What is the treatment for metabolic acidosis?

Treatment of Metabolic Acidosis

The primary treatment for metabolic acidosis is addressing the underlying cause while maintaining serum bicarbonate at or above 22 mmol/L, which may require sodium bicarbonate administration for metabolic acidosis or ventilatory support for respiratory acidosis. 1

Approach to Treatment

• Treatment should always be directed at the underlying cause of metabolic acidosis, such as insulin for diabetic ketoacidosis, restoring tissue perfusion in lactic acidosis, or addressing the specific type of renal tubular acidosis 1
• Sodium bicarbonate is indicated in the treatment of metabolic acidosis which may occur in severe renal disease, uncontrolled diabetes, circulatory insufficiency due to shock, severe dehydration, extracorporeal circulation of blood, cardiac arrest, and severe primary lactic acidosis 2
• Sodium bicarbonate should NOT be used to treat metabolic acidosis arising from tissue hypoperfusion in sepsis without careful consideration, as it may worsen intracellular acidosis 3, 4

Sodium Bicarbonate Administration

• For severe metabolic acidosis (pH < 7.1 and bicarbonate < 6 mEq/L), sodium bicarbonate therapy may have limited benefit but can improve survival in patients with accompanying acute kidney injury 5
• 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 5-10 minutes if necessary 2
• For less urgent forms of metabolic acidosis, the recommended dose is approximately 2-5 mEq/kg of body weight over a 4-8 hour period, depending on the severity of acidosis 2
• For chronic metabolic acidosis, oral sodium bicarbonate at 2-4 g/day (25-50 mEq/day) is suggested 1

Monitoring and Precautions

• Bicarbonate therapy should always be planned in a stepwise fashion since the degree of response from a given dose is not precisely predictable 2
• It is generally unwise to attempt full correction of a low total CO2 content during the first 24 hours of therapy, as this may lead to unrecognized alkalosis due to delayed ventilatory adjustment 2
• Monitoring should include blood gases, plasma osmolarity, arterial blood lactate, hemodynamics, and cardiac rhythm 2
• Caution should be observed when rapidly infusing large quantities of bicarbonate as solutions are hypertonic and may produce an undesirable rise in plasma sodium concentration 2
• Regular monitoring of electrolytes, particularly potassium levels, is crucial as acidosis can cause hyperkalemia due to transcellular shift of potassium 3

Special Considerations

• For chronic kidney disease patients, the American Journal of Kidney Diseases recommends treating acidosis when serum bicarbonate is consistently < 18 mmol/L to prevent bone and muscle metabolism abnormalities 3
• For diabetic ketoacidosis, focus on insulin therapy, fluid resuscitation, and electrolyte replacement rather than bicarbonate, as bicarbonate has not been shown to improve resolution of acidosis or time to discharge 3, 1
• For patients with mixed acidosis with high PaCO2 levels, THAM (tris(hydroxymethyl)aminomethane) may be preferred over sodium bicarbonate as it doesn't increase PaCO2 6
• THAM may also be the alkalizing agent of choice in patients with hypernatremia, as it leads to a decrease in serum sodium, while sodium bicarbonate increases it 6
• For patients with hyperkalemia, sodium bicarbonate is preferred over THAM as it decreases serum potassium levels 6

Evidence from Recent Research

• A 2018 multicenter randomized controlled trial (BICAR-ICU) found that in patients with severe metabolic acidemia, sodium bicarbonate had no effect on the primary composite outcome of death and organ failure in the general population 7
• However, the same trial showed that sodium bicarbonate decreased mortality in the subgroup of patients with acute kidney injury 7
• Potential adverse effects of bicarbonate administration include exacerbation of intracellular acidosis, reduction in ionized calcium, and production of hyperosmolality 8

Remember that while treating the biochemical abnormality is important, addressing the underlying cause of metabolic acidosis remains the cornerstone of therapy.