Continuous Dialysis with Bicarbonate/Lactate-Buffered Peritoneal Dialysis Fluids Results in a Long-Term Improvement in Ex Vivo Peritoneal Macrophage Function

ABSTRACT. To circumvent the potentially negative consequences of long-term exposure to unphysiologic acidic lactate-buffered peritoneal dialysis fluids (PDF), neutral pH solutions buffered with bicarbonate/lactate have recently been introduced in phase 2 and 3 clinical trials. This study examines the longitudinal changes in peritoneal macrophage (PMO) function in patients dialyzed continuously with either lactate (LPD; 40 mM lactate, pH 5.2)-buffered or bicarbonate/lactate (TBL; 25 mM/15 mM bicarbonate/lactate, pH 7.3)-buffered PDF. Before the study, during the run in period of a phase 3 clinical trial, all patients had been taking LPD for at least the previous 18 wk. At the beginning of the study (day 0), both constitutive and serum-treated zymosan (STZ) stimulated tumor necrosis factor alpha (TNF-α) synthesis were assessed in PMO isolated from 12-h dwell effluent (with 1.36% glucose) in all patients. The patients were subsequently randomized to either continuous TBL or LPD therapy and PMO function was assessed after further 3- and 6-mo periods in all patients. At all time points measured STZ induced a dose-dependent increase in PMO TNF-α secretion ( P = 0.043 versus control for doses greater than 100 μg/ml). In patients continuously dialyzed with LPD, constitutive PMO TNF-α synthesis levels (mean ± SEM, pg/10 6 PMO per18 h, n = 5 patients) were 154 ± 65, 261 ± 60, and 101 ± 99 at 0, 3, and 6 mo, respectively. Stimulated STZ (1000 μg/ml) levels were 1340 ± 519, 1046 ± 586, and 758 ± 250 at 0, 3, and 6 mo, respectively. In patients dialyzed with TBL, constitutive PMO TNF-α synthesis levels (pg/10 6 PMO per 18 h, n = 5 patients) were 300 ± 136, 106 ± 35, and 213 ± 62 at 0, 3, and 6 mo, respectively. Stimulated STZ (1000 μg/ml) levels were 1969 ± 751, 1541 ± 330, and 2670 ± 671 at 0, 3, and 6 mo, respectively. At 6 mo, STZ-stimulated PMO TNF-α synthesis was significantly higher in patients treated with TBL compared with those treated with LPD ( P = 0.0035). These data suggest that in patients continuously dialyzed with a neutral pH solution, there is a long-term improvement in PMO function compared with patients on conventional therapy. Better PMO function suggests improved host defense status and may affect the peritoneum’s susceptibility to infection and potentially reduce the negative consequences of repeated intraperitoneal inflammation on long-term membrane function.