LOSS OF PERITONEAL ULTRAFILTRATION: AN INTERNATIONAL DETECTIVE STORY

The International Ultralfiltration Survey is a cooperative study of ultrafiltration and the various factors, which affect it. The organizers of this survey asked first whether the study could confinn reports of low ultrafiltration rates in many French patients maintained on CAPD. Indeed the first (I) and second (2) reports from the survey have provided this confirmation. Secondly, a significant, inverse relationship has been seen between ultrafiltration rate and glucose absorption. Thirdly, we tried to detennine whether age, time on CAPD, infection rate, or choice of solution brand would identify the patients with relatively lower rates of ultrafiltrati on. Initially, we found significantly lower values of ultrafiltration in patients using solutions containing acetate as a buffer. However, in the first report the lactate solutions almost entirely were from a single company and the acetate solutions were from two other companies. Thus, we could not exclude the possibility that the acetate was an "innocent bystander" and that other major intercompany differences in containers and water purification were responsible for the differences in ultrafiltration. Preliminary data in the second report suggests that acetate may be "innocent" or may be one of several possible factors in a specific brand. Patients using lactate solutions ( other than Brand A) appear to have as low ultrafiltration rates and rapid glucose absorption as those using acetate solutions. Thus, to date, patients with low ultrafiltration usually have used solutions (either lactate or acetate) from companies other than Brand A. These findings are preliminary only. The survey will be expanded to include more patients using brands already in the survey and, hopefully, to patients using still other brands. The early findings are supported by longitudinal analyses from single centers which show progressive decreases in ultrafiltrati on in patients using brands other than Brand A (3). Our survey found little evidence to suggest that age or peritonitis rate make an important contribution to decreasing ultrafiltration. Time on CAPD may be important, but mainly in patients using brands other than Brand A . Many questions remained unanswered. Does rapid glucose absorption and low ultrafiltration indicate peritoneal injury? Are the factors responsible for such injury related to the buffer anion, water contamination, particulate matter or byproducts of glucose decomposition or plastic containers ? Does loss of ultrafiltrati on have any association with eventual development of sclerosing peritonitis? It is of interest that most, if not all, sclerosing peritonitis has been reported in patients previously on intermittent peritoneal dialysis and exposed to acetate containing concentrated solutions or in patients on CAPD using brands other than Brand A. We intend to continue this survey and hope that these observations will stimulate research, which will answer the questions herein.