[Relationship between peritoneal equilibration test and surface tension of peritoneal effluent in CAPD patients]

Surface phenomena resulting from interactions between molecules occur commonly in nature. Peritoneal effluent is a mixture of organic and inorganic substances both macro- and micromolecular. Surfactants present in dialysate affect its surface properties. Among them are: proteins, phospholipids, fatty acids. Our aim in this study was to investigate relationships between peritoneal membrane solute transport characteristics and surface tension of peritoneal effluent. The study was conducted in 40 CAPD patients who were stable, without peritonitis (24 M, 16F), age 51.5 +/- 15.8 (range 30-79) mean CAPD duration 26.4 +/- 20.6 months (range 4-72). Standard peritoneal equilibration test (sPET) was done in all patients. Dialysate surface tension (ST) values after 4 hours dewell were determined using Wilhelmy Plate method. Mean ST values of individual dialysate sample based on 10 measurements were calculated. According to the PET values patients were divided into two groups: group 1 (high/high average transporters, n = 26) and group 2 (low average/low transporters, n = 14). Patients in group 1 had significantly lower ST of dialysate than patients in group 2 (51.2 +/- 4.8 vs 57.9 +/- 1.4 mN/m), p<0.01. The lowest values of ST (48.5 +/- 5 mN/m) were found in patients classified as high transporters (n = 8). Correlation's: significant negative correlation was found between ST and D4/P4 for creatinine (r = -0.45, p<0.005) and significant positive correlation between ST and D4/DO for glucose (r = 0.48, p = 0.003). We conclude that there are significant relationships between peritoneal transport status and surface tension of peritoneal effluent. High transporters have significantly higher concentrations of surfactants in dialysis effluent.