Antibacterial peritoneal defence in automated peritoneal dialysis: Advantages of tidal over continuous cyclic peritoneal dialysis?

In tidal peritoneal dialysis (TPD) only a part of the infuseddialysate is drained with each exchange, leaving a residualvolume on top of which fresh fluid is cycled. As the persistentpresence of a buffered intraperitoneal reserve volume mightfavour peritoneal macrophage (PMO) function, PMO obtained fromeight patients during a 3-h continuous cyclic peritoneal dialysis(CCPD) or TPD session were studied in a randomized cross-overtrial. PMO were studied for uptake of E. coli (complement-dependent)and S. epidermidis (antibody-dependent), as well as for theirkilling capacity and peak chemiluminescence response. In addition,dialysate was sampled during both treatment sessions and studiedfor pH, osmolality, and effect on the viability of donor phagocytesand mesothelial cells. TPD-derived PMO were significantly better able to phagocytoseE. coli than CCPD-PMO (48 ±8 versus 33±6% uptake,P<0.05), whereas the other tested functional capacities revealedno significant difference between TPD- and CCPD-PMO. DuringTPD dialysate pH ranged from 6 to 7 as compared to a pH rangefrom 5 to 7 in CCPD. The presence of a residual dialysate volumeresulted in less wash-out of cells and opsonins early in thetreatment, and to some extent blunted the noxious effects offresh dialysis solutions. Overall, however, tidal PD appearedto have no advantage over CCPD regarding preservation of peritonealdefences.