What is the treatment for a Comprehensive Metabolic Panel (CMP) showing low carbon dioxide (CO2) levels, specifically 18, indicating metabolic acidosis?

From the Guidelines

A CO2 level of 18 on a Comprehensive Metabolic Panel (CMP) indicates mild metabolic acidosis, which requires treatment to address the underlying cause, and according to the most recent evidence, pharmacologic treatment should be considered when bicarbonate < 18 mmol/l 1. The immediate recommendation is to identify and treat the primary condition causing the low bicarbonate level.

• Common treatments include oral sodium bicarbonate supplements (650-1300 mg 1-4 times daily) for mild cases, or IV sodium bicarbonate for severe cases.
• Addressing fluid status with IV fluids containing bicarbonate may be necessary if dehydration is present.
• The underlying cause must be identified, which could include kidney disease, diabetic ketoacidosis, severe diarrhea, or certain medications.
• Monitoring of electrolytes and acid-base status should continue during treatment, ensuring that treatment does not result in serum bicarbonate concentrations exceeding the upper limit of normal and does not adversely affect BP control, serum potassium, or fluid status 2. This low CO2 level reflects decreased bicarbonate in the blood, which serves as an important buffer to maintain blood pH.
• Without adequate bicarbonate, the blood becomes more acidic, potentially affecting multiple organ systems and causing symptoms like fatigue, shortness of breath, and confusion.
• Treatment aims to restore normal acid-base balance while addressing the primary condition, and a reasonable goal would be to increase bicarbonate levels toward but not greater than the normal range with sodium bicarbonate or other agents 1.

From the FDA Drug Label

In general, it is unwise to attempt full correction of a low total CO2 content during the first 24 hours of therapy, since this may be accompanied by an unrecognized alkalosis because of a delay in the readjustment of ventilation to normal Owing to this lag, the achievement of total CO2 content of about 20 mEq/liter at the end of the first day of therapy will usually be associated with a normal blood pH. 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

The treatment for a CO2 level of 18 is sodium bicarbonate (IV). The dose is approximately 2 to 5 mEq/kg of body weight over a period of 4 to 8 hours, depending on the severity of the acidosis. The goal is to achieve a total CO2 content of about 20 mEq/liter at the end of the first day of therapy, which will usually be associated with a normal blood pH 3.

From the Research

Metabolic Acidosis Treatment

• The treatment of metabolic acidosis is controversial, with some studies suggesting that bicarbonate therapy may not be effective in reducing morbidity and mortality 4.
• Bicarbonate therapy is indicated for patients with severe metabolic acidosis, particularly those with an arterial blood pH of < or =7.0 5.
• The amount of bicarbonate given should be calculated to bring the pH up to 7.2 5.
• However, the current literature suggests limited benefit from bicarbonate therapy for patients with severe metabolic acidosis (pH < 7.1 and bicarbonate < 6 mEq/L) 6.
• Bicarbonate therapy may be beneficial for patients with accompanying acute kidney injury 6.

CO2 Levels and Metabolic Acidosis

• Metabolic acidosis is characterized by a primary reduction in serum bicarbonate (HCO(3)(-)) concentration, a secondary decrease in the arterial partial pressure of carbon dioxide (PaCO(2)) 7.
• The calculation of the serum anion gap, calculated as [Na(+)] - ([HCO(3)(-)] + [Cl(-)]), aids diagnosis by classifying the disorders into categories of normal (hyperchloremic) anion gap or elevated anion gap 7.
• CO2 levels, such as CO2 18, may be relevant in the diagnosis and treatment of metabolic acidosis, but the exact relationship is not clearly established in the provided studies.

Treatment Strategies

• The management of acid-base disorders always calls for precise diagnosis and treatment of the underlying disease 6.
• The use of base to treat acute metabolic acidosis is controversial because of a lack of definitive benefit and because of potential complications 7.
• New therapeutics for acute metabolic acidosis control are under development, since bicarbonate treatment can induce serious side effects 8.
• Bicarbonate has been shown to improve clinically relevant endpoints in the critically ill, even if higher pH values (>7.3) are targeted 8.