In vitro effects of bicarbonate- versus lactate-buffered continuous ambulatory peritoneal dialysis fluids on peritoneal macrophage function

Peritoneal Defense Using Icodextrin Or Glucose for Daytime Dwell in Ccpd Patients

Objective

To investigate peritoneal defense during icodextrin use in continuous cyclic peritoneal dialysis (CCPD).

Design

In an open, prospective, 2-year follow-up study, CCPD patients were randomized to either glucose (Glu) or icodextrin (Ico) for their long daytime dwell.

Setting

University hospital and teaching hospital.

Patients

Both established and patients new to CCPD were included. A life expectancy of more than 2 years, a stable clinical condition, and written informed consent were necessary before entry. Patients aged under 18 years, those who had peritonitis in the previous month, and women of childbearing potential, unless taking adequate contraceptive precautions, were excluded. Thirty-eight patients (19 Glu, 19 Ico) started the study. The median follow-up was 16 and 17 months for Glu and Ico respectively (range 0.5 – 25 months and 5 – 25 months, respectively).

Outcome Measures

Peritoneal defense characteristics and peritoneal dialysis-related infections were recorded every 3 months.

Results

Total peritoneal white cell count tended to decrease over time in both groups. After 1 year, absolute numbers and percentages of effluent peritoneal macrophages (PMΦs) were significantly higher in Ico than in Glu patients; this difference in the percentage persisted after 2 years. Percentage of mesothelial cells increased over time in Ico patients. The phagocytic capacity of PMΦs decreased over time, resulting in a borderline significant difference for coagulase-negative staphylococci ( p = 0.05) and a significant difference for Escherichia coli ( p < 0.05) phagocytosis in favor of Ico patients. PMΦ oxidative metabolism remained stable over time without a difference between the groups. PMΦ cytokine production and effluent opsonic capacity also remained stable over time. Finally, 16 peritonitis episodes in Glu and 14 in Ico patients occurred. Glucose patients had 37 and Ico patients 32 exit-site infections during the study.

Conclusion

CCPD patients using Ico did equally as well as Glu-treated patients with respect to clinical infections and most peritoneal defense characteristics. However, in a few peritoneal defense tests, Ico-treated patients did better.

A Randomized Controlled Trial of a Bicarbonate and a Bicarbonate/Lactate-Containing Dialysis Solution in Capd

Objective

To evaluate the safety and efficacy of bicarbonate and bicarbonate/lactate-based PD fluids.

Design

A randomly allocated prospective controlled trial lasting eight weeks.

Setting

Five renal units in Europe.

Patients

Individuals who have been treated by CAPD for at least three months and who have had at least one month's therapy with 40 mmol/L lactate PD fluid. Those with recent infection, diabetes or other serious illness are excluded. Forty-seven individuals have entered the study so far.

Interventions

Patients are randomly allocated to three groups. Group 1 receive 40 mmol/L lactate dialysate, Group 2 are given 38 mmol/L bicarbonate fluid and Group 3 are tested with a 25 mmol/L bicarbonate and 15 mmol/L lactate dialysate.

Outcome measures

The primary outcome measure is the plasma bicarbonate level. Adverse events and ease of use of the two-chambered bags used by Groups 2 and 3 are also being assessed.

Results

To date, plasma bicarbonate levels have been the same in all treatment groups up to the end of the trial period. There are no differences in serum lactate levels. No side effects are attributable to the test fluids. The patients have managed the two-chambered bags successfully.

Conclusion

This trial is still ongoing, but to date, neutral bicarbonate based fluids have been as effective as lactate dialysate in treating uremic acidosis.

Plasticizers and Inhibition of Leukocyte Function in Vitro

Objectives

To evaluate the influence of the plasticizer metabolites of di(2-ethylhexyl)phthalate (DEHP), mono(2-ethylhexyl)phthalate (ME HP), 2-ethylhexanol (2-EH), and phthalic acid (PA) on various immune functions of poly-morphonuclear blood leukocytes (PMNL) and monocytes (MN). ME HP, 2-EH, and PA are the main hydrolysis products of DE HP. Since DE HP is leached out of the plastic matrix, patients on hemodialysis and continuous ambulatory peritoneal dialysis are exposed to considerable amounts of DE HP and its metabolites.

Setting

Teaching hospital, Department of Nephrology.

Participants

Ten healthy volunteers.

Measurements

After incubation of leukocytes in solutions with different plasticizer concentrations, oxidative respiratory metabolism was determined by luminolenhanced chemiluminescence (CL) after stimulation with phorbol myristate acetate (PMA). Furthermore, superoxide (02) generation was measured by cytochrome c reduction.

Results

At pH 5.4, a dose-dependent decrease of luminol-enhanced CL response was found in all assays. For ME HP and PA the level of significance was reached at 10 mg/L and 1 mg/L, respectively. Superoxide generation by PMNL and MN at pH 5.4 was also suppressed by ME HP and PA. At pH 7.4, only a slight suppression of oxidative metabolism at higher concentrations was observed. After incubation of the cells in a solution containing all DE HP metabolites (ME HP, PA, and 2-EH), a significant suppressive effect of CL at pH 5.4 could be observed at final plasticizer concentrations of 0.5 mg/L.

Conclusions

A dose-dependent impairment of leukocyte oxidative metabolism at a low pH could be demonstrated. The suppressive effect was particularly marked after incubation of the cells in solutions containing a mixture of the main plasticizers. At pH 5.4, we observed a slight alteration even at concentrations very close to those that could be found in commercially available peritoneal dialysis fluids. These results might point toward a possible synergistic detrimental effect of the different DE HP metabolites on leukocyte function, with possible clinical relevance.

Acidosis Correction with a new 25 Mmol/L Bicarbonate/15 Mmol/L Lactate Peritoneal Dialysis Solution

Objective

The aim of this study was to evaluate the effects of a combined 25 mmol/L bicarbonate/15 mmol/L lactate-based solution (Bic/Lac), compared to a 35 mmol/L lactate solution (Lac) — the most commonly used solution for patients in southern Europe — on the venous plasma bicarbonate level in patients treated with continuous ambulatory peritoneal dialysis (CAPD).

Design

This was a randomized, parallel, controlled, open-label study, with patients studied for a period of 3 months preceded by a 1-month baseline and followed by a 1-month follow-up. Patients used the 35 mmol/L lactate solution during baseline and follow-up periods.

Setting

Four Spanish nephrology centers.

Patients

Thirty-one (20 Bic/Lac, 11 Lac) well-dialyzed (creatinine clearance > 55 L/week/1.73 m2body surface area) CAPD patients.

Interventions

Blood samples were taken for biochemistry tests at all visits. A physical examination was completed at baseline and month 3, and a medical update was completed after 1, 2, and 3 months, and at the follow-up visit. Adverse-event monitoring and notation of prescription changes were carried out continuously.

Main Outcome Measure

Effect on venous plasma bicarbonate level.

Results

Venous plasma bicarbonate rose by 3.1 mmol/L (confidence intervals 1.6 – 4.8), from a baseline level of 23.0 mmol/L during the treatment period in those patients treated with Bic/Lac ( p < 0.05 vs Lac). The number of acidotic patients (venous plasma bicarbonate < 24 mmol/L) was statistically significantly reduced at every treatment period visit in the Bic/Lac group ( p < 0.05). There were no adverse findings with respect to vital signs, physical examination, or clinical symptoms, apart from one death in the control group.

Conclusions

The new Bic/Lac solution allowed better correction of acid–base status than the lactate solution.

Effect of Bicarbonate-Based Dialysis Solutions on Intracellular Ph (Phi) and Tnfα Production by Peritoneal Macrophages

Objective

To compare the effect of Dianeal and two newly-formulated bicarbonate-based peritoneal solutions on intracellular pH (pHi), tumor necrosis factor-α (TNFα) mRNA level, and TNFα secretion by peritoneal macrophages (PMΦ).

Design and Measurements

Peritoneal macrophages were isolated from dialysates collected after overnight dwells in peritonitis -free continuous ambulatory peritoneal dialysis patients. Dialysis solutions contained 1.5% or 4.25% dextrose. HCO3 concentrations of bicarbonate(TB)and bicarbonate/lactate-buffered (TBL) solution were 38 mM and 25 mM, respectively. TBL also contained lactate at a concentration of 15 mM. pCO2 levels were 78 mmHg and 51 mmHg, respectively. In all experiments pC02 was carefully maintained at a stable level. The pHi was measured by spectrofluorometry in BCECF-Ioaded PMΦ exposed to different dialysis solutions or Hank's balanced salt solution. TNFα levels were measured by ELISA in the supernatant of lipopolysaccharide (LPS) stimulated PMΦ after their incubation in different solutions for 15 and 30 minutes. TNFα mRNA was measured by reverse transcriptase polymerase chain reaction (RT PCR) of total RNA extracted from LPS-stimulated PMΦ after their incubation in different solutions for 30 minutes. β-actin mRNA was used as the control.

Results

Dianeal caused a profound drop in pHi to below 6.2. Following an initial drop, pHi stabilized after 4 minutes at levels of 6.96 and 6.8 after incubation in TB and TBL, respectively. In comparison to the control solution, a fall of 11% and 21% in TNFα secretion was seen after incubation in TB for 15 and 30 minutes, respectively, and 15% and 26% after incubation in TBL. Under identical conditions, Dianeal (Baxter, McGaw Park, IL, U.S.A.) caused 59% and >95% suppression of TNFα secretion. Accordingly, TNFα mRNA level in PMΦ was severely depressed by Dianeal but no detectable inhibition was observed following incubation for 30 minutes in TB and TBL. When dextrose concentration in TB and TBL was increased from 1.5% to 4.25%, TNFα secretion by PMΦ was not suppressed by more than 49%, even after 30 minutes incubation. Moreover, suppression of TNFα mRNA levels could not be detected with TB or TBL even at high dextrose concentrations.

Conclusions

In contrast to Dianeal, both bicarbonate based solutions caused only a mild drop in pHi of PMΦ. We postulate this effect to be responsible for the improved capacity of PMΦ to secrete TNFα when incubated in bicarbonate-based solutions compared to Dianeal. Reflecting its known cytotoxicity, dextrose in high concentrations diminishes the protective effect of TB and TBL on immune function of PMΦ. TBL is as effective as TB in preventing the deleterious effect of Dianeal on PMΦ function.

Effects of a pH 7.4, lactate-based and a pH 7.4, bicarbonate-based peritoneal dialysis solutions on neutrophil superoxide generation

Neutrophil superoxide formation was similar when cells were incubated in self-made, non-autoclaved, pH 7.4, lactate-based peritoneal dialysis solutions or in their self-made, non-autoclaved, pH 7.4, bicarbonate-based counterparts. On the other hand, commercially available, autoclaved, pH 7.4, lactate-based peritoneal dialysis solutions resulted in inhibition of superoxide production when compared to their self-made, non-autoclaved, pH 7.4, lactate-based or bicarbonate-based counterparts. The cause for this inhibition of superoxide generation is at present unknown.

Peritoneal Dialysis Fluid-Induced Fragmentation of Golgi Apparatus as a Biocompatibility Marker

In vitro biocompatibility assessments that consider physiologically appropriate conditions of cell exposure to peritoneal dialysis fluids (PDFs) are still awaited. In this study, we found that fragmentation of Golgi apparatus occurred in a pH-dependent manner within 30-min exposure to five distinct commercially available PDFs, which showed no marked difference in their effects on cell viability in the conventional MTT assay. Fluorescence microscopy analysis of labeling antibody against cis-Golgi protein GM130 indicated that the stacked cisternal structure was maintained in the perinuclear area of both M199 culture medium and a neutral-pH PDF groups. However, this specific structure became partially disassembled over time even in a neutral-pH PDF, and fragmentation was markedly enhanced in cells exposed to neutralized-pH PDFs in correspondence with their intracellular pH; moreover, in acidic PDFs, Golgi staining was diffuse and scattered in the entire cytoplasm and showed partial aggregation. The Golgi fragmentation markedly observed with the neutralized PDFs could be reversed by replacing either the media with a neutral-pH medium or a mixture of PDF and PD effluent (PDF) in a gradient manner mimicking clinical conditions. Furthermore, although weaker than pH effect, notable effects of other PDF-related factors were also observed after 30-min exposure to pH-adjusted PDFs. Lastly, the results of studies conducted using MAPK/SAPK inhibitors indicated that the mechanism underlying the Golgi fragmentation described here differs from that associated with the fragmentation that occurs at the G2/M checkpoint in the cell cycle. We conclude that Golgi fragmentation is suitable for rapid biocompatibility assessment of PDF not only because of its strong pH dependence but also because the fragmentation is recognizably affected by PDF constituents.

A new peritoneal dialysis fluid for Japanese patients: a randomized non-inferiority clinical trial of safety and efficacy

BACKGROUND

We report here two new peritoneal dialysis fluids (PDFs) for Japan [BLR 250, BLR 350 (Baxter Limited, Japan)]. The PDFs use two-chamber systems, and have bicarbonate and lactate buffer to a total of 35 mmol/L. In separate trials, the new PDFs were compared to two "standard" systems [PD-4, PD-2 (Baxter Limited, Japan)]. The trials aimed to demonstrate non-inferiority of peritoneal creatinine clearance (pCcr), peritoneal urea clearance (pCurea) and ultrafiltration volume (UF), and compare acid-base and electrolyte balance.

METHODS

We performed randomized, multicenter, parallel group, controlled, open-label clinical trials in stable continuous ambulatory peritoneal dialysis (CAPD) patients. The primary endpoints were pCcr and UF. The secondary endpoints were serum bicarbonate and peritoneal urea clearance. The active phase was 8 weeks. These trials were performed as non-inferiority studies, with the lower limit of non-inferiority for pCcr and UF set at 3.2 L/week/1.73 m² and 0.12 L/day, respectively.

RESULTS

108 patients (28 centers) and 103 patients (29 centers) took part in the two trials. Groups were well balanced at baseline. The investigative PDFs were non-inferior to the "standard" ones in terms of primary endpoints, comparable in terms of pCurea, and superior in terms acid-base balance, especially correcting those with over-alkalinization at baseline.

CONCLUSIONS

We demonstrated fundamental functionality of two new PDFs and showed superior acid-base balance. Given the propensity of Japanese CAPD patients for alkalosis, it is important to avoid metabolic alkalosis which is associated with increased cardiovascular mortality risk and accelerated vascular calcification. The new PDFs are important progress of CAPD treatment for Japanese patients.

Bicarbonate versus lactate solutions for acute peritoneal dialysis

BACKGROUND

The high mortality rate among critically ill patients with acute kidney injury (AKI) remains an unsolved problem in intensive care medicine, despite the use of renal replacement therapy (RRT). Increasing evidence from clinical studies in adults and children suggests that the new peritoneal dialysis (PD) fluids may allow for better long-term preservation of peritoneal morphology and function. Formation of glucose degradation products (GDPs) can be reduced and even avoided with the use of newer "biocompatible" solutions. However, it is still unclear if there are any differences in using conventional (lactate) solutions compared with low GDP (bicarbonate) solutions for acute PD.

OBJECTIVES

To look at the benefits and harms of bicarbonate versus lactate solutions in acute PD.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (from 1966), EMBASE (from 1980), Latin American and Caribbean Health Sciences Literature Database LILACS (from 1982), and reference lists of articles.Date of last search: 6 May 2014.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing bicarbonate to lactate solution for acute PD.

DATA COLLECTION AND ANALYSIS

Two authors independently assess the methodological quality of studies. One author abstracted data onto a standard form, and a second author checked data extraction. We used the random-effects model and expressed the results as relative risk (RR) for dichotomous outcomes and mean difference (MD) for continuous outcomes with 95% confidence intervals (CI).

MAIN RESULTS

We included one study (20 patients) in this review. In shock patients, bicarbonate did not differ from lactate with respect to mortality (RR 0.50, 95% CI 0.06 to 3.91); however there were significant differences in blood lactate (MD -1.60 mmol/L, 95% CI -2.04 to -1.16), serum bicarbonate (MD 5.00 mmol/L, 95% CI 3.26 to 6.74) and blood pH (MD 0.12, 95% CI 0.06 to 0.18). In non-shock patients there was a significance difference in blood lactate (MD -0.60 mmol/L, 95% CI -0.85 to -0.35) but not in serum bicarbonate (MD 1.10 mmol/L, 95% CI -0.27 to 2.47) or blood pH (MD -0.02, 95% CI -0.02 to -0.06). Other outcomes could not be analysed because of the limited data available.

AUTHORS' CONCLUSIONS

There is no strong evidence that any clinical advantage for patients requiring acute PD for AKI when comparing conventional (lactate) with low GDP dialysis solutions (bicarbonate).

Bicarbonate versus lactate solutions for acute peritoneal dialysis

BACKGROUND

The high mortality rate among critically ill patients with acute kidney injury (AKI) remains an unsolved problem in intensive care medicine, despite the use of renal replacement therapy (RRT). Increasing evidence from clinical studies in adults and children suggests that the new peritoneal dialysis (PD) fluids may allow for better long-term preservation of peritoneal morphology and function. Formation of glucose degradation products (GDPs) can be reduced and even avoided with the use of newer "biocompatible" solutions. However, it is still unclear if there are any differences in using conventional (lactate) solutions compared with low GDP (bicarbonate) solutions for acute PD.

OBJECTIVES

To look at the benefits and harms of bicarbonate versus lactate solutions in acute PD.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (from 1966), EMBASE (from 1980), Latin American and Caribbean Health Sciences Literature Database LILACS (from 1982), and reference lists of articles.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing bicarbonate to lactate solution for acute PD.

DATA COLLECTION AND ANALYSIS

Two authors independently assess the methodological quality of studies. One author abstracted data onto a standard form, and a second author checked data extraction. We used the random-effects model and expressed the results as relative risk (RR) for dichotomous outcomes and mean difference (MD) for continuous outcomes with 95% confidence intervals (CI).

MAIN RESULTS

We included one study (20 patients) in this review. In shock patients, bicarbonate did not differ from lactate with respect to mortality (RR 0.50, 95% CI 0.06 to 3.91); however there were significant differences in blood lactate (MD -1.60 mmol/L, 95% CI -2.04 to -1.16), serum bicarbonate (MD 5.00 mmol/L, 95% CI 3.26 to 6.74) and blood pH (MD 0.12, 95% CI 0.06 to 0.18). In non-shock patients there was a significance difference in blood lactate (MD -0.60 mmol/L, 95% CI -0.85 to -0.35) but not in serum bicarbonate (MD 1.10 mmol/L, 95% CI -0.27 to 2.47) or blood pH (MD -0.02, 95% CI -0.02 to -0.06). Other outcomes could not be analysed because of the limited data available.

AUTHORS' CONCLUSIONS

There is no strong evidence that any clinical advantage for patients requiring acute PD for AKI when comparing conventional (lactate) with low GDP dialysis solutions (bicarbonate).

Carbon dioxide suppresses macrophage superoxide anion production independent of extracellular pH and mitochondrial activity

BACKGROUND

Superoxide anions released by activated macrophages during surgery are considered to be responsible for local cellular damage. Application of CO2 pneumoperitoneum during laparoscopy affects superoxide anion release, but the underlying mechanism remains unclear and the data reported are conflicting. We investigated the direct and pH-mediated impact of CO2 and air on macrophage superoxide anion production.

METHODS

Cells of the NR 8383 rat macrophage cell line were incubated for 2 hours in 5% CO2, 100% CO2, and room air or pH 7.4, pH 6.5, and pH 5.5. The extracellular pH was monitored during incubation. At 0, 2, and 6 hours after incubation, the release of superoxide anions was determined fluorometrically. The mitochondrial activity was determined via the conversion of MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] during and after incubation.

RESULTS

Extracellular pH decreased to 6.4 during incubation in a CO2 atmosphere. The release of superoxide anions was significantly reduced immediately after CO2 incubation. It was restored at all other time-points. Decreasing the extracellular pH to 6.5 had no effect on superoxide anion release, whereas acidification of the extracellular milieu to pH 5.5 significantly suppressed subsequent superoxide release. Mitochondrial activity was significantly decreased by CO2 up to 2 hours and by acidic milieu up to 6 hours. Incubation in room air had no effect.

CONCLUSIONS

Incubation in CO2 can directly suppress macrophage superoxide anion production. This effect is of short duration, fully reversible, and not correlated to changes in extracellular pH or mitochondrial activity. Air contamination does not affect macrophage superoxide anion release. We speculate that CO2 pneumoperitoneum could attenuate the intraoperative free radical production by directly inhibiting superoxide anion release of macrophages without long-lasting suppression of macrophages and their capacity to release superoxide anions postoperatively.

In vitro biocompatibility performance of Physioneal

In vitro biocompatibility performance of Physioneal. toneal dialysis (PD) has been a successful and effective form of chronic renal replacement therapy since its introduction over 20 years ago. Despite its overall success, there is a growing body of evidence that suggests shortcomings in the preservation of membrane integrity. This has led to the development of several second-generation PD solutions that demonstrate improved biocompatibility. Physioneal, a neutral pH, bicarbonate/lactate-buffered solution, was one of the first of these new PD solutions to become commercially available. This review will focus on one of the first preclinical stages in the development of Physioneal: studies on in vitro biocompatibility testing. Studies in leukocyte, mesothelial cell, and fibroblast populations demonstrated significantly improved biocompatibility of neutral pH, bicarbonate/lactate-based solutions compared to conventional solutions. The solutions contributed to improved leukocyte viability and response to bacterial infection (e.g., phagocytosis, superoxide radical generation, and endotoxin-stimulated cytokine release). Studies on peritoneal mesothelial cells demonstrate improved cell viability, proliferation, and response to proinflammatory stimuli, and a reduced potential for angiogenesis and peritoneal fibrosis, all suggesting a better preservation of membrane structure and function. The bicarbonate/lactate-based solutions demonstrated decreased cytotoxicity and preserved cell growth in fibroblast cultures as well. In vitro biocompatibility testing has clearly demonstrated that neutral pH, bicarbonate/lactate-buffered Physioneal solutions are superior to conventional solutions in preserving cell viability and function in cell populations that contribute to peritoneal homeostasis. This positive assessment now provides a foundation and rationale for moving forward with the next stages in preclinical testing: in vivo animal models and human ex vivo studies.

Innovative approaches to the preservation of the peritoneal membrane: from bench to bedside

The functional integrity of the peritoneal membrane is of critical importance for the long-term success of peritoneal dialysis therapy. In addition to water and solute transport properties, the function of the membrane encompasses complex interactions with immune cells, invading microorganisms, and dialysis fluid components. During chronic peritoneal dialysis, intraperitoneal homeostasis is threatened by the repeated exposure to an unphysiologic environment that is created by the instilled solutions. Whereas their acidic pH and hyperosmolality were shown to primarily induce alterations of acute cell function, long-term peritoneal function might be affected by the repeated exposure to high concentrations of glucose and glucose degradation products. In addition to their intrinsic toxicity, these might induce or accelerate glycation processes, such as formation and deposition of advanced glycation end products in the peritoneal membrane. Presently, a new generation of dual-chambered peritoneal dialysis solutions combining the advantages of neutral pH and reduced glucose degradation products content is being introduced into clinical practice. In addition to an improved in vitro biocompatibility profile, emerging clinical trials of these novel solutions indicate that they might also improve the host defense status, membrane transport characteristics, ultrafiltration capacity, and effluent markers of peritoneal membrane integrity, while being safe and effective in correcting uremic acidosis and providing relief of inflow pain. Overall, these findings suggest that these new dialysis solutions might constitute an important step toward better preservation of long-term peritoneal membrane function during peritoneal dialysis.

Better correction of metabolic acidosis, blood pressure control, and phagocytosis with bicarbonate compared to lactate solution in acute peritoneal dialysis

Lactate solution has been the standard dialysate fluid for a long time. However, it tends to convert back into lactic acid in poor tissue-perfusion states. The aim of this study was to evaluate the efficacy of magnesium (Mg)- and calcium (Ca)-free bicarbonate solution compared with lactate solution in acute peritoneal dialysis (PD). Renal failure patients who were indicated for dialysis and needed acute PD were classified as shock and nonshock groups, and then were randomized to receive either bicarbonate or lactate solution. Twenty patients were enrolled in this study (5 in each subgroup). In the shock group, there were more rapid improvements and significantly higher levels of blood pH (7.40 +/- 0.04 versus 7.28 +/- 0.05, p < 0.05), serum bicarbonate (23.30 +/- 1.46 versus 18.37 +/- 1.25 mmol/L, p < 0.05), systolic pressure (106.80 +/- 3.68 versus 97.44 +/- 3.94 mm Hg, p < 0.05), mean arterial pressure (80.72 +/- 2.01 versus 73.28 +/- 2.41 mm Hg, p < 0.05), percentages of phagocytosis of circulating leukocytes (65.85% +/- 2.22 versus 52.12% +/- 2.71, p < 0.05), and percentages of positive nitroblue tetrazolium (NBT) reduction test without and with stimulation (14.43 +/- 1.93 versus 9.43 +/- 2.12, p < 0.05 and 65.08 +/- 6.80 versus 50.23 +/- 4.21, p < 0.05, respectively) in the bicarbonate subgroup compared with the lactate subgroup. In the nonshock group, blood pH, serum bicarbonate, and phagocytosis assays in both subgroups were comparable. Lactic acidosis was more rapidly recovered and was significantly lower with bicarbonate solution for both shock and nonshock groups (3.63 +/- 0.37 versus 5.21 +/- 0.30 mmol/L, p < 0.05 and 2.92 +/- 0.40 versus 3.44 +/- 0.34 mmol/L, p < 0.05, respectively). Peritoneal urea and creatinine clearances in both subgroups were comparable for both shock and nonshock groups. There was no peritonitis observed during the study. Serum Mg and Ca levels in the bicarbonate subgroup were significantly lower, but no clinical and electrocardiographic abnormality were observed. We concluded that Mg- and Ca-free bicarbonate solution could be safely used and had better outcomes in correction of metabolic acidosis, blood pressure control, and nonspecific systemic host defense with comparable efficacy when compared to lactate solution. It should be the dialysate of choice for acute PD especially in the poor tissue-perfusion states such as shock, lactic acidosis, and multiple organ failure.

In vivo exposure to bicarbonate/lactate- and bicarbonate-buffered peritoneal dialysis fluids improves ex vivo peritoneal macrophage function

The impact on peritoneal macrophage (PMO) function of acidic lactate-buffered (Lac-PDF [PD4]; 40 mmol/L of lactate; pH 5.2) and neutral-pH, bicarbonate-buffered (TB; 38 mmol/L of bicarbonate; pH 7. 3) and bicarbonate/lactate-buffered (TBL; 25 mmol/L of bicarbonate/15 mmol/L of lactate; pH 7.3) peritoneal dialysis fluids (PDFs) was compared during a study of continuous therapy with PD4, TB, or TBL. During a run-in phase of 6 weeks when all patients (n = 15) were treated with their regular dialysis regimen with Lac-PDF, median PMO tumor necrosis factor alpha (TNFalpha) release values were 203.6, 89.9, and 115.5 pg TNFalpha/10(6) PMO in the patients subsequently randomized to the PD4, TB, and TBL treatment groups, respectively. Median stimulated TNFalpha values (serum-treated zymosan [STZ], 10 microgram/mL) were 1,894.6, 567.3, and 554.5 pg TNFalpha/10(6) PMO in the same groups, respectively. During the trial phase of 12 weeks, when the three groups of patients (n = 5 per group) were randomized to continuous treatment with PD4, TB, or TBL, median constitutive TNFalpha release values were 204.7, 131.4, and 155.4 pg TNFalpha/10(6) PMO, respectively. Stimulated TNFalpha values (STZ, 10 microgram/mL) were 1,911, 1,832, and 1,378 pg TNFalpha/10(6) PMO in the same groups, respectively. Repeated-measures analysis of variance comparing the run-in phase with the trial phase showed that PMO TNFalpha release was significantly elevated in patients treated with both TB (P = 0.040) and TBL (P = 0.014) but not in patients treated with Lac-PDF (P = 0. 795). These data suggest that patients continuously exposed to bicarbonate- and bicarbonate/lactate-buffered PDFs might have better preserved PMO function and thus improved host defense status.

Biocompatibility and buffers: effect of bicarbonate-buffered peritoneal dialysis fluids on peritoneal cell function

BACKGROUND

Conventional peritoneal dialysis fluids (PDF) have been shown to compromise the function of both leukocytes and human peritoneal mesothelial cells (HPMC). Various in vitro studies have identified the low initial pH in combination with high lactate content, as well as the hyperosmolality and high glucose concentration present in currently used solutions as the primary determinants of their bioincompatibility. Bicarbonate buffered PDF (at neutral pH) display improved in vitro biocompatibility as compared to conventional, lactate buffered PDF. However, little information is currently available regarding the potential impact of PDF on the function of human peritoneal fibroblasts (HPFB), the major cell population present in peritoneal interstitium.

METHODS

The current study compares the effect of bicarbonate and lactate buffered PDF in a model system of resting peritoneal mesothelial cells and fibroblasts cultured from human omentum. Interleukin-1 beta-stimulated IL-6 release from HPMC and HPFB was used as the cell functional parameter.

RESULTS

While short (30 min) pre-exposure to lactate buffered PDF significantly reduced the IL-1 beta-stimulated IL-6 release from HPMC during a subsequent recovery period (24 hr), a significant decrease in HPMC IL-6 secretion with bicarbonate buffered PDF was only observed after prolonged (> or = 60 min) exposure. In contrast, no significant IL-6 inhibition was detected with HPFB pre-exposed to PDF for up to 90 minutes. A significant suppression of HPFB IL-6 secretion was only observed in coincubation experiments (24 hr) with dilutions of both types of PDF.

CONCLUSIONS

These results indicate that (i) bicarbonate buffered PDF are less inhibitory to peritoneal cell function as compared to conventional, lactate buffered PDF; and (ii) HPFB may be more resistant than HPMC to bioincompatible PDF.

Osmotic agents and buffers in peritoneal dialysis solution: monocyte cytokine release and in vitro cytotoxicity

Peritonitis remains a major problem in peritoneal dialysis. The incidence of peritonitis may be reduced by the use of more "biocompatible" peritoneal dialysis solutions that do not impair local host defense mechanisms, such as occurs with conventional lactate-buffered glucose solutions. In the present study, we investigated the use of bicarbonate and lactate as buffer systems and glucose, amino acids, and glucose polymer as osmotic agents on specific cellular functions of isolated fresh blood monocytes in vitro. The bicarbonate-buffered solutions had a physiologic pH (7.0 to 7.6). Lactate-buffered solutions were tested with a pH between 5.5 and 7.3. RPMI 1640 (Roswell Park Memorial Institute, supplied by Biochrom, Berlin, Germany) and phosphate-buffered saline were used as control mediums. The test solutions were incubated with 200,000 monocytes/mL for 45 minutes followed by a 1:1 mix with RPMI 1640 (with supplements) during a 24- or 4-hour tetrazolium bromide test (MTT test) recovery period. Constitutive and lipopolysaccharide (LPS)-stimulated release of interleukin-1beta (IL-1beta) and IL-6 in the supernatants as parameters of cellular host defense and lactate dehydrogenase concentrations and MTT-formazan production as parameters for cell cytotoxicity were measured. Significantly higher IL-6 and IL-1beta release was found in the bicarbonate-buffered solutions, both under basal conditions and after LPS stimulation, compared with the lactate-buffered solutions (LPS stimulation: 1% amino acids/34 mmol/L bicarbonate, IL-1beta: 1,166 +/- 192 pg/mL; 1.5% glucose/34 mmol/L bicarbonate, IL-1beta: 752 +/- 107 pg/mL; 1.5% glucose/35 mmol/L lactate/pH 5.5, IL-1beta: 174 +/- 51 pg/mL). Some of these differences could even be detected in spent dialysate after a 6-hour dwell in continuous ambulatory peritoneal dialysis patients (n = 10). A lower degree of cellular cytotoxicity (lactate dehydrogenase activity) and better-preserved metabolic activity (MTT test) also were found for the bicarbonate-buffered solutions. Amino acids (1%) proved to be comparable to glucose (1.5%) as an osmotic agent at a neutral pH with regard to LPS-stimulated cytokine release and cytotoxicity. The incubation with a glucose polymer solution (7.5% glucose polymer in phosphate-buffered saline, pH 7.3) resulted in a significantly lowered cytokine release (LPS stimulation: IL-1beta, 69 +/- 19 pg/mL) compared with the other solutions with neutral pH (P < 0.01). These results suggest that bicarbonate as a buffer provided better biocompatibility with regard to mononuclear cytokine release and viability compared with lactate. Amino acids and glucose were equivalent to these parameters at a physiologic pH. The glucose polymer solution, however, was associated with a marked depression of cytokine release.