Physiological saline is not a biocompatible peritoneal dialysis solution

• We have previously demonstrated that daily exposure to dialysis fluid results in significantly increased peritoneal lymphatic flow. In this study, we investigated if daily intraperitoneal infusion of saline (isotonic, glucose free) could cause similar changes. Sixteen male SD rats received daily infusion (i.p) of 20 ml saline for ten days (Saline group). Twenty-four hours after the last infusion, a 4 hour dwell study using 25 ml 3.86% glucose dialysis solution with frequent dialysate and blood sampling was done in each rat as well as in rats which did not receive daily infusion (Control, n=8). Radiolabeled human albumin (RISA) was added to the solution as an intraperitoneal volume marker. Radioactivity, glucose, urea, sodium, and potassium were measured for each sample. In a separate study, the RISA absorption to peritoneal tissue was also determined. Results The net ultrafiltration was significantly decreased in the daily infusion group (p<0.05). However, the apparent volume at 3 minutes of the dwell was markedly increased; this was due to a significant increase in the RISA binding (1.5–12.0% in the Saline group vs. 0.45–1.12% in the Control group) to peritoneal tissues as assessed by measurement of RISA recovery at 3 min of the dwell. This resulted in a significant overestimation both of the intraperitoneal volume (IPV) at 3 min and the (apparent) fluid absorption rate (as estimated by the transport of RISA out of peritoneal cavity): 0.087±0.026 ml/min in the Saline group vs. 0.052±0.007 ml/min in the Control group, p<0.001. The direct lymphatic flow as estimated by the clearance of RISA to plasma (which should not be affected by the RISA binding) also increased markedly (0.021±0.005 ml/min in the Saline group vs. 0.008±0.001 ml/min in the control group). There was no significant difference in the D/P values for small solutes (urea, sodium, potassium, urate) and D/D0 for glucose between the two groups. Conclusions 1) Daily infusion of physiological saline into peritoneal cavity may increase the peritoneal lymphatic flow; 2) The significant (apparent) increase in IPV shortly after infusion may suggest increased RISA binding to peritoneal tissues (which may be related to the damage of the tissues, and results in overestimation of the peritoneal fluid absorption rate); 3) Saline is not a biocompatible peritoneal dialysis solution, and should therefore not be used as a control or flush solution.

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