Tricyclic Antidepressant Overdose

1. See Also
   1. Tricyclic Antidepressant
   2. QRS Widening
2. Signs and Symptoms
   1. Coma
   2. Confusion
   3. Delirium
   4. Mydriasis (dilated pupils)
   5. Dry Mouth
   6. Hypotension
   7. Seizures
   8. Tachycardia
   9. Urinary Incontinence
3. Diagnostics: EKG Findings
   1. R Wave in aVR (elevation of the terminal 40 msec)
      1. Tall R Wave in aVR suggests Right Ventricular Strain
   2. QRS Widening
      1. Also seen with Cocaine and Diphenhydramine
4. Labs
   1. Venous Blood Gas (VBG)
      1. Obtain serial levels until stabilized
   2. Toxicology labs
      1. Serum Acetaminophen Level
      2. Serum Salicylate Level
      3. Urine Drug Screen
      4. Avoid Tricyclic Antidepressant levels
         1. TCA levels are send-out labs that do not assist in acute management
5. Precautions
   1. Avoid provocative agents
      1. Avoid Physostigmine
      2. Avoid Class IA Antiarrhythmics (e.g. Procainamide, Quinine)
      3. Avoid Class IC Antiarrhythmics
      4. Avoid barbiturates and Phenytoin (see Seizures below)
   2. Avoid reducing Heart Rate
      1. Tachycardia decreases the QT Interval and is protective against Torsades de Pointes
6. Management: General
   1. Intubate early in serious Tricyclic Overdose (due to rapid decompensation)
      1. Succinylcholine is preferred paralytic (unless Hyperkalemia) due to risk of Respiratory Acidosis with longer acting agent
7. Management: Seizures
   1. Benzodiazepines: Lorazepam (Ativan)
      1. Adult: Lorazepam 2 to 4 mg IV
      2. Child: Lorazepam 0.05 to 0.1 mg/kg
   2. Avoid barbiturates
   3. Avoid Phenytoin (Dilantin)
8. Management: Prolonged QRS interval (>120 ms)
   1. Background
      1. Sodium Bicarbonate mechanism
         1. Alkalinize blood and increases drug binding, volume of distribution and drug urinary excretion
         2. Sodium loading helps to overcome the TCA blocking of the sodium channels
         3. Even multiple repeat doses of Sodium Bicarbonate are unlikely to causes significant Hypernatremia or Metabolic Alkalosis
   2. Children
      1. Sodium Bicarbonate 1-2 mEq/kg up to 50 mEq bolus
   3. Adults
      1. Sodium Bicarbonate
         1. Start: 2-4 ampules
         2. Titrate: 2 ampules every 2 minutes until QRS narrows (may require 15-20 ampules)
      2. Other adjunctive measures
         1. Lidocaine (Class IB Antiarrhythmic)
            1. Fast association and dissociation allows displacement of TCA from cardiac cells
            2. Results in increased repolarization time and QRS narrowing
         2. Ventilator
            1. Maintain standard Tidal Volumes (6-8 ml/kg) at an increased Respiratory Rate (at least 16-18 bpm)
            2. Adjust Respiratory Rate to a goal VBG pH 7.45 to 7.55
         3. Activated Charcoal
            1. Risk of aspiration even when intubated (do not give unless intubated with cuffed tube)
            2. Indicated in refractory QRS Widening to numerous bicarbonate ampules (e.g. more than 10 ampules)
               1. Suggests continued Tricyclic Antidepressant absorption (especially if decreased gastrointestinal motility)
9. Management: Hypotension
   1. Tricyclic Antidepressants is an alpha blocker and results in Hypotension
   2. Goal: Low to normal Blood Pressure and adquate critical end-organ perfusion
   3. Adult
      1. Norepinephrine 8-12 mcg/min or
      2. Phenylephrine
   4. Child
      1. Dopamine 0.1 mcg/kg/min (may titrate for Blood Pressure to a maximum of 6 mcg/min)
10. References
    1. Swadron and Nordt in Majoewsky (2013) EM:Rap 13(3):5-7
    2. Henry (2006) Pediatr Clin North Am 53(2): 293-315