Download PDF: Principles of Treatment of Poisoning (ISA Focus)
Access detailed PDF notes or potential PPT presentations covering the Principles of Treatment of Poisoning, with a focus on concepts often relevant for "Important Short Answers" (ISA) in examinations. This resource outlines the core strategies for managing poisoned patients, including initial stabilization, methods of decontamination, techniques to enhance toxin elimination, and the judicious use of specific antidotes. Essential for students of medicine, pharmacy, nursing, and emergency care professionals. Download your free poisoning treatment principles PDF or view it online.
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Core Principles in the Management of Acute Poisoning
Acute poisoning is a medical emergency requiring rapid assessment and systematic intervention to minimize harm and prevent mortality. The management approach is guided by several fundamental principles, often tested as "Important Short Answers" (ISA) in medical and pharmacy curricula. These principles ensure comprehensive care from initial contact to recovery.
I. Stabilization and Supportive Care (The "ABCDEs")
This is the paramount initial step, often performed concurrently with assessment and before definitive identification of the poison. The goal is to maintain vital physiological functions.
- A - Airway: Assess and ensure a patent airway. If compromised (e.g., due to depressed consciousness, laryngeal edema), secure it via endotracheal intubation. Remove any foreign bodies.
- B - Breathing: Evaluate respiratory rate, depth, effort, and oxygen saturation. Administer supplemental oxygen. Provide assisted ventilation (bag-valve-mask or mechanical ventilation) if breathing is inadequate or absent.
- C - Circulation: Monitor heart rate, blood pressure, peripheral perfusion, and cardiac rhythm (ECG). Establish intravenous (IV) access for fluid resuscitation and drug administration. Treat hypotension with IV fluids (crystalloids) and vasopressors if necessary. Manage arrhythmias according to ACLS/PALS guidelines.
- D - Disability/Dextrose/Decontamination (Initial):
- Disability: Assess neurological status (e.g., Glasgow Coma Scale, pupillary response). Consider causes of altered mental status.
- Dextrose: Check blood glucose level promptly. Administer IV dextrose to hypoglycemic patients. In adults with altered mental status of unknown cause, empirical administration of thiamine (before glucose, especially in suspected alcoholics) and naloxone (for suspected opioid overdose) may be considered.
- E - Exposure/Environment: Completely undress the patient to remove contaminated clothing (preventing ongoing dermal absorption) and to facilitate a thorough examination for signs of trauma or exposure. Maintain normothermia.
Continuous monitoring of vital signs, urine output, and mental status is crucial.
II. Decontamination: Preventing Further Absorption
The aim is to reduce the absorption of the ingested, inhaled, or dermally exposed toxin. The choice of method depends on the toxin, route, time since exposure, and patient's condition.
- External Decontamination:
- Skin: Remove contaminated clothing. Irrigate affected skin copiously with water and mild soap. Healthcare providers must use personal protective equipment (PPE).
- Eyes: Irrigate affected eyes immediately and continuously with saline or water for at least 15-30 minutes.
- Gastrointestinal (GI) Decontamination (for ingested poisons):
- Activated Charcoal (Single Dose): The most common method. Adsorbs many toxins in the GI tract, preventing systemic absorption. Most effective if given within 1-2 hours of ingestion. Dose: 1 g/kg. Contraindicated for caustics, hydrocarbons, heavy metals (iron, lithium, lead), alcohols, and when the airway is unprotected.
- Gastric Lavage ("Stomach Pump"): Rarely indicated. May be considered for potentially life-threatening ingestions of substances not adsorbed by charcoal, if performed within 1 hour of ingestion by experienced personnel and with a protected airway. Risks include aspiration, esophageal/gastric injury.
- Whole Bowel Irrigation (WBI): Administration of large volumes of polyethylene glycol electrolyte solution (e.g., GoLYTELY) to mechanically cleanse the entire GI tract. Indicated for sustained-release formulations, body packers, and toxins poorly adsorbed by charcoal (e.g., iron, lithium).
- Syrup of Ipecac (Inducing Emesis): No longer recommended due to limited efficacy, risk of aspiration, and potential to delay administration of charcoal or antidotes.
III. Enhancement of Toxin Elimination
These techniques aim to accelerate the removal of absorbed toxins from the body. They are reserved for severe poisonings with specific toxins possessing favorable pharmacokinetic properties.
- Multiple-Dose Activated Charcoal (MDAC): Repeated doses of charcoal to interrupt enterohepatic or enteroenteric recirculation of certain drugs (e.g., phenobarbital, carbamazepine, dapsone, theophylline, quinine), enhancing their gut dialysis.
- Forced Diuresis and Urinary pH Alteration:
- Alkaline Diuresis: IV sodium bicarbonate to alkalinize urine (pH 7.5-8.5), promoting ionization and renal excretion of weak acids (e.g., salicylates, phenobarbital). Requires careful fluid and electrolyte monitoring.
- Acid Diuresis: Not recommended due to risks (e.g., rhabdomyolysis, acidosis).
- Extracorporeal Methods (e.g., "Dialysis"):
- Hemodialysis (HD): Effective for toxins that are water-soluble, have low molecular weight, small volume of distribution, and low protein binding (e.g., salicylates, methanol, ethylene glycol, lithium, phenobarbital, theophylline).
- Hemoperfusion: Blood passes through a cartridge containing an adsorbent (charcoal or resin). Useful for drugs with higher protein binding or lipid solubility.
- Continuous Renal Replacement Therapies (CRRT): Can be used in critically ill, hemodynamically unstable patients.
- Plasma Exchange (Plasmapheresis): Removes toxins bound to plasma proteins or autoantibodies.
IV. Administration of Specific Antidotes
Antidotes counteract the effects of specific poisons by various mechanisms (e.g., competitive antagonism, chelation, metabolic pathway alteration). Their availability is limited to a subset of toxins.
- Examples:
- Naloxone for opioids.
- N-acetylcysteine (NAC) for paracetamol/acetaminophen.
- Atropine & Pralidoxime for organophosphates/carbamates.
- Flumazenil for benzodiazepines (use with extreme caution).
- Fomepizole or Ethanol for methanol/ethylene glycol.
- Digoxin-specific antibody fragments (DigiFab) for digoxin.
- Hydroxocobalamin or Sodium thiosulfate/Sodium nitrite for cyanide.
- Deferoxamine for iron.
- Timely administration of the correct antidote can be life-saving. Always consult a Poison Control Center or toxicologist.
V. Observation, Diagnosis, and Further Management
This includes obtaining a detailed history, performing a thorough physical examination, targeted laboratory investigations (toxidrome recognition, drug screening, specific toxin levels), and continuous monitoring for complications. Psychiatric evaluation is essential for intentional poisonings. Collaboration with Poison Control Centers is highly recommended.
Effective management of poisoning relies on a structured approach, prioritizing life support, followed by measures to limit absorption, enhance elimination, and administer specific antidotes when appropriate, all while providing ongoing supportive care.
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