1. Toxicology/Poisoning
Acute Medicine Teaching
Divya Ramadasan
ST3

2. 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)

3. 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)

4. 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)

5. Background
UK has one of the highest rates of deliberate self harm (DSH) in Europe
Accidental or DSH account for 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.

6. 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.

7. 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

8. 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 ?

9. 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

10. 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

11. 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

12. Exposure Signs of injury, rashes and possible needle track marks
Temperature

13. Lethality Assessment Knowledge of substance, time taken and dose
Collateral history from family, friends, paramedics

14. Diagnostic clues from Primary assessment
Sign
Drug
↑ RR
Aspirin
Ethylene Glycol
↓ RR
Opioids
CNS depressants B
Sign
Drug
↑ HR
Antidepressants
Sympathomimetics
Amphetamines
Cocaine
↓ HR
Β blockers
Digoxin
Clonidine
↑ BP C

15. Sign
Drug
Small pupils
Opioids
Cholinesterase inhibitors
Large pupils
TCAs
Anticholinergic
Antihistamines
Ephedrine
Amphetamines
Cocaine
Coma
Barbiturates
Benzodiazepines
Ethanol D

16. Sign
Drug
↓◦ C
TCAs
Barbiturates
Phenothiazines
↑◦C
Amphetamines
Cocaine E

17. Investigations ECG FBC, UEs, LFTs, Glucose, INR, CK, Lactate
Paracetamol &salicylate levels
ABG
Pregnancy Test
CXR
Drug levels: Iron, Lithium, Digoxin

18. 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

19. 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

20. 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

21. 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

22. 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…

23. 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

24. 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 -
INR >3
INR >4.5
Any rise in INR
Encephalopathy
Creatinine > 200 micromol/L
Creatinine >200
micromol/L
Creatinine >250micromol/L
Hypoglycaemia
Devlin, J,O’Grady J Indications for referral and assessment in
adult liver transplantation: a clinical guideline. BSG Guidelines in Gastroenterology,p2.Available from:

25. 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

26. 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

27. Beta-Blocker Overdose
Antidotes:
Glucagon
High dose insulin euglycaemic therapy
Consider intralipid if refractory to standard measures

28. 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 hours with peak effects after 24 hours

29. 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

30. 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

31. Graudins A, Lee HM, Druda D. 2016
Graudins A, Lee HM, Druda D Calcium channel antagonist and beta-blocker overdose: antidotes and adjunct therapies. Br J Clin Pharmacol. 81(3),pp Available from doi: /bcp Review.

32. 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

33. Scenario
16 year old boy takes an overdose of mother’s tablets following an exam. Allows you to take an ABG…
pH: ( )
pO2: (10–14)
pCO2: (4.5–6.0)
HCO3: (22-26)
BE: (-2 to +2)
Other values within normal range

34. A few hours later complains of feeling unwell and ringing in his ears
A few hours later complains of feeling unwell and ringing in his ears. A repeat ABG : pH: 7.15 ( ) 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

35. What’s the diagnosis ?
How would you manage this patient?

36. Aspirin (Salicylate) overdose
Early Features
Late Features
Hypokalaemia
Metabolic acidosis
Alkalosis
Hypoprothrombinaemia
Tinnitus
Hypoglycaemia
Sweating
Pulmonary oedema
Acute Kidney injury

37. Plasma levels 6 hours after ingestion :
300–500 mg/l (mild toxicity)
500–700 mg/l (moderate toxicity)
>750 mg/l (severe toxicity)

38. Key aspects of management
Activated charcoal
Correct electrolyte and metabolic abnormalities
Urinary Alkalinisation
Haemodialysis

39. Haemodialysis in Poisoning
Effective in poisoning with :
-Salicylate
-Isopropanol ( after shave lotions and window cleaning solutions)
-Lithium
-Methanol
-Ethylene Glycol
-Ethanol
-Barbiturates

40. 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…

41. ECG

42. What does it show? Atrial Fibrillation Broad-complex tachycardia
Narrow complex tachycardia
Sinus rhythm

43. What is the 1st line of management?
Amiodarone
Calcium
Magnesium
Sodium Bicarbonate

44. Even in the absence of an acidosis consider alkalinisation with IV Sodium Bicarbonate in patients with :
QRS duration >120msec
Arrhythmias
Hypotension resistant to fluid resuscitation

45. TCA Overdose Clinical Features: Neurological Sedation, coma , seizures
Cardiac
Tachycardia, hypotension, conduction abnormalities
Anti-cholinergic
Dilated pupils, dry mouth, absent bowel sounds, urinary retention

46. TCA Overdose 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 )

47. Novel Psychoactive Substances
Aka ‘Legal highs’
Most common :
Synthetic Cannabinoid receptor agonists: ‘spice’
Synthetic Cathinones – amphetamine derivatives eg. Mephedrone (MCAT)

48. 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.

49. 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

50. Management Stop the causal drugs Cooling Benzodiazepines
Specific 5HT2 receptor anatgonists
Mild cases: cyproheptadine
More severe: chlorpromazine

51. 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
Low Intent
Medium Intent
29+ High Intent

52. Risk Assessment
There is a greater risk of repeated attempts the higher the intent rating
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 Bowie, MD: Charles.

53. Further reading/resources
UK National Poisons Information Service.
Lane,N (ed), Powter, L (ed), Patel, S (ed) Best of Five MCQs For The Acute Medicine SCE. Ist Edition. U.K. Oxford University Press.