General toxicology

1. Fundamental Concepts & Definitions

• Poison: Any substance that produces harm or even death to a living organism.
• • Lecturer's Emphasis: The word "any" is critical for the definition and points will be deducted if it's missing.
• Clinical Toxicology: The specific pathology caused by poisons and the management of that pathology.
• Types of Drug Doses (Lecturer's List):
• 1. Loading Dose
  2. Sub-Clinical / Sub-Therapeutic Dose
  3. Therapeutic Dose
  4. Overdose
  5. Toxic Dose
  6. Lethal Dose (The dose that causes death)
• Classification of Poisoning:
• • According to their nature (Solid, Liquid, Gas)
  • According to their mode of action (Local, Remote, Double)
  • According to their target organs
• Factors Affecting the Toxic Response

2. Diagnosis of Poisoning

How to Suspect a Toxicological Case

The lecturer highlighted 3 main signs of suspicion (from Slide 8):

1. Sudden deterioration of conscious level in a previously healthy individual.
2. Sudden appearance of severe vomiting without a history of food poisoning.
3. Appearance of psychiatric manifestations in a previously healthy individual.

Toxidromes (Key Syndromes)

• Definition: A specific syndrome (collection of signs) caused by a specific toxin.
• Cholinergic Toxidrome:
• • Mnemonics (Slide 11):
  • • DUMBELS: Diarrhea, Urination, Miosis, Bradycardia/Bronchospasm, Emesis, Lacrimation, Salivation/Sweating
    • SLUDGE: Salivation, Lacrimation, Urination, Defecation, GI upset, Emesis
  • Antidote (Slide 12):
  • • Atropine: For muscarinic effects.
    • Pralidoxime: Reverses cholinesterase phosphorylation.
• Anticholinergic Toxidrome:
• • Classic Mnemonic (Slide 14):
  • • "Dry as a bone" (Dry mucous membranes)
    • "Mad as a hatter" (Mental status changes)
    • "Red as a beet" (Flushed skin)
    • "Blind as a bat" (Mydriasis - dilated pupils)
    • "Hot as a hare" (Fever)
• Clinical Pearl: Differentiating Toxidromes (Slide 15)
• • Sympathomimetic vs. Anticholinergic: Both can cause tachycardia, hypertension, and mydriasis.
  • The Key Difference: Sweating.
  • • Sympathomimetic patients are typically sweaty.
    • Anticholinergic patients are dry ("Dry as a bone").

Investigations

• Toxicological Screening (Slide 31): The simple, essential "spot test" done on urine, often with a dipstick, to look for color changes.
• Signs of Lateralization (Slide 30): Neurological signs indicating a focal issue.
• • Unequal pupils
  • Deviation of the eyes to one side
  • Tilting of the head
  • Facial asymmetry
• Swallowed Radio-Opaque Object (e.g., coin, battery): The appropriate initial investigation is an X-ray to determine its location.

3. General Management of the Poisoned Patient

A-B-C-D Approach

• "D" = Drugs (The "Coma Cocktail")
• • Lecturer's Emphasis: This must be memorized ("like your name"). It is given empirically to any patient with an undiagnosed coma.
  • 1. Glucose (50%): To correct hypoglycemia.
  • 2. Thiamine (100mg): To correct/prevent Wernicke's encephalopathy (given before glucose if alcoholism is suspected).
  • 3. Naloxone (0.4-2mg): To reverse opiate overdose.
• Flumazenil (Benzodiazepine Antagonist) - A CRITICAL WARNING
• • DO NOT give Flumazenil routinely to an undiagnosed coma patient.
  • Reason (Slide 93): If the patient has a mixed overdose (e.g., with Tricyclic Antidepressants), reversing the benzodiazepines can unleash a fatal-arrhythmia or seizure.

"Elimination" vs. "Enhanced Elimination" (Lecturer's Concept)

• 1. Elimination (GIT Decontamination): Removing the poison from the GIT.
• 2. Enhanced Elimination: Removing the poison after it has been absorbed into the blood.

1. Elimination (GIT) Methods

A. Emesis (Inducing Vomiting)

• Contraindications (Slides 52-53):
• • Substance: Corrosives (acid/alkali), Hydrocarbons (risk of aspiration), Convulsants (can trigger a seizure).
  • Patient: Unconscious, comatose, or decreased gag reflex.
• CRITICAL WARNING (Slide 54): NEVER use salty water to induce emesis. It can cause fatal hypernatremia (high sodium).

B. Gastric Lavage (Stomach Pumping)

• Time Factor: Generally ineffective >2 hours after ingestion.
• Exceptions (Delayed Lavage IS useful for):
• • Poisons with delayed gastric emptying (e.g., TCAs, Atropine)
  • Poisons that form concretions/bezoars (e.g., Salicylates)
  • Poisons eliminated back into the GIT (e.g., Opiates)

C. Activated Charcoal (AC)

• Dose (Slide 66):
• • Unknown amount: 1 gm/kg of body weight.
  • Known amount: 5-10 times the weight of the ingested poison.
• NOT Effective For (Slide 64):
• • Iron
  • Alcohols
  • Cyanide
  • Lead & Mercury (Heavy Metals)

D. Dilution / Neutralization

• For Strong Acid Ingestion: Give a buffering agent like milk.
• CRITICAL WARNING: NEVER give a strong alkali to "neutralize" a strong acid (or vice versa). This causes an exothermic (heat) reaction and can perforate the stomach.

2. Enhanced Elimination (Blood) Methods

• Guiding Principle: Choose the method that is easier, simpler, cheaper, and effective (الأسهل، الأيسر، الأرخص، الفعال).
• Forced Diuresis (Urination):
• • This is the simplest initial method.
  • Just giving water is not enough.
  • Uses osmotic diuretics like Mannitol (Slide 70).
• Dialysis:
• • General Definition (Slide 73): Allowing blood to contact a semi-permeable membrane to remove substances via a concentration gradient (not just "kidney dialysis").
  • Primary Indication for Hemodialysis (Slide 73): Used when the patient's kidney function is already impaired (e.g., they have renal failure).
  • Contraindication: Ineffective for large molecules or highly protein-bound toxins (like heavy metals).