What is the recommended approach to managing low serum bicarbonate levels in patients with Chronic Kidney Disease (CKD) according to the Kidney Disease: Improving Global Outcomes (KDIGO) CKD Work Group?

Management of Metabolic Acidosis in Chronic Kidney Disease According to KDIGO 2024 Guidelines

A serum bicarbonate of <18 mmol/L should be avoided, although correction of a low serum bicarbonate to the normal range using pharmacological treatment or dietary intervention has not been shown to reduce the risk for kidney failure.

Current Guideline Recommendations

According to the 2024 KDIGO Clinical Practice Guideline for the evaluation and management of CKD, the approach to metabolic acidosis is addressed through practice points rather than formal recommendations, indicating the limited strength of evidence in this area:

• Practice Point 3.10.1: In people with CKD, consider use of pharmacological treatment with or without dietary intervention to prevent development of acidosis with potential clinical implications (e.g., serum bicarbonate <18 mmol/L in adults) 1

• Practice Point 3.10.2: Monitor treatment for metabolic acidosis to ensure it does not result in serum bicarbonate concentrations exceeding the upper limit of normal and does not adversely affect BP control, serum potassium, or fluid status 1

Evidence Analysis and Clinical Implications

Threshold for Intervention

• The KDIGO 2024 guideline specifically mentions serum bicarbonate <18 mmol/L as the threshold at which intervention should be considered in adults with CKD 1
• This is a more conservative threshold than some earlier recommendations that suggested treatment at <22 mmol/L

Efficacy of Interventions

• The KDOQI US Commentary on the KDIGO 2024 guideline notes that clinical trials examining treatment of metabolic acidosis in CKD have been limited 1
• A large clinical trial examining veverimer (to correct metabolic acidosis) did not demonstrate a decline in a composite CKD progression outcome, which was attributed to the lack of difference in serum bicarbonate between treatment and control groups 1

Treatment Options

• Treatment options include:
  • Oral sodium bicarbonate supplementation
  • Dietary interventions (alkaline-rich plant-based diet)
  • Newer agents like veverimer (though evidence for CKD progression is lacking)

Monitoring Considerations

When treating metabolic acidosis in CKD patients:

• Monitor serum bicarbonate levels to avoid exceeding the upper limit of normal
• Watch for adverse effects on:
  • Blood pressure control
  • Serum potassium levels
  • Fluid status 1

Potential Benefits of Treatment

While definitive evidence for reduced kidney failure risk is lacking, treating metabolic acidosis may provide other benefits:

• Reduction in muscle wasting
• Improvement in bone disease
• Potential slowing of CKD progression 2
• Some studies suggest higher serum bicarbonate levels within the normal range may be associated with better outcomes 3, 4

Common Pitfalls and Caveats

1. Fluid overload risk: Sodium bicarbonate supplementation adds sodium load, which may worsen hypertension or fluid retention in susceptible patients
2. Overcorrection: Exceeding normal bicarbonate levels should be avoided
3. Focusing only on bicarbonate: Treatment should be part of comprehensive CKD management
4. Ignoring underlying causes: Addressing the cause of metabolic acidosis is important alongside correction

Conclusion

The current KDIGO 2024 guideline takes a conservative approach to metabolic acidosis management in CKD, recommending intervention primarily when serum bicarbonate falls below 18 mmol/L. While treatment with oral sodium bicarbonate or dietary interventions is suggested at this threshold, there is insufficient evidence to conclude that such interventions definitively reduce the risk of kidney failure.