How to Reduce 3-Deoxyglucosone and Acetaldehyde in Peritoneal Dialysis Fluids

Objective

3-Deoxyglucosone (3-DG) and acetaldehyde were found to be the major reactive carbonyl compounds in conventional heat-sterilized peritoneal dialysis fluids (PDFs). The aim of this study was to identify factors in the production of PDFs promoting or inhibiting the formation of acetaldehyde and 3-DG.

Design

Single-chamber bag PDFs with different buffer systems and pH values were analyzed for acetaldehyde. 3-Deoxyglucosone was determined in double-chamber bag PDFs with different pH values, in commercially available samples, and in double-chamber products stored under defined conditions.

Results

Acetaldehyde was found in the presence of lactate and malate, whereas in 2-hydroxybutanoate-buffered solution propionaldehyde was detected instead. Between pH 5.0 and 6.0 the acetaldehyde content in lactate-buffered solutions increased strongly. The concentration of 3-DG in the chamber containing glucose in double-chamber bags increased between pH 3.0 and 5.0 by a factor of 6. 3-Deoxyglucosone concentrations in commercially available products vary greatly, reflecting the different pH values of these products. A time- and temperature-dependent reaction leads to a reduction in 3-DG and an increase in 5-hydroxymethyl-furan-2-carbaldehyde during storage.

Conclusion

Acetaldehyde is produced by a reaction that requires both lactate and glucose. Thus, its formation can be prevented by a separation of the reaction partners, glucose and lactate, in a double-chamber bag. In double-chamber bags, pH greatly influences the formation of 3-DG. Minimal formation is observed in the region of pH 3.0. This finding should be taken into account for the development of new double-chamber bag PDFs.

FirstIn VitroandIn VivoExperiences with Stay·Safe Balance, A pH-Neutral Solution in a Dual-Chambered Bag

In addition to low pH and high osmolarity, glucose degradation products (GDPs) are considered to play a major role in the bioincompatibility of peritoneal dialysis fluids (PDFs). The formation of GDPs can be reduced by separating the glucose component of the solution (kept at very low pH) from the lactate component of the solution (kept at alkaline pH) during sterilization and storage. This development has been achieved by the use of a dual-chambered bag. Immediately before infusion, the seam between the two chambers is opened, and the contents are mixed. The result is a fluid with a more physiologic pH in the range 6.8 – 7.4.

Concentrations of 3-deoxyglucosone (3-DG), methyl-glyoxal (MG), acetaldehyde (AA), and formaldehyde (FA) in Stay·Safe Balance (Fresenius Medical Care, Bad Homburg, Germany) were remarkably reduced when compared to conventional PD solution [conventional PDF (1.5% glucose): 172 μmol/L, 6 μmol/L, 152 μmol/L, and 7 μmol/L respectively; Stay·Safe Balance (1.5% glucose): 42 μmolL, < 1 μmol/L, < 2 μmol/L, and < 3 μmol/L respectively; conventional PDF (4.25% glucose): 324 μmol/L, 10 μmol/L, 182 μmol/L, and 13 μmol/L respectively; Stay·Safe Balance (4.25% glucose): 60 μmol/L, < 1 μmol/L, < 2 μmol/L, and < 3 μmol/L respectively).

Human peritoneal mesothelial cells (HPMCs) were exposed to a control solution, a conventional PDF [CAPD 2, 1.5% glucose (Fresenius Medical Care, Bad Homburg, Germany)], and Stay·Safe Balance, either in a co-incubation model (24-hour PDF exposure) or in a pre-incubation model (30-min PDF exposure), followed by 24-hour recovery in culture medium. Interleukin-1β (IL-1β)–stimulated (1 ng/mL) IL-6 secretion from HPMCs was assessed by ELISA. Exposure of HPMCs to conventional PDF resulted in a significant reduction in IL-6 release, which was fully restored following exposure to Stay·Safe Balance. In addition to the short-term investigations, long-term in vitro studies were also carried out. All fluids had near-neutral pH and were changed every second day. After 1, 3, 5, 7, 10, and 13 days of exposure, cell viability was assessed. Whereas exposure to conventional PDF resulted in a significant reduction in HPMC viability after just 3 – 5 days, no significant toxicity of filter-sterilized or dual-chambered fluid was observed for up to 13 days.

An observational study with 9 patients suggested that the efficacy of Stay·Safe Balance is equivalent to that of conventional solution. However, even short-term treatment (8 ± 1 weeks) with this more biocompatible solution seems to improve mesothelial cell mass as indicated by a rise in cancer antigen 125 (CA125) from a baseline of 47 ± 37 U/ min to 172 ± 90 U/min.

Our data indicate that Stay·Safe Balance may help to better preserve peritoneal membrane cell function. An ongoing European multicenter study is expected to confirm these results.

An instrumental variable approach finds no associated harm or benefit with early dialysis initiation in the United States

The estimated glomerular filtration rate (eGFR) at dialysis initiation has been rising. Observational studies suggest harm, but may be confounded by unmeasured factors. As instrumental variable methods may be less biased we performed a retrospective cohort study of 310,932 patients starting dialysis between 2006 to 2008 and registered in the United States Renal Data System in order to describe geographic variation in eGFR at dialysis initiation and determine its association with mortality. Patients were grouped into 804 health service areas by zip code. Individual eGFR at dialysis initiation averaged 10.8 ml/min/1.73m² but varied geographically. Only 11% of the variation in mean health service areas-level eGFR at dialysis initiation was accounted for by patient characteristics. We calculated demographic-adjusted mean eGFR at dialysis initiation in the health service areas using the 2006 and 2007 incident cohort as our instrument and estimated the association between individual eGFR at dialysis initiation and mortality in the 2008 incident cohort using the 2 stage residual inclusion method. Among 89,547 patients starting dialysis in 2008 with eGFR 5 to 20 ml/min/1.73m², eGFR at initiation was not associated with mortality over a median of 15.5 months [hazard ratio 1.025 per 1 ml/min/1.73m² for eGFR 5 to 14 ml/min/1.73m²; and 0.973 per 1 ml/min/1.73m² for eGFR 14 to 20 ml/min/1.73m²]. Thus, there was no associated harm or benefit from early dialysis initiation in the United States.

Factors associated with suboptimal initiation of dialysis despite early nephrologist referral

BACKGROUND

STARRT recently demonstrated that many patients experience suboptimal dialysis starts (defined as initiation as an inpatient and/or with a central venous catheter), even when followed by a nephrologist for >12 months (NDT 2011). However, STARRT did not identify the factors associated with suboptimal initiation of dialysis. The objectives of this study were to extend the results of STARRT by ascertaining the factors leading to suboptimal initiation of dialysis in patients who were referred at least 12 months prior to commencement of dialysis.

METHODS

At each of the three Toronto centers, charts of consecutive incident RRT patients were identified from 1 January 2009 to 31 December 2010, with predetermined data extracted.

RESULTS

A total of 436 incident RRT patients were studied; 52.4% were followed by a nephrologist for >12 months prior to the initiation of dialysis. Suboptimal starts occurred in 56.4% of these patients. No attempt at arteriovenous fistula (AVF) or arteriovenous graft (AVG) prior to initiation was made in 65% of these starts. Factors contributing to suboptimal starts despite early referral included patient-related delays (31.25%), acute-on-chronic kidney disease (31.25%), surgical delays (16.41%), late decision-making (8.59%) and others (12.50%). The percentage of optimal starts with early referral among 14 nephrologists ranged from 33 to 72%.

CONCLUSIONS

Most patients started dialysis in a suboptimal manner, despite an extended period of pre-dialysis care. Nephrologists should take responsibility for suboptimal initiation of dialysis despite early referral and test methods that attempt to prevent this.

Suboptimal initiation of dialysis with and without early referral to a nephrologist

BACKGROUND

Our objective was to examine patients who initiate renal replacement therapy (RRT) at 10 representative Canadian centers, characterize their initiation as inpatient or outpatient and describe their initial type of dialysis access, duration of pre-dialysis care and clinical status at the time of dialysis initiation. We also examined the impact of an optimal dialysis start (i.e. initiated as an outpatient with an arteriovenous fistula, arteriovenous graft or peritoneal dialysis catheter) on subsequent health outcomes.

METHODS

Charts of consecutive incident RRT patients were identified from 1 July to 31 December 2006. Information was collected until 6 months after the initiation or until death, transplant or transfer.

RESULTS

Three hundred and thirty-nine incident RRT patients were studied: 39.6% initiated as an inpatient; 54% started hemodialysis (HD) with a central venous catheter; 15.3% had <1 month predialysis care, while 64.6% had >1 year. Optimal starts occurred in 39.5% of patients. For HD patients, optimal starts occurred in 19.8%. Suboptimal starts were noted in patients referred <12 months prior to end-stage renal disease (44%) and in patients referred earlier (56%). The composite end point of death, transfusion or subsequent hospitalization was significantly reduced with an optimal start [hazard ratio 0.47 (95% confidence interval 0.32-0.68), P = 0.0001].

CONCLUSIONS

Suboptimal initiation of dialysis is common in patients referred early or late. The benefits of early referral are lost if dialysis is initiated suboptimally. There is a need to identify factors that lead to suboptimal initiation despite early referral.

The timing of dialysis initiation affects the incidence of renal replacement therapy

BACKGROUND

Variations in the timing of dialysis initiation may explain some geographical variations in renal replacement therapy (RRT) incidence, but this effect has never been quantified.

METHODS

Using data from the French Renal Epidemiology and Information Network registry, we quantified the association between RRT incidence in 2006-07 and median estimated glomerular filtration rate (eGFR) values before starting dialysis at the administrative district level with geographically appropriate methods.

RESULTS

Crude RRT incidence varied from 80.4 to 238.6 pmi between administrative districts, and median eGFR at dialysis initiation from 5.9 to 11.8 ml/min/1.73 m(2). Age- and sex-adjusted RRT incidence, associated with a 1.2-ml/min/1.73m(2) increase in median eGFR, rose 8% (4-13%) before and 9% (5-13%) after controlling for the effect of nine potential socioeconomic and medical risk factors.

CONCLUSION

The impact of increased eGFR at initiation should be taken into account in guidelines recommending earlier dialysis start.

Age and comorbidity may explain the paradoxical association of an early dialysis start with poor survival

Starting patients on dialysis early has been increasing in incidence in several countries. However, some studies have questioned its utility, finding a counter-intuitive effect of increased mortality when dialysis was started at a higher estimated glomerular filtration rate (eGFR). To examine this issue in more detail we measured mortality hazard ratios associated with Modification of Diet in Renal Disease eGFR at dialysis initiation for 11,685 patients from the French REIN Registry, with sequential adjustment for a number of covariates. The eGFR was analyzed both quantitatively by 5-ml/min per 1.73 m(2) increments and by demi-decile (i.e., 5 percentiles of the distribution); the 15th demi-decile, including values around 10 ml/min per 1.73 m(2), was our reference point. The patients more likely to begin dialysis at a higher eGFR were older male patients; had diabetes, cardiovascular diseases, or low body mass index and level of albuminemia; or were started with peritoneal dialysis. During a median follow-up of 21.9 months, 3945 patients died. The 2-year crude survival decreased from 79 to 46%, with increasing eGFR from less than 5 to over 20 ml/min per 1.73 m(2). Each 5-ml/min/1.73 m(2) increase in eGFR was associated with a 40% increase in crude mortality risk, which weakened to 9%, but remained statistically significant after adjusting for the above covariates. Analysis by demi-decile showed only the highest to be at significantly higher risk. Hence we found that age and patient condition strongly determine the decision to start dialysis and may explain most of the inverse association between eGFR and survival.

Positive effects of protein restriction in patients with chronic kidney disease

OBJECTIVES

The potential benefit or harm of low-protein diets (LPDs) for patients with chronic kidney disease has been debated. This study sought to investigate the effects of treatment with LPDs on nutritional markers, morbidity, and survival during subsequent dialysis. A second objective was to evaluate the effect of LPDs on renal function and the start of dialysis.

DESIGN

This was a retrospective study of medical records.

SETTING

The setting was an outpatient nephrology and dialysis clinic.

PATIENTS

One-hundred twenty-two renal patients were recruited from the central dialysis registry of one clinic. The patients had been followed by a nephrologist for > or =6 months before dialysis. Sixty-one patients were treated with LPDs, and an equal number of control patients not treated with LPDs were matched for sex, age, dialysis modality, diabetes, and start of dialysis.

MAIN OUTCOME MEASURES

Main outcome measures included weight and weight change, serum albumin, glomerular filtration rate, morbidity, and mortality.

RESULTS

There was less mean weight loss in the LPD group the year before dialysis (0.14 kg/month, compared with the control group at 0.36 kg/month, P < .05). The level of serum albumin was higher in the LPD group at the start of dialysis (P < .01). The mean rate of progression during the 6 months before dialysis was lower in the LPD group (4.1 mL/min/year) than in the control group (13.4 mL/min/year) (P < .001). The LPD group had fewer days of hospitalization at the start of dialysis than the control group (8.2 vs 15.4 days, respectively, P < .01). There was no difference in mortality between groups 1, 2, or 5 years after starting dialysis.

CONCLUSIONS

Low-protein diets can reduce patient morbidity, preserve renal function, relieve uremic symptoms and improve nutritional status. The results suggest that LPDs can postpone the start of dialysis for 6 months, and entail substantial cost-savings. Low-protein diets should be used more generally in the renal community.

Adverse Prognostic Indicators in Continuous Ambulatory Peritoneal Dialysis Patients without Obvious Vascular or Nutritional Comorbidities

Objectives

Factors that predict the occurrence of vascular events and poor patient survival in continuous ambulatory peritoneal dialysis (CAPD) patients have not been clearly defined. Previous studies have focused on nonselective CAPD patients, in whom pre-existing comorbidity or poor health might complicate interpretation of the significance of individual factors. The present study was conducted with CAPD patients without severe vascular and nutritional comorbidity.

Patients and Methods

This single-center, prospective, observational study was conducted with 66 prevalent CAPD patients without co-existing severe vascular or nutritional problems. The patients were enrolled in January 1999. We monitored baseline demographic data and clinical and laboratory characteristics including average clinic blood pressure (BP), hemoglobin (Hb), serum albumin, intact parathyroid hormone (iPTH), serum cholesterol, triglycerides, dialysate-to-plasma (D/P) creatinine, dialysis adequacy [Kt/V and creatinine clearance (CCr)], and protein equivalent of nitrogen appearance. We followed the patients for 3 years. Outcome measures were actuarial patient survival, time to occurrence of cerebrovascular accident (CVA) and acute myocardial infarction (AMI), technique survival, and hospitalization rate.

Results

Mean age of the patients was 56.7 ± 10.3 years. Mean duration on CAPD at the time of enrollment was 36.4 ± 21.7 months. Nineteen of the patients (28.8%) had diabetes. Most of the patients [ n = 55 (83.3%)] were using three 2-L exchanges daily. Mean body weight was 56.3 ± 12.2 kg. Mean total weekly Kt/V was 1.91 ± 0.47, and mean total weekly CCr was 75.3 ± 30.6 L/1.73 m2. Actuarial patient survival was 96.9% at 1 year, 90.5% at 2 years, and 75.3% at 3 years. Overall technique survival was 96.9% at 1 year, 95.1% at 2 years, and 89.1% at 3 years. Multivariate analysis showed that age, diabetes mellitus (DM), and body size (weight or surface area) were independent predictors of patient survival. We estimated that a 1-kg increase in body weight was associated with a 6% increase in the relative risk of death ( p = 0.015; 95% confidence interval: 1.013 to 1.126). Patients with a body weight of 60 kg or less showed a significantly better 3-year survival as compared with patients with body weight greater than 60 kg (88.1% vs 58.3%, p = 0.0042). No significant predictors were identified for technique failure or occurrence of a major vascular event. High BP and DM were independent predictors for hospitalization. Dialysis adequacy indices and serum albumin showed no significant effect on any outcome measure.

Conclusions

Our study showed that, in addition to age and DM, body size could also be a significant factor affecting survival of CAPD patients. However, the underlying causative mechanisms remain unclear and require further study.

Impact of timing of initiation of dialysis on mortality

Previous studies showed that sicker patients were initiated on dialysis at higher GFR as estimated by the Modification of Diet in Renal Disease (MDRD) formula. It was previously shown that patients with low creatinine production were malnourished and had low serum creatinine levels and creatinine clearances (CrCl) but high MDRD GFR at initiation of dialysis. Therefore, a propensity score approach was used to examine the associations of MDRD GFR and measured CrCl at the initiation of dialysis with subsequent mortality. Baseline data and outcomes were obtained from the Dialysis Morbidity Mortality Study Wave II. Propensity scores for early initiation derived by logistic regression were used in Cox models to examine mortality. Each 5-ml/min increase in MDRD GFR at initiation of dialysis in the entire cohort was associated with increased hazard of death in multivariable Cox model (hazard ratio [HR] 1.14; P = 0.002). In the subgroup of patients with reported CrCl, higher MDRD GFR was associated with increased risk of death (for each 5-ml/min increase, HR 1.27; P < 0.001) but not CrCl (for each 5-ml/min increase, HR 0.98; P = 0.81). These divergent results might reflect erroneous GFR estimation by the MDRD formula. Furthermore, these data do not support earlier initiation of dialysis. Therefore, for patients without clinical indications for initiation of dialysis, the appropriate GFR level for initiation of dialysis is unknown.

Acceleration of neutrophil apoptosis by glucose-containing peritoneal dialysis solutions: role of caspases

Commercial, glucose-containing peritoneal dialysis (PD) solutions have deleterious effects on leukocytes and mesothelial cells that contribute to an impaired peritoneal defense. However, the molecular mechanisms of these deleterious effects are poorly understood. The effect of PD solutions on neutrophil viability, the molecular mechanisms of cell death, its functional consequences, and the possibilities for pharmacologic modulation have now been studied. The effect of newly available, bicarbonate-buffered PD solutions were further investigated. Lactate-buffered, glucose-containing PD solutions increased the apoptosis rate of cultured neutrophils (control media versus 4.25% glucose PD solution: 31 +/- 3% versus 52 +/- 3% apoptosis at 24 h, P < 0.001). Bicarbonate-buffered, 4.25% glucose-containing PD solutions with low concentration of glucose degradation products did not increase the rate of apoptosis. Apoptosis induced by lactate-buffered, 4.25% glucose PD solutions was not related to hyperosmolality or acidic pH and was not reproduced by increasing the glucose concentration by the addition of glucose to a commercial, lactate-buffered fluid. Neutrophil apoptosis was associated with caspase-3 activation. Inhibition of caspase-3 by the use of the caspase-3 inhibitor acetyl-Asp-Glu-Val-Asp-fmk or the broad-spectrum caspase inhibitor benzyloxycarbonyl-Val-Ala-DL-Asp-fluoromethylketone (zVAD-fmk) prevented features of apoptosis, such as morphologic changes, internucleosomal DNA degradation, and the appearance of hypodiploid cells and increased the number of viable, trypan blue-excluding neutrophils. Furthermore, zVAD-fmk increased neutrophil phagocytosis of bacteria. However, the caspase-1 inhibitor acetyl-Tyr-Val-Ala-Asp-aldehyde did not prevent cell death. These data suggest that unidentified components in commercial, lactate-buffered, high-glucose PD fluid accelerate the rate of neutrophil apoptosis. Glucose degradation products may be such unidentified components. Acceleration of neutrophil apoptosis may contribute to the impaired local defense system of patients undergoing PD.

Evaluation of renal Kt/V as a marker of renal function in predialysis patients

BACKGROUND

The use of renal Kt/V (r-Kt/V) as an indicator for the need of dialysis initiation has been recommended in the NKF-DOQI guidelines. In analogy to clinical practice in peritoneal dialysis, a fall of r-Kt/V below a threshold of 2.0 per week may indicate inadequate renal toxin elimination. However, there are no studies linking r-Kt/V with other parameters of glomerular filtration rate (GFR) in predialysis patients, and the validity of r-Kt/V as parameter for timing of dialysis initiation is unknown.

METHODS

Renal function was assessed repeatedly in 125 patients (N = 465 measurements). In predialysis patients (r-Kt/V <2.5 per week) r-Kt/V was compared with creatinine [CCr], urea [CUr], averaged creatinine/urea clearance [CCr/Ur], Cockcroft-Gault formula [CCG], and MDRD prediction equation 6 (MDRD6-GFR). The diagnostic performance of r-Kt/V as a parameter for timing the initiation of dialysis was evaluated.

RESULTS

Renal Kt/V <2.5 was prevalent in 24.9% of cases (N = 116, mean 1.92 +/- 0.34). In this group mean CCr was 13.8 +/- 4.9, mean CUr 6.7 +/- 1.3, and CCr/Ur 10.2 +/- 2.9 mL/min/1.73 m2. There was no correlation of r-Kt/V with serum creatinine and MDRD6-GFR, but a significantly positive correlation with CCr/Ur (r2 = 0.3382, P < 0.001). Sensitivity of r-Kt/V to detect CCr/Ur < 10.5 mL/min/1.73 m2, defined as the threshold for dialysis initiation, was 73.6% with a specificity of 91.9%.

CONCLUSIONS

These results suggest that r-Kt/V is a parameter of acceptable specificity but poor sensitivity for the timing of dialysis initiation. Additional measures of renal function, such as the average of measured creatinine and urea clearance, also should be taken into consideration when deciding on the timing of dialysis initiation prior to the development of clinical signs of uremia and malnutrition.