Is bicarbonate (bicarb) therapy necessary for a patient with anion gap metabolic acidosis during a prolonged fast?

From the Guidelines

Bicarbonate therapy is generally not necessary for patients with anion gap metabolic acidosis during a prolonged fast. During fasting, the body produces ketones (acetoacetate and beta-hydroxybutyrate) as alternative fuel sources, resulting in a mild to moderate ketoacidosis with an elevated anion gap. This physiologic adaptation is typically self-limiting and resolves with refeeding. The acidosis during fasting is usually well-tolerated by the body and does not require intervention with bicarbonate supplementation. In fact, administering bicarbonate may interfere with the body's compensatory mechanisms and could potentially cause harm by inducing paradoxical central nervous system acidosis or electrolyte imbalances. Some studies, such as the one published in Diabetes Care 1, suggest that bicarbonate may be beneficial in patients with a pH < 6.9, but this is more relevant to diabetic ketoacidosis (DKA) rather than physiologic ketoacidosis from fasting. Key points to consider in management include:

• The body naturally compensates for the acidosis through increased respiratory rate (respiratory compensation) and renal mechanisms
• Providing appropriate nutrition and hydration to break the fast safely is the primary focus of management
• Bicarbonate therapy might be considered if the patient develops severe acidosis (pH < 7.1), has compromised cardiopulmonary function, or shows signs of clinical deterioration.

From the FDA Drug Label

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. Bicarbonate therapy should always be planned in a stepwise fashion since the degree of response from a given dose is not precisely predictable

The use of bicarbonate therapy in a patient with anion gap metabolic acidosis during a prolonged fast is not explicitly indicated in the provided drug labels. However, the labels do provide guidance on the treatment of metabolic acidosis in general.

• The decision to administer bicarbonate should be based on the severity of the acidosis and the clinical condition of the patient.
• Bicarbonate therapy should be planned in a stepwise fashion, with careful monitoring of the patient's response to treatment.
• The labels do not provide specific guidance on the treatment of anion gap metabolic acidosis during a prolonged fast, and therefore, no conclusion can be drawn regarding the necessity of bicarbonate therapy in this specific scenario 2, 2.

From the Research

Anion Gap Metabolic Acidosis in Prolonged Fasting

• Anion gap metabolic acidosis during a prolonged fast can be caused by various factors, including the accumulation of organic acids such as ketoacids or lactic acid 3.
• The calculation of the serum anion gap can aid in diagnosis by classifying the disorders into categories of normal or elevated anion gap 3, 4.
• In the context of a prolonged fast, the development of anion gap metabolic acidosis may not necessarily be worrisome, as it can be a physiological response to the fasting state 3.

Bicarbonate Therapy

• The use of bicarbonate therapy in the treatment of acute metabolic acidosis is controversial due to a lack of definitive benefit and potential complications 3.
• However, in cases of chronic metabolic acidosis, bicarbonate therapy may be associated with improved cellular function and few complications 3.
• The decision to administer bicarbonate therapy should be based on the underlying cause of the metabolic acidosis and the patient's overall clinical condition 3, 5.

Diagnostic Approach

• The anion gap calculation can provide vital clues that direct the clinician toward the correct diagnosis of high anion gap metabolic acidosis 5.
• Other diagnostic methods, such as the Stewart physiochemical and modified base excess methods, can also be used to evaluate complex metabolic acid-base disorders 6.
• A comprehensive diagnostic approach should include the calculation of the anion gap, as well as other relevant laboratory tests and clinical evaluations 7, 4, 5.