II. Symptoms: Anticholinergic Toxicity
III. Signs and Symptoms
- Altered Level of Consciousness, confusion, Delirium or coma
- Hypotension
- Seizures
- Tachycardia
- Urinary Incontinence
IV. Diagnostics: EKG Findings
-
R Wave in aVR (elevation of the terminal 40 msec)
- Tall R Wave in aVR suggests Right Ventricular Strain
-
QRS Widening >0.1 s
- Also seen with Cocaine and Diphenhydramine
- QRS >0.16 s is associated with Seizures and Dysrhythmias
- Sinus Tachycardia
- Torsades de Pointes
V. Labs
-
Venous Blood Gas (VBG)
- Obtain serial levels until stabilized
- Toxicology labs
- Serum Acetaminophen Level
- Serum Salicylate Level
- Urine Drug Screen
- Avoid Tricyclic Antidepressant levels
- TCA levels are send-out labs that do not assist in acute management
VI. Precautions
- Avoid provocative agents
- Avoid Physostigmine
- Avoid Class IA Antiarrhythmics (e.g. Procainamide, Quinine)
- Avoid Class IC Antiarrhythmics
- Avoid Barbiturates and Phenytoin (see Seizures below)
- Avoid reducing Heart Rate
- Tachycardia decreases the QT Interval and is protective against Torsades de Pointes
VII. Management: General
- Significant risk with ingestions >10 mg/kg
- Intubate early in serious Tricyclic Overdose (due to rapid decompensation)
- Succinylcholine is preferred paralytic (unless Hyperkalemia) less Respiratory Acidosis than with longer acting agent
- Gastric Decontamination if early presentation (Activated Charcoal, consider Gastric Lavage)
VIII. Management: Seizures
- Benzodiazepines: Lorazepam (Ativan)
- Avoid Barbiturates
- Avoid Phenytoin (Dilantin)
IX. Management: Prolonged QRS interval (>0.1 s)
- Background
- Sodium Bicarbonate mechanism
- Alkalinize blood and increases drug binding, volume of distribution and drug urinary excretion
- Sodium loading helps to overcome the TCA blocking of the Sodium channels
- Even multiple repeat doses of Sodium Bicarbonate are safe
- Unlikely to causes significant Hypernatremia or Metabolic Alkalosis
- Sodium Bicarbonate mechanism
- Children
- Sodium Bicarbonate 1-2 mEq/kg up to 50 mEq bolus
- Adults
- Sodium Bicarbonate
- Start: 2-4 ampules
- Titrate: 2 ampules every 2 minutes until QRS narrows (may require 15-20 ampules)
- Goal VBG pH 7.45 to 7.55
- Other adjunctive measures
- Lidocaine (Class IB Antiarrhythmic)
- Fast association and dissociation allows displacement of TCA from cardiac cells
- Results in increased repolarization time and QRS narrowing
- Ventilator
- Maintain standard Tidal Volumes (6-8 ml/kg) at an increased Respiratory Rate (at least 16-18 bpm)
- Adjust Respiratory Rate to a goal VBG pH 7.45 to 7.55
- Activated Charcoal
- Risk of aspiration even when intubated (do not give unless intubated with cuffed tube)
- Indicated in refractory QRS Widening to numerous bicarbonate ampules (e.g. more than 10 ampules)
- Suggests continued Tricyclic Antidepressant absorption (esp. if decreased GI motility)
- Lidocaine (Class IB Antiarrhythmic)
- Sodium Bicarbonate
X. Management: Hypotension
- Tricyclic Antidepressants is an alpha blocker and results in Hypotension
- Goal: Low to normal Blood Pressure and adquate critical end-organ perfusion
-
Vasopressors
- Norepinephrine 4 mg/500 cc D5W at 0.1 to 0.2 mcg/kg/min (adults - 8-12 mcg/min)
- Dopamine is not generally recommended as may exacerbate tricyclic beta mediated effects
- Other measures
- Consider intra-aortic balloon pump
XI. References
- (2016) CALS Manual, 14th ed, 1:132-3
- Swadron and Nordt in Majoewsky (2013) EM:Rap 13(3):5-7
- Henry (2006) Pediatr Clin North Am 53(2): 293-315 [PubMed]
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Related Studies
| Concepts | Injury or Poisoning (T037) |
| English | tricyclic antidepressant toxicity, tricyclic antidepressant toxicity (diagnosis), toxicity from tricyclic antidepressant |
