The untoward effects of the anions of dialysis fluids

Citric Acid-Containing Dialysate and Survival Rate in the Dialysis Outcomes and Practice Patterns Study

Background

Metabolic acidosis is a common threat for patients on hemodialysis, managed by alkaline dialysate. The main base is bicarbonate, to which small amounts of acetic, citric, or hydrochloric acid are added. The first two are metabolized to bicarbonate, mostly by the liver. Citric acid-containing dialysate might improve dialysis efficiency, anticoagulation, calcification propensity score, and intradialytic hemodynamic stability. However, a recent report from the French dialysis registry suggested this dialysate increases mortality risk. This prompted us to assess whether citric acid-containing bicarbonate-based dialysate was associated with mortality in the international Dialysis Outcomes and Practice Patterns Study (DOPPS).

Methods

Detailed patient-based information on dialysate composition was collected in DOPPS phases 5 and 6 (2012-2017). Cox regression was used to model the association between baseline bicarbonate dialysate containing citric acid versus not containing citric acid and mortality among DOPPS countries and phases where citric acid-containing dialysate was used.

Results

Citric acid-containing dialysate was most commonly used in Japan, Italy, and Belgium (25%, 25%, 21% and of patients who were DOPPS phase 6, respectively) and used in <10% of patients in other countries. Among 11,306 patients in DOPPS country and phases with at least 15 patients using citric acid-containing dialysate, patient demographics, comorbidities, and laboratories were similar among patients using (14%) versus not using (86%) citric acid-containing dialysate. After accounting for case mix, we did not observe a directional association between citric acid-containing dialysate use (any versus none) and mortality (HR, 1.14; 95% CI, 0.97 to 1.34), nor did we find evidence of a dose-dependent relationship when parameterizing the citric acid concentration in the dialysate as 1, 2, and 3+ mEq/L.

Conclusions

The use of citric acid-containing dialysate was not associated with greater risk of all-cause mortality in patients on hemodialysis participating in DOPPS. Clinical indications for the use of citric acid-containing dialysate deserve further investigation.

Short Term Clinical Study with Bicarbonate-Containing Peritoneal Dialysis Solution

Objective

The evaluation of the efficacy, adequacy, clinical tolerance, and safety of a new bicarbonate continuous ambulatory peritoneal dialysis (CAPD) solution.

Design and Patients

A 6–week cross-over clinical study in 6 stable CAPD patients was performed. After a control period (2 weeks) with a standard CAPD solution (lactate, 35 mmol/L), a two-chamber bag containing 34 mmol/L of bicarbonate was used for 4 weeks. A breakable valve divided the two chambers, one containing bicarbonate and the other calcium. The two solutions were mixed just before use, thus avoiding the calcium and magnesium carbonate precipitation.

Results

No differences between control and study periods were found for blood urea nitrogen, creatinine, total proteins, albumin, total and ionized calcium, phosphate, sodium, potassium, chlorine, and hemoglobin. Blood bicarbonate significantly increased from 21.25±2.02 to 23.36±1.15 (p<0.05) during the study. The peritoneal equilibration tests for urea nitrogen, creatinine, proteins, sodium, potassium, and glucose were slightly reduced during bicarbonate dialysate, but this effect was compensated for by a slight increase of ultrafiltration, thus keeping peritoneal clearances constant. Residual renal function did not change during the study. No side effects occurred during the bicarbonate period.

Conclusion

A CAPD bicarbonate solution is effective in uremic acidosis correction, does not affect dialysis adequacy, is safe, and well tolerated.

Factors Affecting Bicarbonate Transfer with Bicarbonate-Containing CAPD Solution

Objective

To evaluate bicarbonate fluxes across the peritoneal membrane and bicarbonate gain in patients treated with continuous ambulatory peritoneal dialysis (CAPD) using dialysis solutions with different bicarbonate concentrations.

Patients and Design

Ninety-seven exchanges, using different dwell times and glucose and bicarbonate concentrations were performed in 43 stable CAPD patients. Dialysate effluent bicarbonate concentration and volumes were measured at different dwell times. Net dialytic bicarbonate gain was calculated. Patients’ acid-base status was determined at the middle of the dwell.

Results

In prolonged dwells (6 –12 hours)thedialysate effluent bicarbonate concentration correlated with arterial plasma bicarbonate concentration (F = 129, p < 0.0001), but not with ultrafiltration rate or dialysis solution bicarbonate concentration. In 4-hour dwells, effluent bicarbonate concentration correlated with both plasma bicarbonate concentration and ultrafiltration rate (F = 32.52, p < 0.0001 and F = 4.4, p < 0.05, respectively). The effluent bicarbonate concentration may be predicted from the patient's plasma bicarbonate concentration and net ultrafiltration rate for either a 4-hour or prolonged (6 –12 hours) dwell time. Net bicarbonate gain by the patient correlated with ultrafiltration rate, plasma bicarbonate, and dialysis solution bicarbonate concentration (F = 100.56, p < 0.0001 at 4 hours and F = 108.08, p < 0.0001 at 6 12 hours), with the ultrafiltration rate being the predominant parameter.

Conclusions

The effluent bicarbonate concentration is related to plasma bicarbonate concentration, with ultrafiltration playing a marginal role only during short dwells. However, the ultrafiltration rate has a profound effect on net patient bicarbonate gain. Multiple linear regression analysis allows the prediction of the effect of acid-base status, ultrafiltration, dwell time, and dialysis solution bicarbonate content on net patient bicarbonate gain. It seems that bicarbonate content in the CAPD dialysis solution should be progressively increased with increasing solution osmolality.

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.

Development of Toxic Degradation Products during Heat Sterilization of Glucose-Containing Fluids for Peritoneal Dialysis: Influence of Time and Temperature

Objective

Fluids for peritoneal dialysis (PD) cause cytotoxic reactions in many different in vitro systems. The low pH, the high osmolality of the fluids, and the glucose degradation products formed during heat sterilization have been considered responsible. In the present study, we investigate the influence of temperature and time during heat sterilization of PD fluids and glucose solutions on glucose degradation and cytotoxicity of the solutions.

Design

Ampoules containing PD-fluid or glucose solution were heated in an oil bath to predetermined F o values (combinations of time and temperature giving equal energy/bacteriallethality). Cytotoxicity of the solutions was measured as groWth inhibition of cultured L-929 fibroblasts. Glucose degradation was measured as UV absorbance at 228 and 284 nm.

Results

The same general pattern was seen in both PD fluid and glucose solution. Cytotoxicity decreased from 90% to 15% when the sterilization temperature was increased from 115° to 140°C and concomitantly the length of time shortened in order to maintain equal bacteriallethality. Under the same conditions, degradation products, measured as UV absorbance at 284 nm, decreased from 0.2 to 0.02.

Conclusion

To minimizethe development of cytotoxic breakdown products, high temperatures over short periods of time should be used to heat-sterilize PD fluids. Even as small an increase as 5°C at around 120°C will improve the quality of the solutions.

Clinical Evaluation of a Peritoneal Dialysis Solution with 33 mmol/L Bicarbonate

Objective

To evaluate the efficacy and safety of a new peritoneal dialysis solution with 33 mmol/L bicarbonate.

Design

In an acute, prospective, randomized crossover study, 8 patients were randomized in two groups of 4. On the first study day, the first group performed two consecutive 4-hour exchanges with a dialysis solution containing 35 mmol/L lactate: the first exchange with 13.6 g/L and the second with 38.6 g/L dextrose. On the second study day, the same type of exchanges were performed with bicarbonate. The second group underwent the same treatment, but used bicarbonate solutions on the first day and control solutions on the second study day. Thirty-three patients participated in a 2-month prospective and randomized study. After a 4-week baseline period using solutions containing 40 mmol/L lactate, the patients were dialyzed with either 33 mmol/L bicarbonate solutions or 40 mmol/L lactate solutions.

Setting

Peritoneal dialysis units at the University Hospital of Brescia and the Niguarda Hospital of Milan, Italy.

Results

Acute study: Control and bicarbonate solutions had similar effects on blood chemistries and peritoneal transport. Chronic study: Mean venous bicarbonate concentrations remained unchanged in the control group (26.6 -27.2 mmol/L), but decreased significantly in the bicarbonate group from 28.8 mmol/L at the start of the study to 23.0 mmol/L after 2 months of bicarbonate administration. Other biochemical parameters remained unchanged.

Conclusion

A peritoneal dialysis solution with a bicarbonate level of 33 mmol/L does not adequately correct uremic acidosis.

Neutrophilic Intracellular Acidosis Induced by Conventional, Lactate-Containing Peritoneal Dialysis Solutions

Exposure of human neutrophils to a conventional, acidic, lactate-containing peritoneal dialysis solution (PDS) resulted in the development of a prompt and substantial intracellular acidosis. It is possible that this intracellular acidosis contributes to cellular dysfunction.

Accidental Death Due to Erroneous Intravenous Infusion of Hypertonic Saline Solution for Hemodialysis

The case of a continuous hemodialysis patient who died shortly after erroneous infusion with undiluted hypertonic solution is reported. Autopsy showed small parenchymal hemorrhages in all organs. Although producers take measures to prevent such errors by hospital staff, further steps are suggested for types of dialysis requiring reinfusion of large quantities of reinfusion hemodialysis solution.

Fluids for Prevention and Management of Acute Kidney Injury

Fluids are the only known method of attenuating renal injury. Furthermore, whether for hydration, resuscitation or renal replacement therapy, fluid prescriptions must be tailored to the fluid and electrolyte, cardiovascular status and residual renal function of the patient. Different fluids have significantly different effects both on volume expansion as well as on the electrolyte and acid-base balance; while controversial, different fluids may even influence renal function differently. This systematic review focuses on fluids for prevention and management of acute kidney injury. We have reviewed the available evidence and have made recommendations for clinical practice and future studies.

Con: Higher serum bicarbonate in dialysis patients is protective

Metabolic acidosis is often observed in advanced chronic kidney disease, with deleterious consequences on the nutritional status, bone and mineral status, inflammation and mortality. Through clearance of the daily acid load and a net gain in alkaline buffers, dialysis therapy is aimed at correcting metabolic acidosis. A normal bicarbonate serum concentration is the recommended target in dialysis patients. However, several studies have shown that a mild degree of metabolic acidosis in patients treated with dialysis is associated with better nutritional status, higher protein intake and improved survival. Conversely, a high bicarbonate serum concentration is associated with poor nutritional status and lower survival. It is likely that mild acidosis results from a dietary acid load linked to animal protein intake. In contrast, a high bicarbonate concentration in patients treated with dialysis could result mainly from an insufficient dietary acid load, i.e. low protein intake. Therefore, a high pre-dialysis serum bicarbonate concentration should prompt nephrologists to carry out nutritional investigations to detect insufficient dietary protein intake. In any case, a high bicarbonate concentration should be neither a goal of dialysis therapy nor an index of adequate dialysis, whereas mild acidosis could be considered as an indicator of appropriate protein intake.

[Acetate-free hemodialysis: what does it mean?]

Substituting bicarbonate by acetate in dialysis fluids has been proposed for avoiding precipitation of calcium and magnesium carbonates. However, acetate hemodialysis has been abandoned because of deleterious effects of acetate. Conventional bicarbonate hemodialysis is not totally acetate-free, because 3 to 7 mEq/l of acetic acid are added to the dialysate. Acetate-free hemodialysis is possible with another acid (chlorhydric acid or citric acid) or without acid by using some techniques of low-efficiency hemodiafiltration, as acetate-free biofiltration, which avoids the deleterious effect of blood acidification into the dialyzer. In this paper, advantages and disadvantages of different techniques of acetate-free hemodialysis are discussed.

Acid-base effects of a bicarbonate-balanced priming fluid during cardiopulmonary bypass: comparison with Plasma-Lyte 148. A randomised single-blinded study

Fluid-induced metabolic acidosis can be harmful and can complicate cardiopulmonary bypass. In an attempt to prevent this disturbance, we designed a bicarbonate-based crystalloid circuit prime balanced on physico-chemical principles with a strong ion difference of 24 mEq/l and compared its acid-base effects with those of Plasma-Lyte 148, a multiple electrolyte replacement solution containing acetate plus gluconate totalling 50 mEq/l. Twenty patients with normal acid-base status undergoing elective cardiac surgery were randomised 1:1 to a 2 litre prime of either bicarbonate-balanced fluid or Plasma-Lyte 148. With the trial fluid, metabolic acid-base status was normal following bypass initiation (standard base excess 0.1 (1.3) mEq/l, mean, SD), whereas Plasma-Lyte 148 produced a slight metabolic acidosis (standard base excess -2.2 (2.1) mEq/l). Estimated group difference after baseline adjustment was 3.6 mEq/l (95% confidence interval 2.1 to 5.1 mEq/l, P=0.0001). By late bypass, mean standard base excess in both groups was normal (0.8 (2.2) mEq/l vs. -0.8 (1.3) mEq/l, P=0.5). Strong ion gap values were unaltered with the trial fluid, but with Plasma-Lyte 148 increased significantly on bypass initiation (15.2 (2.5) mEq/l vs. 2.5 (1.5) mEq/l, P < 0.0001), remaining elevated in late bypass (8.4 (3.4) mEq/l vs. 5.8 (2.4) mEq/l, P < 0.05). We conclude that a bicarbonate-based crystalloid with a strong ion difference of 24 mEq/l is balanced for cardiopulmonary bypass in patients with normal acid-base status, whereas Plasma-Lyte 148 triggers a surge of unmeasured anions, persisting throughout bypass. These are likely to be gluconate and/or acetate. Whether surges of exogenous anions during bypass can be harmful requires further study.

Unmeasured anions: the unknown unknowns

Evidence is emerging that elevated concentrations of the intermediates of the citric acid cycle may contribute to unmeasured anions in critical illness. Both the anion gap and the strong ion gap are used as scanning tools for recognition of these anions. The mechanisms underlying these elevations and their significance require further clarification.

Development of a clipped single-bag with bicarbonate replacement fluid to ensure proper mixing

A clipped single-bag for bicarbonate replacement fluid was developed to ensure proper mixing before administering to the patient. Nonmixture can cause imbalances of electrolytes and pH, which is a key problem for the current double-bag type bicarbonate replacement fluid sets. To resolve this problem, this single bag properly mixes the solutions before use. The new bag consists of a clip that is placed in the middle to keep the two solutions separated and sealed. When the caregiver is ready to administer treatment, the bag is simply unfolded and the clip automatically detaches, releasing the fluids. Thereby, the bicarbonate fluids are effectively mixed. An optimal clip size with an outer diameter of 16 mm and thickness of 2 mm was determined using compression tests and drop tests. This bag may be a safer and more effective way to provide proper replacement fluid supply for both hemofiltration and hemodiafiltration.

Composition and clinical use of hemodialysates

A thorough knowledge and understanding of the principles underlying the preparation and the clinical application of hemodialysates can help us provide exemplary patient care to individuals having end-stage renal disease. It is prudent to be conversant with the following: (a) how each ingredient in a dialysate works, (b) the clinical circumstances under which the concentration of an ingredient can be altered, and (c) the special situations in which unconventional ingredients can be introduced into a dialysate. The potential to enrich dialysates with appropriate ingredients (such as iron compounds) is limited only by the boundaries of our imagination.

On-line haemodiafiltration with and without acetate

BACKGROUND

In patients on on-line convective treatments, given the considerable quantity of dialysis fluid re-infused, the small amount of acetate present in bicarbonate dialysis fluid as a pH stabilizing factor may allow a significant transfer of that anion to the patient, possibly inducing cytokine activation.

METHODS

To verify this hypothesis, we performed on-line haemodiafiltration (OL-HDF) with (3 mmol/l) and without acetate in dialysis fluid in a cross-over randomized order on 12 prevalent patients.

RESULTS

In comparison with the pre-treatment values, plasma acetate levels were unchanged during and after acetate-free OL-HDF, while they were 5-6 times higher in the course of OL-HDF containing acetate in dialysis fluid; plasma acetate levels returned to basal values 2 h after the end of the procedure. The total increase of bases in the patient attributable to acetate was 36%. Plasma bicarbonate values at the end of treatment were significantly lower in treatments without acetate, as compared to those with acetate. Interleukin-6 plasma levels were super-imposable at the beginning and in the course of the two methods compared, but there was a tendency towards a greater increase at an interval of 2 h following OL-HDF with acetate.

CONCLUSIONS

Our preliminary results confirm the assumption that body gain of acetate is particularly high in convective treatments, while acetate-free OL-HDF slows down acetate burden. Clinical advantages due to these effects should be evaluated in properly designed prospective studies.

Effects of customized bicarbonate buffered solutions for continuous renal replacement therapies on polymorphonuclear leukocytes function and viability

It has previously been shown that the mixture of bicarbonate and calcium in the solutions used for continuous renal replacement therapy led to crystallization and significant changes in calcium concentration and pH. The aim of this study was to investigate the impact of bicarbonate/calcium and lactate/calcium solutions for Continuous Renal Replacement Therapies (CRRT) on the viability and function of polymorphonuclear cells (PMN). We tested four customized bicarbonate buffered solutions: single bag (bicarbonate and calcium mixed 24 h before testing), double bag (mixed immediately before testing), filtered single bag and double bag solutions, and a commercial lactate buffered solution. Blood from 6 volunteers was incubated with the solutions for 30 min followed by PMN isolation. After overnight incubation, viability, phagocytosis, and peroxide production by PMN were determined by flow cytometry. There was no difference between the test solutions with respect to PMN viability and function. Therefore, the presence of microcrystals and the consequent changes in electrolyte concentrations do not seem to impair PMN function.

Acid–base balance in acute renal failure and renal replacement therapy

The approach to acid-base balance based on the concept of strong ions, initially proposed by Stewart, is briefly overviewed. The anion gap and the strong anion gap are both discussed. Comments are made on the strong ion difference of fluids administered to patients and their impact on acid-base status will be commented. Renal failure patients have an altered acid-base balance; most commonly, a mixed type of metabolic acidosis (hyperchloraemic, and of a high anion gap) is observed. The consequences of renal metabolic acidosis are described. Finally, the impact of renal replacement therapy on acid-base balance is exposed; different modalities of renal replacement are considered in regard to their alkalinizing performance.

Buffer transport in peritoneal dialysis

Buffer transport in peritoneal dialysis. The success of peritoneal dialysis as a robust modality of renal replacement therapy has invited a quest for ameliorations in its underlying technology aimed at enhancing patient satisfaction and preserving the central instrument of the therapy, namely the peritoneal membrane. The health and longevity of the membrane have motivated and continue to drive a series of iterative innovations in the composition, methods of production, and delivery of dialysis solutions. It is the purpose of this article to review aspects of these innovations pertaining to buffer composition in dialysis solutions and the peritoneal mechanisms of buffer transport.

The Acute Dialysis Quality Initiative--part VII: fluid composition and management in CRRT

Fluid composition and management are important parts of continuous renal replacement therapy (CRRT). Most commercially available CRRT solutions are able to reestablish electrolyte homeostasis provided some phosphate supplementation is given. Supraphysiologic glucose concentrations should be avoided. Predilution fluid replacement allows higher ultrafiltration rates and can be considered as an adjunct to the anticoagulation regimen. Lactate is an effective buffer in most CRRT patients. Bicarbonate is preferred in patients with lactic acidosis and/or liver failure. When citrate is used as anticoagulant, frequent monitoring of pH is required. The clinical consequences of CRRT-induced decreases of body temperature are not clear. Substitution fluid should be sterile, but the bacteriologic requirements for CRRT dialysate are less clear. There is no consensus on the optimal parameters to monitor fluid management. Integrated balancing systems have theoretical advantages over adaptive use of intravenous fluid pumps. Although there is evidence that volume overload is associated with adverse outcome, there is no evidence that fluid removal per se improves outcome in critically ill patients with or without acute renal failure.

Customized bicarbonate buffered dialysate and replacement solutions for continuous renal replacement therapies: effect of crystallization on the measured levels of electrolytes and buffer

The aim of this study was to investigate the impact of the addition of calcium to bicarbonate solutions for continuous renal replacement therapy (CRRT). We tested single bag (bicarbonate and calcium mixed 24 h before testing) and double bag solutions (mixed immediately before) with and without the addition of 4 mEq/L of acetate. Prescribed calcium varied from 0 to 5 mEq/L. All test solutions containing calcium showed crystallization at light microscopy. The double bag solutions decreased but did not prevent crystallization. The addition of acetate did not interfere with crystallization. Crystallization, as measured by the weight of the crystals after filtration of the solutions, showed a significant positive correlation with the calcium deficit (prescribed minus measured) and with partial pressure of carbon dioxide. The measured level of calcium was lower than expected and correlated with crystallization. Our results suggest that the use of bicarbonate solutions containing calcium as replacement fluids for CRRT is a potentially unsafe procedure.

Bicarbonate/lactate-based peritoneal dialysis solution increases cancer antigen 125 and decreases hyaluronic acid levels

BACKGROUND

In a randomized, controlled trial comparing a pH neutral, bicarbonate/lactate (B/L)-buffered PD solution to conventional acidic, lactate-buffered solution (C), the overnight dialysate levels of markers of inflammation/wound healing [hyaluronic acid (HA)], mesothelial cell mass/membrane integrity [cancer antigen 125 (CA125)], and fibrosis [transforming growth factor-beta1 (TGF-beta1) and procollagen I peptides (PICP)] were assessed over a six-month treatment period.

METHODS

One hundred six patients were randomized (2:1) to either the B/L group or C group. Overnight effluents were collected at entry into the study (time = 0 all patients on control solution) and then at three and six months after randomization. Aliquots were filtered, stored frozen, and assayed for HA, CA125, TGF-beta1, and PICP. Differences between groups were assessed by repeated-measures analysis of variance for unbalanced data using the SAS procedure MIXED.

RESULTS

In patients treated with B/L, there was a significant (P = 0.03) increase in CA125 after six months compared with time = 0 (19.76 +/- 11.8 vs. 24.4 +/- 13.8 U/mL; mean +/- SD; N = 51). In the same group of patients, HA levels were significantly decreased at both three and six months in the B/L-treated group (time = 0, 336.0 +/- 195.2; time = 3 months, 250.6 +/- 167.6; and time = 6 months, 290.5 +/- 224.6 ng/mL; mean +/- SD; P = 0.006, N = 47 and P = 0.003, N = 48, respectively). No significant changes in CA125 or HA levels were observed in the control group. There were no significant changes observed in the levels of PICP or TGF-beta1 in the B/L or C group over the six-month treatment period.

CONCLUSIONS

These results suggest that continuous therapy with the B/L solutions modulates the levels of putative markers of peritoneal membrane integrity and inflammation. In the long term, this may positively impact the peritoneal membrane, increasing its life as a dialyzing organ.

Effects of bicarbonate- and lactate-buffered replacement fluids on cardiovascular outcome in CVVH patients

BACKGROUND

Bicarbonate-buffered replacement fluid (RF-bic) in continuous venovenous hemofiltration (CVVH) may be superior to lactate-buffered replacement fluid (RF-lac) in acute renal failure. In an open, randomized, multicenter study, we investigated the effects of RF-bic and RF-lac on cardiovascular outcome in patients requiring CVVH following acute renal failure.

METHODS

One hundred seventeen patients between the age of 18 and 80 years were randomized to CVVH either with RF-bic (N = 61) or RF-lac (N = 56). Patients were treated with CVVH for five days or until either renal function was restored or the patient was removed from the study. Data were analyzed on day 5 or according to the "last observation carried forward" (LOCF) option. Adverse events were classified according to the WHO-Adverse Reaction Terminology system.

RESULTS

Blood lactate levels were significantly lower and blood bicarbonate levels were significantly higher in patients treated with RF-bic than in those treated with RF-lac (lactate, 17.4 +/- 8.5 vs. 28.7 +/- 10.4 mg/dL, P < 0.05; bicarbonate, 23.7 +/- 0.4 vs. 21.8 +/- 0.5 mmol/L, P < 0. 01). The number of hypotensive crises was lower in RF-bic-treated patients than in RF-lac-treated patients (RF-bic 14 out of 61 patients, RF-lac in 29 out of 56 patients; 0.26 +/- 0.09 vs. 0.60 +/- 0.31 episodes per 24 h, P < 0.05). Nine out of 61 patients (15%) treated with RF-bic and 21 out of 56 patients (38%) treated with RF-lac developed cardiovascular events during CVVH therapy (P < 0. 01). A multiple regression analysis showed that the occurrence of cardiovascular events was dependent on replacement fluid and previous cardiovascular disease and not on age or blood pressure. Patients with cardiac failure died less frequently in the group treated with RF-bic (7 out of 24, 29%) than in the group treated with RF-lac (12 out of 21, 57%, P = 0.058). In patients with septic shock, lethality was comparable in both groups (RF-bic, 10 out of 27, 37%; RF-lac, 7 out of 20, 35%, P = NS).

CONCLUSIONS

The results show that the administration of RF-bic solution was superior in normalizing acidosis of patients without the risk of alkalosis. The data also suggest that the use of RF-bic during CVVH reduces cardiovascular events in critically ill patients with acute renal failure, particularly those with previous cardiovascular disease or heart failure.

Use of different buffers in peritoneal dialysis

A buffer is included in the peritoneal dialysis solution in order to offset the hydrogen ions normally produced during the metabolic processes. Nowadays, the buffer used is lactate, and its concentration in conventional peritoneal dialysis fluids is 35 or 40 mmol/L. Despite the general thought that peritoneal dialysis adequately corrects uremic acidosis, several studies have demonstrated that more than 50% of patients present mild to moderate acidosis with the solution containing 35 mmol/L of lactate, although with a 40 mmol/L solution this percentage decreases, a substantial number of patients still remain acidotic. This acid-base derangement is characterized by a normal pH and a below-normal plasma bicarbonate concentration, although the external body base balance is in equilibrium. There is evidence that this condition contributes to uremic osteodystrophy and has a detrimental effect on protein metabolism. Conventional solutions also affect mesothelial cell viability and local leukocyte function and have potential systemic effects such as the impairment of cellular redox state. New solutions containing pure bicarbonate or a mixture of bicarbonate and lactate have recently been investigated. A bicarbonate solution containing 34 mmol/L significantly increased plasma bicarbonate levels as compared with the lactate 35 mmol/L solution. It has been demonstrated that bicarbonate solutions have better biocompatibility than the lactate buffered solution and substantially reduce abdominal discomfort experienced by a certain percentage of patients during the solution infusion. These studies demonstrated that the bicarbonate-buffered CAPD solution is safe, well-tolerated, and does not present any, even potential, side effects. Thus, it seems reasonable to consider the bicarbonate buffered solution the standard instead of the alternative, and it might entirely replace lactate as buffer in peritoneal dialysis fluid.

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.

Continuous veno-venous haemodialysis with a novel bicarbonate dialysis solution: prospective cross-over comparison with a lactate buffered solution

OBJECTIVE

To compare acid-base balance, lactate concentration and haemodynamic parameters during continuous veno-venous haemodialysis (CVVHD) using bicarbonate or a lactate buffered dialysate.

METHODS

DESIGN

prospective randomized cross-over design;

SETTING

Multicentre combined adult surgical and medical intensive care units. Patients; 26 critically ill patients starting CVVHD for acute renal failure.

INTERVENTIONS

Each patient to receive 48 h of bicarbonate dialysate and 48 h of lactate dialysate with the order of the 48 h block randomized at trial entry.

RESULTS

The serum bicarbonate increased from baseline in both the lactate and bicarbonate groups over the first 48 h of treatment (16.3+/-1.53 to 22.2+/-1.41 mmol/l and 18.9+/-2.02 to 22.2+/-1.18 mmol/l, respectively) and continued to rise towards normal over the next 48 h after cross-over to the other dialysate. The H+ and pCO2 only trended higher in the lactate group. Unlike the acid base parameters, serum lactate levels varied depending on the dialysate composition. The patients initially randomized to the lactate dialysate had higher serum lactate levels and these tended to increase further after 48 h of dialysis from 2.4+/-0.8 to 2.6+/-0.4 mmol/l. However, in the following 48 h the lactate levels fell to 1.8+/-0.6 (P = 0.039) while patients were being treated with the bicarbonate dialysate. Similar results were seen in the patients initially randomized to the bicarbonate dialysate. Serum lactate remained stable over the first 48h (1.4+/-0.2 to 1.5+/-0.1 mmol/l) but after cross-over to the lactate dialysate increased to 3.1+/-0.7 mmol/l (P = 0.051). Overall, lactate levels were significantly higher during dialysis with lactate buffered solution than bicarbonate buffered solution (2.92+/-0.45 vs. 1.61+/-0.25 mmol/l P = 0.01). Mean arterial pressure trended higher during bicarbonate dialysis but did not reach statistical significance (lactate vs. bicarbonate; 71.1+/-3.1 vs. 81.3+/-5.8 mm Hg). Subgroup analysis of the patients with abnormal liver indices or increased lactate levels at initiation of dialysis (n = 15) revealed only a trend toward better bicarbonate control (lactate vs. bicarbonate; 22.00+/-1.73 vs. 22.86+/-1.09, P = 0.2). However, in this group with hepatic insufficiency elevations in serum lactate were even greater during lactate compared to the bicarbonate dialysis (3.39+/-0.68 vs. 1.78+/-0.42 P = 0.036). Patients who had elevations of lactate during lactate dialysis had a high mortality (6 of 7). These patients had an even greater disparity in lactate levels (4.3+/-1.4 vs. 1.3 +/-0.3) and blood pressure (68.0+/- 7.7 vs. 87.2+/-17.1) between lactate and bicarbonate dialysis. Due to small patient numbers these comparisons did not achieve statistical significance.

CONCLUSION

During continuous veno venous haemodialysis a bicarbonate buffered dialysis solution provided equal acid-base control but maintained more normal lactate levels than a lactate buffered dialysis solution.

Randomized long-term evaluation of bicarbonate-buffered CAPD solution

BACKGROUND

Over the past 15 years, lactate has been used successfully as a buffer in peritoneal dialysis solutions, although its effectiveness in the correction of uremic acidosis and its biocompatibility on peritoneal resident cells have been questioned. In addition, some investigators have suggested other potential adverse metabolic effects resulting from the unphysiologically high lactate flux into the body during CAPD. These potential problems associated with lactate-containing CAPD solution prompted the search for alternative buffer-containing solutions. Bicarbonate, the physiological buffer, was considered when the problem of calcium and magnesium carbonate solubility was solved by the use of a two-compartment bag system, allowing the mixing of bicarbonate and divalent cations immediately before infusion. The long-term tolerance, safety, efficacy and therapeutic value of a bicarbonate-buffered peritoneal dialysis solution were evaluated in this study.

METHODS

This open, randomized, controlled, multicenter study comparing a 34 mmol/liter bicarbonate- with a 35 mmol/liter lactate-buffered peritoneal dialysis solution was performed in two consecutive 12-week-treatment phases. Fourteen Centers participated in this trial.

RESULTS

A total of 69 out of initially 123 randomized patients completed the six-month study period (36 patients in the bicarbonate group and 33 in the lactate group). While the arterial acid base status of the total study population did not change during the study period and no significant difference was observed between the two treatment groups, the acid-base status of patients in the bicarbonate group entering the study with a metabolic acidosis significantly improved (mean +/- SD; blood pH: baseline = 7.361 +/- 0.05, week 12 = 7.380 +/- 0.04, P < 0.05; week 24 = 7.388 +/- 0.03 P < 0.05; plasma bicarbonate: baseline = 19.49 +/- 3.01 mmol/liter, week 12 = 21.16 +/- 2.63 mmol/liter, P < 0.01; week 24 = 21.51 +/- 2.42 mmol/liter, P < 0.01). No significant changes were recorded in acidotic patients treated with the conventional lactate-buffered solution. The changes in plasma bicarbonate from baseline during the study was significantly different between the groups (week 12: lactate = +0.11 +/- 2.21 mmol/liter, bicarbonate = +1.69 +/- 2.55 mmol/liter, P < 0.05, 95% confidence interval for the difference 0.21 to 2.94 mmol/liter; week 24: lactate = +0.03 +/- 2.48 mmol/liter, bicarbonate = +1.82 +/- 2. 96 mmol/liter, P < 0.05, 95% confidence interval for the difference 0.16 to 3.42 mmol/liter). The normalized protein catabolic rate (nPCR) slightly but significantly decreased in the lactate group (baseline -0.90 +/- 0.23 g/kg/day, week 24 -0.83 +/- 0.21 g/kg/day, P < 0.01) and increased in the bicarbonate group (baseline +0.89 +/- 0.28 g/kg/day, week 24 +0.92 +/- 0.26 g/kg/day, P < 0.05). Changes from baseline between groups were significant (week 24, lactate = -0. 099 +/- 0.15 g/kg/day, bicarbonate = 0.049 +/- 0.12 g/kg/day, P < 0. 01, 95% confidence interval for the difference 0.068 to 0.229 g/kg/day). Other evaluated parameters (biochemical profile, peritoneal function parameters, dialysate protein loss) did not differ significantly between the two groups. No adverse effects related to the study solution were recorded.

CONCLUSIONS

These results support the efficacy and safety of bicarbonate-buffered peritoneal solutions in a controlled randomized comparison for up to six months. Peritoneal dialysis solutions containing the physiological buffer bicarbonate might effectively replace conventional lactate-buffered CAPD solutions.

Substitution of acetic acid for hydrochloric acid in the bicarbonate buffered dialysate

In a multicenter study including 5 dialysis units, blood acetate changes during 4 h dialysis sessions in 141 patients treated with a 4 mM acetate-containing bicarbonate dialysate (ABD) were evaluated and compared to the values of 114 patients using an acetate-free bicarbonate dialysate (AFD). Acetate-free bicarbonate dialysate was delivered by a dialysis machine from the mixing with water for dialysis of a 1/26.2 bicarbonate concentrate, and a 1/35 acid-concentrate in which acetic acid was substituted for hydrochloric acid (Soludia, Fourquevaux, France). This new type of dialysate was routinely in use for 3 years on average (range, from 2 to 5 years). All patients fasted before and during dialysis. Blood samples were withdrawn at the start and at the end of dialysis sessions. The acetate plasma concentration was determined using the acetyl-CoA synthetase enzymatic method (Boehringer, Manheim, Germany). In patients treated with ABD whose predialysis blood acetate levels were in the physiologic range of < or = 100 microM (n = 113), the acetate plasma concentration increased from a predialysis mean value of 22+/-3 microM to a postdialysis mean value of 222+/-11 microM in 88 patients (78% of patients) whereas the acetate plasma concentration changes remained in the range of physiologic values from 21+/-6 to 58+/-7 microM in the other 25 patients. In contrast, patients treated with AFD whose predialysis blood acetate levels were in the physiologic range (n = 108), acetate plasma concentration increased from a predialysis mean value of 49+/-6 microM to 160+/-19 microM in only 13 patients (12% of patients) whereas acetate plasma concentration changes remained in the range of physiologic values of 23+/-2 to 41+/-3 microM in most of the patients of this group. In this study, a significant number of patients, whether receiving standard or acetate-free bicarbonate dialysates, exhibited an extremely high acetate plasma concentration at the start of the dialysis session. Hyperacetatemia was controlled with AFD in patients whose predialysis acetate plasma concentration of 316+/-82 decreased to 55 +/-23 microM (n = 6) at the end of the dialysis session whereas the acetate plasma concentration remained high when the predialysis concentration was 580+/-76 microM, with a postdialysis concentration of 233+/-39 microM (n = 28). It is concluded that in patients whose predialysis blood acetate levels were in the physiologic range, acetate-containing bicarbonate dialysate induces hyperacetatemia whereas postdialysis blood acetate remains in the normal range in such dialysis patients treated with acetate-free dialysate. Chronic hyperacetatemia, which could be found in dialysis patients, is well controlled by dialysis using an acetate-free dialysate.