Poisoning Flashcards
What are the two non-selective toxic actions of chemicals
- Local irritation-site of exposure, denaturing macromolecules causing injury
- Strong alkali/acid
What is a selective toxic action of the chemical?
Give 2 common examples.
Selective refers to interference with a specific biochemical pathway, therefore, chemical has to be absorbed and distributed to a specific pathway.
2 examples:
1. Rattex: interferes with Vit K pathway, essentially superwarfarin (lots of bleeding)
- Paracetamol: depletion of glutathione results in accumulation of NAPQI (glutathione needed to conjugate NAPQI which is a toxic metabolite)
List 3 methods of gastric decontamination
- emesis/lavage
- activated charcoal
- whole bowel irrigation
What is eye decontamination?
run normal water/saline into the eyes for 15-30min
2 methods to stimulate emesis
Stimulation of pharynx
Ipecacuanha
Contraindications to using emesis to eliminate a toxic substance
Impaired level of consciousness
Corrosive substances
Hydrocarbons
Risk of seizures
2 instances where gastric lavage is useful
- ingestion less than 1-2 hours previous
2. large amount of toxic solid substance
Contraindications to gastric lavage
- Hydrocarbons/corrosive substances
2. Risk of GI haemorrhage
Instances where activated charcoal is useful
- salicylates
- barbiturates
- digoxin
- TCAs
- paracetamol
- Ingestion less than 2 hours (this can be lenient)
When is Multi-Dose Activated Charcoal (MDAC) useful?
Severely poisoned patients
Sustained-release tablets
Enterohepatic cycling (estrogen, TCAs)
Drugs secreted into bile or intestine (digoxin)
When is Activated Charcoal contraindicated?
1. substances that are not absorbed by the body eg. Strong acids or alkalis Iron salts Lithium Petroleum products Cyanide
Other contraindications include:
Endoscopy due
Antidote by mouth
When is Whole Bowel Irrigation contraindicated?
- Bowel obstruction
- Compromised airway (giving lots of fluids can produce a gag reflex)
- Ileus
When is Whole Bowel Irrigation useful?
Iron overload, body packers
What are the 3 ways of enhancing drug clearance?
Urinary alkalinisation
Haemodialysis
Charcoal haemoperfusion
Urinary alkalinisation
Used in salicylate overdose
Increases elimination by maintaining urine pH > 7.5
IV administration of sodium bicarbonate
Needs high care facility -Monitor potassium
Haemodialysis
Salicylates
lithium
methanol
Charcoal haemoperfusion
Barbs
Theophylline
Carbamezapine
Symptomatic care
Seizures eg cocaine
Hypoventilation eg opiates
Hypoglycaemia eg salicylates
Hypotension treatment
fluids, vasopressors, inotropes
Hypertension treatment
benzodiazepines, sodium nitroprusside
Arrhythmia
Bradycardia, eg β-blockers: use atropine, pacing
Tachycardia, eg cocaine, stimulants: use benzodiazepines
Stable VT: eg TCAs: use sodium bicarbonate, lidocaine
Antidote for Digoxin
Digoxin immune fab
Antidote for Paracetamol
Acetylcysteine
Antidote for Opioids
Naloxone
Antidote for Benzos
Flumazenil
Antidote for Iron
Deferoxamine
