Medical Term for Low Bicarbonate Levels
The medical term for low bicarbonate levels in the blood is metabolic acidosis, characterized by serum bicarbonate concentrations below 22 mmol/L. 1
Understanding Metabolic Acidosis
- Metabolic acidosis refers to a condition where there is a primary reduction in serum bicarbonate (<22 mmol/L), typically associated with blood pH <7.35 1
- It occurs when there is a relative accumulation of plasma anions in excess of cations, which reduces plasma pH 2
- The body attempts to compensate for metabolic acidosis by increasing ventilation to eliminate CO₂ 1
Classification of Metabolic Acidosis
Metabolic acidosis can be classified based on the serum anion gap:
- Normal anion gap (hyperchloremic) acidosis: Often seen in renal tubular acidosis or diarrhea 2
- High anion gap acidosis: Commonly occurs in conditions like diabetic ketoacidosis, lactic acidosis, or advanced chronic kidney disease 3
- These categories can overlap in some clinical scenarios 2
Causes of Low Bicarbonate
- Renal causes: Decreased ability to excrete acids or reabsorb bicarbonate in chronic kidney disease 4
- Increased acid production: From conditions like diabetic ketoacidosis or lactic acidosis 2
- Gastrointestinal losses: Bicarbonate loss through diarrhea 5
- Diet-related: Western diets high in animal protein and low in fruits and vegetables can lead to chronic low-grade metabolic acidosis 6
Clinical Significance
- Low bicarbonate levels are associated with muscle wasting, bone disease, hypoalbuminemia, and inflammation 4
- In chronic kidney disease, metabolic acidosis can accelerate kidney function decline through multiple pathways 6
- Acidosis stimulates endothelin 1 secretion and angiotensin II production, which may promote renal fibrosis 6
- Correction of acidemia has been associated with increased serum albumin and decreased protein degradation rates 6
Diagnostic Considerations
- A comprehensive evaluation should include measurement of serum bicarbonate, arterial blood gases (to determine pH and PaCO₂), and calculation of the anion gap 1
- It's important to differentiate between true metabolic acidosis and hypobicarbonatemia due to chronic respiratory alkalosis, which can be misdiagnosed 7
- Urine anion gap can be used as a surrogate marker of urine ammonium excretion to help differentiate between metabolic acidosis and chronic respiratory alkalosis 7
Management Implications
- Treatment should focus on addressing the underlying cause of metabolic acidosis 8
- In chronic kidney disease, bicarbonate supplementation is suggested when serum bicarbonate concentration is <22 mmol/L 1, 4
- Sodium bicarbonate supplementation or increased fruit and vegetable intake can help treat high net endogenous acid production 6
- Increasing fruit and vegetable intake not only raises plasma bicarbonate levels but may also decrease systolic blood pressure and body weight 6