When should sodium bicarbonate be given for metabolic acidosis?

From the Guidelines

Sodium bicarbonate should be administered for metabolic acidosis only in specific clinical scenarios, primarily when pH is severely low (below 7.1) and the acidosis is causing hemodynamic instability or cardiac dysfunction, as stated in the 2010 American Heart Association guidelines 1. The use of sodium bicarbonate in metabolic acidosis is a topic of ongoing debate, with some studies suggesting its use in specific situations, such as severe acidosis, hyperkalemia, or tricyclic antidepressant overdose 1. However, the majority of studies have shown no benefit or found a relationship with poor outcome 1. Some key points to consider when deciding whether to administer sodium bicarbonate for metabolic acidosis include:

• The severity of the acidosis, with a pH below 7.1 being a critical threshold 1
• The presence of hemodynamic instability or cardiac dysfunction, which may be exacerbated by the acidosis 1
• The underlying cause of the metabolic acidosis, which should be treated concurrently with any bicarbonate therapy 1
• The potential risks and complications of sodium bicarbonate therapy, including volume overload, hypernatremia, and paradoxical cerebrospinal fluid acidosis 1 In terms of dosing, an initial dose of 1 mEq/kg is typical, with subsequent dosing guided by serial blood gas measurements and clinical assessment 1. It is essential to note that the primary approach to metabolic acidosis should always focus on treating the underlying cause rather than simply correcting the pH, and that sodium bicarbonate therapy should be used cautiously and only in specific clinical scenarios 1.

From the FDA Drug Label

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 to 10 minutes if necessary (as indicated by arterial pH and blood gas monitoring) to reverse the acidosis. 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.

Sodium bicarbonate administration for metabolic acidosis should be considered in the following situations:

• Cardiac arrest: a rapid intravenous dose of 44.6 to 100 mEq may be given initially, and continued as needed.
• Severe metabolic acidosis: 2 to 5 mEq/kg body weight over a period of 4 to 8 hours may be administered.
• Metabolic acidosis associated with shock: therapy should be monitored closely, with measurement of blood gases, plasma osmolarity, and other parameters. Sodium bicarbonate therapy should always be planned in a stepwise fashion, with careful monitoring of the patient's response 2.

From the Research

Indications for Sodium Bicarbonate in Metabolic Acidosis

• Sodium bicarbonate may be considered for patients with severe metabolic acidosis, defined as a pH < 7.2 with HCO3- < 8 mEq/L in plasma 3.
• The current literature suggests limited benefit from bicarbonate therapy for patients with severe metabolic acidosis (pH < 7.1 and bicarbonate < 6 mEq/L), but it may yield improvement in survival for patients with accompanying acute kidney injury 4.
• Bicarbonate therapy may be beneficial in patients with vasopressor-dependent metabolic acidosis, as it was associated with higher mean arterial pressure at 6 hours and a lower odds ratio for ICU mortality 5.

Administration and Monitoring

• Intravenous NaHCO3 should be administered judiciously, with monitoring of serial evaluation of the internal environment, especially arterial blood gases, plasma electrolytes, and ionized calcium 3.
• Isotonic solutions should be preferred instead of hypertonic bicarbonate to prevent hypernatremia, and calcium should be provided for hypocalcemia to improve cardiovascular function 3.
• The development of hypernatremia, hypokalemia, ionic hypocalcemia, rebound alkalosis, and intracellular acidosis should be prevented or managed promptly 3, 6.

Specific Considerations

• The management of acid-base disorders always calls for precise diagnosis and treatment of the underlying disease, and sodium bicarbonate therapy should be considered as an additional means to combat systemic acidity itself 4.
• Patients with advanced chronic kidney disease may show metabolic acidosis due to increased unmeasured anions and hyperchloremia, and sodium bicarbonate administration might attenuate the negative impact on progression of kidney dysfunction, but further evaluation is required 6.
• Sodium bicarbonate is the predominant buffer used in dialysis fluids, and patients on maintenance dialysis may experience a transient metabolic alkalosis of variable severity during sessions 6.