Last Updated on February 25, 2019 by FRCEM Intermediate

Overview:

• TCAs are weak bases (pKa 8.5) that can cause life-threatening sodium channel toxicity
• Ingestion of 15 mg/kg tricyclic antidepressants would be expected to result in serious, potentially life-threatening

Examinations

• CVS – dry mucous membranes, tachycardia, hypertension -> hypotension -> cardiovascular collapse (arrhythmia), postural hypotension, dehydration
• CNS – nystagmus, dizziness, agitation, decreases level of consciousness, unconscious/coma, seizures, increase in tone, clonus, tremor, hypereflexia, pupillary dilation, blurred vision
• GI – N+V, abdominal pain, dry mouth, ileus
• METABOLIC – severe metabolic acidosis, fever
• GU – urinary retention
• SKIN – flushed

Investigations

• ABG – metabolic acidosis
• ECG:
  -> sinus tachycardia
  -> PR prolongation
  -> RAD
  -> R wave > 3mm in aVR
  -> prolonged QT interval (>430ms)
  -> QRS prolongation (>100ms)
  -> VF/VT/asystole
  -> 2nd or 3rd HB
  -> RBBB
• Bloods – renal impairmen

Management

• Consider activated charcoal if the patient presents within 1 hour of ingesting a toxic dose. A second dose of charcoal should be considered after 1 – 2 hours in patients with features of toxicity.
• In adults consider immediate administration of 50 – 100 mL of 8.4% sodium bicarbonate
  • Hypotension
  • Wide QRS or arrhythmias
  • Seizures
  • Metabolic acidosis
• If metabolic acidosis persists despite correction of hypoxia and adequate fluid resuscitation, consider correction with intravenous sodium bicarbonate.
• Agitation: Diazepam
• Convulsions: Benzodiazepines.NB. Avoid phenytoin
• If cardiotoxicity is unresponsive to the above consider the use of a lipid emulsion; 5 mL/kg of 20% Intralipid as an intravenous bolus followed by 0.25 – 0.5 mL/kg/min for 30 – 60 minutes, to an initial maximum of 500 mL.
• All patients should be observed for at least 6 hours after ingestion.