Clinical Toxicology – Pearls from ICEM 2014

Screen Shot 2014-06-10 at 11.02.34 AM IMG_20140610_085536

Clinical Toxicology 1

The Approach to the Poisoned Patient (Dr Lau Fei-lung)

  • (1) Dose – It’s the Dose “that makes the poison
  • (2) Patient factors – individual factors that affect the likelihood of toxicity
  • Resuscitation of the Poisoned Patient
      • Self Protection (Universal Precautions) – consider your own safety first
      • In the initial phase of management it is important to address the patients “ABC” which may include intubation with mechanical ventilation
      • Administration of emergency treatment in the Emergency Department (ED) may be required
Resuscitation of the Toxicology Patient
Resuscitation of the Toxicology Patient
  • Types of Poisoning
    • Accidental
    • Self-harm
    • Recreational
    • Forensic
  • Rapid Assessment of the Poisoned Patient in the ED
      • History (which substance, which form, how much, when and why)
      • Vital Signs (key initiation of immediate intervention in theEmergency Department)
          • For Example for Bradycardia remember “PACED
          • Propranolol, Anticholinesterase, Calcium Channel Blocker, Ethanol, Digoxin
      • Examination (i.e. pupils, neurological, skin etc.)
      • Investigations (ECG, Blood Sugar, Paracetamol Levels, Blood Gas)
      • Consider Specific Toxidromes
      • It is important to determine a risk assessment and likely severity of the poisoning:
Risk Assessment
Risk Assessment
      • Initiate management of the patient based on assessment of risk versus benefit to the patient
      • Consult expert help early
  • Further Management of the Poisoned Patient
      • Specific Treatment and “Antidotes”
      • Supportive Care
      • Decontamination
      • Re-exposure Termination (Enhanced Elimination)
Toxicology Overview (Murray et al)
Toxicology Overview (Murray et al)

RSS icon

Clinical Toxicology 2

Update on Antidotes (Dr Robert Hoffman)

Overdose has passed Traffic Accidents in term of the number of deaths in the USA

Prescription Opioids and IV Opioids are a major issue – Naloxone is often used as an “Antidote

  • Naloxone
      • Pure competitive antagonist
      • The consequence of this is it “does nothing” in those who have no opioids on board
      • The drug is very short acting so may required an infusion (give 2/3 of the effective bolus per hour)
      • Naloxone doesn’t work oral but is effective by multiple other routes (IV, SC, IM, trachea, nasal)
      • Avoid or reduced the dose for Opioid Dependent
      • Dr Hoffman suggests 0.05mg IV unless impending respiratory arrest in the dependent patient
      • Large doses have been associated with Acute Respiratory Distress Syndrome (ARDS)

Screen Shot 2014-06-10 at 1.18.55 PM

Anticholinergic Syndrome can have a wide variety of causes – some consider Physostigmine the antidote

  • Physostigmine
      • A good ‘reversal agent’ for anticholinergic syndrome – many toxicologists are reluctant to give
      • Not a competitive antagonist – increases acetylcholine – will make anyone cholinergic and therefore can have significant side effects
      • Case reports in the 1980s suggested significant cardiac toxicity – however, this was in the context of aberrant ECG findings and mixed overdoses
      • More recent studies (retrospective) favour its controlled use
      • If we are going to use this we need
          • a relatively normal ECG
          • slow infusion (over 5-10 minutes)
          • any cholinergic effects or patient back to normal should trigger you to stop

Screen Shot 2014-06-10 at 1.20.23 PM

Organophosphates – massive issue in developing countries

  • Atropine
      • Reversal of Muscarinic Symptoms
      • Dose – it is suggested that we start relatively high with our Atropine dosing and double the dose every 3-5 minutes (does over 32mg are often required)
      • End Points  – Drying of Secretions (don’t worry about pupils)


  • Praladoxime
      • Shown to work in the “test tube” environment – can reactivate the Cholinesterase enzyme in the lab
      • In human studies significant contradiction in two studies
          • The case for –
          • The case against –
      • Using the treatment – not for “bolus” – will cause acute weakness

images images-1

Cyanide – rapidly acting poison (rarely survive to hospital)

  • Cyanide blocks the last step in oxidative phosphorylation
    • = catastrophic effect on energy metabolism
    • = rapid death
  • Various Antidotes
      • Sodium Nitrite – can be effective but drops BP
      • Thiosulphate – can be effective but a risk of Methhaemoglobinaemia
      • B12 – ‘Hydroxocobalamin’ – mops upCyandide 2.5 -5grams IV – first choice in USA
        • Can be given with (in addition to) Thiosulphate
        • Causes Red Urine, Red Skin etc.
          • Everything turns red‘ (warn nurses and the lab!) – this will have a significant effect lab results (troponin, creatinine) as well as the pulse oximeter and COHb


  • Methhaemaglobinaemia
      • Methylene Blue – can be an effective therapy
      • G6PD – is not contraindication or reason for failure of this treatment (the speakers cited issues with 1970s case report by Rosen et al that has created a myth that the treatment is ineffective in the absence of NAPDH – in fact the poisoning caused a reduction in the levels of NAPDH)

RSS icon

Clinical Toxicology 3

Decontamination (Dr Robert Hoffman)

Appears to be Common Sense

Lavage, Charcoal and Bowel Irrigation should be effective  (at least in theory)

In reality mixed results in literature

  • Ipecac – not recommended by the ICEM conference speakers (for use in developed countries)
  • Gastric Lavage – this area is a controversial issueamoungst toxicologists
      • Dr Hoffman and the other ICEM speakers disagree with the “position statements” of the Clinical Toxicologists “never to use Lavage”
      • They believe that early lavage may be used selectively
      • Of note, a paper by Li Yi in 2009 suggested that early lavage in critically unwell poisoned patients in China resulted in a reduced mortality but the authors did not conclude that lavage was indicated
      • A massive Colchicine overdose, chemotheraphy OD or lethal Aspirin OD would be examples of overdoses when Dr Hoffman and the other speakers would consider Gastric Lavage
  • Whole Bowel Irrigation
      • a good way to “alienate your nurses” –  but can be used in specific circumstances:
        • Consider in large metal (e.g. iron) overdoses and sustained release drugs
  • Enhanced Elimination (EE)
      • Dialysis – effective with drugs of small molecular weight, lack of intracellular binding, low protein binding and low volume of distributions
      • The Extracorporeal Treatments in Poisoning Workgroup (EXTRIP) – currently looking at evidence
          • Indications may include – Aspirin OD, Severe Paracetamol OD, Lithium OD, Carbamazepine OD,  Methanol OD,
          • No evidence in TCA and a variety of other toxins – the results of the EXTRIP analysis will be published in the coming months to help us rationalise the use of EE and dialysis

RSS icon