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Tricyclic Antidepressants (TCA) Toxicity Protocol

Tricyclic Antidepressants (TCA) Toxicity Protocol

TRICYCLIC ANTIDEPRESSANTS (TCAs) TOXICITY

1. Toxic Dose & Risk Stratification

  • < 5mg/kg: Minimal symptoms.
  • 5 - 10mg/kg: Drowsiness and mild anticholinergic features.
  • > 10mg/kg: Potentially life threatening (Coma, hypotension, seizures, cardiac dysrhythmias).
    Note: Anticholinergic affects are often masked by the coma.
  • > 30mg/kg: Severe toxicity with pH-dependent cardiotoxicity and coma expected to last > 24 hours.
Timing: Severe toxicity usually manifests within 2 hours but any overdose requires close cardiac monitoring for 6 hours post ingestion.

2. Clinical Manifestations

CVS Toxicity

  • Sinus tachycardia, hypotension.
  • QTc prolongation, wide QRS.
  • Prolonged PR, V Tach, VF.

CNS

  • Drowsy → Coma.
  • Seizures.
  • Hallucinations, Agitation.
  • Extra pyramidal symptoms.

Others

  • Anticholinergic syndrome.
  • Metabolic acidosis.
  • Aspiration pneumonia.

3. Initial Assessment & Management

Vitally Unstable
ABCD Management
Vitally Stable
Check Manifestations
Scenario Actions
No Manifestations 1) Observe vital signs & consciousness - ECG.
2) No signs for 6-12 hours.
3) Discharge.
Manifestations (Mild) 1) Give AC 1gm/kg orally.
2) GL if large dose within 2hrs (ETI).
3) Observe vital signs & consciousness - ECG.
Manifestations (Mod & Severe) 1) AC (ETI in coma).
2) DO: CBC, Na, K, RBS, KFT, ABG, CPK, Ca, Mg, urine screen.
3) ECG.
If deteriorated: ICU ADMISSION.

4. Extra Pyramidal Symptoms Management

  • Diphenhydramine: IV or IM 50 to 100 mg (1-2 mg/kg in children), additional doses can be used if repeated.
  • Benzodiazepines: (diazepam 0.1 mg/kg intravenously).
  • Cogentin.

5. Interventions for Deterioration (ICU)

Arrhythmia & QRS Prolongation

Trigger: QRS > 2.5 small squares or Vent. Arrhythmia.

Sodium Bicarbonate (NaHCO3):
  • Bolus: 1-2 meq/KG (check K level). Can repeat after 3-5min till QRS narrows. Target PH 7.50-7.55.
  • Infusion: 150mEq in 1L of D5W continuous infusion at double maintenance rate (Target PH 7.50-7.55).
  • Xylocaine (for VT OR VF): Loading: 1-2 mg/kg slow IV bolus. Maintenance: 20 - 50 ug/kg/min.
  • MgSO4: (For VT, VF, Torsade de pointes, ↑ QT) 25 - 50 mg/kg (max 2 g) IV over 2 min.
  • Torsade de pointes: DC conversion > MgSo4 OR overdrive pacing.
  • WARNING: Cordarone may aggravate cardiotoxicity.
Refractory Poisoning (Cardiac Arrest):
IV lipid emulsion 20%: Bolus (1.5 mL/kg) followed by infusion of 0.25 mL/kg/min for 30-60 mins OR to max total dose 10ml/kg.

Hypotension

  1. Start with I.V saline up to 30 ml/Kg.
  2. If no improvement give NaHCO3: 1-2 mEq/kg IV boluses (repeat 3-5min, target pH ≤ 7.55).
  3. Norepinephrine.
  4. NaHCO3 infusion (same as arrhythmia protocol).

Seizures & Agitation

  • Seizures: Benzodiazepines (diazepam) 0.1-0.2mg/kg/dose → Barbiturate.
    Refractory: Midazolam or propofol infusion.
  • Agitation: Restrain & Benzodiazepine.
General Ward/ICU Care: Care of respiration & coma. Observe vital signs.
Discharge Criteria: Improved with No S&S for 6h.