Neutrophil gelatinase-associated lipocalin in peritoneal effluent: evaluation in peritoneal dialysis patients in basal condition

PURPOSE

In the present study, we assessed expression of neutrophil gelatinase-associated lipocalin (NGAL) in peritoneal effluent (pNGAL) from peritoneal dialysis (PD) patients, and we evaluated factors that might affect its level in basal conditions.

METHODS

Our cross-sectional study included all 69 patients on PD at our institution. We evaluated patient history, hydration status, residual renal function, indices of dialysis adequacy, peritoneal transport type, serum C-reactive protein, ferritin, serum NGAL (sNGAL) and pNGAL. Univariate and multivariate linear regression models were used to evaluate predictors of pNGAL.

RESULTS

Of the study patients, 39 (56.5%) were men, and 54 (78.3%) were on continuous ambulatory PD. Median age in the group was 61 years [interquartile range (IQR): 46.5 - 71 years]. Median sNGAL was 487 ng/mL (IQR: 407 - 586 ng/mL), and median pNGAL was 35 ng/mL (IQR: 21 - 46 ng/mL). dNGAL correlated directly with weekly dialytic clearance of creatinine (ρ = 0.291, p = 0.02) and with sNGAL (ρ = 0.269, p = 0.031). The same variables were also independent predictors of pNGAL (β = 0.30 and 0.29 respectively, both p < 0.05) in multivariate analysis.

CONCLUSIONS

In our analysis, basal levels of pNGAL were influenced by sNGAL and by dialytic clearance of creatinine.

Abdominal aortic calcification is an independent predictor of cardiovascular events in peritoneal dialysis patients

Abdominal aortic calcification (AAC) is reported as a predictor for cardiovascular events in general population and in hemodialysis patients. At present, there are no AAC data in peritoneal dialysis. The purpose of this study was to evaluate the prognostic role of AAC score on cardiovascular events in peritoneal dialysis patients. Seventy-four peritoneal dialysis patients were enrolled. AAC was measured on baseline lateral abdomen radiographs by the semi-quantitative method as described by Kauppila. The other cardiovascular risk factors were obtained from patient history and blood examination. The Kaplan-Meier method was used to evaluate freedom from cardiovascular events, and differences were assessed with the log-rank statistic. Multivariate Cox regression models addressed time to cardiovascular events. The median period of follow-up was 30.5months (IQR 19.4-32.7). During follow-up, there were 29 cardiovascular events (39.2%). In univariable analysis, patient's age (HR=1.050; P=0.001), urine output (HR=0.999; P=0.02), and AAC stratified by tertiles (overall P-value<0.001) were significantly associated with cardiovascular events. In multivariable regression analysis, AAC score stratified by tertiles was the only independent predictor for cardiovascular events (overall P-value<0.001). To our knowledge, we have shown for the first time that AAC score is an independent predictor of cardiovascular events in peritoneal dialysis patients. Risk stratification by assessment of AAC score may provide important information for the management of cardiovascular disease in peritoneal dialysis patients without any additional expense, because these patients have several abdominal X-ray scans to evaluate the catheter position.

Phosphate Kinetics during Different Dialysis Modalities

BACKGROUND

An abnormal serum phosphate concentration is common in acute renal failure patients, with a reported incidence of 65-80%. Phosphate removal and kinetics during intermittent hemodialysis (IHD) have been investigated, but there is no information on its kinetics during slow low-efficiency dialysis (SLED) and continuous renal replacement therapy (CRRT).

METHODS

Eight IHD, 8 SLED, and 10 continuous venovenous hemofiltration (CVVH) patients with a residual renal clearance of <4.0 ml/min were studied during a single treatment to evaluate phosphate removal and kinetics. CVVH was studied the first 24 h after initiation. Dialysis/replacement fluid contained no phosphate. Kt/V, clearance of urea (Ku), inorganic phosphate (Kp) and solute removal was determined by direct dialysate quantification (DDQ).

RESULTS

Kp recorded with the three techniques were: IHD, 126.9 +/- 18.4 ml/min; SLED, 58.0 +/- 15.8 ml/min, and CVVH, 31.5 +/- 6.0 ml/min. However, in shorter dialysis treatment the total removal of phosphate was significantly lower than in longer dialysis (IHD, 29.9 +/- 7.7 mmol; SLED, 37.6 +/- 9.6 mmol; CVVH, 66.7 +/- 18.9 mmol, p = 0.001). The duration of treatment is the only factor determining phosphate removal (r = 0.7, p < 0.0001 by linear correlation model). Like IHD, phosphate kinetics during SLED could not be explained by the two-pool kinetic model, and the rebound of phosphate extended beyond 1 h after dialysis. Rebound, however, is less marked than in short dialysis.

CONCLUSION

These results are reliable evidence about amount of phosphate removal and behavior of intradialytic phosphate kinetics in renal failure patients undergoing different dialysis modalities. These data will help clinicians plan phosphate supplementation and treatment intensity.

Application of body composition monitoring to peritoneal dialysis patients

Assessment of body fluids in peritoneal dialysis is an important issue in the treatment of renal failure. Overhydration is related with hypertension and left ventricular hypertrophy and dehydration leads to hypotension and reduction of residual renal function. Bioimpedance analysis (BIA) provides objective information in assessment of hydration status of the patients. In the past BIA was not widely used in patients undergoing peritoneal dialysis. Our aim was to estimate the status of hydration in our peritoneal dialysis population by body composition monitoring (BCM) device to modify our pharmacological and dialysis policy. We used a Fresenius Body Composition Monitor, a whole-body bioimpedance spectroscopy (50 frequencies, 5-1,000 kHz ), to assess the body composition of 97 patients on peritoneal dialysis in our center. The patients were subjected to a physical examination every three months: We measured body weight, 24 h diuresis and performed a BIA session. BIA measurements were repeated according to different clinical situations. Every patient underwent BIA at least on two different occasions. Our preliminary results have found a strict correlation between weight increase or decrease and the results (total body water, extracellular water, lean mass index) shown by BCM. Modifications of therapy in patients dehydrated restored a satisfying amount of diuresis. Hypertensive overhydrated patients changed their scheduled treatment improving their blood pressure and achieving a lower body weight. Bio impedance analysis is the most reliable, repetitive, not invasive, simple, portable and relatively inexpensive technique to assess the fluid status of a dialysis patient is bioimpedance.

Albumin Dialysis and Plasma Filtration Adsorption Dialysis System

Albumin-bound toxins are important in the pathophysiology of liver failure, systemic inflammatory response syndrome, and poisoning. Due to its intrinsic ability to bind molecules, albumin has been used in blood purification techniques, such as single pass albumin dialysis, the molecular adsorbent recirculating system and the Prometheus systems. Plasma filtration adsorption dialysis is the latest technology that can combine the best processes of blood/plasma purification in order to determine a selective and effective purification of molecules implicated in liver failure.

Effectiveness of sodium hypochlorite in the prevention of catheter related infections

Vascular access in hemodialysis is a major point of concern in the management of chronic patients. Although arteriovenous fistula remains as the access of first choice, tunneled central venous catheters are still commonly used. Infection remains the principal cause of catheter dysfunction or loss. Many protocols have been used in order to prevent exit site infections and bacteremia. We describe our experience with the use of sodium hypochlorite, an electrolytic chloroxidizer used as a topical disinfectant. It has been shown to be active against a broad spectrum of potential pathogens and has other specific advantages compared to other cleansing agents, including its non-toxic, non-irritating nature and its low cost. We conclude that sodium hypochlorite solution in different concentrations (10 and 50%) is effective in preventing exit site infections and bacteremia associated with tunneled central venous catheters in chronic hemodialysis patients.

A new home based bioimpedance system for PD

Fluid overload and uncontrolled hypertension may be considered important mortality risk factors in peritoneal dialysis (PD) population. Even malnutrition is highly prevalent in PD patients. It is now well established that lower levels of serum markers of nutrition such as albumin, creatinine, and prealbumin are associated with increased mortality in PD patients [Fein, P.A. et al: Adv Perit Dial 2002;18:195-199]. Moreover cardiovascular disease is a leading cause of death in patients with end-stage renal disease, and hypertension and volume expansion are highly prevalent in long-term PD patients. Many studies in hemodialysis and in PD have demonstrated that phase sensitive bioelectrical impedance analysis is a widely used and proven method for evaluating patient's body composition. The vectorial bioimpedance analysis is a validated system to evaluate the hydration and nutritional state of hemodialysis and PD patients with acceptable sensitivity and specificity. The aim of this study is to evaluate the reliability and accuracy of the new multifrequency BodyComp bioimpedance analyzer as a home based tool versus traditional Bia Vector.

Sequential convective therapies (SCT): a prospective study on feasibility, safety, adequacy and tolerance of on-line hemofiltration and hemodiafiltration in sequence

Sequential dialysis techniques (i.e pure ultrafiltration followed by dialysis) have been used in the past, due to their capability to remove large volumes of fluids without inducing hemodynamic instability. The disadvantages of inadequate efficiency and lack of technology lead to the decline of such methods. Hemofiltration (HF) and hemodiafiltration (HDF) are recently being utilized in a greater proportion thanks to on-line fluid preparation systems. Each process (HF and HDF) has its own benefits in the removal of small, medium and high-molecular weight substances and in hemodynamic stability. Sequential convective therapies (SCT) such as hemofiltration-hemodiafiltration in sequence (HF-HDF) may combine the benefits and eliminate the disadvantages of each method and should be studied in order to explore their potential application in modern dialysis. Furthermore they can be easily applied nowadays, due to the development of new sophisticated dialysis machines. In order to evaluate the feasibility, safety, efficiency and tolerance of different SCT methods we studied 3 schedules: SCT1: 1h pre-dilution HF followed by 3h of post-dilution HDF (in the HF mode we lost 25% of the total fluid that had to be removed). SCT2: 1h pre-dilution HF followed by 3h of post-dilution HDF (in the HF mode we lost 50% of the total fluid that had to be removed). SCT3: 2h pre-dilution HF followed by 2h of post-dilution HDF (in the HF mode we lost 50% of the total fluid that had to be removed). We studied 6 chronic hemodialysis patients using the same machine (AK200 ULTRA), with on-line fluid preparation system and the same type of dialyzer (Polyflux 210). SCT schedules were compared to on-line HF, on-line HDF and high flux dialysis performed with the same dialyzers. The treatments resulted safe, easy, feasible and well tolerated with an improved hemodynamic response to high volume convective therapies. Adequacy of treatment was satisfactory in all SCT schedules while middle molecular weight solute clearance and removal resulted higher in treatments with higher convective component. SCT might represent an interesting option for the future especially in patients with hemodynamic instability and requirements for interventions during treatment.

Sequential hemofiltration-hemodiafiltration technique: all in one?

Sequential dialysis techniques (i.e. pure ultrafiltration followed by dialysis) have been used in the past, due to their capability to remove large volumes of fluids without inducing hemodynamic instability. The disadvantages of the inadequate dialysis and the lack of technology lead to the decline such methods. Hemofiltration (HF) and hemodiafiltration (HDF) are recently being utilized in a greater proportion thanks to the on line fluid preparation systems. Each process (HF and HDF) has its own benefits in the removal of small, medium and high-molecular weight substances and in the hemodynamic stability. Sequential hemofiltration/ hemodiafiltration (SHF/HDF), may combine the benefits and eliminate the disadvantages of each method. Furthermore they can be easily applied nowadays, due to the development of new high technological hemodialysis machines. In order to evaluate the feasibility and the effects of SHF/HDF we studied 7 chronic hemodialysis patients (6 months of treatment with SHF/HDF switched to 6 months of SHDF/HF), using the same machine (AK200 ULTRA), with on line fluid preparation system and the same type of dialyzer (Polyflux 210). The feasibility of such techniques (SHF/HDF or vice versa) resulted excellent. All sessions left the patients in a condition of well-being making fulltime work. No difference was observed between the different period of treatment, but a reduction in pre value was observed in calcium-phosphorous product, C-reactive protein and beta2-microglobulin, at the end of the sequential techniques. SHF/HDF therapy is a very promising technique. Further studies are needed to better explore the potential of such a therapeutic approach in the quality of life, the hemodialysis adequacy and the hemodynamic stability of our patients.

Monocyte apoptosis in uremia is normalized with continuous blood purification modalities

Uremia is associated with a state of immune dysfunction. Dysregulation of homeostasis may be directly related to abnormal apoptosis regulation in uremia, which is crucial for the maintenance of the biological system. We demonstrated that plasma from three groups of uremic subjects, i.e. hemodialysis (HD) patients, peritoneal dialysis (PD) patients and patients with predialysis chronic renal failure (CRF), has different apoptotic potential on U937 monocytes. The plasma of HD and CRF subjects when incubated with U937 cells induced higher levels of apoptosis compared with that of PD and control subjects (HD 26.08 +/- 11.39, CRF 24.87 +/- 9.07, PD 12.13 +/- 4.51, controls 11.69 +/- 4.02). Furthermore, the phagocytic ability of U937 cells incubated with the various plasma demonstrated an impaired response in the HD and CRF subjects (HD 27.56 +/- 6.67, CRF 30.24 +/- 9.08, PD 36.55 +/- 9.80, controls 40.04 +/- 6.98). These results suggest that continuous blood purification, such as in PD, may have advantages over intermittent therapies in removing uremic apoptotic molecules and potentially maintaining biological function and homeostasis.

Caspase-3 and -8 activation and cytokine removal with a novel cellulose triacetate super-permeable membrane in an in vitro sepsis model

Pro-apoptotic molecules are generated during sepsis which may be responsible for alteration of organ function in sepsis. Removal of systemic apoptotic activity may affect recovery from sepsis. Current high flux membranes might not be sufficiently permeable to eliminate pro-apoptotic factors. We evaluated the elimination of pro-apoptotic factors induced by LPS in human whole blood by a super-permeable cellulose triacetate membrane (SUREFLUX FH 150, Nipro, Osaka, Japan) in comparison to a standard high flux cellulose triacetate membrane (UT 700, Nipro, Osaka, Japan) and a polyethersulfone plasmafilter (Bellco, Mirandola Italy) in an in vitro blood circulation. We spiked human whole blood with lipopolysaccharide from Escherichia coli (Serotype 026-86, 10 mg/ml), incubated it for 3 hours to allow cytokine generation and recirculated it at 300 ml/min for 3 hours. The UF line was first returned to the blood module at 10 min. After this, the UF was drained from 10 to 60 min at a rate of 1000 ml/h. Zero balance was obtained by re-infusion of bicarbonate buffered hemofiltration fluid. Apoptosis was assessed on U937 monocytes (incubated with plasma or ultrafiltrate) by fluorescence microscopy dyes (Hoechst 33342, propidium iodide) and annexin V flow cytometry. Caspase-3 and Caspase-8 activity was assessed on the recirculated blood monocytes by spectrophotometric methods. IL-2, IL-10 and TNFalpha were determined by commercially available ELISAs. Sieving coefficients and clearances were determined for the different cytokines. Caspase-3 and Caspase-8 were activated by LPS and remained either stable or increased during in vitro circulation. Apoptosis activity of U937 cells, when incubated with the ultrafiltrate, increased in parallel with arterial plasma values (for Uf: UT700 = 23.1%; Sureflux FH150 = 42.5%). However, by 60 min the apoptotic activity recorded with the ultrafiltrate was reduced to the levels of arterial plasma (for Uf: UT700 = 19.8%; Sureflux FH150 = 11.2%). Sieving coefficients in the super-permeable membrane were significantly higher for all measured cytokines in comparison to the standard high flux membrane (e.g. TNFalpha 0.72 vs 0.03 p < 0.001) and close to the values observed for the plasmafiltration membrane. Nevertheless protein losses measured by albumin leakage were much lower with the Sureflux filter in comparison to the plasmafilter. In conclusion, pro-apoptotic factors can be eliminated by dialytic membranes with the removal rate maximized by using super high flux dialysers which may represent a compromise between hemofiltration and plasmafiltration membranes.

Analysis of outcome of pregnancy in type 1 diabetics treated with insulin pump or conventional insulin therapy

We evaluated the outcome of pregnancies followed between 1990 and 2000 in 93 women with type 1 diabetes, treated with conventional intensive insulin therapy (n=68) or continuous subcutaneous insulin infusion (n=25). We evaluated metabolic control (fasting and 1-hour post-prandial plasma glucose and HbA1c levels), spontaneous or induced abortions, time and mode of delivery, maternal outcome (pregnancy-induced hypertension, preeclampsia, placental insufficiency, hydramnios, hypoglycemic coma, ketoacidosis) and fetal outcome (weight, hypoglycemia, hypocalcemia, hyperbilirubinemia, fetal distress, asphyxia, hyaline membrane disease, polycythemia, shoulder dystocia, malformations). Patients treated with insulin pump more frequently had background retinopathy and clinical neuropathy. No significant differences were observed between the two groups in metabolic control and maternal outcome. Glycemic control, non-optimal in the prepregnancy state, improved significantly during pregnancy, as shown by the progressive reduction in HbA1c levels. As regards fetal outcome, no differences were observed between the two groups in morbidity and especially in malformation rate. Patients with malformed babies did not have optimal metabolic control at conception. Thus, maternal and perinatal outcomes were comparable in patients treated with insulin pump and continuous subcutaneous insulin therapy, and depended on metabolic control. In patients in higher White's class and with more unstable glycemia, we achieved metabolic control and outcomes comparable with those of women of lower White's class and more stable glycemic values using the insulin pump. Our data suggest that insulin pump therapy is useful in problematic, complicated cases of women who want a baby.

Noninvasive transcutaneous access flow measurement before and after hemodialysis: impact of hematocrit and blood pressure

BACKGROUND/AIMS

The dialysis outcome is strongly affected by the function of the vascular access. It has been suggested that access clotting may be related to increased hematocrit (Hct) or excessive ultrafiltration during dialysis. The present study was designed to evaluate the changes of vascular access flow during hemodialysis in 18 end-stage renal disease patients with native arteriovenous fistulas and the possible correlations with Hct and mean arterial pressure (MAP).

METHODS

We utilized a noninvasive vascular access flow measurement technique, based on a transcutaneous optical sensor, to evaluate the flow in the access before and after a single hemodialysis session. At the beginning and at the end of the session, the blood flow was measured noninvasively, placing the sensor approximately 2 in from the point of insertion of the arterial needle. At the same time, Hct and MAP were measured directly. All patients were on hemodialysis for more than 3 months.

RESULTS

There was a significant increase in Hct, likely due to ultrafiltration and consequent hemoconcentration, from the beginning to the end of the dialysis session. In detail, the Hct increased from 32.6 +/- 1.9 to 35.4 +/- 1.8% (p < 0.001), while the MAP did not present significant variations. The blood flow did not show significant variations, increasing from 780 +/- 312 to 919 +/- 411 ml/min after the session. Because of the stability of the MAP, we could dissociate the effects of the Hct from those of the MAP on blood flow variations.

CONCLUSION

Our study suggests that the blood flow in native fistulas is not affected by the acute rise in Hct due to ultrafiltration during hemodialysis. The transcutaneous access flow measurement technique appears to be reliable and accurate, and it could represent an important diagnostic tool.

Iron management in hemodialysis patients: optimizing outcomes in Vicenza, Italy

The management of anemia in uremic patients undergoing hemodialysis requires the appropriate combination of erythropoietin treatment, iron supplementation, and on occasion androgen therapy. Identifying and correcting functional iron deficiency is crucial to optimizing erythropoietin efficiency. Recently, however, the trend to administer maintenance iron with resultant high serum ferritin and high transferrin saturation has led to an increase in reports of iron overload. Oral iron supplementation is inexpensive and safe, but poor patient compliance and reduced intestinal absorption may limit its efficacy. Intravenous iron, on the other hand, is effective, and its safety is related to the iron salt used. Currently available data suggest that iron saccharate may be the safest iron salt available for intravenous administration, although iron gluconate is safer than the dextran forms of intravenous iron. It should be kept in mind, however, that all forms of intravenous iron may have the potential of inducing iron overload. At this time, the levels of ferritin that define iron overload are not clearly established. The side effects of iron overload are well recognized (infections, malignancies, vascular diseases); however, no guidelines exist for safe practice. There are many markers of iron deficiency, with serum ferritin and hypochromic red cell percentage currently the best markers available in clinical practice.

Effects of novel manufacturing technology on blood and dialysate flow distribution in a new low flux "alpha Polysulfone" hemodialyzer

The main target for low flux hemodialyzers is an efficient low molecular weight solutes clearance. Such efficiency is largely dependent on the optimization of diffusion between blood and dialysis solution. The diffusion process can be impaired if there is a mismatch between blood and dialysate flow distribution in the dialyzer. Thus optimized flow distribution both in the blood and dialysate compartment becomes quintessential for the maximal efficiency of the diffusion process within the hemodialyzer. The present paper describes the distribution of the blood and dialysate flows in a new low flux polysulfone hollow fiber hemodialyzer characterized by a specific undulation of the fibers and a new cutting technology of the fibers for an improved micro-flow condition in the blood compartment headers. Twelve Diacap alpha Polysulfone LO PS 15 (1.5 sqm) (B. Braun Medizintechnologie, Melsungen Germany) were employed for the study. Six were analyzed in vitro and six were studied in vivo. Blood flow distribution was studied in vitro by dye injection in the blood compartment during experimental extracorporeal circulation utilizing human blood with hematocrit adjusted at 33%. Sequential images were obtained with a helical scanner in a fixed longitudinal section of the dialyzer 1 cm thick. Average and regional blood flow velocities were measured utilizing the reconstructed imaging sequence. The method allowed the calculation of single fiber blood flow (SF Qb) and the mass transfer zone (MTR) definition in digitally subtracted images. The patterns 20-10 and 40-30 were utilized. The same technology was used to evaluate flow distribution in the dialysate compartment after dye injection in the Hansen's connector. Regional dialysate flow was calculated in central and peripheral sample areas of 1 cm2. Six in vivo hemodialysis treatments on patients with end stage renal disease were performed at three different blood flow rates (250-350 and 450 ml/min) in order to measure urea, creatinine and phosphate clearance. Macroscopic and densitometrical analysis revealed that flow distribution was homogeneous in the blood compartment while in the dialysate compartment a slight difference between the peripheral and central regions in terms of flow velocity was observed. This however was not generating channeling phenomena. Urea creatinine and phosphate clearances were remarkably high and so were the Kt/V observed in all sessions, especially in relation to the studied blood flows. In conclusion, a significant blood to dialysate flow match with optimized countercurrent flow condition was observed in the studied hollow fiber hemodialyzers. Such optimization might be due both to the improved dialyzer design at the level of the blood header and to the specific fiber undulation that prevents dialysate channeling.