Two-in-one protocol: simultaneous small-pore and ultrasmall-pore peritoneal transport quantification

Area of Science:

• Nephrology
• Peritoneal Dialysis
• Membrane Physiology

Background:

• Reduced free water transport (FWT) through ultrasmall pores is linked to net ultrafiltration failure (UFF) in peritoneal dialysis (PD).
• The modified peritoneal equilibration test (PET) estimates FWT by measuring the dialysate sodium (Na) concentration dip.
• Current methods may not fully capture FWT and small-pore ultrafiltration (SPUF) dynamics simultaneously.

Purpose of the Study:

• To simultaneously quantify small-solute transport, FWT, and SPUF during a single modified PET procedure.
• To assess the feasibility of measuring FWT and SPUF in PD patients.
• To investigate the relationship between FWT, SPUF, and UFF.

Main Methods:

• A 4-hour, 3.86% glucose PET was conducted in 70 PD patients.
• Ultrafiltration (UF) was measured at 60 minutes.
• Calculations included dialysate-to-plasma ratios (D/P) of creatinine and Na, Na dip, and delta dialysate Na (ΔDNa(0-60)) to determine FWT and SPUF.

Main Results:

• Sodium sieving strongly correlated with corrected FWT (r = 0.41, p = 0.005).
• Total UF correlated better with FWT (r = 0.46, p < 0.0001) than with Na sieving measurements.
• UFF patients exhibited lower FWT (89 mL vs 164 mL, p < 0.05) and higher D/P creatinine (0.75 vs 0.70, p < 0.05) compared to normal UF patients.

Conclusions:

• Simultaneous measurement of FWT and SPUF is feasible during a modified 3.86% glucose PET.
• FWT is a crucial parameter for detecting UFF causes, alongside increased effective capillary surface.
• Longer PD vintage was associated with reduced UF and FWT.