15.5 Poisoning + TCA od

Question 1

a) Outline the general principles in the management of poisoning by oral ingestion? (40%)

Answer 1

> > This is a medical emergency.
I would call for help and would assess and
manage the patient simultaneously
following an ABCDE approach.

> > If there is any possibility of
e.g. organophosphate poisoning, then staff
protection should be considered.

> > Airway:
• Oxygen 15 l/min via non-rebreathe bag.
• Intubate if unable to maintain own airway due to reduced or falling conscious level.

> > Respiratory:
• Continuous oxygen saturations monitoring.
• Assess ventilatory adequacy and for signs of respiratory distress.
• Auscultate chest.

> > Cardiovascular:
• Large-bore intravenous access.

• Continuous ECG and
noninvasive blood pressure measurement.

• Intra-arterial blood pressure
monitoring should be initiated as soon as
possible.

> > Neurological:
• Monitor GCS, which may deteriorate.

> > Exposure:
• Full examination.
• Check capillary blood glucose.

> > History:
• Ascertain likely poison
(information from ambulance crew, family,
empty packets or bottles found with patient,
current prescriptions),

quantity ingested and
whether taken with alcohol.

• Attempt to establish likely
interval between ingestion and presentation.

• Ascertain comorbidities and other regular medications that may cause interactions etc.

> > Blood tests:
• Arterial blood gas
(pH, lactate, and to assess ventilatory adequacy),

full blood count,
urea and electrolytes,
glucose,
liver function tests,
paracetamol levels

(four hours post exposure, ideally),
urine toxicology screen.

> > Radiology:
• Chest radiograph;
pulmonary oedema may occur
with salicylate or
opiate poisoning.

• Abdominal radiograph if considering body packing.

> > Advice from Toxbase, re:
• Specific antidotes.
• Gastric decontamination.
• Alkaline diuresis.
• Haemodialysis.

Question 2

b) What are the mechanisms of toxicity of a tricyclic antidepressant (TCA) overdose? (10%)

Answer 2

Sodium channel blockade
Cardiac depression,
decrease in cardiac output,
hypotension, arrhythmias, seizures.

Alpha adrenergic blockade
Hypotension.

Anticholinergic effects
Mydriasis, tachycardia, hypotension,
ileus, irritability,
confusion, seizures, coma,
urinary retention, pyrexia.

Reduced norepinephrine
and serotonin reuptake
Hypotension.

Question 3

c) List the clinical features of a
TCA overdose (20%) and how
the associated life threatening
complications are managed. (30%)

Answer 3

Respiratory depression, decreased
level of consciousness, coma.

• Intubation, ventilation

Seizures.
Benzodiazepines, anaesthesia

Acidosis, prolonged QRS.
Sodium bicarbonate (increases sodium levels to
compete with receptor blockade, alkalinises blood
to reduce affinity of TCA for sodium channel).

Arrhythmias
• Magnesium, lidocaine, management of
acidosis as previously

Hypotension.
• Intravenous fluid boluses.
• Alpha agonists.
• Glucagon (stimulates adenylate cyclase, which
increases myocardial calcium causing
increase in heart rate and contractility).

Cardiac arrest.
• ALS guided resuscitation.

Pyrexia.
Patient cooling.

• All adverse reactions.
• Activated charcoal reduces absorption of TCA
and so reduces all adverse effects

• Life-threatening adverse
neurological and cardiac symptoms,
resistant to other treatments.
• Intralipid.
• Consideration of ECMO.