Management of Poisoned Patient Notes

Toxicokinetics

  • Definition: Study of the disposition of poisons in the body, similar to pharmacokinetics, which involves absorption, distribution, and elimination of poisons.

  • Key Concepts:

    • Volume of Distribution:

      • Anti-depressants and anti-malarial drugs have large volumes of distribution, making them hard to remove via dialysis.

      • Drugs with low volumes of distribution (e.g., Lithium, Salicylates, Phenytoin) can be removed easily by dialysis and diuresis.

  • Excretion or Clearance:

    • Weak Acids: More effectively eliminated by urinary alkalinization.

    • Weak Bases: More effectively eliminated by urinary acidification.

    • Examples of Drugs:

      • Urinary Acidification: Amphetamine, Chloroquine, Levorphanol.

      • Urinary Alkalinization: Acetazolamide, Nitrofurantoin, Phenobarbital, Probenecid, Salicylates.

Toxicodynamics

  • Definition: Study of the harmful effects of toxins.

  • Examples of Toxin Effects:

    • Symptoms of Overdose:

    • Hypertension and Tachycardia: Seen in overdosages of Amphetamine, Cocaine, and Antimuscarinic agents.

    • Hypotension and Bradycardia: Seen in overdoses of Calcium Channel Blockers, Beta Blockers, and Sedative Hypnotics.

  • Causes of Death in Toxic Patients:

    • Sedatives and narcotics can lead to respiratory depression, coma, and aspiration of gastric contents.

    • Stimulants and certain antidepressants can cause seizures, vomiting, and respiratory depression.

    • Cardiovascular issues can arise from drugs like Tricyclic Antidepressants and Digitalis, while liver damage can result from Acetaminophen and certain heavy metals.

Management of the Poisoned Patient

  1. Vital Functions

    • Airway: Establish first; ensure effective ventilation.

    • Breathing: Ensure breathing is maintained.

    • Circulation: Evaluate and support circulation; monitor blood pressure and cardiac rhythm.

    • Immediate Treatment: Provide 50% dextrose to comatose patients immediately after blood is drawn for laboratory tests to prevent brain damage.

  2. Identification of Poisons

    • Data Collection: History and physical examination are essential.

    • Laboratory Tests:

      • Anion Gap: Normal range is 12-16 mEq/L. A significant increase indicates metabolic acidosis.

      • Osmolar Gap: Difference between measured osmolarity and predicted osmolarity. Can indicate intoxication by substances with low molecular weight.

    • Serum Potassium Levels: Critical for assessing myocardial function; Hyperkalemia and Hypokalemia need to be assessed.

  3. Decontamination

    • Methods of Decontamination:

      • Syrup of Ipecac: Induces vomiting in conscious patients.

      • Gastric Lavage: Used for unconscious patients (non-corrosive agents) to remove toxins.

      • Activated Charcoal: Effective in adsorbing remaining drug toxins and can be given orally or via NGT.

      • Dilution of Certain Agents: Use of gastric lavage carefully with corrosive agents is contraindicated.

      • Topical Agents: Insecticides and solvents require washing of skin and removal of contaminated clothing.

Antidotes and Key Interventions

  • Antidotes for Specific Poisons:

    • Acetylcysteine for Acetaminophen overdose (best within 8-10 hours).

    • Atropine for cholinesterase inhibitors (organophosphates).

    • Bicarbonate sodium for membrane depressants and various cardiotoxic agents.

    • Many metals have specific chelating antidotes (e.g., EDTA for lead, Dimercaprol for arsenic).

  • Key Interventions:

    • Support vital functions: airway and respiration, manage seizures and hyperthermia.

    • Monitor and correct metabolic imbalances, manage urine pH to enhance drug elimination (alkalize/acidify as indicated).

Toxic Syndromes by Drug Group

  • Each drug group presents specific clinical features that must be recognized:

  • Antimuscarinics: (e.g., Atropine)

    • Symptoms include delirium, agitation, hallucinations, tachycardia, and mydriasis.

  • Cholinomimetics: (e.g., Organophosphates)

    • Symptoms include anxiety, agitation, paralysis, miosis, and the "DUMBELLS" syndrome (Diarrhea, Urination, Miosis, Bronchospasm, Emesis, Lacrimation, Salivation).

  • Opioids: (e.g., Morphine)

    • Symptoms include lethargy, pinpoint pupils, respiratory depression.

  • Salicylates: Symptoms include tinnitus, confusion, hyperventilation, and metabolic acidosis.

  • Sedative Hypnotics: Symptoms include lethargy, decreased muscle tone, respiratory depression, and hypotension.

  • Stimulants: Symptoms include agitation, tachycardia, seizures, and hyperthermia.

  • Heavy Metals & Others: Present unique toxicities such as renal failure from Ethylene Glycol and CNS effects from Methanol.

  • Mushrooms: (e.g., Amanita)

    • Symptoms include severe nausea, vomiting, and delayed hepatic failure.

Recognizing these syndromes is critical for timely and effective first-line treatment in the management of poisoned patients.