What is the cause of metabolic acidosis due to diarrhea?

From the Guidelines

Metabolic acidosis from diarrhea should be treated primarily by addressing the underlying cause while providing supportive care, focusing on rehydration with isotonic fluids and correcting electrolyte imbalances. The treatment approach involves rehydrating the patient with isotonic fluids like normal saline or lactated Ringer's solution, typically starting with 20-30 mL/kg bolus for adults with significant dehydration, followed by maintenance fluids 1. For severe acidosis (pH <7.2 or bicarbonate <12 mEq/L) with hemodynamic instability, sodium bicarbonate may be administered at 1-2 mEq/kg IV over 1-2 hours. Oral rehydration solutions containing glucose and electrolytes (like WHO formula with 2.9g sodium chloride, 1.5g potassium chloride, 2.9g sodium citrate, and 13.5g glucose per liter) are effective for mild to moderate cases. It is essential to treat the underlying cause of diarrhea, which may include antibiotics for bacterial infections, antiparasitics for parasitic infections, or discontinuation of offending medications. Monitoring electrolytes, particularly potassium, is crucial as correction of acidosis can worsen hypokalemia. The acidosis develops because bicarbonate is normally secreted into the intestines and reabsorbed; with diarrhea, this bicarbonate is lost, leading to decreased serum bicarbonate levels and a compensatory increase in respiratory rate to eliminate carbon dioxide and minimize pH changes. In cases where methemoglobinemia is present due to diarrhea and acidosis, aggressive hydration and bicarbonate to correct the acidosis alone may be sufficient if the methemoglobin level is < 20% 1. Preventive measures, such as hand hygiene, proper food preparation and storage, and avoidance of high-risk foods, can also reduce the incidence of diarrhea and subsequent metabolic acidosis 1.

From the FDA Drug Label

Sodium bicarbonate also is indicated in severe diarrhea which is often accompanied by a significant loss of bicarbonate. Treatment of metabolic acidosis should, if possible, be superimposed on measures designed to control the basic cause of the acidosis Vigorous bicarbonate therapy is required in any form of metabolic acidosis where a rapid increase in plasma total C02 content is crucial - e. g., ... severe dehydration

• Metabolic acidosis from diarrhea can be treated with sodium bicarbonate (IV) as it is often accompanied by a significant loss of bicarbonate.
• The treatment should be used to minimize risks inherent to the acidosis itself, while also addressing the underlying cause of the diarrhea.
• Vigorous bicarbonate therapy may be required in cases of severe dehydration, which can be a complication of diarrhea 2

From the Research

Metabolic Acidosis from Diarrhea

• Metabolic acidosis can occur due to diarrhea, as it leads to the loss of bicarbonate ions in the stool 3.
• The treatment of metabolic acidosis due to diarrhea involves the replacement of lost fluids and electrolytes, including bicarbonate 4.
• In cases of severe dehydration and acidosis, intravenous fluids and bicarbonate may be necessary to restore circulation and correct blood pH levels 4.
• The use of bicarbonate therapy in metabolic acidosis is controversial, and its administration should be individualized based on the patient's clinical situation 3.
• In general, bicarbonate should be given at an arterial blood pH of ≤7.0, and the amount given should be calculated to bring the pH up to 7.2 3.

Treatment Strategies

• Oral rehydration therapy (ORT) is recommended for patients with mild-to-moderate dehydration, using commercially available oral solutions containing 45-75 mEq/l of Na+ 4.
• Intravenous fluids should be used in patients with severe dehydration, with 60-100 ml/kg of 0.9% saline given in the first 2-4 hours to restore circulation 4.
• Oliguric patients with severe acidosis should receive a physiological dose of bicarbonate to correct blood pH levels to 7.25 4.
• The addition of 20 mEq/l K+ to rehydration solutions can help repair cellular K+ deficits without the risk of hyperkalemia 4.

Management of Metabolic Acidosis

• The management of metabolic acidosis should focus on treating the underlying cause of the condition, rather than just the acid-base disorder itself 5, 6.
• The use of bicarbonate therapy in metabolic acidosis can improve clinically relevant endpoints in critically ill patients, even if higher pH values (>7.3) are targeted 6.
• However, bicarbonate therapy can also have serious side effects, and new therapeutics for metabolic acidosis control are being developed 6.