What changes in peritoneal dialysis (PD) can increase fluid removal?

Peritoneal Dialysis Changes to Increase Fluid Removal

To increase fluid removal in peritoneal dialysis, use icodextrin for long dwells (nocturnal in CAPD, daytime in APD), avoid long-duration dwells with glucose solutions that lead to fluid reabsorption, and increase exchange frequency rather than relying on hypertonic glucose. 1

Optimize Dwell Time Management

The most critical intervention is avoiding long-duration dwells that cause net fluid reabsorption. 1

For APD Patients:

• Shorten or eliminate the daytime dwell by leaving the patient "dry" for part of the day, or drain and replace the day dwell partway through 1
• Alternatively, use icodextrin solution for the long day dwell, which maintains ultrafiltration throughout the dwell without glucose-related reabsorption 1, 2

For CAPD Patients:

• Switch to APD without a long day dwell, or use a night-exchange device to divide the nocturnal dwell into two shorter dwells 1
• Use icodextrin for the long nocturnal dwell to increase peritoneal ultrafiltration and decrease extracellular fluid volume 1, 2

The rationale is that glucose-based solutions lose their osmotic gradient over time, leading to fluid reabsorption after 4-6 hours, whereas icodextrin maintains a sustained osmotic gradient. 1

Increase Exchange Frequency

Increasing the number of exchanges per day enhances ultrafiltration more effectively than increasing dwell volumes alone. 1

• In CAPD, increase from 4 to 5 daily exchanges 1
• This strategy is particularly beneficial for enhancing ultrafiltration, though adherence may be poor and quality of life considerations are important 1
• Increased frequency of exchanges may have greater benefit in enhancing ultrafiltration compared to simply increasing dwell volumes 1

Use Alternative Osmotic Agents

Icodextrin is superior to hypertonic glucose for long dwells. 1, 2

• Randomized controlled trials demonstrate that icodextrin increases peritoneal ultrafiltration and decreases extracellular fluid volume 1, 2
• Icodextrin maintains ultrafiltration throughout long dwells without the membrane damage and metabolic complications associated with hypertonic glucose 1, 2
• Once icodextrin is in place for long dwells, there is no need to drain early to optimize ultrafiltration 1

Novel Approaches:

• Steady concentration peritoneal dialysis (using continuous glucose infusion to maintain intraperitoneal glucose concentration) results in higher ultrafiltration rates (124-168 mL/h vs 40 mL/h with standard dwells) and more efficient glucose use 3

Minimize Hypertonic Glucose Solutions

Avoid consistent use of hypertonic glucose solutions due to peritoneal membrane damage and adverse metabolic effects. 1, 2

• Hypertonic glucose raises concerns about membrane deterioration, supported by recent studies 1
• Increased systemic glucose absorption leads to hyperglycemia, hyperlipidemia, hyperinsulinemia, and obesity 1
• The preferred approach is to optimize dwell times and use icodextrin rather than escalating glucose concentrations 1, 2

Adjunctive Pharmacologic Strategies

For Patients with Residual Kidney Function:

• High-dose loop diuretics enhance urinary sodium and water removal and improve volume status 1, 2
• ACE inhibitors or ARBs maintain urinary volume and clearance better over time 1, 2

Dietary Interventions:

• Restrict dietary sodium intake (<2g/day) to reduce the need for aggressive ultrafiltration 1, 2
• Sodium and water restriction is fundamental to maintaining euvolemia 1

Modality Selection Considerations

CAPD provides greater ultrafiltration and sodium removal than APD cyclers alone. 4

• CAPD achieves ultrafiltration of 650 (300-1100) mL/day vs 337 (103-598) mL/day for APD without a day exchange 4
• CAPD removes 79 (33-132) mmol sodium/day vs 23 (-2 to 51) mmol/day for APD 4
• APD with a daytime exchange provides intermediate results: 474 (171-830) mL/day ultrafiltration and 51 (9-91) mmol/day sodium removal 4
• This difference persists even after adjusting for the flush-before-fill technique in CAPD 4

Critical Monitoring Parameters

Review drain volumes monthly, with particular attention to overnight dwells in CAPD and daytime dwells in APD. 1, 5

• Net peritoneal fluid absorption during long dwells must be identified and corrected 1, 5
• Impaired ultrafiltration affects 3% of patients at 1 year and 31% after 6 years 5
• Total fluid removal (ultrafiltration plus urine volume) is a strong predictor of survival (RR 0.90 for every 100 mL/24h increase) 5

Common Pitfalls to Avoid

• Do not rely solely on hypertonic glucose to achieve ultrafiltration targets, as this damages the peritoneal membrane over time 1, 2, 5
• Do not allow long dwells with glucose-based solutions to continue if drain volumes are inadequate, as this indicates fluid reabsorption 1, 5
• Do not ignore residual kidney function preservation, as this contributes significantly to total fluid removal 2, 5
• In hypertensive or volume-overloaded patients, ultrafiltration should not be negative for any exchanges 5