How to manage metabolic acidosis with hypobicarbonatemia and acidemia?

From the Guidelines

To manage metabolic acidosis with hypobicarbonatemia and acidemia, the primary goal is to normalize serum bicarbonate levels, and this can be achieved by oral supplementation with bicarbonate salts, such as sodium bicarbonate, at a dose of 2 to 4 g/d or 25 to 50 mEq/d, as well as by using higher dialysate bicarbonate concentrations. The management of metabolic acidosis is crucial as it is associated with increased oxidation of branched chain amino acids, increased protein degradation, and decreased albumin synthesis 1.

Key Considerations

• Monitoring serum bicarbonate levels regularly, at monthly intervals, is essential to assess the severity of metabolic acidosis and to guide treatment decisions 1.
• The target serum bicarbonate level should be at or above 22 mmol/L to minimize the adverse effects of acidemia on protein metabolism and overall health 1.
• Higher concentrations of bicarbonate in hemodialysate, such as 38 mmol/L, can safely increase predialysis serum bicarbonate concentrations, offering an alternative or complementary approach to oral supplementation 1.

Treatment Approach

• Oral sodium bicarbonate supplementation is a effective method to increase serum bicarbonate concentrations, with doses ranging from 2 to 4 g/d or 25 to 50 mEq/d 1.
• In patients undergoing continuous peritoneal dialysis (CPD), higher dialysate lactate or bicarbonate levels, in addition to oral sodium bicarbonate, may be used to raise serum bicarbonate levels 1.
• Correction of acidemia due to metabolic acidosis has been associated with several beneficial outcomes, including increased serum albumin, decreased protein degradation rates, and increased plasma concentrations of branched chain amino acids and total essential amino acids 1.

Clinical Implications

• The eradication of acidemia may promote greater body weight gain, increased mid-arm circumference, and potentially reduce hospital stays, as suggested by long-term studies in CPD patients 1.
• It is essential to individualize treatment based on the patient's specific needs, the underlying cause of metabolic acidosis, and their response to therapy, ensuring that serum bicarbonate levels are normalized without overcorrection.

From the FDA Drug Label

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 In metabolic acidosis associated with shock, therapy should be monitored by measuring blood gases, plasma osmolarity, arterial blood lactate, hemodynamics and cardiac rhythm. Bicarbonate therapy should always be planned in a stepwise fashion since the degree of response from a given dose is not precisely predictable Initially an infusion of 2 to 5 mEq/kg body weight over a period of 4 to 8 hours will produce a measurable improvement in the abnormal acid-base status of the blood.

To manage metabolic acidosis with hypobicarbonatemia and acidemia, sodium bicarbonate can be administered intravenously. The recommended dose is 2 to 5 mEq/kg of body weight over a period of 4 to 8 hours, depending on the severity of the acidosis.

• Key considerations include:
  • Monitoring blood gases, plasma osmolarity, arterial blood lactate, hemodynamics, and cardiac rhythm
  • Planning therapy in a stepwise fashion to avoid overcorrection
  • Aiming for a total CO2 content of about 20 mEq/liter at the end of the first day of therapy to achieve a normal blood pH 2

From the Research

Management of Metabolic Acidosis

To manage metabolic acidosis with hypobicarbonatemia and acidemia, several strategies can be employed:

• Fluid therapy to lower muscle venous Pco2 and ensure effective removal of hydrogen ions by bicarbonate buffer in muscle, as discussed in 3
• Administration of insulin, but with caution in patients with low plasma potassium levels to avoid hypokalemia and cardiac arrhythmias, as suggested in 3
• Use of sodium bicarbonate in adult patients with moderately severe acidemia (pH < 7.20 and plasma bicarbonate level < 12mmol/L) who are at risk for worsening acidemia, particularly if hemodynamically unstable, as recommended in 3
• Avoidance of sodium bicarbonate administration in children with DKA, except in cases of very severe acidemia and hemodynamic instability refractory to saline administration, as advised in 3

Diagnostic Approach

A diagnostic algorithm can be used to identify the underlying cause of metabolic acidosis, including:

• Application of Henderson-Hasselbalch and Stewart methods to diagnose the metabolic acidosis mechanism, as discussed in 4
• Use of ketosis and venous and capillary lactatemia to aid in diagnosis, as mentioned in 4
• Consideration of pH, lactatemia, and its kinetics for patient referral in pre-hospital and emergency departments, as suggested in 4

Bicarbonate Therapy

Bicarbonate therapy may be beneficial in certain cases of metabolic acidosis:

• Limited benefit from bicarbonate therapy for patients with severe metabolic acidosis (pH < 7.1 and bicarbonate < 6 mEq/L), as found in 5
• Improvement in survival for patients with accompanying acute kidney injury, as reported in 5
• Association between early sodium bicarbonate administration and lower ICU mortality in patients with vasopressor dependency, as observed in 6

Treatment Considerations

Treatment of metabolic acidosis should be individualized and based on the underlying cause:

• Cessation of acid production via improvement of tissue oxygenation as the only effective treatment for organic acidosis, as stated in 7
• Controversy surrounding the use of sodium bicarbonate in treating acute metabolic acidosis, with some studies suggesting it fails to reduce morbidity and mortality despite improving acid-base parameters, as discussed in 7