Lecture 18: Poisons and poisoning Flashcards
What are some steps to diagnosing a suspected poisoning case:
- History
- Pupils
- Skin
- Odour
- Clinical chemistry (blood, urine)
- ECG
Whats the value of history in an overdose?
History
- Patients rarely lie
- But may be unreliable
- > Sedation
- > Amnesic drug effects
Constricted pupils indicate:
Constricted =
- Opiates (morphine)
- Clonidine
- Anti-cholinesterases
Dilated pupils indicate:
Dilated
- Atropine
- Tricylic antidepressants
- Amphetamine / MDMA
Sweating skin indicates:
Sweating:
- > Increased = Amphetamine
- > Decreased = Atropine
What does bullae indicate?
Bullae (Blistering tissues b/c hypoxia)
- Carbon monoxide
- [Barbituates]
What odours indicate?
Odours -> Ethanol (smells drink) -> Garlic = Arsenic = Organophosphates (insectiside) -> Almonds = Cyanide
What blood chemistry can you find?
Blood
- Salicylate (aspirin)
- Paracetamol
- Ethanol
- CO
- Tricyclics
- Digoxin
- Theophylline
What can you find in the urine?
- Salicylate
- Opioids
- Tricyclics
What can be found on ECG?
ECG
- Long PR = Ca channel blocker (Verapamil)
- Wide QRS = Na channel (Amitriptyline)
- Long QT = Potassium channel (Amiodarone)
Whats the immediate treatment for a poison suspect?
A = Airway B = Breathing C = Circulation
What are the methods for treating drug overdose etc?
Decrease absorption
Increase elimination
Specific antidotes
What are some methods for decreased absorption:
- [Emesis]
- [Gastric lavage]
- Activated charcoal (IMPORTANT)
- Fullers earth (or activated charcoal) for paraquat
What are some methods of increased elimination:
- Activated charcoal (enteral dialysis)
- Haemoperfusion
- Haemodialysis
Whats haemoperfusion used for?
Charcoal for theophylline
Ion exchange for salicylate
Whats haemodialysis used for?
Methanol (wood alcohol) Ethylene glycol (anti-freeze)
What are five specific antidotes:
- N-acetylcystiene = Paracetamol
- Naloxone = Morphine
- Flumazenil = benzodiazepines
- Ethanol = methanol
- Fomepizole = Ethylene glycol, methanol
What are four chelations used for antidotes?
Desferrioxamine -> Iron
Edetate -> Lead
Penicillamine -> Copper, mercury
Hydroxycobalamin -> Cyanide
Whats an antidote for anti-cholinesterases OD?
Atropine / pralidoxime
Whats an antidote for warfarin OD?
Vitamin K
What are some protein binding agents?
Digoxin F (ab) -> Digoxin
Idarucizumab F (ab) -> Dibagatran
Andexanet -> Apixaban, Rivaroxaban
Whats a specific antidote for paracetamol hepatotoxicity?
- Minor metabolite is NAPQI = Formed by CYP2E1 (induced by ethanol) - NAPQI inactivated by glutathione - Liver damage caused by NAPQI - Glutathione reserves used up by large doses
What are the clinical applications of CP knowledge to OD?
Approach to poisonings
- ABC and general support
- Specific antidotes are uncommon
- Use physiology and pharmacology to assist in diagnosis
- Consider factors affecting drug clearance if enhanced elimination procedures if used.