Antibacterial peritoneal defence in automated peritoneal dialysis: advantages of tidal over continuous cyclic...

In tidal peritoneal dialysis (TPD) only a part of the infused dialysate is drained with each exchange, leaving a residual volume on top of which fresh fluid is cycled. As the persistent presence of a buffered intraperitoneal reserve volume might favour peritoneal macrophage (PMO) function, PMO obtained from eight patients during a 3-h continuous cyclic peritoneal dialysis (CCPD) or TPD session were studied in a randomized cross-over trial. PMO were studied for uptake of E. coli (complement-dependent) and S. epidermidis (antibody-dependent), as well as for their killing capacity and peak chemiluminescence response. In addition, dialysate was sampled during both treatment sessions and studied for pH, osmolality, and effect on the viability of donor phagocytes and mesothelial cells. TPD-derived PMO were significantly better able to phagocytose E. coli than CCPD-PMO (48 +/- 8 versus 33 +/- 6% uptake, P < 0.05), whereas the other tested functional capacities revealed no significant difference between TPD- and CCPD-PMO. During TPD dialysate pH ranged from 6 to 7 as compared to a pH range from 5 to 7 in CCPD. The presence of a residual dialysate volume resulted in less wash-out of cells and opsonins early in the treatment, and to some extent blunted the noxious effects of fresh dialysis solutions. Overall, however, tidal PD appeared to have no advantage over CCPD regarding preservation of peritoneal defences.