When is it appropriate to initiate therapy with Sodium Bicarbonate (NaHCO3) for metabolic acidosis?

From the Guidelines

Sodium bicarbonate (NaHCO3) therapy for metabolic acidosis should be initiated when the serum bicarbonate level falls below 22 mmol/L, as recommended by the clinical practice guidelines for nutrition in chronic renal failure 1.

Key Considerations

• The goal of NaHCO3 therapy is to maintain serum bicarbonate at or above 22 mmol/L to prevent the adverse effects of metabolic acidosis, such as increased protein degradation and decreased albumin synthesis 1.
• NaHCO3 can be administered orally, typically at a dose of 2-4 g/d or 25-50 mEq/d, to effectively increase serum bicarbonate concentrations 1.
• In patients with chronic renal failure, correction of metabolic acidosis has been associated with increased serum albumin, decreased protein degradation rates, and improved overall health outcomes 1.
• The Renal Physicians Association clinical practice guideline also recommends correcting chronic metabolic acidosis to a serum bicarbonate level of 22 mmol/L in patients with a GFR of 30 ml/min per 1.73 m2 1.

Important Notes

• NaHCO3 therapy should be individualized based on the patient's underlying condition, severity of acidosis, and other clinical factors.
• Clinicians should monitor patients for potential complications of NaHCO3 therapy, including volume overload, hypernatremia, and hyperosmolality.
• The therapeutic goal of NaHCO3 therapy is to raise the serum bicarbonate level to a safer range, rather than to completely normalize pH, while addressing the underlying cause of metabolic acidosis.

From the FDA Drug Label

Sodium Bicarbonate Injection, USP is indicated in the treatment of metabolic acidosis which may occur in severe renal disease, uncontrolled diabetes, circulatory insufficiency due to shock or severe dehydration, extracorporeal circulation of blood, cardiac arrest and severe primary lactic acidosis Treatment of metabolic acidosis should, if possible, be superimposed on measures designed to control the basic cause of the acidosis - e.g., insulin in uncomplicated diabetes, blood volume restoration in shock. But since an appreciable time interval may elapse before all of the ancillary effects are brought about, bicarbonate therapy is indicated to minimize risks inherent to the acidosis itself. 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.

Initiation of Therapy: Therapy with NaHCO3 (sodium bicarbonate) for metabolic acidosis is appropriate when:

• The patient has severe renal disease, uncontrolled diabetes, circulatory insufficiency due to shock or severe dehydration, extracorporeal circulation of blood, cardiac arrest, or severe primary lactic acidosis.
• Measures to control the basic cause of the acidosis are being implemented, but an appreciable time interval may elapse before these effects are brought about.
• A rapid increase in plasma total CO2 content is crucial, such as in cardiac arrest, circulatory insufficiency due to shock or severe dehydration, and in severe primary lactic acidosis or severe diabetic acidosis. It is essential to monitor the patient's response to therapy and adjust the dose accordingly 2, 2.

From the Research

Initiation of Therapy with NaHCO3 for Metabolic Acidosis

• Severe metabolic acidosis is defined by a pH < 7.2 with HCO3- < 8 mE- q/L in plasma, and its best treatment is to correct the underlying cause 3.
• However, acidemia produces multiple complications, and intravenous NaHCO3 can buffer severe acidemia, preventing the associated damage and gaining time while the causal disease is corrected 3.
• The indication for NaHCO3 therapy requires a risk-benefit assessment, considering its complications, such as hypernatremia, hypokalemia, ionic hypocalcemia, rebound alkalosis, and intracellular acidosis 3.
• Therapy must be "adapted" and administered judiciously, with monitoring of serial evaluation of the internal environment, especially arterial blood gases, plasma electrolytes, and ionized calcium 3.

Considerations for NaHCO3 Administration

• Isotonic solutions should be preferred instead of hypertonic bicarbonate to prevent the development of hypernatremia 3.
• Calcium must be provided for hypocalcemia to improve cardiovascular function, and in mechanically ventilated patients, a respiratory response similar to the one that would develop physiologically must be established to extract excess CO2 and avoid intracellular acidosis 3.
• The calculation of the serum anion gap can aid in the diagnosis of metabolic acidosis, classifying the disorders into categories of normal (hyperchloremic) anion gap or elevated anion gap 4.

Effects of NaHCO3 on Metabolic Acidosis

• The administration of NaHCO3 can lead to significant alkalinization of the extracellular fluid (ECF), and the majority of the administered NaHCO3 is retained in the ECF 5.
• Treatment of metabolic acidosis with sodium bicarbonate can improve kidney and patient survival in chronic kidney disease (CKD) patients 6.
• Correction of metabolic acidosis with bicarbonate administration can also improve insulin resistance in diabetic patients with CKD 7.