Carlo Crepaldi

Impact of spacing filaments external to hollow fibers on dialysate flow distribution and dialyzer performance.

A new type of dialyzer (PAN 650 SF Asahi) is analyzed in terms of hydraulic properties, solute clearances and dialysate flow distribution. The new type of dialyzer is a polyacrylonitrile hollow fiber filter, equipped with spacing filaments placed externally to the fibers to facilitate dialysate distribution and avoid channeling. The new filter is compared with a similar filter without spacing filaments. For this purpose, blood and dialysate side clearances have been measured in sequential dialysis session carried out randomly in the same patients. Furthermore, a last generation helical scanner (X-Press / HS1, Toshiba) has been utilized to analyze in vitro the flow distribution of dialysate inside the dialyzer. A contrast medium was injected and a sequence of images has been achieved on a longitudinal section of the dialyzer. This new method permits to avoid any bias due to the cylindrical shape of the dialyzer, since a 10 mm thick rectangular section is analyzed and not the entire body of the filter. The dialyzers equipped with spacing filaments displayed a significant improvement of the dialysate distribution as demonstrated by the radiological pattern. In detail, despite a channeling phenomenon in the peripherical region of the bundle is still present, this is remarkably reduced in comparison with the channelling phenomenon observed in the standard dialyzers. This improved distribution is confirmed by a significant improvement of the solute clearances.

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.

Peritoneal Dialysis in Patients with Refractory Congestive Heart Failure: A Systematic Review

Background: Refractory congestive heart failure (RCHF) is associated with a high mortality rate and is a major contributor to hospital admissions. Peritoneal dialysis (PD) is an option to control volume overload and perhaps improve outcomes in this challenging patient population. The aim of this systematic review is to describe the relative risk-benefit ratio based on data reported regarding the use of PD in RCHF. This study was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. An electronic search of PubMed, Embase, and the Cochrane Library was performed to identify relevant studies published from January 1951 to February 2014. Eligible studies selected were prospective or retrospective adult population studies on PD in the setting of RCHF. The following clinical outcomes were used to assess PD therapy: (1) hospitalization rates; (2) heart function; (3) renal function; (4) fluid overload, and (5) adverse clinical outcomes. Summary: Of 864 citations, we excluded 843 citations and included 21 studies (n = 673 patients). After PD, hospitalization days declined significantly (p = 0.0001), and heart function improved significantly (left ventricular ejection fraction: p = 0.0013; New York Heart Association classification: p = 0.0000). There were no statistically significant differences in glomerular filtration rate after PD treatment in non-chronic kidney disease stage 5D patients (p = 0.1065). Among patients treated with PD, body weight decreased significantly (p = 0.0006). The yearly average peritonitis rate was 14.5%, and the average yearly mortality was 20.3%. Key Messages: This systematic review suggests that PD may be an effective and safe therapeutic tool for patients with RCHF.

BETA 2-MICROGLOBULIN REMOVAL BY SYNTHETIC DIALYSIS MEMBRANES. MECHANISMS AND KINETICS OF THE MOLECULE

Beta 2-microglobulin (ß2-m) accumulation represents a possible complication of long term dialysis. It is therefore important to evaluate the capacity of removal of this molecule from the patient by different dialysis membranes. The present study is aimed at evaluating the mechanisms involved in ß2-m removal by three different synthetic membranes: a) highly asymmetric hydrophobic polysulfone (Biosulfane, NMC), b) moderately asymmetric and hydrophobic polysulfone (PS600, Fresenius), c) Polyacylonitrile (AN69HF, Hospal). The adsorption capacity and sieving coefficients of the three membranes for native and labeled ß2-m were studied in vitro utilizing human blood. The amount adsorbed by the membrane was measured by the elution of the molecule obtained with a detergent solution. Clearances, total removal and membrane adsorption were studied in six patients treated in a randomized sequence with the three membranes. For this purpose, plasma and dialysate measurements as well as total collection of spent dialysate and ß2-m elution from the used dialyzers were carried out. Ex novo generation of ß2-m did not take place during in vitro circulation. The molecule was removed by the studied membranes both by filtration and adsorption. The Biosulfane membrane removed ß2-m mostly by adsorption while the PS600 membrane removed ß2-m almost entirely by filtration. Intermediate behaviour was shown by AN69 membrane. Similar quantities of ß2-m were removed from the patients with the three membranes. Total removal could only be precisely measured by adding the quantity of ß2-m eluted from the membrane to the amount recovered in the spent dialysate. Out of total removal, adsorption was more than 90% with Biosulfane, while only 5% with the PS600. These findings contribute to the understanding of the discrepancy found between the clearance measured from the plasma side and that measured from the dialysate side. In conclusion, clearance and sieving measurements for ß2-m cannot be correctly performed unless the capacity of adsorption of the membrane is taken into account.

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.

Baseline hydration status in incident peritoneal dialysis patients: the initiative of patient outcomes in dialysis (IPOD-PD study)

Background Non-euvolaemia in peritoneal dialysis (PD) patients is associated with elevated mortality risk. There is an urgent need to collect data to help us understand the association between clinical practices and hydration and nutritional status, and their effects on patient outcome. Methods The aim of this prospective international, longitudinal observational cohort study is to follow up the hydration and nutritional status, as measured by bioimpedance spectroscopy using the body composition monitor (BCM) of incident PD patients for up to 5 years. Measures of hydration and nutritional status and of clinical, biochemical and therapy-related data are collected directly before start of PD treatment, at 1 and 3 months, and then every 3 months. This paper presents the protocol and a pre-specified analysis of baseline data of the cohort. Results A total of 1092 patients (58.1% male, 58.0 ± 15.3 years) from 135 centres in 32 countries were included. Median fluid overload (FO) was 2.0 L (males) and 0.9 L (females). Less than half of the patients were normohydrated (38.7%), whereas FO > 1.1 L was seen in 56.5%. Systolic and diastolic blood pressure were 139.5 ± 21.8 and 80.0 ± 12.8 mmHg, respectively, and 25.1% of patients had congestive heart failure [New York Heart Association (NYHA) 1 or higher]. A substantial number of patients judged to be not overhydrated on clinical judgement appeared to be overhydrated by BCM measurement. Overhydration at baseline was independently associated with male gender and diabetic status. Conclusions The majority of patients starting on PD are overhydrated already at start of PD. This may have important consequences on clinical outcomes and preservation of residual renal function. Substantial reclassification of hydration status by BCM versus on a clinical basis was necessary, especially in patients who were not overtly overhydrated. Both clinical appreciation and bioimpedance should be combined in clinical decision-making on hydration status.

Noninvasive Transcutaneous Access Flow Measurement before and after Hemodialysis: Impact of Hematocrit and Blood Pressure

Background/Aim: 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. Conclusions: 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.

Quality standards for predialysis education: results from a consensus conference

This position statement was compiled following an expert meeting in March 2013, Zurich, Switzerland. Attendees were invited from a spread of European renal units with established and respected renal replacement therapy option education programmes. Discussions centred around optimal ways of creating an education team, setting realistic and meaningful objectives for patient education, and assessing the quality of education delivered.

Ultrafiltration and Clearance Studies in Human Isolated Peritoneal Vascular Loops

Eight samples of human peritoneal tissue were obtained from patients undergoing hemicholectomy for cancer. An artery and a vein were cannulated and perfused with blood in vitro with a special circuit able to provide different perfusion pressures. Ultrafiltration and clearance studies were performed in these samples. Both ultrafiltration and small-solute clearances linearly correlated with the blood flow, demonstrating a strong dependence on this parameter. The peritoneal capillary showed a typical filtration pressure equilibrium with a constant filtration fraction at different blood flows. The results suggest that the blood flow may be a factor limiting the efficiency of peritoneal dialysis both in terms of mass transfer coefficients and maximal ultrafiltration rates.