Lecture on Sodium Bicarbonate (Bicarb)

Historical Context

• 1791: French chemist first made sodium carbonate.
• 1950s: First use of IV sodium bicarbonate.
• Currently considered an essential medication by the WHO.

Medical Uses

• Most widely used buffering agent for treatment of persistent metabolic acidosis.
  • Conditions: hypoperfusion, diabetic ketoacidosis, lactic acidosis, hyperkalemia.
• Mechanism: Increases plasma bicarbonate, buffers excess hydrogen ions, raises pH, reverses acidosis.

ICU Use Cases

1. Metabolic Acidosis
   • Important to correct for effective use of vasopressors.
   • Less effective in acidic environments (pH < 7.1).
2. Cardiac Arrest
   • Use cautiously; can cause paradoxical acidosis due to CO2 production.
   • Withhold early unless acidosis is evident.
3. Severe Hyperkalemia
   • Used when potassium > 6 mEq/L.
   • Drives extracellular potassium into cells.
4. Diabetic Ketoacidosis
   • Use is debatable; outcomes similar with or without bicarb.
5. Hydration Protocol Prior to Contrast Injection
   • Conflicting evidence on benefits for preventing post-contrast nephropathy.
6. Drug Toxicities
   • Examples: aspirin, tricyclic antidepressants, methanol, salicylates, barbiturate overdoses.

Contraindications

• Metabolic or respiratory alkalosis.
• Loss of chloride (e.g., excessive vomiting, continuous GI suction).
• Caution: renal insufficiency, heart failure, edematous sodium-retaining conditions.

Adverse Effects

• Alkalosis
  • Increase in pH; can lead to compromised oxygen release (left shift in oxyhemoglobin dissociation curve).
  • Potential for lactic acidosis.
• Edema

Administration

• Common Concentrations
  • IV Push: 50 mEq in 50 mL vial ("amp of bicarb").
  • IV Infusions:
    • 150 mEq in a liter of fluid.
    • 250 mEq in 250 mL (bicarb fusion for severe cases).
• Dosing
  • IV Push: Typically 50 mEq.
  • IV Infusion: 0.5–1 mEq/kg/hr.

Pharmacokinetics

• IV Administration: Immediate onset and peak.
• Duration: 1–2 hours or during infusion.
• Kidney Regulation: Regulates plasma concentration, affects urine acidification and alkalinization.

Monitoring and Safety

• Avoid risk of alkalosis: Obtain and monitor blood pH, PO2, PCO2, serum electrolytes.
• Monitor lab values: Potassium, sodium, CO2, lactate, bicarb levels.
• Watch for fluid/solute overload, overhydration, potential heart failure, and pulmonary edema.
• Avoid mixing with calcium: Precipitate formation.

Conclusion

• Review of sodium bicarb's uses, effects, and administration considerations.
• Monitoring and safety are crucial when using this medication.