Clinical Toxicology

Question 1

It is often impossible to establish with certainty the identity of the poison and the size of the dose. Why is this not usually important?

Answer 1

Because only a few poisons (such as opioids,
paracetamol, and iron) have specific antidotes. Few patients require active removal of the poison.
In most patients, treatment is directed at managing symptoms as they arise.

Question 2

Management of suspected poisoning?

Answer 2

Resuscitation + Stabilization
Evaluation
Identify what you can
Symptomatic care + monitoring
Prevention of deterioration
Treat symptoms
Specific antidotes

Question 3

Resuscitation & Stabilization - how do you assess/manage a suspected poisoning patient?

Answer 3

Airway – Evaluation of patency ± correction ± Oxygen
Breathing – RR, air entry, SpO2…
Circulation – central pulse, central cap refill, brachial BP, ECG… ± iv fluids
Disability – AVPU scale; pupils; capillary blood glucose
Everything else - Temperature

Question 4

What is it important to ask about in the history of a suspected poisoning patient?

Answer 4

What drug(s) were taken?
What dose/number of tablets were taken?
When where they taken?
Were they taken all at once or staggered?
Are there empty packets/bottles of drugs?
Witnesses?
What co-morbidities are present?
What are the concomitant drugs/toxins?
Is there evidence of high suicidal risk (notes etc.)?
Allergies?
Last meal?
Previous poisonings?
Current symptoms?

Question 5

Examination of a suspected poisoning patient.

Answer 5

What are the cardio-respiratory observations?
Is there evidence of specific organ failure?
What is the temperature?
Is the patient sweating?
What is the level of consciousness?
What are the pupil size/pupillary responses to light?
Are there signs of CNS involvement?
Agitation; neck stiffness; clonus

Question 6

How should a suspected poisoning be investigated?

Answer 6

Can we test for the specific poison of interest?
What tests are required for monitoring of likely
affected organs?

Question 7

How can absorption be prevented?

Answer 7

Activated charcoal within 1h ingestion - 50mg orally in conscious patient, or 50mg by NG tube if obtunded and protect airway
Gastric lavage

Question 8

What substances don’t bind to charcoal?

Answer 8

Ethylene glycol, Iron, Lithium, Methanol, Strong acids and alkalis

Question 9

What substances is gastric lavage indicated for?

Answer 9

iron, lithium

Question 10

What drugs is enhanced elimination indicated for?

Answer 10

carbamezepine, dapsone, phenobarbital, quinine, theophylline

Question 11

What is the dosage for enhanced elimination (using charcoal)?

Answer 11

Multi-dose activated charcoal

50g every 4hours

Question 12

Other methods of enhanced elimination? (2)

Answer 12

Haemdialysis for drugs with low volume of distribution e.g. aspirin, toxic alcohols, lithium, valproate
Urine alkalinization for aspirin (TCAs)

Question 13

Beta blocker overdose - symptoms?

Answer 13

Presents with hypotension and bradycardia

Associated features include hypothermia and hypoglycaemia

Question 14

Beta blocker overdose treatment.

Answer 14

Atropine 0.5-2mg ivi for bradycardia
Glucagon 5-10mg iv bolus + 50-150 mcg/kg/h titrated to clinical response can cause nausea and vomiting, hyperglycaemia
High-dose insulin (1u/kg bolus + 0.5-2u/kg/h) + 10%
dextrose
Temporary wire pacemaker/external pacing

Question 15

TCA overdose symptoms?

Answer 15

• anti-muscarinic effects (confusion, agitation, dry skin, hyperthermia, thirst, dry mouth, mydriasis, tachycardia, urinary retention, ileus)
• myocardial sodium channel blockade (broad QRS, any arrthythmia from asystole to VF)
• alpha-1 adrenergic antagonism
• CNS effects (confusion, delirium, myoclonus, seizures)

Question 16

TCA overdose treatment?

Answer 16

If acidotic or QRS widening, give iv sodium
bicarbonate
If cardiac rhythm abnormalities fail to respond to
above, consider intra-lipid iv

Question 17

Paracetamol overdose treatment.

Answer 17

Quenching of glutathione prevents destruction of
toxic metabolite
Monitor INR, ALT, creatinine and liver tenderness
pre and post treatment
Measure paracetamol as soon after 4h post ingestion as possible
If above nomogram, give full treatment of N-
acetylcysteine iv

Question 18

Aspirin overdose - what level is toxic/fatal?

Answer 18

<125mg/kg unlikely severe toxicity

>500mg/kg possibly fatal

Question 19

Aspirin overdose symptoms?

Answer 19

Initial respiratory alkalosis, followed by severe
metabolic acidosis
Nausea, vomiting, hypoglycaemia, hyperpyrexia,
non-cardiogenic pulmonary oedema, coma

Question 20

Aspirin overdose treatment?

Answer 20

sodium bicarbonate

haemodialysis

Question 21

Techniques to enhance elimination of overdose should be routinely used - true or false?

Answer 21

False

Question 22

Serum drug levels are useful to guide management of

overdose in the majority of cases - true or false?

Answer 22

False

Question 23

There is only 1 treatment-nomogram line to guide the use of antidote in paracetamol poisoning - true or false?

Answer 23

True

Question 24

Both glucagon and insulin may be appropriate treatments in beta blocker overdose - true or false?

Answer 24

True

Question 25

Sodium bicarbonate is the most useful anti-arrhythmic in tricyclic antidepressant overdose - true or false?

Answer 25

True