Metabolic Acidosis
Not yet clinically reviewed
This protocol was migrated from the earlier Pharmapedia and Ward Guide apps for educational use. Follow your hospital's own policies and consult seniors when in doubt.
Introduction
Metabolic acidosis is characterized by decreased pH and serum HCO3 − concentrations, which can result from adding organic acid to extracellular fluid (e.g., lactic acid and ketoacids), loss of HCO3 − stores (e.g., diarrhea), or accumulation of endogenous acids due to impaired renal function (e.g., phosphates and sulfates).
Clinical Presentation
- Relatively asymptomatic; major manifestations are bone demineralization with the development of rickets in children and osteomalacia and osteopenia in adults.
- Acute severe metabolic acidemia (pH<7.2) involves the cardiovascular, respiratory, and central nervous systems. Hyperventilation is often the first sign of metabolic acidosis. Respiratory compensation may occur as Kussmaul respirations (i.e., deep, rapid respirations characteristic of diabetic ketoacidosis).
Treatment
- The primary treatment is to correct the underlying disorder. Additional treatment depends on the severity and onset of acidosis.
- Manage asymptomatic patients with mild to moderate acidemia (HCO3 − 12–20mEq/L [12–20 mmol/L]; pH 7.2–7.4) with gradual correction of the acidemia over days to weeks using oral sodium bicarbonate or other alkali preparations.
- Alkali therapy can be used to treat patients with acute severe metabolic acidosis due to hyperchloremic acidosis, but its role is controversial in patients with lactic acidosis. Therapeutic options include sodium bicarbonate and tromethamine. ✓ Sodium bicarbonate is recommended to raise arterial pH to 7.2. However, no controlled clinical studies have demonstrated reduced morbidity and mortality compared with general supportive care. If IV sodium bicarbonate is administered, the goal is to increase, not normalize, pH to 7.2 and HCO3 − to 8 to 10 mEq/L (8–10 mmol/L). ✓ Tromethamine, a highly alkaline solution, is a sodium-free organic amine that acts as a proton acceptor to prevent or correct acidosis. However, no evidence exists that tromethamine is beneficial or more efficacious than sodium bicarbonate. The usual empiric dosage for tromethamine is 1 to 5 mmol/kg administered IV over 1 hour.