TCA overdose

Question 1

4 receptors inhibited by TCA OD

Answer 1

i. Central and peripheral acetylcholine receptors
ii. α adrenergic receptors peripherally
iii. Noradrenalin and serotonin reuptake
iv. Fast sodium channels in myocardial cells

Question 2

What dose of TCA is fatal?

Answer 2

a. >10 mg/kg life-threatening
b. >20 mg/kg coma, cardiotoxicity

Question 3

Clinical manifestations of TCA OD

Answer 3

Myocardial sodium channel antagonism - hypotension, wide QRS –> VT/VF
Inhibition of noradrenaline and serotonin re-uptake - coma, seizures
Anticholinergic effects (tachycardia, vomiting, blurred vision, ataxia, delirium, urinary retention, ileus)
Antiadrenergic - vasodilatation

Question 4

Management

Answer 4

Decontamination: charcoal if within 2 hours, those who ingest doses of >10-15 mg/kg should be given charcoal following intubation
Intubate/ventilate to an alkalosis (7.5-7.55 to avoid potentiation of toxicity)
Sodium bicarbonate 2 mmol/kg if
a) Wide QRS or ventricular arrythmia
b) Hypotension resistant to fluid resuscitation
c) seizures (results in acidosis) or prolonged intubation (leads to acidosis)