What is the approach to managing hyponatremia in patients with end-stage renal disease (ESRD) on peritoneal dialysis (PD) versus hemodialysis (HD)?

Approach to Hyponatremia in PD vs HD Patients

In dialysis patients with hyponatremia, the management strategy fundamentally differs between modalities: for HD patients, adjust the dialysate sodium to 128-130 mEq/L with reduced blood flow rates to control correction speed, while for PD patients, switch from APD to manual CAPD with shorter, more frequent exchanges to prevent fluid reabsorption that worsens hypervolemic hyponatremia. 1, 2, 3

Initial Assessment Common to Both Modalities

• Rule out non-volume causes first: Evaluate for hypothyroidism, hypoaldosteronism, and medication effects before attributing hyponatremia solely to volume overload 1
• Assess residual kidney function (RKF): Lower RKF is strongly associated with hyponatremia in dialysis patients, with hyponatremic patients having significantly lower RKF (1.97 ± 2.3 mL/min vs 4.31 ± 5.01 mL/min in normonatremic patients) 4
• Check serum potassium: Falls in serum sodium correlate with lower potassium levels, suggesting sodium and potassium depletion from malnutrition may contribute to hyponatremia in the clinical setting 4

Hemodialysis-Specific Management

Dialysis Prescription Modifications

• Use low dialysate sodium concentration (128-130 mEq/L) to control the rate of sodium correction and prevent overly rapid rises that risk osmotic demyelination syndrome 2, 3
• Reduce blood flow rate to 50 mL/min initially to achieve a controlled sodium rise of approximately 1-2 mEq/L per hour during the first HD session 2, 3
• Gradually increase blood flow to 100 mL/min in subsequent sessions once initial correction is underway, allowing sodium to rise by approximately 2 mEq/L per hour 2
• Target sodium correction of 4-8 mEq/L per day, not exceeding 10-12 mEq/L in 24 hours to minimize risk of osmotic demyelination syndrome 5

Volume Management

• Gently probe and adjust target dry weight downward to address the underlying volume overload driving hypervolemic hyponatremia 1
• Increase treatment time and/or frequency to improve volume control and sodium removal without rapid shifts 6, 1
• Optimize ultrafiltration rate to balance achieving euvolemia while minimizing hemodynamic instability 1

Adjunctive Measures

• Restrict dietary sodium to 2-3 g/day to reduce interdialytic weight gain and improve volume control 6, 1
• Limit fluid intake between sessions to minimize volume accumulation 1
• Consider high-dose loop diuretics in patients with residual kidney function to enhance urinary sodium and water removal 6, 1

Peritoneal Dialysis-Specific Management

Critical Modality Adjustment

• Switch from APD to manual CAPD when hyponatremia and volume overload are present, as long APD day dwells (8-16 hours) cause net peritoneal fluid reabsorption that directly worsens hypervolemic hyponatremia 7, 1
• Implement 4-5 shorter exchanges per day with CAPD to prevent the fluid reabsorption that occurs with prolonged dwells and maximize cumulative ultrafiltration 7, 1
• Never allow negative ultrafiltration (fluid absorption) in any exchange when managing volume overload and hyponatremia, as this directly worsens the clinical condition 7, 1

Solution and Dwell Time Optimization

• Use icodextrin solution for any necessary long dwells to maintain ultrafiltration throughout extended dwell times, as RCTs demonstrate it increases peritoneal ultrafiltration and decreases extracellular fluid volume 7, 6, 1
• Shorten dwell times with glucose-based solutions especially for high and high-average transporters who experience rapid equilibration and fluid reabsorption 7, 1
• Avoid or eliminate long day dwells in APD that allow significant fluid reabsorption over 8-16 hours 7, 1

What NOT to Do in PD

• Do not rely on hypertonic 4.25% glucose solutions to compensate for poor ultrafiltration, as frequent use damages the peritoneal membrane and causes adverse metabolic effects 7, 1
• Do not assume standard APD provides adequate volume control in patients with fluid overload—modality selection must prioritize ultrafiltration capacity over convenience 7, 1
• Fluid restriction is rarely effective in dialysis patients with hypervolemic hyponatremia and should not be the primary intervention 1

Additional PD Strategies

• Preserve residual kidney function through avoiding nephrotoxins and intradialytic hypotension, as RKF is strongly associated with better volume control and higher serum sodium levels 6, 1, 4
• Restrict dietary sodium intake if persistent hyponatremia and fluid overload are present 6, 1
• Monitor icodextrin use: Serum sodium correlates negatively with daily volume of instilled icodextrin (r = -0.476, p = 0.0001), suggesting careful monitoring is needed 4

Monitoring and Follow-up for Both Modalities

• Assess volume status and serum sodium monthly in stable patients 1
• Evaluate drain volume (PD), residual kidney function, and dietary compliance at each assessment 1
• Monitor for osmotic demyelination syndrome with onset typically 2-7 days after rapid sodium correction, presenting with seizure, encephalopathy, dysarthria, dysphagia, oculomotor dysfunction, and quadriparesis 5

Emergency Considerations

• Vasopressin antagonists (vaptans) may be considered short-term in hospitalized patients with persistent severe hyponatremia despite optimized dialysis prescription and active cognitive symptoms, though evidence in dialysis populations is limited 1
• Hypertonic saline administration (outside of emergency symptomatic cases) is only partially effective, short-lived, and increases ascites/edema in hypervolemic states 1

Key Pitfall to Avoid

The most common error is assuming hyponatremia in dialysis patients requires fluid restriction or hypertonic saline—instead, the primary intervention is optimizing the dialysis prescription to achieve euvolemia through controlled sodium removal (HD) or preventing fluid reabsorption (PD). 1