What does the dialysate level of matrix metalloproteinase 2 tell us?

Long-term peritoneal dialysis leads to encapsulating peritoneal sclerosis (EPS), which is a rare but often fatal complication. The pathogenesis of EPS is characterized by increased inflammation, neoangiogenesis, epithelial-mesenchymal transition (EMT), and fibrosis. Matrix metalloproteinase 2 (MMP-2), which degrades type IV collagen, plays an important role in pathogenesis. Clinical trials report that dialysate levels of MMP-2 can be used as an early marker of peritoneal sclerosis. We aimed to determine the association of MMP-2 with peritoneal function, histology, and effluent cytokine levels in an experimental EPS model in rats. We evaluated data for 71 rats from our various studies using an experimental EPS model. Functional assessment was performed using a 1-hour peritoneal equilibration test with peritoneal dialysis fluid containing 3.86% glucose. Specimens of parietal peritoneum were examined with light microscopy for histologic evaluation. Parietal peritoneum thickness and submesothelial area were measured. Fibrosis, number of vessels, neovascularization, and cellular infiltration were evaluated by one pathologist. The relationships between MMP-2 and other parameters were analyzed using Pearson correlation analysis. Dialysate levels of MMP-2 reflect both functional and histologic change in peritoneum. Levels of MMP-2 were negatively correlated with net ultrafiltration, effluent protein levels, and end (1-hour)-to-initial dialysate concentration ratio of glucose. Cytokines such as vascular endothelial growth factor transforming growth factor beta, monocyte chemotactic protein 1, and osteopontin-which are known to play important roles in neovascularization, inflammation, and EMT leading to fibrosis-were correlated with MMP-2. In peritoneal dialysis patients, MMP-2 levels may be an early marker of EPS and EMT

GDPs and AGEs: impact on cardiovascular toxicity in dialysis patients

Glucose degradation products (GDPs) are highly reactive precursors of advanced glycation end-products (AGEs). High glucose concentrations, GDPs, and AGEs can activate specific pathways, including inflammatory and oxidative stress response pathways, which may adversely affect the cardiovascular system. This review discusses the impact and possible mechanisms of action of GDPs and AGEs with regard to cardiovascular toxicity in chronic kidney disease patients. The AGE-RAGE pathway appears to be particularly important in the pathogenesis of cardiovascular diseases in dialysis patients. In the absence of definitive proof from randomized controlled trials, mounting evidence suggests that high levels of GDPs and AGEs play a role in the pathophysiology of cardiotoxicity.

Prothrombin fragment 1 + 2 (F1 + 2) in effluent is a useful marker for peritoneal permeability in peritoneal dialysis patients using neutral dialysate

To clarify the influence of neutral dialysate (ND) on peritoneum, we examined changes in peritoneal permeability and in various markers of the coagulation and fibrinolytic system in effluent and the correlations between peritoneal permeability and those markers in peritoneal dialysis (PD) patients using ND. We evaluated 14 patients (8 men, 6 women; mean age: 58.6 +/- 12.0 years) who started PD using ND. The peritoneal equilibration test (PET) was performed to assess dialysate-to-plasma ratio for creatinine (D/P Cr) as peritoneal permeability. Coagulation markers [thrombin-antithrombin complex, fibrin monomer (FM), prothrombin fragment 1+2 (F1 + 2)] and fibrinolytic markers (fibrin degradation products, D-dimer) in effluent were also measured. At 2 years, FM in effluent was significantly lower (p = 0.006). The other markers and the D/P Cr did not change significantly. At the initiation of PD and at 2 years, D/P Cr was significantly correlated with F1 + 2 (r = 0.70 and 0.76 respectively, p < 0.01). Furthermore, multiple regression analysis showed that only F1 + 2 was correlated with D/P Cr at 2 years (r = 0.79, p = 0.004). These results suggest that ND has little influence on coagulation and fibrinolytic markers in effluent. In addition, F1 + 2 is a useful marker for peritoneal permeability in PD patients using ND.

Bicarbonate versus lactate solutions for acute peritoneal dialysis

BACKGROUND

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

OBJECTIVES

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

SEARCH STRATEGY

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

SELECTION CRITERIA

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

DATA COLLECTION AND ANALYSIS

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

MAIN RESULTS

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

AUTHORS' CONCLUSIONS

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

Contribution of residual renal function on peritoneal solute transport in dialysis patients

BACKGROUND

Increased peritoneal solute transport rate (PSTR) is primarily a consequence of continuous exposure to bioincompatible glucose-based peritoneal dialysis (PD) solutions. However, relationships between increasing PSTR and dialysate glucose load remain unclear. As some PD patients with preserved residual renal function do not show increased PSTR despite long-term PD, we examined whether loss of residual renal function is associated with increased PSTR on long-term PD.

METHODS

We evaluated 35 patients who started PD between 1997 and 2002 and received continuous PD treatment for >6 years. Data included baseline clinical data, residual renal function, urea and creatinine clearance, dialysate glucose load, ultrafiltration, and the use of icodextrin and renin-angiotensin system inhibitors. Peritoneal equilibration test results and data were collected annually for 6 years.

RESULTS

Both the glomerular filtration rate and urine volume at 6 years on PD showed significant negative correlations with the dialysate-to-plasma creatinine ratio (D/P Cr) at 6 years (r = -0.716 and r = -0.717, respectively). Multivariate analysis showed only urine volume at 6 years on PD as an independent covariate of the D/P Cr at 6 years on PD.

CONCLUSIONS

Loss of residual renal function is directly associated with increased PSTR in patients on long-term PD.

HPLC study of uremic fluids related to optical dialysis adequacy monitoring

PURPOSE

The aim of this study was to investigate uremia-related high-performance liquid chromatography (HPLC) ultraviolet (UV) absorbance profiles of serum and spent dialysate and to study the removal of uremic retention solutes in connection with optical dialysis adequacy monitoring.

METHODS

10 uremic patients were investigated using online spectrophotometry at a wavelength of 280 nm over the course of 30 hemodialysis treatments. The dialysate and blood samples were taken and analyzed simultaneously using standard biochemical methods and reversed-phase HPLC. Filters with cutoff at 3 kDa and 70 kDa were used for the pre-treatment of the serum. The chromatographic peaks were detected by a UV detector at wavelengths of 254 and 280 nm.

RESULTS

This study indicated that the main solute responsible for UV absorbance in the spent dialysate is a low-molecular-weight, water-soluble, non-protein-bound compound uric acid (UA). Three additional uremic retention solutes - creatinine (CR), indoxyl sulphate (IS) and hippuric acid (HA) - were identified from the HPLC profiles. The number of detected HPLC peaks was not significantly different for a serum filtered through the 3 kDa or 70 kDa cutoff filters, and was lower for the spent dialysate, indicating that the molecular weight (MW) of the main UV chromophores in the uremic fluids did not exceed 3 kDa. The reduction ratio (RR) estimated by the total area of HPLC peaks at 254 nm and 280 nm in the serum and by the online UV absorbance at 280 nm was best related to the removal of small water-soluble non-protein bound solutes like urea (UR), CR and UA.

CONCLUSIONS

The present study contributes new information on the removal of uremic retention solutes during hemodialysis and on the origin of the optical dialysis adequacy monitoring signal.

Analytical interferences in point-of-care testing glucometers by icodextrin and its metabolites: an overview

Current point-of-care testing (POCT) glucometers are based on various test principles. Two major method groups dominate the market: glucose oxidase-based systems and glucose dehydrogenase-based systems using pyrroloquinoline quinone (GDH-PQQ) as a cofactor. The GDH-PQQ-based glucometers are replacing the older glucose oxidase-based systems because of their lower sensitivity for oxygen. On the other hand, the GDH-PQQ test method results in falsely elevated blood glucose levels in peritoneal dialysis patients receiving solutions containing icodextrin (e.g., Extraneal; Baxter, Brussels, Belgium). Icodextrin is metabolized in the systemic circulation into different glucose polymers, but mainly maltose, which interferes with the GDH-PQQ-based method. Clinicians should be aware of this analytical interference. The POCT glucometers based on the GDH-PQQ method should preferably not be used in this high-risk population and POCT glucose results inconsistent with clinical suspicion of hypoglycemic coma should be retested with another testing system.

[Chronic kidney disease (CKD) and bone. Management of chronic kidney disease-mineral and bone disorder in peritoneal dialysis patients]

The peritoneal dialysate calcium concentration is an important factor in chronic kidney disease-mineral and bone disorder (CKD-MBD), because dialysate calcium concentrations strongly influence the serum calcium, phosphate, and parathyroid hormone (PTH) levels and the dosage of phosphate binders/vitamin D analogs. High-calcium dialysate has been used to correct hypocalcemia in end-stage renal disease (ESRD). Subsequently, a low-calcium dialysate was produced to increase the dosage of calcium-containing phosphate binders and vitamin D analogs without causing hypercalcemia. However, not enough is known about the effect of low-calcium dialysate in peritoneal dialysis. When we choose low-calcium dialysate, we should keep the risks of deteriorating secondary hyperparathyroidism in mind.

Effects of ionized sodium concentrations on ultrafiltration rate in peritoneal dialysis using lactate and lactate/bicarbonate solutions

OBJECTIVE

To investigate the possible effects of different concentrations of ionized sodium (NaI) on peritoneal ultrafiltration (UF) rate using lactate (Lac) and lactate/bicarbonate (Lac/Bic) dialysis solutions.

DESIGN

Two random consecutive (after an interval of 48 hours) peritoneal equilibration tests (PETs) were performed in 13 patients (4 males and 9 females) on regular continuous ambulatory peritoneal dialysis (PD) treatment for at least 3 months. Two different PD solutions containing anhydrous glucose 3.86% were used: a 40 mmol/L Lac solution and a 15/25 mmol/L mixed Lac/Bic solution. Concentrations of total sodium (NaT) and NaI were measured by flame photometer and direct ion-selective electrode respectively.

RESULTS

Dialysate concentrations of NaT were not different during PETs using Lac and Lac/Bic. Dialysate concentrations of NaI in fresh PD solutions were different (133.3 +/- 1.7 vs 128.2 +/- 3.9 mmol, p < 0.0001); however, these differences disappeared just after the end of the infusion of the fresh solutions. Peritoneal UF rate was not significantly different during PETs using Lac versus Lac/Bic (609 +/- 301 mL vs 542 +/- 362 mL). The dialysate-to-plasma ratios of sodium concentrations at 60 minutes of the PETs (which are expressions of free water transport) were not different using Lac versus Lac/Bic (0.89 +/- 0.04 vs 0.89 +/- 0.04 respectively, p = 0.96). All the other classical parameters of the PET were not different between Lac and Lac/Bic.

CONCLUSIONS

The higher dialysate concentrations of NaI due to lower dialysate pH and consequently the higher effective osmolality of the fresh Lac PD solutions did not influence peritoneal UF rate, probably because of the fast reduction of NaI concentrations due to rapid correction of dialysate pH at the end of the infusion of Lac solutions into the peritoneal cavity.

How long is the warranty period for nil or low coronary artery calcium in patients new to hemodialysis?

BACKGROUND

Coronary artery calcification (CAC) is common in patients with advanced chronic kidney disease on dialysis. A sizeable proportion of patients has no or minimal CAC at the inception of dialysis, but it is unclear how long they remain free of it.

METHODS

For the purpose of this study, 36 incident hemodialysis patients were submitted to sequential chest computed tomography to quantify CAC at baseline, 6, 12, 18 and 30 months.

RESULTS

Among them, 15 had absent or minimal CAC score (CACS 0 to 30) and 21 had a CACS>30 at baseline. Overall, the median baseline CACS was 129 (interquartile range [IQR]=0-709) and it increased to 364 (IQR=8.3-1683) at study completion (182% increase). Among the 15 patients with minimal CACS, only 3 progressed and the median CACS increase was 20, as opposed to 15 of 21 patients with a baseline CACS>30 whose median progression was 431 (p<0.02). The 18 patients who had CACS progression were older (68.5 vs. 57.3 years, p=0.0081) and exhibited a poorer control of mineral metabolism (phosphorus 5.2 vs. 4.9 mg/ dL, p=0.048; corrected calcium x phosphorus product [CaxP] 49.3 vs. 46.2 mg2/dL2, p=0.001) than the patients without progression. On multivariable analysis, independent predictors of progression were baseline CACS (p=0.038) and time-averaged Cax;P (p=0.077).

CONCLUSION

These data suggest that absent or low CAC at baseline is associated with minimal progression even up to 30 months. Careful management of mineral metabolism appears to be one of the main factors that limit progression of CAC.

Use of iron sucrose in dialysis patients sensitive to iron dextran

This study aimed to assess the safety and efficacy of iron sucrose in hemodialysis (HD) patients with documented hypersensitivity reactions to iron dextran. Of 205 HD patients who received low molecular weight iron dextran, 15 (7.3%) patients developed documented hypersensitivity reactions. The patients were treated with iron sucrose (100 mg administered as an intravenous push over 5-10 minutes once a week) for 8 weeks. Complete blood count, serum iron, serum ferritin, and parathyroid hormone were measured at the beginning and at the end of the study (except parathyroid hormone). All patients received subcutaneous erythropoietin at a constant dose of 5000 IU twice weekly unless a change was required. All the patients completed the study period and none of them developed hypersensitivity reactions to iron sucrose. The mean hematocrit increased from 23.8% to 32.27% (p < 0.0001), the mean serum ferritin from 185 ng/mL to 599 ng/mL (p < 0.0001), and the mean serum iron from 29.3 ng/dL to 76.8 ng/dL (p = 0.01). We conclude that iron sucrose is safe and effective in HD patients with documented hypersensitivity reactions to low molecular weight iron dextran.

The influence of dialysate calcium on progression of arterial stiffness in peritoneal dialysis patients

BACKGROUND

One of the origins of cardiovascular disease in dialysis patients is arterial stiffness. The aim of our study was to assess the relationship between the calcium content of peritoneal dialysis (PD) solution and arterial stiffness.

PATIENTS AND METHODS

We enrolled into the study 49 PD patients who had been treated with the same PD solution for the preceding 6 months. The calcium content of the PD solution was 1.25 mmol/L in 34 patients (low-Ca group) and 1.75 mmol/L in 15 patients (high-Ca group). Study patients were followed for 6 months on the same PD prescription. Arterial stiffness was assessed by measurement of augmentation index (AI) and brachial pulse wave velocity (PWV) at baseline and at month 6 (SphygmoCor: Atcor Medical, West Ryde, NSW, Australia). Demographic data were recorded from patient charts.

RESULTS

Mean age of the whole group was 51 +/- 11 years, prevalence of diabetes was 14%, duration of PD was 43 +/- 30 months, percentage of women was 45%, and percentage of patients using a cycler was 33%. We observed no differences between groups with regard to those variables or creatinine clearance, residual renal function, Ca, phosphorus, parathormone, C-reactive protein, lipid parameters, and use of phosphate binder with or without Ca content. Mean arterial pressure was higher in the high-Ca group, but the difference was not statistically significant (100 +/- 22 mmHg vs 88 +/- 18 mmHg, p = 0.06). At baseline, AI was significantly higher in the high-Ca group than in the low-Ca group (27% +/- 10% vs 21% +/- 9%, p < 0.05). Measurements of PWV were not different between the groups (8.4 +/- 1.1 m/s vs 8.5 +/- 1.7 m/s). Measurement of arterial stiffness parameters at month 6 revealed that PWV had increased in the high-Ca group (to 9.6 +/- 2.3 m/s from 8.4 +/- 1.1 m/s, p < 0.05), but had not changed in the low-Ca group (to 8.2 +/- 1.9 m/s from 8.5 +/- 1.7 m/s). The AI did not change in either group.

CONCLUSIONS

These data suggest that Ca exposure through PD solution plays a role in the progression of arterial stiffness, which may be related to increased vascular calcification.

Peritoneal defense mechanisms--the effects of new peritoneal dialysis solutions

It remains to be determined whether the peritoneal dialysis procedure induces abnormalities in the normal host defenses of the abdominal cavity and whether these perturbations are important in the pathogenesis of peritonitis. The peritoneum is a smooth membrane that lines the abdominal cavity and participates in the diffusion of water and solutes during peritoneal dialysis. The diaphragmatic lymphatic uptake and the opsonization of micro-organisms, with phagocytosis and killing by peritoneal macrophages, mesothelial cells, lymphocytes, polymorphonuclear leukocytes, and newly defined proteins such as defensins, play a combined role in the peritoneal host defense. Because the composition of earlier peritoneal dialysis fluids is clearly non-physiologic, continuous exposure of peritoneal cells to these solutions may result in an impairment of the local peritoneal host defense mechanisms. However, with the newer solutions, it has been shown that peritoneal defense mechanisms may improve.

Correlation of plasma and peritoneal diasylate clomipramine concentration with hemodynamic recovery after intralipid infusion in rabbits

OBJECTIVES

Drug sequestration to an expanded plasma lipid phase has been proposed as a potential mechanism of action for lipid emulsions in lipophilic cardiotoxin overdose. The authors set out to document plasma and peritoneal diasylate clomipramine concentration after resuscitation with lipid emulsion in a rabbit model of clomipramine-induced hypotension.

METHODS

Twenty sedated mechanically ventilated New Zealand White rabbits were allocated to receive either 12 mL/kg 20% Intralipid or 12 mL/kg saline solution, following clomipramine infusion to 50% baseline mean arterial pressure (MAP). Hemodynamic parameters and serum clomipramine concentration were determined to 59 minutes. Peritoneal dialysis with 20% Intralipid or saline solution was evaluated for clomipramine concentration.

RESULTS

Mean arterial pressure was greater in lipid-treated animals as assessed by repeated-measures analysis of variance (F[1,14] = 6.84; p = 0.020). Lipid infusion was associated with elevated plasma clomipramine concentration and reduced initial volume of distribution (Vd; 5.7 [+/-1.6] L/kg lipid vs. 15.9 [+/-7.2] L/kg saline; p = 0.0001). Peritoneal diasylate clomipramine concentration was greater in lipid-treated animals (366.2 [+/-186.2] microg/L lipid vs. 37.7 [+/-13.8] microg/L saline; p = 0.002).

CONCLUSIONS

Amelioration of clomipramine-induced hypotension with lipid infusion is associated with reduced initial Vd and elevated plasma clomipramine concentration consistent with intravascular drug-lipid sequestration. Concomitant peritoneal dialysis with lipid emulsion enhances clomipramine extraction.

Effects of interleukin-6 T15A single nucleotide polymorphism on baseline peritoneal solute transport rate in incident peritoneal dialysis patients

OBJECTIVE

To study the genetic effects of various inflammatory cytokines on peritoneal solute transport rate (PSTR) in incident Korean peritoneal dialysis (PD) patients.

DESIGN

Case-control association study.

METHODS

132 patients with baseline peritoneal equilibration test within 1-3 months after starting PD were enrolled. We analyzed the influence of single nucleotide polymorphisms (SNPs) of interleukin-6 (IL-6; -572G/C, T15A), tumor necrosis factor-alpha (TNF-alpha; -1031C/T, -863C/A, -308G/A), and IL-10 (-1082A/G, -592A/C) on baseline PSTR. Clinical parameters such as age, gender, presence of diabetes mellitus, comorbidity, C-reactive protein, and residual renal function were also included as covariates.

RESULTS

The T15A SNP of IL-6 (rs13306435) was associated with PSTR. Patients with TA genotype (n=18) had significantly lower D4/P creatinine (0.65+/-0.087 vs 0.73+/-0.110, p=0.0046) and higher D4/D0 glucose (0.39+/-0.174 vs 0.31+/-0.119, p=0.027) than patients with TT genotype (n=114). The log value of the dialysate appearance rate of IL-6 had a strong positive correlation with D4/P creatinine (r2=0.1294, p<0.0001) and was significantly lower in the TA genotype than the TT genotype (201.7+/-14.42 vs 116.8+/-88.91 pg/minute, p=0.0358). By multiple logistic regression, TA genotype was negatively associated with a higher PSTR (high or high average; odds ratio 0.18; 95% confidence interval 0.048-0.666).

CONCLUSIONS

In incident Korean PD patients, T15A polymorphism of IL-6 is associated with dialysate IL-6 concentration and baseline PSTR.

Stability of tobramycin and ceftazidime in icodextrin peritoneal dialysis solution

PURPOSE

The data describing the compatibility of tobramycin and ceftazidime in icodextrin-based peritoneal dialysis (PD) solution is limited. The objective of this study was to assess the chemical stability of tobramycin and ceftazidime in icodextrin PD solution in polyvinyl chloride containers.

METHODS

Commercially available 2-L bags of icodextrin 7.5% PD solution were used for each sample. Nine tobramycin study samples were prepared by adding 80 mg tobramycin HCl to each bag. Nine ceftazidime samples were prepared by adding 1000 mg ceftazidime to each bag. Three bags of tobramycin-icodextrin solution were stored under each of the following conditions: refrigeration (4 degrees C), room temperature (25 degrees C), and body temperature (37 degrees C). Three bags of ceftazidime-icodextrin solution were also stored at each of the respective temperatures. Samples were withdrawn from each bag immediately after preparation and at predetermined intervals (1, 2, 4, 6, 8, 12, 24, 48, 72, 96, 120, 168, and 336 hours after preparation). Solutions were visually inspected for precipitation, cloudiness, and discoloration at each sampling interval. All samples were immediately frozen (-80 degrees C) after collection and stored prior to assay. Total concentrations of tobramycin and ceftazidime in dialysate fluid were determined by high-performance liquid chromatography. The last time point when tobramycin or ceftazidime concentration was >90% from baseline was used to denote stability.

RESULTS

All solutions were clear in appearance and no color change or precipitation was observed during the study. For tobramycin, under refrigeration, a mean of 94.6%+/-2.3% of the initial concentration remained at 336 hours (14 days); at room temperature, 90.5%+/-4.3% remained at 168 hours (7 days); at body temperature, 90.0%+/-8.1% remained at 24 hours. For ceftazidime, under refrigeration, a mean of 98.0%+/-0.3% of the initial concentration remained at 168 hours (7 days); at room temperature, 91.6%+/-2.0% remained at 48 hours; at body temperature, 93.9%+/-1.1% remained at 8 hours. Stability was not assessed beyond these respective time points.

CONCLUSION

Premixed tobramycin-icodextrin PD solution remains stable for 336 hours (14 days) when refrigerated (4 degrees C) and for 168 hours (7 days) at room temperature (25 degrees C). Ceftazidime-icodextrin PD solution is stable for 168 hours and 48 hours, respectively, when stored at 4 degrees C and 25 degrees C. It is recommended that the bags be kept refrigerated whenever possible. Tobramycin-icodextrin solution stored at body temperature was stable up to 24 hours, and ceftazidime-icodextrin solutions up to 8 hours, permitting the practice of pre-warming solutions prior to administration.