USMLE Prep - Medical Reference Library

Tricyclic Antidepressant Overdose — Sodium Bicarbonate Protocol

System: Toxicology • Reviewed: Aug 31, 2025 • Step 1Step 2Step 3

Synopsis:

Life-threatening sodium channel blockade causing wide QRS and arrhythmias; treat with IV sodium bicarbonate boluses/infusion, benzodiazepines for seizures, and supportive care.

Key Points

  • Stabilize ABCs; begin targeted evaluation without delaying life-saving therapy.
  • Use system-specific risk tools to guide testing and disposition.
  • Order high-yield tests first; escalate imaging when indicated.
  • Start evidence-based initial therapy and reassess frequently.

Algorithm

  1. Primary survey and vitals; IV access and monitors.
  2. Focused history/physical; identify red flags and likely etiologies.
  3. Order system-appropriate labs and imaging (see Investigations).
  4. Initiate guideline-based empiric therapy (see Pharmacology).
  5. Reassess response; arrange consultation and definitive management.

Clinical Synopsis & Reasoning

For Tca Overdose Sodium Bicarb, frame the differential by acuity and pathophysiology, then align diagnostics to the leading hypotheses. Prioritize stabilization while obtaining high‑yield studies such as CBC (Baseline hematology), BMP (Electrolytes/renal). Incorporate bedside imaging and targeted labs to define severity and identify complications; synthesize results with clinical trajectory to refine the working diagnosis and disposition needs.


Treatment Strategy & Disposition

Initiate disease‑directed therapy alongside supportive care, titrating to objective response. Pharmacologic options commonly include Analgesia/Antipyretics. Use validated frameworks (e.g., ECG Risk Markers) to guide escalation and site of care. Address precipitating factors, de‑escalate empiric therapies with data, and arrange follow‑up for monitoring and risk‑factor modification; admit patients with instability, high risk of deterioration, or needs for close monitoring.


Epidemiology / Risk Factors

  • Risk factors vary by condition and patient profile

Investigations

TestRole / RationaleTypical FindingsNotes
CBCBaseline hematologyAbnormal counts
BMPElectrolytes/renalDerangements

ECG Risk Markers

FindingImplication
QRS ≥100 msSeizure risk
QRS ≥160 msVentricular arrhythmia risk
Right axis deviation of terminal 40 msSodium channel blockade

Pharmacology

MedicationMechanismOnsetRole in TherapyLimitations
Sodium bicarbonate (IV)Alkalinization/Na⁺ loadMinutesQRS widening/hypotensionHypokalemia, alkalemia
BenzodiazepineGABA-A potentiationMinutesSeizuresRespiratory depression
Lipid emulsion (selected)Lipid sinkMinutesRefractory instabilityFat overload syndrome (rare)

Prognosis / Complications

  • Prognosis depends on severity, comorbidities, and timeliness of care

Patient Education / Counseling

  • Explain red flags and when to seek emergent care.
  • Reinforce medication adherence and follow-up plan.

Notes

Activated charcoal within 2 hours if protected airway. Monitor potassium; hypokalemia can worsen QRS with alkalemia.


References

  1. ACMT Toxicology Guidance — TCAs — Link
  2. Poison Control Resources — Link