The influence of solution composition on protein loss during peritoneal dialysis

A number of recent studies in man [1–3] and rats [1, 4, 5] has investigated the influence of the composition of commercial peritoneal dialysis solutions on the microcirculation and on the removal of solutes during peritoneal dialysis. One of those studies [3] demonstrated that dialysis with a normal osmolality Krebs solution greatly enhanced the concentration of protein in the drainage solution in comparison to that obtained with commercial, 1.5% dextrose solutions. We proposed that these results represented an effect of osmolality on interstitial movement of protein [6]. Since protein movement in the interstitium probably occurs through water channels in the gel-like matrix of the interstitium [7, 8], a change to a high osmolality dialysis solution could dehydrate the interstitium. This would increase the resistance to protein movement and thus decrease the loss of protein in the dialysate. During the first few exchanges, the high osmolality of commercial dialysis solutions could also pull residual protein out of the interstitium because it produced a generalized dehydration of the interstitial tissues. This would lead to large concentrations of protein in the drainage solution during the first few exchanges and then a progressive fall in dialysate protein with subsequent exchanges. An alternative hypothesis to explain such results would be that there is simply a washout of residual protein from the peritoneal cavity or from tissue spaces within the cavity.The following studies were designed to test which of these two hypotheses, an increased resistance to protein movement through dehydration of the interstitial tissue or a washout of residual protein already present in the peritoneal cavity, could explain our previous findings [3]