Sodium bicarbonate (NaHCO₃) is the primary antidote for TCA toxicity. As these are, by far, the most common cause of cardiac arrest in out of hospital poisonings - patients with drug overdose presenting in cardiac arrest or arresting shortly after arrival should receive a bolus of 1 ampoule of NaHCO₃.

The patient should then be hyperventilated.

• Also see: Tricyclic antidepressants, bupropion, propranolol, flecainide, local anesthetic agents.
• Adult:
  • 💊 Sodium bicarbonate 1-2 mmol/kg IV (i.e. 1-2 mL/kg of 8.4% NaHCO3), q2min.
• Child:
  • 💊👶 Sodium bicarbonate 1-2 mmol/kg IV (i.e. 1-2 mL/kg of 8.4% NaHCO3), q2min.
• Repeat boluses until signs of cardiotoxicity (QRS widening, wide complex dysrhythmias) improve.
• Do not exceed serum pH 7.55, Na⁺ 155 mmol/L.

• Also see: Salicylate toxicity.
• Alkalinization therapy in salicylate toxicity works by ↓ CNS redistribution of salicylates (alters drug distribution), and enhances urinary elimination (ion trapping).
• Adult:
  • 💊 Sodium bicarbonate 1-2 mmol/kg IV (i.e. 1-2 mL/kg of 8.4% NaHCO3), as initial dose, then start infusion.
  • 💊 Sodium bicarbonate 25 mmol/hr IV infusion.
    • e.g. 150 mmol of Sodium bicarbonate in 850 mL 5% dextrose, at 250 mL/hr.
• Child:
  • 💊👶 Sodium bicarbonate 1-2 mmol/kg IV (i.e. 1-2 mL/kg of 8.4% NaHCO3), as initial dose, then start infusion.
  • 💊👶 Sodium bicarbonate 1.5-2× patient's hourly maintenance fluid requirement (weight-based) IV infusion, then titrate to goal pH.
• Maintain normokalemia.
• Goals:
  • Serum pH 7.5-7.55.
  • Urinary pH >7.5.
  • Urine output 2-3 mL/kg/hr.

• Metabolic or respiratory alkalosis - do not exceed pH 7.55.
• Severe hypernatremia - do not exceed Na⁺ 155 mmol/L.
• Hypokalemia.
• Acute pulmonary edema.

Renal impairment:

Hepatic impairment:

• Renal: fluid overload, acute pulmonary edema.
• Metabolic: metabolic alkalosis, hypernatremia, hypokalemia, hyperosmolarity.
• Skin: local phlebitis, cellulitis, extravasation injury.

Mechanism of action: Hypertonic sodium bicarbonate (e.g. 8.4%) ameliorates toxicity by multiple mechanisms, including ↑ extracellular sodium concentration, ↑ plasma bicarbonate concentration, ↑ serum pH, and ↑ urinary pH.

The pharmacokinetics of sodium bicarbonate are challenging to measure, as the bicarbonate component rapidly buffers H⁺ ions and is converted into CO₂.

Absorption:

• Oral bioavailability: good oral bioavailability if ingested.

Distribution:

• Vd: 0.2-0.4 L/kg.

Metabolism:

• Reacts with H⁺ to form H₂O and CO₂.
• Bicarbonate contributes to 80% of extracellular buffering capacity.

Excretion:

• CO₂ is exhaled.
• Bicarbonate and Na⁺ is excreted renally.

Formulation: Sodium bicarbonate 8.4% vials/ampoules contain 1 mmol/mL of sodium bicarbonate solution.

Useful general references: