Is calcium protective in End-Stage Renal Disease (ESRD) patients on hemodialysis (HD)?

Calcium Management in ESRD Patients on Hemodialysis

For ESRD patients on hemodialysis, a dialysate calcium concentration of 1.50 mmol/L or higher is recommended to maintain neutral or positive calcium balance, which helps prevent secondary hyperparathyroidism and bone mineral density loss while avoiding hypercalcemia. 1

Calcium Balance in ESRD Patients

• Calcium balance in hemodialysis patients is affected by multiple factors including dietary intake, calcium-based phosphate binder use, vitamin D status, dialysate calcium concentration, and ultrafiltration volumes 2
• Patients on intensive hemodialysis who discontinue calcium-based phosphate binders are at particular risk for negative calcium balance when using low calcium dialysate (1.25 mmol/L) 1, 3
• Mass-balance studies have shown that 1.5 mmol/L dialysate calcium is required to maintain neutral calcium balance (without considering calcium from phosphate binders) 1

Benefits of Adequate Calcium Replacement

• Prevents worsening of secondary hyperparathyroidism 1
• Maintains or improves bone mineral density (BMD) 1
• Reduces risk of fragility fractures 1
• Helps manage bone alkaline phosphatase and PTH levels 1
• Improves hemodynamic stability during dialysis, though ultrafiltration rates also play a major role 1

Evidence Supporting Higher Dialysate Calcium

• Studies show that increasing dialysate calcium concentration from 1.25 to 1.75 mmol/L reverses increases in alkaline phosphatase and PTH levels in patients on intensive hemodialysis 1, 2
• Bone mineral density improved in 8 patients, remained stable in 6 patients, and worsened in only 2 patients after 12 months of treatment with higher dialysate calcium 1
• In a study of 38 patients receiving long-frequent hemodialysis, coronary calcification did not worsen after 1 year despite increasing dialysate calcium concentration 1

Potential Risks and Monitoring

• Theoretical risk of positive calcium balance promoting vascular and soft tissue calcification, particularly in patients who continue to require calcium-based phosphate binders and vitamin D 1, 4
• However, current literature consisting of case reports and small cohort studies does not support worsening of vascular or ectopic calcification with appropriate calcium replacement 1, 3
• Regular monitoring of serum calcium, phosphate, PTH, and alkaline phosphatase levels is essential 2
• Rising bone alkaline phosphatase and PTH levels suggest that higher dialysate calcium may be required 1

Algorithm for Calcium Management in ESRD Patients on Hemodialysis

1. Start with dialysate calcium of 1.50 mmol/L 1
2. Monitor serum calcium, phosphate, PTH, and alkaline phosphatase levels regularly 2
3. If alkaline phosphatase and PTH levels increase, consider increasing dialysate calcium up to 1.75 mmol/L 1, 2
4. Consider reducing dialysate calcium if predialysis hypercalcemia or oversuppression of PTH occurs 1
5. Take into account other factors affecting calcium balance:
   • Ongoing use of calcium-based phosphate binders 1
   • Frequency of hemodialysis 1
   • Ultrafiltration volumes 1

Common Pitfalls to Avoid

• Using low calcium dialysate (1.25 mmol/L) in patients who have discontinued calcium-based phosphate binders 1, 3
• Ignoring rising alkaline phosphatase and PTH levels, which may indicate need for higher dialysate calcium 1
• Failure to consider all sources of calcium intake (dietary, binders, dialysate) when managing calcium balance 3
• Excessive focus on phosphate control without considering calcium balance 5