13 - Poisons and poisoning Flashcards
What is treatment of poisoning largely based on?
Enhancing the elimination and antidotes
2 types of poisoning?
Acute overdose
Chronic exposure
Main things to look at when diagnosing poisoning?
- history
- pupils
- skin
- odour
- blood
- urine
History?
- patients rarely lie
- because of the types of poisons they often OD on (amnesics and sedatives) they may be unreliable
Constricted pupils?
Opiates (morphine)
Anti-cholinesterases
Dilated?
MDMA
Atropine
Tricyclic anti-depressants (amitriptyline - anti-cholinergic)
Sweating?
Increased - ampethamine
Decreased - atropine
Bullae?
Are large blisters
Caused by CO poisoning
Odour?
- ethanol
- garlic
> arsenic or organophosphates (anti-cholinesterases) - almonds
> cyanide
Blood?
- salicylate
- paracetamol
- ethanol
- CO
- digoxin
- theophyline
Urine?
- salicylate
- opiods (low conc in blood but conc in urine)
- tricyclics
Treatment?
General supportive (Airway, Breathing, Circulation)
Decrease absorption
Increase elimination
Specific antidote
4 Ways to decrease absorption?
- Emesis (vomit)
- Gastric lavage (stomach pump)
- Activated charcoal
- Fuller’s earth (used for paraquat - herbicide)
Emesis
Syrup of ipecac
Gastric lavage
stomach pump
must have reflexes
NOT for corrosives or hydrocarbons as can make worse
Activated charcoal
Give 50 grams every 4 hours Binds drug (inactivate or bind the drug before it is absorbed)
How to increase elimination?
- activated charcoal (binds drug in the gut to eliminate)
- haemoperfusion
- haemodialysis
- diuresis
Activated charcoal to increase elimination?
Things absorbed across the gut wall to so by passive absorption. Will diffuse from the blood back into the gut and bind charcoal to increase elimination.
Also known as enteral dialysis
Haemo-perfusion?
Cannulation of blood over CHARCOAL (theophylline) or ion exchange (aspirin) then back into the body. Is invasive
Haemodialysis
Good to increase the elimination of small molecules such as methanol and ethylene glycol
Diuresis?
Enhances urinary elimination i.e. salicylate from aspirin
Salicylate is an acid so give HCO3- to enhance the acid elimination
Paracetomal overdose
N - acetylcysteine
Morphine overdose
Naloxone
Methanol overdose
Ethanol (competitive)
Anti-cholinesterases overdose
Atropine and pralidoxime
Paracetomol hepatotoxicity?
- minor metabolite is NAPQI usually inactivated by glutathione but these reserves are used up in OD.
- NAPQI causes liver damage
- ethanol induces the CYP2E1
- acetylcystiene binds NAPQI and increase glutathione levels
