TCA POISONING / TRICYCLIC ANTIDEPRESSANT POISONING :

 TCA POISONING / TRICYCLIC ANTIDEPRESSANT POISONING :

This is usually caused by Tri cyclic Antidepressants poisoning like

Amitryptiline

Imipramine

Dothiepin

But it may also occur due to other medications such as Atropine and Procyclidine.

Atropine is also present in Atropa Belladona ( deadly Nightshade )

Clinical Features :

Common Features include :

Tachycardia

Hot Dry skin

Dry mouth

Drowsiness leading to Coma

Dilated pupils

Ataxia

Urinary retention

Jerky limb movements.

Unconscious patients will have divergent squint ,

Increased muscle tone

Increased Reflexes,

Myoclonus and

Extensor plantar responses.

In deep coma, there will be muscle flaccidity with no detectable reflexes and respiratory depression requiring IPPV.

Convulsions occur in 10 percent of unconscious patients and may precipitate cardiac arrest.

Patients recovering from coma often suffer  delirium and hallucinations and have jerky limb movements and severe dysarthria.

ECG Findings :

Sinus tachycardia is usual.

But as the severity of poisoning increases, the PR interval and the QRS complex also increases.

Theese changes may help  confirm the clinical diagnosis of tricyclic poisoning in an unconscious patient.

The p wave maybe superimposed on the preceding  T wave giving the impression of VT  when the rhythm is actually sinus tachycardia with prolonged conduction.

In very severe poisoning ventricular arrhythmias and bradycardia can occur especially in patients who are hypoxic.

Death may result from cardiorespiratory depression and acidosis.

Management :

Clear Airway

Maintain ventilation.

Give supportive treatment and provide nursing care.

Observe continuously as the patient has the potential for rapid deterioration.

Monitor ECG during gastric lavage or unconscious patients or post ictal patients.

Perform gastric lavage if less than 1 hour since overdose or longer and if patient is in coma.

Activated charcoal should be given.

Single brief fits do not warrant any treatment but iv diazepam should be given in case of prolonged fits.

Most cardiac arrhythmias occur in the patients of TCA overdose while they are unconscious within a fe hours of overdose..

These can usually be treated in most cases by correction of Hypoxia and Acidosis.

8.4 % of sodium bicarbonate ( 50 – 100 ml in adult ) ( 1ml/kg in child ) may produce a dramatic improvement in cardiac rhythm and output.

This is achieved by altering protein binding and reducing active free Tricyclic drug.

Avoid anti arrhythmic drug

Donot use physostigmine salicylate  or flumazenil which ca precipitate fits.

Unconscious patients usually improve over 12 hours and rgain consciousness with in 36 hours

Delirium and hallucinations may persist over 2 -3 days

And may require sedation in large doses with diazepam ( 20 – 30 mg PO every 2-3 hours )