Acute Poisoning 3rd year Pharmacology

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Acute Poisoning 3rd year Pharmacology

• Sian Veysey
• Emergency Medicine Consultant
• BRI

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Lecture summary

• Epidemiology of poisoning
• General principles of management
• Clinical pictures
• Specific therapies

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Acute Poisoning

• Recreational / deliberate / accidental
• 4,000 deaths / year from poisoning
• OD Common
• 3 5 of ED attendances
• Females gt males
• 13 take multiple drugs
• gt 50 with alcohol

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General management

• Initial resuscitation if required
• History
• Examination
• Investigations
• Treatment

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History

• Fact finding mission patient, paramedics,
  family, friends, GP, empty packets, vomit !!??
• What ?
• When ?
• How ?
• How much ? ( mg / kg )
• What else ?
• Why ?

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Examination

• Airway
• Breathing
• Circulation
• Disability
• Dont Ever Forget the Glucose
• Exposure

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Examination

• A / B airway clear
• resp rate depth
• O2 saturations
• C pulse, BP
• D coma score / GCS
• agitation / fits
• pupils
• E temperature, BM, track marks sweating,
  trauma, alcohol

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Investigations

• Baseline obs, BM
• Us Es, LFTs, CK
• FBC, clotting screen
• Paracetamol salicylate level
• ECG
• Arterial blood gases
• Other eg. CXR, CT
• Urine toxicology screen

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Sources of info

• National Poisons Information Centre
• Toxbase
• BNF
• Tablet identification aids
• books

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Treatment

• Largely supportive !
• oxygen, iv access fluids
• Decrease drug absorption
• activated charcoal within 1 hour
• ( whole bowel irrigation )
• ( gastric lavage )
• Increase drug elimination
• urinary alkalisation
• haemodialysis/perfusion /plasma exchange

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Antidotes

• Paracetamol
• Opiates
• Beta blockers
• Iron
• Carbon monoxide
• Methanol
• benzodiazepines

• N-acetylcysteine
• Naloxone
• Glucagon
• Desferrioxamine
• Oxygen
• Ethanol
• flumazenil

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Specific poisons

• Paracetamol
• Aspirin / salicylate
• Opiates
• Tricyclic antidepressants

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Paracetamol

• 50 of all OD episodes !
• 100 200 deaths / year
• Specific antidote very effective !!
• No specific clinical features other than liver
  failure
• Beware vomiting toxic levels
• Always suspect paracetamol even if patient
  denies!!

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Paracetamol - mechanism

• Glutathione conjugates with paracetamol breakdown
  product
• non toxic
• Paracetamol uses up glutathione stores
• Toxic metabolites build up binds to hepatic
  cell membranes
• liver necrosis !!

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Paracetamol - management

• Time of ingestion !!!
• Amount taken
• Risk factors for liver enzyme induction
• chronic/alcohol excess,drugs,malnutrition
• Bloods at 4 hours after ingestion
• Blood levels dictate use of antidote
• Use the paracetamol graph !!
• If in doubt or late presentation give the
  treatment and obtain advise!!!

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N acetyl cysteine

• Specific antidote for paracetamol
• Precursor in production of glutathione
• Most effective within 10 hours
• Given ivi for 24 hours
• Give on blood levels if done early
• or if staggered OD
• or delayed presentation after 10 hours
• Check LFTs clotting after treatment !!

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Salicylate ( Aspirin )- mechanism

• Direct effect on respiratory centres
• Hyperventilation
• Kidney compensates by excreting alkali
• Inhibition of normal metabolic pathways
• Overall, initial respiratory alkalosis then
• severe metabolic acidosis

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Salicylate ( Aspirin ) clinical picture

• Hyperventilation
• Bounding pulses
• Vomiting, dehydration
• Tinnitus, vertigo, sweating
• Hypoglycaemia
• Coma, confusion
• High temp, GI bleeds
• Renal failure, clotting problems

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Salicylate ( Aspirin )- management

• ABCDEFG
• Blood levels at 4 hours and repeated till peaks
• Supportive treatment
• Decrease absorption activated charcoal
• Increase elimination urinary alkalisation with
  sodium bicarb
• Haemodialysis if life threatened

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Opiates

• Common
• Heroin, methadone, codeine, morphine
• Recreational
• Beware elderly on the wards
• Act on mu receptors

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Opiates - clinical picture

• Respiratory depression
• Cardiovascular depression
• Coma
• Pinpoint pupils

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Opiates - management

• ABCDEFG
• High flow oxygen, resp support
• Opioid antagonist at receptor level
• Naloxone
• Beware - rapid onset good
• - rapid offset problem
• Consider im depot , repeat iv doses or iv
  infusion

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Tricyclic antidepresants

• Fairly common
• Very toxic, often fatal
• Treatable if identified and treated aggressively
• Multiple mechanisms, severe effects mediated via
  acidosis produced

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Tricyclic antidepresants- clinical picture

• Largely anti-cholinergic effects
• Resp depression
• Cardiac rhythm disturbances fast / slow
• ECG changes long QT, wide QRS
• Convulsions, Coma, confusion
• Dilated pupils
• Dry mouth eyes, urinary retention, warm dry
  skin

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Tricyclic antidepresants- management

• Be aggressive!!
• ABCDEFG
• Supportive !!
• Reduce absorption activated charcoal
• Often need ITU
• Correct acidosis, arrhythmias and fits with
  sodium bicarb
• Benzodiazepines for seizures

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Questions

• ?

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Summary

• Good history
• ABCDEFG assessment
• Supportive treatment
• Some specific therapies
• Seek help and advise