What is the importance of bicarbonate in the body?

The Importance of Bicarbonate in the Body

Bicarbonate (HCO3-) is a critical buffer in the body that maintains acid-base homeostasis, regulates pH, and supports numerous physiological functions essential for survival.

Acid-Base Regulation

• Bicarbonate is the most predominant extracellular buffer that keeps plasma pH within the physiological range as part of the carbonic acid/bicarbonate (H2CO3/HCO3-) buffer system 1
• Normal serum bicarbonate levels should be maintained at or above 22 mmol/L, particularly in patients with chronic kidney disease or those undergoing maintenance dialysis 2
• Bicarbonate plays a crucial role in neutralizing acids produced through normal metabolism and pathological states 3

Clinical Importance in Metabolic Acidosis

• Bicarbonate therapy is indicated in the treatment of metabolic acidosis which may occur in severe renal disease, uncontrolled diabetes, circulatory insufficiency due to shock, severe dehydration, extracorporeal circulation of blood, cardiac arrest, and severe primary lactic acidosis 4
• In maintenance dialysis patients, maintaining serum bicarbonate at or above 22 mmol/L should be a goal of management to prevent complications of acidemia 2
• Correction of acidemia due to metabolic acidosis has been associated with increased serum albumin, decreased protein degradation rates, and increased plasma concentrations of branched chain amino acids and total essential amino acids 2

Specific Clinical Applications

• Sodium bicarbonate is indicated in the treatment of certain drug intoxications, including barbiturates, salicylates, and methyl alcohol poisoning 4
• It's also used in hemolytic reactions requiring alkalinization of the urine to diminish nephrotoxicity of hemoglobin and its breakdown products 4
• In severe diarrhea, which is often accompanied by significant loss of bicarbonate, sodium bicarbonate replacement may be indicated 4

Limitations and Considerations

• Guidelines suggest against the use of sodium bicarbonate therapy to improve hemodynamics or reduce vasopressor requirements in patients with hypoperfusion-induced lactic acidemia with pH ≥ 7.15 2
• Bicarbonate administration has been associated with sodium and fluid overload, increased lactate and PaCO2, and decreased serum ionized calcium 2
• The effect of sodium bicarbonate administration on hemodynamics and vasopressor requirements at lower pH levels, as well as its effect on clinical outcomes at any pH level, remains uncertain 2

Metabolic Effects

• Acidemia due to metabolic acidosis is associated with increased oxidation of branched chain amino acids (valine, leucine, and isoleucine), increased protein degradation, and decreased albumin synthesis 2
• Correction of acidemia can increase cellular influx and decrease cellular efflux of branched chain amino acids, promoting greater body weight gain and increased mid-arm circumference 2
• In chronic kidney disease patients, correction of acidemia has been associated with fewer hospitalizations 2

Recent Evidence

• A recent target trial emulation found that bicarbonate administration was associated with a small but statistically significant reduction in mortality for patients with metabolic acidosis in intensive care units 5
• The form of bicarbonate supplementation matters - sodium bicarbonate appears more effective than potassium bicarbonate in maintaining bone health during acidosis 6

Administration Guidelines

• For severe acidosis, initial doses of sodium bicarbonate should be carefully titrated based on arterial pH and blood gas monitoring 4
• In less urgent forms of metabolic acidosis, approximately 2 to 5 mEq/kg of body weight may be given over a four-to-eight-hour period, depending on the severity of acidosis 4
• Oral sodium bicarbonate at 2-4 g/day (25-50 mEq/day) can effectively increase serum bicarbonate concentrations in chronic kidney disease patients 2

Bicarbonate's role in maintaining physiological homeostasis cannot be overstated, as it serves as the body's primary defense against potentially life-threatening acid-base disturbances while supporting numerous metabolic processes essential for normal cellular function.