdrawal from substances have the opposite effect

Differential Diagnosis for Specific Signs

Hyperthermia

Hypothermia

Increased Respiratory Rate

Respiratory Depression

Bradycardia

  • P ropranolol/ beta-blockers, poppies (opiates), propoxyphene,

physostigmine

  • A nticholinesterases, antiarrhythmics
  • C lonidine, calcium channel blockers
  • E thanol or other alcohols
  • D igoxin, digitalis

Evaluation

Toxicological Exam

  • All vital signs (Temp, RR, HR, BP)
  • Neurologic exam
    • Level of consciousness
    • Pupillary exam
    • Motor response
    • DTRs
  • Skin Exam - moisture, temp
  • Lung Exam
  • Bowel Sounds
  • ECG (ie. look for QT prolongation, QRS prolongation, etc)

Management

  • Depends on agent
  • See Antidote
  • "Coma cocktail" when suspecting toxic ingestion (mnemonic = "DONT")
    1. Dextrose (50mg IV)
    2. Oxygen
    3. Naloxone (0.2-0.4mg IV/IM, repeat dose 1-2mg)
      • Empiric opioid ingestion treatment
    4. Thiamine (50-100mg)
      • Treat or avoid Wernicke encephalopathy
      • Though some suggest giving thiamine prior to dextrose, do NOT let this delay treatment of hypoglycemia!
      • Case reports of dextrose precipitating Wernicke's involved thiamine-deficient patients receiving prolonged course of IV glucose, NOT with single bolus[1][2]

Disposition

  • Depends on agent

See Also

References

  1. Donnino MW, Vega J, Miller J, Walsh M. Myths and misconceptions of Wernicke's encephalopathy: what every emergency physician should know. Ann Emerg Med. 2007;50(6):715-21.
  2. Gussow, L. Myths of Toxicology: Thiamine Before Dextrose. Emergency medicine news. 2007;29(4):3-11.