A comparison between 1.36% and 3.86% glucose dialysis solution for the assessment of peritoneal membrane function

OBJECTIVE: To assess peritoneal membrane function with respect to fluid transport, parameters of low molecular weight solute transport, and estimations of the function of peritoneal water channels, comparing the results from a 1.36%/1.5% glucose solution with those from a 3.86%/4.25% solution in standardized peritoneal function tests. DESIGN: The study was performed in 40 stable continuous ambulatory peritoneal dialysis (CAPD) patients [median age 50 years (range: 22-74 years); duration of CAPD 9 months (range: 2-45 months)] who underwent two standard peritoneal permeability analyses (SPAs) within 1 month. One SPA used 1.36% glucose; the other, 3.86% glucose. Mass transfer area coefficients (MTACs) and dialysate-to-plasma (D/P) ratios were compared for the two solutions. Also, two different methods of estimating aquaporin-mediated water transport were compared: the sieving of sodium (3.86% glucose) and the difference in net ultrafiltration (deltaNUF), calculated as NUF 3.86% SPA - NUF 1.36% SPA. RESULTS: Median NUF in the 1.36% glucose SPA was -46 mL (range: -582 mL to 238 mL); in the 3.86% SPA, it was 554 mL (range: -274 mL to 1126 mL). The median difference in NUF for the two SPAs was 597 mL (range: 90-1320 mL). No difference between the two solutions was seen for the MTAC of creatinine (11.4 mL/min for 1.36% vs 12.0 mL/min for 3.86%) and absorption of glucose (64% vs 65%, respectively). Also, D/P creatinine was not different: 0.77 (1.36%) and 0.78 (3.86%). However, the ratio of dialysate glucose at 240 minutes and at 0 minutes (Dt/D0) was 0.34 (1.36%) and 0.24 (3.86%), p < 0.01. Values of D/P creatinine from the two glucose solutions were strongly correlated. The intra-individual differences were small and showed a random distribution. Patient transport category was minimally influenced by the tonicity of the dialysate. The minimum D/P Na+ (3.86%) was 0.884, and it was reached after 60 minutes. After correction for Na+ diffusion, D/P Na+ decreased to 0.849 after 120 minutes. The correlation coefficient between the diffusion-corrected D/P Na+ and the deltaNUF was 0.49, p < 0.01. An inverse relationship was present between MTAC creatinine and D/P Na+ (p < 0.01) This correlation can be explained by the rapid disappearance of the osmotic gradient owing to a large vascular surface area. Such a correlation was not present between MTAC creatinine and deltaNUF. CONCLUSIONS: We conclude that a standardized 4-hour peritoneal permeability test using 3.86%/4.25% glucose is the preferred method to assess peritoneal membrane function, including aquaporin-mediated water transport. The D/P Na+ after correction for Na+ diffusion is probably more useful for the assessment of aquaporin-mediated water transport than is deltaNUF obtained with 3.86%/4.25% and 1.36%/1.5% glucose-based dialysis solutions