Overdose & Poisoning
Overdose & Poisoning
Overdose & Poisoning
By
Dr Rephaim T. Mpofu
Look good?
Decreased Drug absorption
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Cathartics – Sole administration of a cathartic,
e.g. sorbitol, magnesium citrate, has no role in
Mx of the poisoned patient
– May be used in conjunction with activated charcoal,
but evidence is lacking
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Whole bowel irrigation – Introduce 1500-
2000ml/h PGE in an adult
– Not recommended for routine use as there is poor
evidence
Increasing poison elimination
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Urine alkalinazation
– Increase drug elimination by alkalinizing urine
– Practically used in the event of salicylate or chlorophenoxy
poisoning
– Urine PH is increased to approx. 7.5 with IV HCO3 to
achieve effect
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Multiple dose activated charcoal
– Studies demonstrate that it increases elimination
significantly, however it has not been shown to reduce M&M
significantly
– Regimen: 50-100g initially, followed by 50g 4 hourly or 25g 2
hourly until charcoal appears in faeces or recovery occurs
Increasing Poison elimination
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Dialysis
– Used in acute renal failure, or in the presence of life
threatening amounts of toxin
– Not used routinely
– Not useful in drugs with a large volume of distribution, e.g.
TCA
Antidotes
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Anticoagulants – Vitamin K
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Benzodiazepines – Flumazenil
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B-blockers – Atropine
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Carbon Monoxide – Oxygen
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Digoxin – Digoxin-specific antibody fragments
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Ethylene glycol – Ethanol/fomepizole
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Iron Salts – Desferrioxamine
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Opioids – Naloxone
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Organophosphates – Atropine
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Paracetamol – N-acetylcysteine
Investigation
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Full blood Count
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Renal Function tests
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Liver function Tests
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Urine Toxicology
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Arterial blood gas
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Electrocardiogram
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Chest X-ray
Toxicology Level testing
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Agents where emergency measurement of
blood concentrations is appropriate:
– Aspirin (salicylate)
– Digoxin
– Ethanol
– Ethylene glycol
– Iron
– Lithium
– Methanol
– Paracetamol
– Theophylline
– Antiepileptic agents (carbamazepine, epilim, phenytoin)
Urine Toxicology Testing
Arterial Blood Gas
Anion Gap
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The anion gap is the difference between primary
measured cations (sodium Na+ and potassium K+)
and the primary measured anions (chloride Cl- and
bicarbonate HCO3-) in serum.
●
This test is most commonly performed in patients who
present with altered mental status, unknown
exposures, acute renal failure, and acute illnesses.
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Ag. Gap = ([Na+] + [K+]) − ([Cl-] + [HCO3−])
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Reference range – 3-11 mEq/l
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Poisoning with most medications will have an
increased anion gap
Electrocardiogram
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ECG is a rapidly available clinical tool that can
help clinicians manage poisoned patients.
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Specific myocardial effects of cardiotoxic drugs
have well-described ECG manifestations that
can aid in the diagnosis and management of
such patients (an understanding of ECG
interpretation and characteristics of
cardiotoxicity will guide you greatly)
Electrocardiogram
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Common ECG findings:
– Tachycardia/Bradycardia
– Right axis deviation
– Prolonged PR/QT intervals
– Widened QRS intervals
– Heart block due to AV node conduction delays
– ST Elevation/depression
– T wave abnormalities
Specific Poisons
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Too many for this presentation!
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Specific mention:
– Aspirin
– Paracetamol
– Paraffin
– Rodenticides
Aspirin
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Mortality risk increases significantly after 10g salicylate
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Aspirin metabolism stimulates the respiratory centre →
respiratory alkalosis → compensation → metabolic
acidosis
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They also affect Krebs cycle and increase acidosis
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Management:
– Glucose
– Activated charcoal
– Vitamin K – overdose has a similar effect to warfarin
– Increase pH to 7.4 with sodium bicarbonate
– Urine alkalinization
– Haemodialysis if initial management fails
Paracetamol
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Most common form of
overdose in UK
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NAPQI - metabolite
that accumulates
once glutathione
stores are depleted
Paracetamol Normogram
Petroleum Products (Paraffin)
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Poor systemic absorption but high risk of chemical
pneumonitis in the event of aspiration
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Features usually appear within hours but may take
days to develop:
– Dyspnoea and Tachypnoea
– Fever
– Crepitations
– Rhonchi
– Signs of pulmonary oedema
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N.B. Milk and activated charcoal are contraindicated
Chemical Pneumonitis
Rodenticides
Rodenticides
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Three common mechanisms of action:
– Anticoagulation – vitamin K epoxide inhibition
– Metal phosphides – toxic phosphine gas
– Hypercalcaemia –
hypervitaminosis/hyperphosphataemia
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Management:
– CMP, Clotting profile, Vitamin K levels
– Give Vitamin K (may require extended Rx if on
superwarfarin)
– Activated Charcoal
Maintenance Management
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Inpatient vs. Outpatient Management
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Continued supportive care
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Suicide Risk assessment
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Psychological Intervention
Suicide Risk Assessment
How to Call a friend
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Poison Information Centre
– Tygerberg Hospital – (021) 931-6129
– Red Cross Children's Hospital – (021) 689-5227
– Universitas Hospital – (082) 491-0160
– Www.sun.ac.za/poisoncentre
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Afritox
References
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Available upon request