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Toxicology/Poisoning
Acute Medicine Teaching
Divya Ramadasan
ST3
AIM Curriculum
 Knowledge:
-Outline the principles of the relevant mental health legislation and
common Law that pertain to the treatment against patient’s will
-Demonstrate knowledge of the role of analytical toxicology
-Demonstrate parameters prompting consideration of liver
transplantation in paracetamol poisoning
-Demonstrate knowledge of the management of the rarer poisons eg. beta
blockers, ACE inhibitors, Calcium channel blockers
-Demonstrate evidence based knowledge for the management of poisons
(2009, Amendments Aug 2012: page 70 of 164)
AIM Curriculum
 Skills:
-Use scoring tools to assess risk of further self harm (eg. Beck’s score)
-Formulate management plan for acute period of care and liaison with
appropriate colleagues and agencies
-Recognise and treat complications of poisoning (eg. aspiration),
including any delayed effects
- Manage cases of the rarer poisons that present to hospital
(2009, Amendments Aug 2012: page 70 of 164)
AIM Curriculum
 Behaviour:
-Recognise importance of psychiatric review pre-discharge in deliberate
self poisoning
-Involve critical care promptly when indicated
-Co-ordinate multiple speciality management of patient (ITU, Renal etc)
(2009, Amendments Aug 2012: page 70 of 164)
Background
 UK has one of the highest rates of deliberate self harm
(DSH) in Europe
 Accidental or DSH account for 150 000 hospital
attendances /year in England & Wales
 Paracetamol is responsible for over half of all poisoning
admissions
 Average sized DGH : 1-2 patients are admitted with an
overdose (OD) in a 24 hour period
Acute Medical Emergencies, The Practical Approach. 2nd Edition. U.K.
Wiley and Blackwell.
Background
 Chronic OD can occur in the elderly and in those with
chronic conditions eg. chronic renal failure
Nb. Presentation can be variable including unusual
behaviour, decreased conscious level, seizures or cardiac
arrhythmias
 Deaths from drug overdose most frequently involve
paracetamol, tricyclic anti-depressants and
benzodiazepines
 Be ware of drugs with high lethality in OD and those with
narrow therapeutic windows
Acute Medical Emergencies, The Practical Approach. 2nd Edition. U.K.
Wiley and Blackwell.
Scenario
 30 year old ♀
 History of DSH and overdoses
 Paramedics are called out to her flat – she had
texted her mom to say that she had taken an
overdose
 At time of referral she is tachycardic, hypotensive
and has a reduced GCS
 Fairly common scenario
 Unknown agents ingested
 CNS and Cardiovascular dysfunction
 Reduced GCS : ? Alcohol related or CNS
depressant medication
 Has the patient sustained a head injury from
drug/alcohol intoxication ?
Assessment
 Airway: Is this patent ?
Nb. Reduced conscious levels will impair protective airway reflexes and
therefore increase risk of regurgitation and aspiration
 Breathing:

Administer O2 as needed

Nb. Adequate oxygen saturation on pulse oximetry does not guarantee
adequate ventilation and CO2 retention may be present with normal
oxygen saturation

Unexplained tachypnoea may reflect a metabolic acidosis resulting
from the OD eg. salicylate
Circulation
 Points to consider:
 Shock in acute poisoning is usually due to hypovolaemia
secondary to peripheral vasodilatation and responds to fluid
resuscitation
 Hypotension is often compounded by poor intake during a
period of reduced consciousness or the diuretic effect of
alcohol
 Is HDU/ ITU support needed?
 Cardiac arrhythmias : correct acidosis, hypoxia and electrolyte
disturbance before using anti-arrhythmic drugs
Disability
 AVPU or GCS, measure pupillary size and
response to light
 Although Glasgow Coma scale not validated
for poisoned patients- remains most useful
objective measure of conscious level
 Glucose level – paracetamol and alcohol can
cause rapid hypoglycaemia
Exposure
 Signs of injury, rashes and possible needle
track marks
 Temperature
Lethality Assessment
 Knowledge of substance, time taken and dose
 Collateral history from family, friends,
paramedics
Diagnostic clues from Primary
assessment
B
Sign
Drug
↑ RR
Aspirin
Ethylene Glycol
↓ RR
Opioids
CNS depressants
Sign
Drug
↑ HR
Antidepressants
Sympathomimetics
Amphetamines
Cocaine
↓ HR
Β blockers
Digoxin
Clonidine
↑ BP
Amphetamines
Cocaine
C
Sign
Drug
Small pupils
Opioids
Cholinesterase
inhibitors
Large pupils
TCAs
Anticholinergic
Antihistamines
Ephedrine
Amphetamines
Cocaine
Coma
Barbiturates
TCAs
Opioids
Benzodiazepines
Ethanol
D
Sign
Drug
↓◦ C
TCAs
Barbiturates
Phenothiazines
↑◦C
Amphetamines
Cocaine
E
Investigations
• ECG
• FBC, UEs, LFTs, Glucose, INR, CK, Lactate
• Paracetamol &salicylate levels
• ABG
• Pregnancy Test
• CXR
• Drug levels: Iron, Lithium, Digoxin
Anion Gap
(Plasma Sodium +Potassium)- (Plasma Chloride +Bicarbonate)
 Normal anion gap : 8-14 mmol/L
 An anion gap >12mmol/l in the context of poisoning:
-Salicylates
-Propylene glycol, Paraldehyde
-Methanol
-Ethylene glycol
-Iron
-Isoniazid
Common Law
 Refusal of treatment :
“The fact that a person has a mental illness does not
automatically mean they lack capacity to make a decision about
medical treatment ”
“ Patients who have capacity (that is, who can understand,
believe, retain and weigh the necessary information) can make
their own decisions to refuse treatment, even if those decisions
appear irrational to the doctor or may place the patient’s health
or their life at risk.”
GMC Consent Guidance: Legal Annex- Common Law
Mental Capacity Act (2005)
To demonstrate capacity individuals should:

Understand in simple language what the treatment is, its purpose
and nature and why it is being proposed

Understand its principal benefits, risks and alternatives

Understand what the consequences of not receiving treatment are

Believe the information

Retain the information long enough to weigh it up in order to
arrive at a decision

Communicate the decision
Assessing the validity of advance
directive/refusals
 Patient was an adult when the decision was made ( 16 in
Scotland, 18 in England, Wales and N. Ireland)
 Patient had capacity to make the decision at the time it was
made
 It must be in writing, signed and witnessed, and include a
statement that it is to apply even if the patient’s life is at stake
(England and Wales only)
 Must be applicable to the current situation
 Must be valid at time. Has patient changed mind over time?
GMC Guidance on Advance Refusals
Scenario
 45 year old ♀ brought into hospital by
husband having found to have taken a
staggered paracetamol overdose. She is
commenced on NAC and has daily bloods…
Which factor is least likely to indicate a poor
prognosis?
• INR >3
• ALT>3000 IU/L
• Glucose 2.4
• PH 7.25
• Creatinine 250 micromol/L
King’s college criteria
Guidelines for referral to specialist centres in cases of paracetamol hepatotoxicity
Day 2
Day 3
Day 4
Arterial PH <7.3
Arterial PH <7.3
-
INR >3
INR >4.5
Any rise in INR
Encephalopathy
Encephalopathy
Encephalopathy
Creatinine > 200
micromol/L
Creatinine >200
micromol/L
Creatinine
>250micromol/L
Hypoglycaemia
Devlin, J,O’Grady J.2000. Indications for referral and assessment in
adult liver transplantation: a clinical guideline. BSG Guidelines in
Gastroenterology,p2.Available
from:http://www.bsg.org.uk/pdf_word_docs/adult_liver.pdf
Beta- Blocker Overdose
 Clinical Features:
• Proportional to the type and the amount ingested
• CVS: hypotension, bradycardia, AV block, heart failure
• RS: Bronchospasm
• Metabolic: hypoglycaemia, hyperkalaemia
• Neuro: stupor, coma, seizures
Beta-Blocker Overdose
 Special consideration:
•
Propanolol- causes sodium channel blockade and causes QRS
widening. Treat with NaHCO3
•
Sotalol- causes potassium efflux blockade which leads to a
long QT. Monitor for Torsades
Beta-Blocker Overdose
 Antidotes:
• Glucagon
• High dose insulin euglycaemic therapy
• Consider intralipid if refractory to standard
measures
Calcium Channel Blocker Overdose
 Clinical features:
• Onset of symptoms is within 1-2 hours of
ingestion (standard preparations)
• Slow release preparations- onset of significant
toxicity may be delayed by 12-16 hours with
peak effects after 24 hours
Calcium Channel Blocker Overdose
• CVS: early signs- bradycardia, 1st degree heart block
and hypotension
Can progress to refractory shock and death
• Metabolic: Hyperglycaemia (marker of severity)
• Neuro: seizures and coma are rare ( ? Signifies co-
ingestant), can occur as a late feature
Calcium Channel Blocker Overdose
 Management:
HDU/ITU care needed for patients exhibiting toxicity
•
•
•
•
•
•
Fluid resuscitation
Calcium Gluconate
High dose insulin euglycaemic therapy
NaHCO3
Cardiac pacing
Intralipid
Graudins A, Lee HM, Druda D.2016.
Calcium channel antagonist and beta-blocker overdose: antidotes
and adjunct therapies.
Br J Clin Pharmacol. 81(3),pp.453-61. Available from doi:
10.1111/bcp.12763. Review.
Ace inhibitor Overdose
• Principal effect: mild-moderate hypotension
• Responds to fluid resuscitation
• Asymptomatic patients require monitoring for 4 hours
• Symptomatic or hypotensive patients need 24 hour
observation
Scenario
O 16 year old boy takes an overdose of mother’s
tablets following an exam. Allows you to take an
ABG…
pH: 7.46
(7.35-7.45)
pO2: 12.5
(10–14)
pCO2: 3.5
(4.5–6.0)
HCO3: 22
(22-26)
BE: +1
(-2 to +2)
Other values within normal range
A few hours later complains of feeling unwell
and ringing in his ears. A repeat ABG :
pH: 7.15
(7.35-7.45)
pO2: 11.0
(10–14)
pCO2: 3.2 (4.5–6.0)
HCO3: 9
(22-26)
BE: -18
(-2 to +2)
Other values within normal range
O What’s the diagnosis ?
O How would you manage this patient?
Aspirin (Salicylate) overdose
Early Features
Late Features
Hypokalaemia
Metabolic acidosis
Alkalosis
Hypoprothrombinaemia
Tinnitus
Hypoglycaemia
Sweating
Pulmonary oedema
Acute Kidney injury
Plasma levels 6 hours after ingestion :
• 300–500 mg/l (mild toxicity)
• 500–700 mg/l (moderate toxicity)
• >750 mg/l (severe toxicity)
Key aspects of management
 Activated charcoal
 Correct electrolyte and metabolic
abnormalities
 Urinary Alkalinisation
 Haemodialysis
Haemodialysis in Poisoning
 Effective in poisoning with :
-Salicylate
-Isopropanol ( after shave lotions and window
cleaning solutions)
-Lithium
-Methanol
-Ethylene Glycol
-Ethanol
-Barbiturates
Scenario
 23 year old♂ brought in by the paramedics
unconscious. Found in his flat surrounded by
packets of amitriptyline. Observations: BP
106/76mmHg, HR 110b.p.m.
GCS E3 M6 V3
 An ECG is performed…
ECG
What does it show?
• Atrial Fibrillation
• Broad-complex tachycardia
• Narrow complex tachycardia
• Sinus rhythm
What is the 1st line of
management?
O Amiodarone
O Calcium
O Magnesium
O Sodium Bicarbonate
Even in the absence of an acidosis consider
alkalinisation with IV Sodium Bicarbonate in
patients with :
O QRS duration >120msec
O Arrhythmias
O Hypotension resistant to fluid resuscitation
TCA Overdose
O Clinical Features:
Neurological
Sedation, coma , seizures
Cardiac
Tachycardia, hypotension,
conduction abnormalities
Anti-cholinergic
Dilated pupils, dry mouth,
absent bowel sounds, urinary
retention
TCA Overdose
O Treatment:
Airway
Breathing
Circulation
- Hypotension: treat with IV fluids
-Conduction abnormalities: IV sodium Bicarbonate
Seizures: Treat with Benzodiazepines
( Do NOT use Phenytoin – due to the propylene glycol solvent )
Novel Psychoactive Substances
 Aka ‘Legal highs’
 Most common :
• Synthetic Cannabinoid receptor agonists:
‘spice’
• Synthetic Cathinones – amphetamine
derivatives eg. Mephedrone (MCAT)
Management
 Safe sedation: use benzodiazepines if needed
 Watch out for hyperpyrexia
 Measure blood sugar
 Consider fluid status – check Na early!
Bonnici K.S., Dargan P.I., Wood D.M.2015 Novel psychoactive substances
or ‘legal highs’, British Journal of Hospital Medicine, 76(9), C130-1.
Serotonin Syndrome
3 types of clinical manifestations(‘CAN’):
 central nervous system
•
altered mental state (agitation, anxiety, confusion or stupor), seizures
 autonomic dysfunction
•
hypertension or hypotension, tachycardia or bradycardia, hyperthermia,
dysrhythmias, flushing, sweating, mydriasis
 neuromuscular dysfunction
•
rigidity (lower limbs more so than upper limbs), hyper-reflexia, clonus
(including ocular), tremor, myoclonus
Management
 Stop the causal drugs
 Cooling
 Benzodiazepines
 Specific 5HT2 receptor anatgonists
• Mild cases: cyproheptadine
• More severe: chlorpromazine
Risk Assessment
 The Suicide Intent scale is a 15-item questionnaire designed
to assess the severity of suicidal intention associated with an
episode of self-harm (Beck et al, 1974).
 1st section ( 8 questions) on ‘circumstance’ and 2nd section (
7 questions) are a ‘self-report’, patient’s feelings and thoughts
at the time of the act
 Each item scores 0-2 and total score between 0-30
15-19
20-28
29+
Low Intent
Medium Intent
High Intent
Risk Assessment
 There is a greater risk of repeated attempts
the higher the intent rating
www.bradfordvts.co.uk has a pdf with the full
questionnaire
Reference:
Beck, A., Schuyler, D. & Herman, J. (1974) Development of suicidal
intent scales. In The Prediction of Suicide (eds A. Beck, H. Resnik & D. J.
Lettieri), pp. 45 -56. Bowie, MD: Charles.
Further reading/resources
 UK National Poisons Information Service.
http://www.toxbase.org
 Lane,N (ed), Powter, L (ed), Patel, S (ed) 2016. Best of Five
MCQs For The Acute Medicine SCE. Ist Edition. U.K. Oxford
University Press.