When should bicarbonate (bicarb) therapy be initiated in patients with metabolic acidosis?

From the Guidelines

Bicarbonate therapy should be initiated in patients with metabolic acidosis when the pH is less than 7.1 or serum bicarbonate is below 12 mEq/L, particularly in severe cases with hemodynamic instability or when acidosis is causing end-organ dysfunction. The decision to start bicarbonate therapy is based on the severity of the acidosis and its impact on the patient's hemodynamic status and end-organ function.

Key Considerations

• The typical dosing begins with sodium bicarbonate 50-100 mEq IV, which can be administered as a slow IV push or infusion, with subsequent doses titrated based on serial blood gas measurements 1.
• For ongoing correction, a continuous infusion of 3 ampules (150 mEq) of sodium bicarbonate in 1L D5W at 150-200 mL/hr may be used.
• Bicarbonate therapy is most beneficial in cases of normal anion gap metabolic acidosis from bicarbonate loss (such as renal tubular acidosis or diarrhea) and certain high anion gap acidoses like lactic acidosis with severe pH depression.
• However, it should be used cautiously as overly aggressive correction can cause paradoxical CNS acidosis, hypokalemia, hypocalcemia, volume overload, and hypernatremia.

Special Situations

• In diabetic ketoacidosis, bicarbonate is generally not recommended unless pH is below 6.9, as insulin therapy and fluid resuscitation typically correct the acidosis effectively 1.
• The underlying cause of acidosis should always be addressed simultaneously, as bicarbonate therapy is supportive rather than definitive treatment.

Monitoring and Adjustment

• Serial blood gas measurements should be used to titrate bicarbonate doses and assess the effectiveness of therapy.
• The goal of therapy is to improve the patient's hemodynamic status and prevent end-organ dysfunction, rather than simply to normalize the pH or bicarbonate level.

Overall, the use of bicarbonate therapy in metabolic acidosis should be guided by the severity of the acidosis, the patient's hemodynamic status, and the presence of end-organ dysfunction, with careful monitoring and adjustment of therapy to avoid potential complications 1.

From the FDA Drug Label

In cardiac arrest, a rapid intravenous dose of one to two 50 mL vials (44.6 to 100 mEq) may be given initially and continued at a rate of 50 mL (44. 6 to 50 mEq) every 5 to 10 minutes if necessary (as indicated by arterial pH and blood gas monitoring) to reverse the acidosis. Vigorous bicarbonate therapy is required in any form of metabolic acidosis where a rapid increase in plasma total CO2 content is crucial - e. g., cardiac arrest, circulatory insufficiency due to shock or severe dehydration, and in severe primary lactic acidosis or severe diabetic acidosis. In less urgent forms of metabolic acidosis, Sodium Bicarbonate Injection, USP may be added to other intravenous fluids The amount of bicarbonate to be given to older children and adults over a four-to-eight-hour period is approximately 2 to 5 mEq/kg of body weight - depending upon the severity of the acidosis as judged by the lowering of total CO2 content, blood pH and clinical condition of the patient

Bicarbonate therapy initiation should be considered in the following situations:

• Cardiac arrest: rapid intravenous dose of 44.6 to 100 mEq
• Severe metabolic acidosis: vigorous bicarbonate therapy required
• Circulatory insufficiency due to shock or severe dehydration: bicarbonate therapy indicated
• Severe primary lactic acidosis or severe diabetic acidosis: vigorous bicarbonate therapy required
• Less urgent forms of metabolic acidosis: bicarbonate may be added to other intravenous fluids, with a dose of approximately 2 to 5 mEq/kg of body weight over a period of 4 to 8 hours 2 2

From the Research

Initiation of Bicarbonate Therapy

Bicarbonate therapy is considered in patients with metabolic acidosis, but the timing of initiation is crucial.

• The decision to start bicarbonate therapy should be based on the severity of the acidosis and the underlying cause 3.
• In general, bicarbonate therapy is recommended for patients with severe metabolic acidosis, defined as a pH less than 6.9 or a serum bicarbonate level less than 10 mmol/L 4.
• For patients with mild to moderate metabolic acidosis, the use of bicarbonate therapy is more controversial, and the decision to initiate therapy should be individualized based on the patient's clinical condition and response to other treatments 5, 3.

Considerations for Bicarbonate Therapy

Several factors should be considered when deciding whether to initiate bicarbonate therapy in patients with metabolic acidosis.

• The presence of hyperkalemia or hypernatremia may influence the choice of alkalinizing agent, with THAM potentially being preferred in patients with hypernatremia or hyperkalemia 5.
• The risk of osmotic demyelination syndrome should be considered when using large amounts of sodium bicarbonate, particularly in patients with diabetic ketoacidosis 4.
• The use of balanced electrolyte solutions, such as Plasma-Lyte A, may help prevent hyperchloremic metabolic acidosis in patients with diabetic ketoacidosis 6.

Monitoring and Adjustment

Close monitoring of the patient's clinical condition, serum electrolytes, and acid-base status is essential when initiating bicarbonate therapy.

• The dose and duration of bicarbonate therapy should be adjusted based on the patient's response to treatment and the underlying cause of the metabolic acidosis 3.
• Regular assessment of the patient's serum sodium level and prompt actions to lower it if it exceeds the threshold may be necessary to prevent complications such as osmotic demyelination syndrome 4.