Poisonning Flashcards
How can be exposed to poisons
Oral
Inhaled
Percutaneous - cyanide, organophosphates
Ocular - industrial
Types of poisonning
Acute, chronic, acute on chronic
Deliberate or accidental
What is digoxin poisoning time wise?
Chronic - elderly too high a dose -> renal failure
Epidemiology of poisoning UK
180,000 cases a year
100,000 aditted
300 die
3,500 deaths outside of hospital
What age groups are most comonly affected by poisonings
1-5 year olds (male>female)
-accidental, daytime
Adolescents, young adults (male=female)
Deliberate self harm, overdose, evening/night, alcohol ass
Top 10 substances poisonings UK
1 - paracetamol (25% all overdoses involve)
2 - ibuprofen
3 - citalopram
zopiclone, fluoxetine, co-codamol, asirin, diazepam, codeine, diclofenac
Most common causes of death from poisoning
Paracetamol
TCAs
Opiates - IV heroin, methadone
Carbon monoxide - house fires
ABC assessment in poisoning
-AW and gag reflex, coma position
B - RR, O2, ABG
C - pulse, BP, perfusion, IV access, IV fluids for hypotension
What medications esp need to watch for circulatory collapse in
Cardiac medications eg B blockers, CCBs
Amphetamines, ecstasy, cocaine, cannabis
What immediate history information need
WHEN
WHAT
Mode and duration of exposure
Symptoms
Later information gathering in poisoning
WHY
Self harm?
Was it concealed
Consider - timing, precautions aainst discovery, medical help, final acts,
Examination in poisoning
Skin colour
Temperature
Pulse rate and rhythm
BP
Coma scale = GCS
Pupils
Muscle tone
Tendon refleces
Resp rate
Needle marks - IVDU, hep, HIV
Blisters
Lacerations, other causes of presentation
What would high temp signify in terms of posionings
Cocaine, amphetamine, ecstasy poisnoning
What may bradycardia suggest about a poisoning
CCB or digoxin
Hypertension after drug overdose what drug
Cocaine
Coma/reduced RR suspect which toxins
Benzos, opiates
Meoisis cause
Opiates
Organophosphates
What causes dilated pupils
Stimulants, anticholinergics, synthetics, cannabis
Routine investigations for overdose presentation
FBC, U+Es, LFTs, creatinine, blood glucose, ABG, ECG, CXR
Tests for specific poison concentrations in drug overdose
Paracetemol
Salicyclate (aspirin)
CarboxylHb - CO
lithium
iron
Methanol
General urine toxicology screen has limited use
What test for CO poisoning
Carboxyl Hb
Management strategies for overdose
Support physiology
Prevent absorption
Specific antidote
Chelation
Enhance elimination
What is time frame for gastric deconatmination methods
Little evidence useful unless used within one hour (may still use within a few hours)
Methods for gastric decontamination
Activated charcoal (99%)
Gastric aspiration/lavage
Induced emesis - no longer used - perforation asp etc
What patients cant gastric decontamination be used in
Unconscious or drowsy unless AW protected <GCS
When is gastric lavage/aspiration sued
very large and life threatening overdoses
Poisons not absorbed by activated charcoal
What should note with gastric lavage
More difficult and hazardous in children
Cuffed endotracheal tube in reduced GCS or drowst patients
Rare niw
Complications of gastric lavage
Gut perforation
Aspiration
Laryngospasm
Water intoxication (hyponatremia)
Dysrhythmias
Pneumothorax
Enhanced early drug absorption
Contraindications gastric lavage
Hydrocarbon ingestion
Caustic substance - risk of aspriation pneumonitis or perforation
What is activated charcoal
Charcoal heated in steam air or CO at 600-900 degrees C - increases surface area
How does activated charcoal work
Adsorbs poison in GI tract by direct contact - reduces absorption
What is activated cahrcoal to drug ratio required to be effective
Variable - 8:1
Give 10 x dose of poison taken up to 50g
How is activated charcoal administered
Unpalatable - suspend in flat cola
NG tube - protect with cuffed endotracheal tibe if gag reflex inadequate
Complications of activated charcoal
Aspiration pneumonitis
Reduced absorption of therapeutic agents eg methionine
Briquette formation -> bowel obstruction
Contraindications for activated charcoal
Absent bowel sounds - ileus
Impaired gag reflex
Unsafe swallow
What poisons is activated charcoal ineffective for
Elemental metals/salts - Lithium, iron, boron, salts
Insecticides - malathion, DDT, N-methyl carbamate
Cyanide
Strong acids/alkalis
alcohols
Hydrocarbons
Methods to increase drug elimination
Multiple dose activated charcoal
Chelation
Urinary alkalinisation
RRTs
Renal replacement therapies for overdose
Haemodialysis
Haemoperfusion
Haemofiltration
Combined - haemofiltration, MARS
How give MultiDACharcoal
50g activated charcoal
further 25g every 3 hours
What need to give with MDAC
Laxative/stool softener to prevent constipation
Mechanism of MDAC
Reduced elimination half life by interfering with enterohepatic circulation (removes drug onto charcoal)
‘GI dialysis’ - onto charcoal, conc gradient OUT of lumen into GI tract nto charcoal
What drugs does MDAC work well for
Carbamazepine
Dapsone (antibiotic)
Phenobarbitone
Quinine
Theophylline
May use in - salicyclate, phenytoin
When is haemodialysis and haemoperfusion useful
small vol of distribution
Low inherent clearance rate (not naturally cleared well by kicneys)
Sufficiently toxic
Small enough to cross dialysis membrane
More free than protein bound
Can bind to activated charcoal - jaemoperfusion
Haemodialysis and haemoperfusion
Haemodialysis - diffusion gradient allow poison to diffuse across semi permeable membrane
Haemoperfusion - activated charcoal filter directly adsorbes poison
Haemofiltration
Suction rather than filtration gradient
What poisons is haemodialysis (on tis own) used for
Toxic alcohols - ethylene glycol, isopropanol, ethanol
Salicyclate - aspirin
Sodium valproate
Lithium
THallium
What drugs can be cleared by haemodrialysis OR haemoperfusion
eg activated charcoal works
Theophylline
Phenytoin
Carbamazepine
Barbituates
Paracetemol antidote
Acetylcysteine
Methionine (glutathione repleters)
Ethylene glycol, methanol antidotes
ethanol, fomepizole
Aim to slow down metabolism - metabolites are toxic
Competitive antagonist
Flumexanil side effects
Mainly seizures
What are chelating agents or fixing agents used to treat
Iron, heavy metals, cyanide
Chelating agents
Desferrioxamine, dimercaprol, edetate (dicobalt or Na Ca), hydroxycalbamin
Antidote for dapsone
Methylene blue
Organophosphates atnidote
Pralidoxime
Digoxin antidote
Digibind
Snake bites antidote
Zagreb antivenom
