Mechanism of Action of Bicanorm (Sodium Bicarbonate) in Acidosis
Sodium bicarbonate (Bicanorm) works in acidosis by providing bicarbonate ions that buffer excess hydrogen ions, raising blood pH and reversing clinical manifestations of acidosis. 1
Basic Mechanism
Sodium bicarbonate dissociates in water to provide:
- Sodium ions (Na+) - principal cation of extracellular fluid
- Bicarbonate ions (HCO3-) - buffer excess hydrogen ions
This buffering action directly addresses the fundamental problem in acidosis - excess hydrogen ion concentration - by neutralizing these ions and raising blood pH.
Physiological Effects
When administered, sodium bicarbonate:
- Increases plasma bicarbonate levels
- Buffers excess hydrogen ion concentration
- Raises blood pH
- Reverses clinical manifestations of acidosis 1
Normally, the body maintains a ratio of 1:20 (carbonic acid:bicarbonate) in extracellular fluid. In acidosis, this ratio is disturbed with excess hydrogen ions, which bicarbonate therapy helps correct.
Clinical Indications
Sodium bicarbonate is indicated for:
- Metabolic acidosis in severe renal disease
- Uncontrolled diabetes with ketoacidosis
- Circulatory insufficiency due to shock
- Severe dehydration
- Cardiac arrest
- Severe primary lactic acidosis
- Drug intoxications (barbiturates, salicylates, methyl alcohol)
- Hemolytic reactions requiring urine alkalinization
- Severe diarrhea with bicarbonate loss 1
Guidelines for Use
Current guidelines recommend:
For severe acidosis only: Sodium bicarbonate therapy should be reserved for severe metabolic acidosis (pH < 7.2) or specific clinical scenarios 2
Not recommended for hypoperfusion-induced acidosis: Guidelines recommend against sodium bicarbonate therapy for improving hemodynamics or reducing vasopressor requirements in patients with hypoperfusion-induced lactic acidemia with pH ≥ 7.15 3
Specific indications: Bicarbonate therapy is appropriate for:
- Severe metabolic acidosis (pH < 7.2)
- Hyperkalemia with acidosis
- Certain drug intoxications
- Renal tubular acidosis
- Chronic kidney disease with persistent acidosis (bicarbonate < 18 mmol/L) 2
Dosing Considerations
For acute severe acidosis, the amount given should be calculated to bring the pH up to approximately 7.2 4. The FDA label indicates that "vigorous bicarbonate therapy is required in any form of metabolic acidosis where a rapid increase in plasma total CO2 content is crucial" 1.
Potential Adverse Effects
Sodium bicarbonate administration has been associated with:
- Sodium and fluid overload
- Increase in lactate and PCO2
- Decrease in serum ionized calcium 3
- Metabolic alkalosis
- Hypernatremia 5
Recent Evidence
The most recent high-quality evidence from the BICAR-ICU trial (2018) showed that in patients with severe metabolic acidemia, sodium bicarbonate had no effect on the primary composite outcome in the general population. However, it decreased mortality in the subgroup of patients with acute kidney injury 5.
Clinical Pitfalls and Caveats
Don't overuse in mild acidosis: Routine use in mild acidosis is not supported by evidence and may cause harm.
Address underlying cause: Treatment of metabolic acidosis should primarily focus on addressing the underlying cause, with bicarbonate therapy as an adjunct 1.
Monitor electrolytes: Sodium bicarbonate can decrease serum potassium and increase sodium levels, requiring careful monitoring 6.
Consider alternatives in specific situations: THAM may be preferred in patients with mixed acidosis with high PaCO2 levels or in hypernatremia 6.
Be cautious with rapid administration: Rapid administration can lead to paradoxical intracellular acidosis and hypocalcemia.
In summary, while Bicanorm (sodium bicarbonate) provides an effective buffer for excess hydrogen ions in acidosis, its use should be targeted to specific clinical scenarios with severe acidosis (pH < 7.2) or specific indications, rather than being used routinely for all forms of acidosis.