What is the recommended approach to bicarbonate replacement in patients with Heart Failure with preserved Ejection Fraction (HFpEF) and Chronic Kidney Disease (CKD) stage 3?

Bicarbonate Replacement in HFpEF and CKD Stage 3

Recommendation

For patients with HFpEF and CKD stage 3 with serum bicarbonate <22 mmol/L, oral sodium bicarbonate supplementation should be given to maintain serum bicarbonate within the normal range, unless contraindicated by volume overload or uncontrolled hypertension. 1

Rationale for Bicarbonate Supplementation

Metabolic acidosis in CKD is associated with:

• Accelerated progression of kidney disease
• Altered bone and vitamin D metabolism
• Muscle wasting
• Impaired albumin synthesis
• Increased kidney angiotensin II levels 2

The 2012 KDIGO guidelines, endorsed by the Canadian Society of Nephrology, suggest treating CKD patients with serum bicarbonate <22 mmol/L to maintain bicarbonate within the normal range 1. This recommendation is particularly relevant for patients with CKD stage 3, where metabolic acidosis begins to develop but is not yet severe.

Special Considerations for HFpEF Patients

When treating patients with both HFpEF and CKD stage 3:

1. Volume status assessment is critical:

   • HFpEF patients frequently present with volume overload
   • Diuretics should be prescribed first to control volume overload and hypertension 1
   • Only after achieving euvolemia should bicarbonate therapy be considered

2. Blood pressure monitoring:

   • Target BP <130/80 mmHg for both HFpEF and CKD patients 1
   • Sodium load from bicarbonate may worsen hypertension
   • Regular BP monitoring is essential when initiating therapy

3. Medication sequencing:

   • First optimize HFpEF treatment with diuretics for volume control
   • Then add ACE inhibitors/ARBs and beta-blockers for BP control 1
   • Consider bicarbonate supplementation only after optimizing these therapies

Dosing and Administration

• Starting dose: 500-650 mg (6-8 mEq) orally 2-3 times daily
• Titrate to maintain serum bicarbonate within normal range (22-26 mmol/L)
• Alternative: Baking soda from food store (1/4 teaspoon = 1g sodium bicarbonate) may be more economical 1
• Monitor serum bicarbonate every 2-4 weeks during initiation and dose adjustment, then monthly once stable 1

Monitoring Parameters

1. Serum bicarbonate: Target 22-26 mmol/L
2. Blood pressure: Ensure BP remains <130/80 mmHg
3. Volume status: Watch for signs of fluid retention
4. Serum potassium: Monitor for hyperkalemia, especially with concurrent RAAS inhibitors
5. Renal function: Follow eGFR for changes
6. Weight: Monitor for fluid retention

Potential Benefits and Risks

Benefits:

• May slow CKD progression 3, 2
• Improves bone metabolism
• Reduces muscle wasting
• Decreases kidney angiotensin II activity 2

Risks:

• Sodium load may worsen hypertension or heart failure
• Gastrointestinal side effects (bloating, flatulence)
• May increase urinary albumin excretion 4
• Not cost-effective in all populations 5

Important Caveats

1. Evidence quality considerations:

   • The UBI study showed that bicarbonate therapy improved kidney and patient survival in CKD stage 3-5 patients 3
   • However, the BiCARB trial in older adults found no improvement in physical function or quality of life 5
   • Consider individual patient factors when deciding on therapy

2. Contraindications:

   • Uncontrolled hypertension
   • Severe volume overload
   • Severe heart failure exacerbation
   • Hypocalcemia (may worsen with alkalinization)

3. Alternative approaches:

   • Base-producing fruits and vegetables may be as effective as sodium bicarbonate in preserving eGFR with less sodium load 2
   • Consider this approach in patients with significant hypertension or fluid retention concerns

Conclusion

Bicarbonate supplementation should be considered for patients with HFpEF and CKD stage 3 when serum bicarbonate is <22 mmol/L, but only after optimizing volume status and blood pressure control. The treatment approach must balance the potential benefits of correcting acidosis against the risks of increased sodium load in patients with heart failure.