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 Receptors and Their Effects

  • Parasympathetic - ACh is transm
    • Muscarinic
      • receptors in heart, eye, lung, GI, skin and sweat glands
      • Bradycardia
      • Miosis
      • Bronchorrhea / Bronchospasm
      • Hyperperistalsis (SLUDGE)
      • Sweating
      • Vasodilation
    • Nicotinic
  • Sympathetic
    • Alpha effects (vessels, eye, skin)
    • Beta effects (heart, lungs)

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 Variable 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

PACED

physostigmine

Tachycardia

FAST

Hypotension

CRASH

Hypertension

CT SCAN

Miosis

COPS

Mydriasis

SAW

Coma

LETHARGIC

Seizures

OTIS CAMPBELL

Skin findings

Diaphoresis

SOAP

Dry skin

Bullous lesions/blisters

Flushed/red appearance

Cyanosis

  • Benzocaine and other local anesthetics
  • Cyanokit, nitrites, nitrates, well water (nitrates)
  • Antimalarials
  • Quinolones
  • Dapsone (used to treat leprosy, PCP pneumonia, toxoplasmosis, dermatitis herpetiformis, brown recluse bite)
  • Aniline dyes
  • Phenazopyridine[1]
  • Nitrates, nitrites
  • Ergotamine toxicity|Ergotamine]]

Acneiform rash

Evaluation

Toxicological Exam

  • All vital signs (Temp, RR, HR, BP) + bedside glucose
  • Neurologic exam
    • Level of consciousness
    • Pupillary exam
    • Motor response
    • DTRs
  • Skin Exam - moisture, temp, evidence of injection drug abuse
  • Lung Exam
  • Bowel Sounds
  • ECG (ie. look for QT prolongation, QRS prolongation, etc)
  • Consider CBC, BMP, urinalysis (with ẞ-HCG if appropriate), urine toxicology screen, serum alcohol concentration, VBG
    • The urine screen is a qualitative test -> positivity ≠ acute toxicity
    • It can be falsely positive due to cross-reactivity
    • It can be falsely negative if the substance ingested does not cross-react with the tested analyte
    • The diagnosis of intoxication is clinical!!!

Management

  • Depends on agent
  • See antidotes
  • "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[2][3]

Disposition

  • Depends on agent

See Also

References

  1. Jeffery WH, Zelicoff AP, Hardy WR. Acquired methemoglobinemia and hemolytic anemia after usual doses of phenazopyridine. Drug Intell Clin Pharm. 1982 Feb;16(2):157-9.
  2. 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.
  3. Gussow, L. Myths of Toxicology: Thiamine Before Dextrose. Emergency medicine news. 2007;29(4):3-11.