[Dilution index as a candidate parameter reflecting dialysis dose in combined peritoneal dialysis and hemodialysis therapy].

Combined peritoneal dialysis and hemodialysis therapy (combined therapy) is recognized as an effective alternate in peritoneal dialysis patients with insufficient water and solute removal, but there is no appropriate index for dialysis dose, as two distinct dialysis procedures are utilized in the same patient. Among several candidate parameters, the dilution index proposed and defined by Yamada, et al as the solute generation rate divided by the distribution volume and time-averaged concentration of the solute might be applicable, because it is unrelated to the method of solute removal. Among 11 patients undergoing combined therapy at Toride Kyodo General Hospital, six patients who had transferred from peritoneal dialysis alone to combined therapy were recruited. All patients received peritoneal dialysis therapy for five consecutive days followed by one day off dialysis before a hemodialysis session on the seventh day every week. Total weekly creatinine and urea removal by residual renal function, peritoneal dialysis, and hemodialysis were measured, and their solute removal on the last(5th) day under peritoneal dialysis was ascertained and correlated with the averaged daily removal of solutes. Hence the value of solute removal obtained on the last day under peritoneal dialysis was multiplied seven times and defined as the weekly solute generation. The distribution volumes of creatinine and urea were defined as 58% of body weight. The time-averaged concentration was obtained from the mean level of a solute before and after a hemodialysis session. During the period followed solely by peritoneal dialysis, the dilution indices for creatinine and urea were 1.22 +/- 0.14 and 1.85 +/- 0.14, respectively. The dilution index after transferring to combined therapy, calculated by the above-mentioned method was increased to 1.72 +/- 0.29 and 2.28 +/- 0.31, respectively. Hence the dilution index may be useful for reflecting dialysis doses even in combined therapy.