The effect of increasing hematocrit on peritoneal transport kinetics

Although it is well established that an increase in hematocrit results in a small decrease in solute transport in hemodialysis patients, the effect of hematocrit on solute transport in peritoneal dialysis patients remains controversial. In hemodialysis patients, the inverse relationship between hematocrit and the transport of small solutes may be explained by the dependence of solute clearance on the rapidity of solute movement from the red blood cell to the dialysate. This movement is determined by several in vivo factors, the most important of which is blood flow. However, in peritoneal dialysis, the effective peritoneal capillary blood flow is several times the maximal urea clearance. Therefore, clearances are usually considered to be independent of blood flow rate and variations in hematocrit should not affect solute transport across the peritoneal membrane. In this study, the effect of an increase in hematocrit on the transport of small solutes in peritoneal dialysis patients is analyzed. The peritoneal equilibration test was performed in 25 continuous ambulatory peritoneal dialysis patients before and after an increase in hematocrit of at least seven points. No significant change was found in ultrafiltration rate or in peritoneal transport characteristics as measured by the peritoneal equilibration test or by mass transfer area coefficients for creatinine, urea, or glucose. In addition, there was no change in these parameters in a control group of 13 continuous ambulatory peritoneal dialysis patients with no significant change in hematocrit. These findings are consistent with the observation that solute clearance for urea and creatinine in peritoneal dialysis is not blood flow dependent.(ABSTRACT TRUNCATED AT 250 WORDS)