Changes of surface tension of dialysate depending on its composition in continuous ambulatory peritoneal dialysis

Surface phenomena resulting from interactions among molecules occur commonly in nature. Surfactants, substances with surface activity, have a big influence on surface tension. They reduce surface tension when added to the solution, even in minimal concentration. The behaviour of surface tension of the dialysate is difficult to properly assess, because of its complex composition. Dialysate is a mixture of organic and inorganic substances, both macro- and micromolecular. Among them are proteins, phospholipids, fatty acids. In the literature there are no publications showing the behaviour of surface tension of the dialysate. The aim of the study was the assessment of changes of dialysate surface tension in non-complicated continuous peritoneal dialysis (CAPD), depending on time of the presence of dialysis fluid in the peritoneal cavity and on the concentration of different substances in it. The study was performed on 39 dialysate samples obtained from 6 patients chronically treated with continuous ambulatory peritoneal dialysis (CAPD). During the study patients had no symptoms of peritonitis. Surface tension of the dialysate was determined, using the Wilhelmy's method. Ten measurements were performed in every sample of the dialysate and the mean values and standard deviation were calculated. Simultaneously the concentrations of sodium, glucose, urea, creatinine, total protein were measured in the dialysate. As a result of the study a significant negative correlation between dialysate protein concentration and surface tension was found. The significant negative correlation between surface tension and the dwell time was also found. There was no significant correlation between the value of surface tension of the dialysate and concentrations of glucose, urea, creatinine and sodium.