Long-term use of 1.1% amino acid dialysis solution in hypoalbuminemic continuous ambulatory peritoneal dialysis patients

INTRODUCTION

Malnutrition is a common problem in patients treated with continuous ambulatory peritoneal dialysis (CAPD). Hypoalbuminemia in CAPD patients is an independent risk factor for death and is associated with malnutrition. Previous short-term studies have examined the use of amino acid based PD solutions in terms of albumin levels and anthropometric changes, but not clinical outcome. We report on the extended use of 1.1% amino acid based peritoneal dialysis solution (Nutrineal) and have assessed clinical utility in terms of nutrition, biochemical indices, dialysis adequacy and clinical outcomes.

METHODS

The effect of Nutrineal was studied retrospectively in 22 patients during the past 30 months. All patients had an albumin level of < 35 g/l prior to commencing Nutrineal, and had either a protein intake < 1.2 g/kg or weight loss of > 5% in the previous 3 months. 19 of the 22 patients underwent an 8-week trial of oral nutritional supplements with no improvement in serum albumin level. Albumin level, normalized protein catabolic rate, weight, Kt/V and creatinine clearance were assessed for all patients prior to Nutrineal and at the end of the study period.

RESULTS

The mean time on Nutrineal therapy was 13.6 months (range 6-26 months). There were no reported side effects of the treatment. There was an average of 1 episode of peritonitis per 23 treatment months, and only 1 patient died (4% annually adjusted mortality cf 8.9% on the peritoneal dialysis program as a whole). There was a significant increase in albumin level from 22.45 +/- 0.97 range 14-33 g/l to 25.68 +/- 1.159 range 16-35 g/l (p = 0.0036). Normalized protein catabolic rate increased significantly, from 0.898 +/- 0.053 to 1.085 +/- 0.056 g/kg/day (p = 0.0057). Weight decreased slightly although this did not reach statistical significance. Kt/V and creatinine clearance both decreased significantly, but remained within the adequate range in > 80% of the patients. There was no significant change in residual renal function (mean residual creatinine clearance 3.8 +/- 0.59 ml/min at the start of the study period, cf 3.4 +/- 0.61 ml/min at the end).

CONCLUSION

These data suggest that Nutrineal can be used safely and effectively for an extended period of time. Such use is associated with a low mortality rate and a low peritonitis rate, although dialysis adequacy is compromised to a degree.

Kinetics of carboxy-terminal propeptide of type I procollagen in pediatric patients undergoing peritoneal dialysis

Carboxy-terminal propeptide of type I procollagen (PICP) is used as a marker of bone formation and, presumably, also peritoneal fibrosis. The aim of the present study was to assess the effect of dialysate PICP level (PICPd) on serum PICP level (PICPs). The study group consisted of 20 patients divided into two groups: group A consisted of 10 children without peritonitis, mean age 13.6 +/- 5 years, 3 on continuous ambulatory peritoneal dialysis (CAPD) and 7 on automated peritoneal dialysis (APD); and group B consisted of 10 children with peritonitis (last episode having occurred at least 2 months before the study), mean age 13.9 +/- 2 years, 8 on CAPD and 2 on APD. Osmolarity of the dialysate fluid in groups A and B was similar (375.7 +/- 42 mOsm/L and 363.1 +/- 16 mOsm/L respectively). The PICPs and PICPd levels, PICP index (PICPd/PICPs), PICP peritoneal clearance (ClPICP), and PICP mass transfer (MTPICP) were measured in both groups. Mean PICPs was higher in group B, but the difference was not significant. No significant differences were seen in the mean values of PICPd, PICP index, ClPICP, and MTPICP between groups. Levels of PICPd correlated positively with ClPICP (r = 0.75, p < 0.001) and negatively with MTPICP (r = -0.89, p < 0.0001). No associations were seen between PICPs and PICPd, ClPICP, and MTPICP. No associations were observed between osmolarity and ClPICP and MTPICP. Serum PICP level in children undergoing peritoneal dialysis does not depend on peritoneal PICP level.

Small-solute and middle-molecule clearances during continuous flow peritoneal dialysis

Previous theoretic and clinical studies have shown that continuous flow peritoneal dialysis (CFPD) provides a high dose of small-solute removal; however, the dose of middle-molecule removal with CFPD therapy has not been evaluated. We used a variable-volume, two-compartment model to calculate theoretical steady-state solute kinetic profiles during CFPD, continuous ambulatory peritoneal dialysis (CAPD), and hemodialysis using a high-flux dialyzer (HFHD), for an anuric 70-kg patient and two measures of dose: equivalent renal clearance (EKR) and standard Kt/V (stdKt/V). Dose measures during each therapy were calculated for five solutes: urea, creatinine, vitamin B12, inulin, and beta 2-microglobulin. Fluid (1 L daily) was assumed to accumulate in and to be removed from the extracellular space, and non renal clearance was assumed to be zero for all solutes except beta 2-microglobulin. Calculated doses for CFPD were higher than for CAPD or HFHD when assessed by either EKR or stdKt/V. Dose enhancements for CFPD were highest for small solutes, but were still considerable for middle molecules. We conclude that CFPD achieves higher doses than CAPD or HFHD for both small-solute and middle-molecule removal.

A rapid assay for icodextrin determination in plasma and dialysate

Icodextrin is a glucose polymer osmotic agent used to achieve sustained ultrafiltration during long peritoneal dialysis dwells. Previous assays for icodextrin in plasma and dialysate samples involved laborious methods, such as gel permeation chromatography with post-column derivatization of the eluted glucose polymers. We developed and validated a simple and more rapid assay for icodextrin using amyloglucosidase to hydrolyze all glucose polymers to glucose. Glucose was determined pre- and post-hydrolysis using a glucose hexokinase assay, and icodextrin concentration was calculated as the difference between glucose levels before and after hydrolysis. The complete hydrolysis of icodextrin to glucose was confirmed using anion exchange chromatography. Recovery studies using icodextrin powder added to plasma or dialysate showed 100% +/- 15% recovery for plasma concentrations from 10 mg/dL to 800 mg/dL and for dialysate concentrations from 50 mg/dL to 800 mg/dL. The percent relative standard deviation (%RSD) based on multiple replicates was within 6%, except at plasma icodextrin concentrations of 10 mg/dL and below. This simple and reliable assay has been used routinely in our laboratory to analyze thousands of plasma and dialysate samples from patients using Extraneal peritoneal dialysis solution (Baxter Healthcare Corporation, Deerfield, IL, U.S.A.).

Influence of pH-neutral peritoneal dialysis solution

We evaluated the influence of a neutral peritoneal dialysis solution (PDS) on the peritoneum. The subjects were 10 stable PD patients using conventional PDS. We substituted pH-neutral PDS (PD Solita A: Shimizu Medical, Tokyo, Japan) for conventional PDS (Gambrosol A: Shimizu Medical). Effluent from 4-hour dwells was collected, and the appearance rate of cancer antigen 125 (CA125-AR) was calculated using the method of Pannekeet et al and corrected to body surface area. The dialysate-to-plasma creatinine (D/P Cr) was obtained, and personal dialysis capacity (PDC) was evaluated at 3-month intervals. Mean daily ultrafiltration volumes did not significantly change when pH-neutral PDS was used. The mean CA125-AR obtained 1 month after substitution was twice as high as that before substitution (139.2 +/- 47.3 U/min/1.73 m2 before substitution vs. 286 +/- 126.2 U/min/1.73 m2 1 month later). However, mean values of CA125-AR were maintained at higher levels and did not significantly vary for 7 months after PD fluid substitution. When the change in CA125-AR (delta CA125-AR) was calculated as the ratio of the CA125-AR value before substitution to that after substitution at the respective measurement points, delta CA125-AR negatively correlated with D/P Cr. However, none of % area, % absorption, or % plasma loss significantly correlated with the delta CA125-AR obtained 6 months later. Although mesothelial cell viability may increase with the use of pH-neutral PDS, the level of the increase may differ depending on the severity of peritoneal damage. In addition, the use of a neutral PD fluid did not improve the endothelial cell system. In the future, development of a novel osmotic pressure-regulating substance substituting for glucose is essential to the development of PD fluids with higher biocompatibility.

Glucocorticoid protects against the development of encapsulating peritoneal sclerosis on peritoneal dialysis

Encapsulating peritoneal sclerosis (EPS) is an important complication of peritoneal dialysis in which all or part of the intestine is enveloped in a fibrous ball resulting in a cocoon. Previously, we reported that acid dialysis solution (DS) induces peritoneal fibrosis. In the present study, we examined the effect of treatment with glucocorticoid (GC) in a model of EPS in rats. We divided 20 male Wistar-Kyoto rats into four groups and dialyzed them with various solutions for 40 days as follows: (1) pH 3.5 DS, 10 mL (pH 3.5, containing 1.35% glucose, n = 5); (2) pH 3.5 DS, 10 mL + GC (0.1 mg dexamethasone daily, n = 5); (3) pH 7.0 DS, 10 mL (n = 5); and (4) pH 7.0 DS, 10 mL + GC (n = 5). At the end of 40 days, all rats were humanely killed by decapitation. Expression of mRNA of aquaporins (AQPs) and glucose transporters (GLUTs) were studied by reverse-transcriptase polymerase chain reaction. In rats treated with pH 3.5 DS, necropsy findings showed evidence of EPS. The typical appearance was multiple surfaces covered with granulation tissue or fibrotic tissue or both. Multiple adhesions were present. Microscopic findings revealed that low-pH DS induced peritoneal fibrosis and loss of mesothelium. In the dialyzed rats, mRNA of AQP-1, AQP-4, GLUT-1, GLUT-4, and GLUT-5 was expressed in peritoneum. In rats treated with pH 3.5 DS, expression of AQPs was significantly suppressed and expression of GLUTs was significantly enhanced. However, glucocorticoid treatment prevented the progression of peritoneal fibrosis and adhesion of peritoneum. In rats treated with pH 7.0 DS, no signs of EPS were seen. Our study suggests that low-pH DS induced the development of EPS. Glucocorticoid protects against the development of EPS on peritoneal dialysis.

Differences in peritoneal equilibration test results in patients aged above or below 60 years

Peritoneal permeability, evaluated using the peritoneal equilibration test (PET), indicates that, in an adult population not selected for age, an increase in the transport rate of small solutes usually occurs in the course of peritoneal dialysis (PD) treatment. We evaluated the dialysate-to-plasma ratio of urea (D/P urea), the D/P creatinine, the ratio of dialysate glucose at a designated dwell time to dialysate glucose at 0 dwell time (D/D0 glucose), and the mass transfer-area coefficients (KBDs) of those solutes in PETs performed in patients aged above or below 60 years who were matched for sex, PD duration, and outcome. The single-center, retrospective study was carried out in a peritoneal dialysis unit in a university hospital. Two groups of PD patients were chosen. Mean age of patients in group I (n = 21; 9 women, 12 men) was 67.7 +/- 4.5 years; PD duration was 20.1 +/- 12.1 months. In group II, the patients (n = 21; 9 women, 12 men) had a mean age of 42.8 +/- 9.1 years, and had been treated with PD for 20.7 +/- 12.1 months. A standard PET was performed according to Twardowski et al every 3 months from PD start to PD end. The first results, the mean results representing the entire PD course, and the last results were compared between groups. In addition, the first and the last results were compared within each group. No significant differences were seen between the groups in peritoneal transport in the first PET. In the last PET, the curves for D/P urea and D/P creatinine, and the KBD for urea, were significantly lower in the older patients than the curves obtained at PD start. In consequence, a tendency toward lower D/P ratios or KBDs for urea and creatinine in the last and mean PETs was observed in group I as compared with group II. No significant changes were seen in the peritoneal transfer of glucose in the course of PD or between groups. Older patients may show a reduction in peritoneal permeability from the vascular to the mesothelial side of the membrane in the course of PD treatment; peritoneal transport in the opposite direction remains unchanged during approximately 20 months from the start of PD treatment. The patients under 60 years of age maintain stable bi-directional permeability under a comparable PD duration.

High-performance liquid chromatography/tandem mass spectrometry assay for the rapid high sensitivity measurement of basal acetylcholine from microdialysates

A high-throughput liquid chromatography tandem mass spectrometry (LC/MS/MS) method has been developed for the analysis of acetylcholine (ACh) in brain dialysates. This separation of ACh is based on cation exchange chromatography with elution buffer consisting of a mixture of ammonium acetate, ammonium formate and acetonitrile. Using isocratic separation conditions, ACh was resolved within a minute and detected using tandem mass spectrometry in the positive ion electrospray mode. The limit of detection for ACh was found to be 1 fmol on column with a S/N ratio of 3:1. The assay has been used routinely for the measurement of ACh in brain dialysates from awake freely moving rats. Furthermore, separation conditions were modified to allow simultaneous measurement of ACh and the acetylcholine esterase inhibitor, neostigmine.

Effect of diabetes on peritoneal function assessed by personal dialysis capacity test in patients undergoing CAPD

BACKGROUND

We evaluated differences in individual peritoneal membrane transport function and nutritional status in patients with diabetes mellitus (DM) and nondiabetic (non-DM) patients on continuous ambulatory peritoneal dialysis (CAPD).

METHODS

We used a newly developed peritoneal function test, personal dialysis capacity, in 88 patients (44 DM and 44 non-DM) on CAPD for 1 to 210 months. Sex, age, past history of peritonitis, and duration of CAPD were matched in DM and non-DM patients.

RESULTS

Serum albumin (mean +/- SEM) was lower in DM compared with non-DM patients: 3.0 +/- 0.1 g/dL (30 +/- 1 g/L) versus 3.5 +/- 0.1 g/dL (35 +/- 1 g/L), P < 0.001. Peritoneal area and dialysis protein loss were greater in DM versus non-DM patients. In multiple linear regression analysis, the only independent predictor of serum albumin in patients with DM was dialysis protein loss. In contrast, age, past history of peritonitis, duration of CAPD, caloric intake, protein nitrogen appearance and protein catabolic rate, and residual renal function did not correlate with serum albumin in DM patients. In non-DM patients, age, duration of CAPD, and past history of peritonitis, but not dialysis protein loss, were independent predictors of serum albumin. There was a significant correlation in DM patients, but not in non-DM CAPD patients, between dialysis protein loss and urinary excretion of protein (r = 0.866, P = 0.0005).

CONCLUSION

In this multicenter study, peritoneal membrane transport and peritoneal protein permeability were significantly higher in DM than in non-DM patients. Hypoproteinemia in DM patients is attributable to the high permeability of the peritoneal membrane undergoing CAPD.

Solutions for APD: special considerations

Automated peritoneal dialysis (APD) has become the fastest growing dialysis modality in Europe and the United States in recent years. Freedom from daytime exchanges, flexibility of prescription, performance in recumbent position leading to enhanced treatment efficacy, and a decreased incidence of peritonitis are the main advantages of APD over CAPD. Studies on new developments of glucose-based PD fluids were performed predominantly in CAPD patients. High volumes and frequent APD cycles in patients may aggravate the adverse effects of standard CAPD fluids on the peritoneal membrane with increasing time on PD. New, glucose-based PD fluids with neutral pH, very low concentrations of glucose degradation products (GDPs), containing either lactate or bicarbonate as buffering substances have been introduced into clinical use recently. With these new fluids, various in vitro, ex vivo, and in vivo studies could demonstrate a better preservation of peritoneal cell viability and growth, less inhibited secretory cell functions, a significant reduction in the formation of advanced glycation end products (AGEs), and clinical signs for an improved preservation of peritoneal mesothelial cells indicated by an increase in effluent CA125. One has to be aware, however, that uremia per se prior to initiation of PD, as well as during PD treatment itself, directly impacts on peritoneal membrane structural changes so that new, more biocompatible PD fluids may not be completely sufficient to prevent morphologic and functional changes of the membrane. Due to a strong sodium sieving during APD, PD fluids with sodium concentrations of 125-130 mmol/L may be beneficial. Systematic calcium kinetic studies have not yet been performed in APD patients. APD fluids should offer a calcium concentration range of 1.0-1.75 mmol/L in order to enable an individualized APD prescription. For long-term APD treatment, better knowledge of peritoneal membrane physiology and PD kinetics should promote individualization of prescriptions. New, pH-neutral PD solutions with minimized amounts of GDPs may be a significant step forward to improved membrane preservation during long-term APD treatment.

Low calcium dialysate increases cardiac relaxation in CAPD patients

OBJECTIVE

To establish whether changes in serum calcium affect left ventricular (LV) function in continuous ambulatory peritoneal dialysis (CAPD) patients.

METHODS

This study was conducted on 28 clinically stable CAPD patients (11 females, 17 males). Left ventricular relaxation and systolic function were echocardiographically examined in all patients during standard dialysate (containing 1.75 mmol/L calcium) treatment. All patients were then changed to low calcium dialysate (1.25 mmol/L calcium) for 1 month and all patients were re-examined echocardiographically. Decrement in isovolumic relaxation time (IVRT) and deceleration time (DT), and increment in the ratio of peak early to peak late diastolic velocities (E/Amax) were admitted as indexes showing improvement in LV relaxation. 17 age- and sex-matched controls were also echocardiographically examined.

RESULTS

Deceleration time, interventricular septal thickness at systole (IVSTS) and diastole (IVSTD), and posterior wall thickness at systole (PWS) and diastole (PWD) were higher in CAPD patients using standard dialysate than in normal controls. With the use of low calcium dialysate, DTs were similar but IVSTS, IVSTD, PWS, and PWD values remained higher. In normal controls, E/Amax values were higher than those in CAPD patients using standard dialysate (p < 0.001) and low calcium dialysate (p = 0.009). Serum intact parathyroid hormone level, weight, clinical volume status, and blood pressure were similar throughout the study period. Serum ionized calcium levels were decreased significantly during low calcium dialysate treatment. The changes in IVRT, DT, and E/Amax suggest improvement in LV relaxation during low calcium dialysate treatment.

CONCLUSION

Left ventricular relaxation is increased with the use of low calcium dialysate compared with standard dialysate treatment. The idea of possible beneficial effects of increment in LV relaxation on cardiovascular morbidity and mortality deserves further studies.

Importance of increased ultrafiltration volume and impact on mortality: sepsis and cytokine story and the role for CVVH

There is growing interest in extracorporeal blood purification therapies (EBPT) as adjuvants in the complex therapy of sepsis and multiple organ dysfunction syndrome (MODS). Nowadays the only routinely used purification technique is 'renal replacement therapy' (RRT) during acute renal failure (ARF), one of the almost inevitable and deadly components of MODS. RRT has been the first and still is the most utilised and effective type of EBPT. Evidence is growing about its ability to maintain homeostatic balance in critically ill patients, and specifically in septic patients with MODS. Clinical trials have been recently designed to modify or improve these therapies. In detail, the following issues have been currently addressed: effects on blood purification provided by different therapies, adequacy of prescription and delivery of therapy, toxins and solutes to be removed with these techniques. Based on these speculations we will briefly review the current understanding of these issues and the rationale for application of RRT in the intensive care unit (ICU). In particular, we will focus on the importance of increased ultrafiltration volume and its impact on mortality in the general ICU population and in septic patients.

Continent jejunal reservoir dialysis for end-stage renal disease: is it possible?

With limited organs available for renal transplantation in comparison with the number of patients on the waiting list, and with the drawbacks of dialysis, other forms of treatment for end-stage renal disease (ESRD) need to be investigated. We propose that using a reconfigured segment of bowel as a reservoir in which dialysate of various compositions can be instilled to remove metabolic wastes usually handled by the kidney may augment or replace renal function in a uremic patient. We have chosen the jejunum and have documented our preliminary findings using hyperosmotic dialysate along with the unique characteristics of continent jejunal reservoir dialysis (CJRD). With further refinements, CJRD may eventually be offered as an alternative treatment for ESRD.

Heat sterilization of peritoneal dialysis solutions influences ingestive behavior in non-uremic rats

BACKGROUND

The appetite inhibitory effect of glucose-based peritoneal dialysis (PD) solutions may be due to glucose as such, or the hyperosmolality of the PD solution, or an effect of glucose degradation products (GDPs) formed in the PD solution during heat sterilization. This was studied in an experimental appetite model in rat.

METHODS

The effect of different experimental PD solutions on ingestive behavior was investigated in non-uremic rats equipped with an implanted intraoral (i.o.) cannula through which a 1 mol/L sucrose solution was infused during tests. The amount of intake was recorded at 30 min after rats were infused intraperitoneally (IP) with 30 mL of different solutions. This method allowed an accurate and reproducible analysis of i.o. intake. The experimental PD solutions tested included (1) glucose based PD solutions with different glucose concentrations, sterilized by heat or microbiological filter, (2) glucose- and mannitol-based PD solutions with the same osmolality, sterilized by heat or microbiological filter; and (3) glucose based PD solutions, using different pH values (pH 3.0, pH 5.5 or pH 7.4) during heat sterilization.

RESULTS

Following IP infusion of solutions, (1) the i.o. intake was significantly inhibited by glucose based, heat sterilized PD solutions and the degree of appetite suppression was related to the concentration of dialysate glucose in a dose-dependent way; (2) the i.o. intake was significantly less suppressed by filter sterilized than by heat sterilized glucose-based solutions; (3) the i.o. intake was significantly less following the IP infusion of glucose-based than following the mannitol-based heat sterilized solutions; however, i.o. intake did not differ between the glucose-based and mannitol-based filter sterilized solutions; and (4) furthermore, the degree of suppression of i.o. intake induced by glucose-based PD solutions was influenced by the pH value during heat sterilization. The lower the pH of the PD solution during heat sterilization, the higher the i.o. intake.

CONCLUSIONS

The IP infusion of glucose-based heat-sterilized PD solutions inhibited food intake in this experimental appetite model, and the degree of suppression depended on the concentration of dialysate glucose and the pH of the solution during heat sterilization. The results suggest that GDPs formed during heat sterilization may exert a more adverse effect than glucose itself on ingestive behavior, and that a reduction of the concentration of GDPs in the PD solution using filter sterilization or a low pH value in the PD solution during heat sterilization may improve food intake.

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.

Effect of increased dialysate volume on peritoneal surface area among peritoneal dialysis patients

Large dialysate volumes are often required to increase solute clearance for peritoneal dialysis patients. The resulting increase in solute clearance might be attributable to an increased plasma-to-dialysate concentration gradient and/or to an increased effective peritoneal surface area. One of the factors affecting the latter is the peritoneal surface area in contact with dialysate (PSA-CD). The aim of this study was to estimate the change in PSA-CD after a 50% increase in the instilled dialysate volume for patients undergoing peritoneal dialysis. PSA-CD was estimated by using a method applying stereologic techniques to computed tomographic (CT) scans of the peritoneal space. The peritoneal cavity of 10 peritoneal dialysis patients was filled with a solution containing dialysate, half-isotonic saline solution, and contrast medium. Peritoneal function tests and CT scanning of the abdomen were performed twice for each patient (with an interval of 1 wk), after instillation of a 2- or 3-L solution. Scanning of thin helical CT sections was performed, and 36 random sections of the abdomen were obtained after reconstruction. A grid was superimposed on the sections. The surface area was estimated by using stereologic methods. After instillation of the 2-L solution, the volume of the peritoneal solution at the time of CT scanning was 2.32 +/- 0.05 L. The PSA-CD was 0.57 +/- 0.03 m(2), ranging from 0.41 to 0.76 m(2). The use of the 3-L solution increased the peritoneal volume by 46 +/- 2%. PSA-CD increased by 18 +/- 2.3% to 0.67 +/- 0.04 m(2) (range, 0.49 to 0.84 m(2); P < 0.01). Creatinine mass transfer increased from 112 +/- 10 mg to 142 +/- 11 mg (P < 0.0001). The slope of the change of the plasma-to-dialysate creatinine concentration gradient with time decreased from -2.26 +/- 0.23 x 10(-2) to -1.97 +/- 0.16 x 10(-2) (P = 0.01). K(BD-0) (permeability-surface area product or mass area transfer coefficient at time 0 of the dwell) increased from 10.6 +/- 0.7 to 13.6 +/- 1.2 ml/min (P < 0.02). These data demonstrate that increasing the instilled dialysate volume by 50% for peritoneal dialysis patients results in significant increases in the PSA-CD and K(BD).

A dual probe characterization of dialysate amino acid levels in the medial prefrontal cortex and ventral tegmental area of the awake freely moving rat

Dual probe microdialysis was employed to characterize the origins of dialysate glutamate, aspartate and gamma-aminobutyric acid (GABA) in the medial prefrontal cortex (mPfc) and to investigate functional interactions between the mPfc and ventral tegmental area (VTA) in awake, freely moving rats. Perfusion with elevated potassium (K(+); KCl, 100 mM, 20 min), low Ca(2+) (0.1 mM, 60 min) or tetrodotoxin (TTX, 10 microM, 100 min) was performed in the mPfc and dialysate levels of glutamate, aspartate and GABA were measured locally and in the VTA. Elevated K(+) in the mPfc rapidly increased dialysate glutamate and aspartate locally (+90+/-10 and +41+/-9% from basal, respectively) and in the VTA (+71+/-14 and +42+/-14%, respectively). MPfc GABA was also rapidly increased (+241+/-62%) while VTA GABA was not affected. Perfusion with low Ca(2+) in the mPfc decreased local glutamate, aspartate and GABA (-26+/-8; -35+/-7 and -45+/-8%, respectively) and decreased only GABA (-40+/-5%) in the VTA. Intra-mPfc TTX increased glutamate and aspartate locally (+82+/-23 and +54+/-27%, respectively) and in the VTA (+84+/-18 and +38+/-17%, respectively). In contrast, intra-mPfc TTX decreased local GABA (-33+6%) while VTA GABA levels were not affected. Taken together, these data confirm the influence of the mPfc upon the ipsilateral VTA and provide evidence for two neuronal pools which contribute to basal extracellular mPfc and VTA glutamate, aspartate and GABA levels, the first pool derived from Na(+)- and Ca(2+)-dependent release and the second derived from voltage-dependent reuptake.

The negative Ca(2+) balance is involved in the stimulation of PTH secretion

The low calcium (Ca(2+)) dialysate have been developed to diminish the risk of hypercalcemia with the administration of active vitamin D and Ca(2+) carbonate as phosphate binder. Today, increasing numbers of hemodialysis (HD) patients have been on the low Ca(2+) dialysate (Ca(2+) = 2.5 mEq/l). However, the clinical consequences of a negative calcium net-balance which may be induced by the use of low Ca dialysate are not well evaluated. In the present study, we explored the effects of low Ca(2+) dialysate on the calcium balance and the PTH secretion. Eighty one chronic HD patients (male/female: 47/34; mean age: 60.2 +/- 1.5 years; mean HD periods: 11.1 +/- 0.8 years) who had been dialyzed with 3.0 mEq/l Ca(2+) dialysate were studied. All patients were transferred to the low Ca dialysate, which actually brought about a negative net-balance in Ca (mean: -94.5 mg) and an increase in serum intact PTH levels (mean: +23.7%: p = 0.03) during a single HD session. However, no changes in serum ionized Ca(2+) were found in spite of negative Ca(2+) balance. One month after change to the low Ca(2+) dialysate (total 12 sessions in each case), serum intact PTH levels increased significantly (186.7 +/- 19.5 vs. 216.2 +/- 21.9 pg/ml: p = 0.01) in spite of the fact that no changes were found in serum ionized Ca(2+), Pi and Mg. This result indicates that the negative Ca(2+) balance during low-Ca(2+) hemodialysis-stimulated PTH secretion, which offset the decrease of serum Ca(2+); a trade-off phenomenon between negative Ca balance and PTH. This suggests that low Ca(2+) dialysate may exaggerate the progression of secondary hyperparathyroidism.

Clinical advantages of new peritoneal dialysis solutions

A review is given of the various mechanisms by which conventional glucose/lactate-based peritoneal dialysis solutions can induce damage to the peritoneal membrane. The potential advantages of newly developed dialysis solutions and the results of recent studies on their use in patients are discussed.

Increased peritoneal membrane permeability is associated with abnormal peritoneal surface layer

OBJECTIVES

We recently showed that the peritoneal surface layer may be an important barrier in modulating peritoneal membrane permeability. In the present study, we investigated the relationship between an increased peritoneal transport rate and the peritoneal surface layer.

METHODS

Male Sprague-Dawley rats (n = 8) received intraperitoneal injections of 4.25% glucose dialysate daily for 1 week. Forty-eight hours after the last injection, a 4-hour dwell study using 25 mL 4.25% glucose dialysate was performed in each rat. The results were compared with those from control rats that received no intraperitoneal injections (n = 8). The peritoneal fluid and small-solute transport characteristics were evaluated. The peritoneal surface layer was studied using an electron microscope. The phospholipids content of the dialysate was also evaluated.

RESULTS

Peritoneal fluid removal was significantly reduced in the daily injection group (30.6 +/- 1.3 mL) as compared with the control group (38.2 +/- 0.6 mL). The peritoneal fluid absorption rate and small-solute transport rate were also significantly higher in the daily injection group as compared with the control group. The amounts of phospholipids in the dialysate were significantly lower in the daily injection group--especially the quantity of phosphatidylcholine. However, lysophosphatidylcholine increased significantly in the daily injection group. Electron microscopy showed that the peritoneal surface layer was almost completely gone in the daily injection group, but that a dense and thick (average 4 microm) peritoneal surface layer was present on the top of the mesothelial cells in the control group.

CONCLUSIONS

Our results suggest that daily injection of hypertonic glucose dialysate significantly increased the peritoneal transport rate. The increased peritoneal transport rate was associated with a significant reduction in the peritoneal surface layer and the phospholipids content of the dialysis effluent.

New animal models for encapsulating peritoneal sclerosis--role of acidic solution

OBJECTIVE

Encapsulating peritoneal sclerosis (EPS), in which all or part of the intestine is enveloped in a fibrous ball resembling a cocoon, is a serious complication of peritoneal dialysis (PD). The aim of the present study was to investigate whether pH-neutral or acidic dialysis solutions induce peritoneal fibrosis.

DESIGN

We divided 18 male Wistar-Kyoto (WKY) rats into three groups and dialyzed them with various solutions as follows: group I, 10 mL acidic dialysis solution (pH 3.8, containing 1.35% glucose), n = 6; group II, 10 mL pH 5.0 dialysis solution, n = 6; and group III, 10 mL neutral dialysis solution (pH 7.0), n = 6. Peritoneal catheters were inserted, and dialysis solution was injected every day for 40 days. At the end of the experiment, a peritoneal equilibration test (PET) was performed. Expression of mRNA of aquaporins 1 and 4 (AQP-1 and AQP-4) in the peritoneum were studied by semiquantitative reverse-transcriptase polymerase chain reaction (RT-PCR).

RESULTS

In rats treated with pH 3.8 dialysis solution, necropsy findings revealed features identical to those of EPS. The typical appearance was of granulation tissue or fibrotic tissue (or both) covering multiple surfaces. Multiple adhesions were present. In microscopic examinations, peritoneal fibrosis and loss of mesothelium were found. In rats treated with pH 7.0 dialysis solution, no signs of EPS were seen. In rats treated with pH 5.0 dialysis solution, milder changes (subserosal thickening and partial adhesion of the peritonea) were observed. The mRNA of AQP-1 and AQP-4 were expressed in the peritonea of the rats. The expression of the AQPs was significantly suppressed in rats treated with pH 3.8 dialysis solution.

CONCLUSIONS

In rats, long-term intraperitoneal injection of acidic dialysis solution produced features typical of EPS in humans. Newly developed neutral dialysis solutions protected the against the development of EPS during peritoneal dialysis in rats.

Adequacy targets can be met in anuric patients by automated peritoneal dialysis: baseline data from EAPOS

OBJECTIVE

Conventional continuous ambulatory peritoneal dialysis (CAPD) in patients without residual renal function and with high solute transport is associated with worse clinical outcomes. Automated peritoneal dialysis (APD) has the potential to improve both solute clearance and ultrafiltration in these circumstances, but its efficacy as a treatment modality is unknown. The European Automated Peritoneal Dialysis Outcomes Study (EAPOS) is a 2-year, prospective, European multicenter study designed to determine APD feasibility and clinical outcomes in anuric patients. The present article describes the baseline data for patients recruited into the study.

DESIGN

All PD patients treated in the participating centers were screened for inclusion criteria [urinary output < 100 mL/24 h, or residual renal function (RRF) < 1 mL/min, or both]. After enrollment, changes were made to the dialysis prescription to achieve a weekly creatinine clearance above 60 L per 1.73 m2 and an ultrafiltration rate above 750 mL in 24 hours.

SETTING

The study is being conducted in 26 dialysis centers in 13 European countries. BASELINE DATA COLLECTION: The information collected includes patient demographics, dialysis prescription, achieved weekly creatinine clearance, and 24-hour ultrafiltration (UF).

RESULTS

The study enrolled 177 anuric patients. Median dialysis duration before enrollment was 22.5 months (range: 0-285 months). Mean solute transport measured as the dialysate-to-plasma ratio of creatinine (D/P(Cr)) was 0.74 +/- 0.12. Patients received APD for a median of 9.0 hours overnight (range: 7-12 hours) using a median of 11.0 L of fluid (range: 6-28.75 L). Median daytime volume was 4.0 L (range: 0.0-9.0 L). Tidal dialysis was used in 26 patients, and icodextrin in 86 patients. At baseline, before treatment optimization, the weekly mean total creatinine clearance was 65.2 +/- 14.4 L/1.73 m2, with 105 patients (60%) achieving the target of more than 60 L/1.73 m2. At baseline, 81% of patients with high transport, 69% with high-average transport, and 40% with low-average transport met the target. At baseline, 70% of patients with a body surface area (BSA) below 1.7 m2, 60% with a BSA of 1.7-2.0 m2, and 56% with a BSA above 2.0 m2 achieved 60 L/1.73 m2 weekly. Median UF was 1090 mL/24 h, and 75% of patients achieved the UF target of more than 750 mL/24 h.

CONCLUSION

This baseline analysis of anuric patients recruited into the EAPOS study demonstrates that a high proportion of anuric patients on APD can achieve dialysis and ultrafiltration targets using a variety of regimes. This 2-year follow-up study aims to optimize APD prescription to reach predefined clearance and ultrafiltration targets, and to observe the resulting clinical outcomes.