Ultrafiltration Rate Levels in Hemodialysis Patients Associated with Weight-Specific Mortality Risks.

BACKGROUND: We hypothesized that the association of ultrafiltration rate with mortality in hemodialysis patients was differentially affected by weight and sex and sought to derive a sex- and weight-indexed ultrafiltration rate measure that captures the differential effects of these parameters on the association of ultrafiltration rate with mortality. METHODS: Data were analyzed from the US Fresenius Kidney Care (FKC) database for 1 year after patient entry into a FKC dialysis unit (baseline) and over 2 years of follow-up for patients receiving thrice-weekly in-center hemodialysis. To investigate the joint effect of baseline-year ultrafiltration rate and postdialysis weight on survival, we fit Cox proportional hazards models using bivariate tensor product spline functions and constructed contour plots of weight-specific mortality hazard ratios over the entire range of ultrafiltration rate values and postdialysis weights (W). RESULTS: In the studied 396,358 patients, the average ultrafiltration rate in ml/h was related to postdialysis weight (W) in kg: 3W+330. Ultrafiltration rates associated with 20% or 40% higher weight-specific mortality risk were 3W+500 and 3W+630 ml/h, respectively, and were 70 ml/h higher in men than in women. Nineteen percent or 7.5% of patients exceeded ultrafiltration rates associated with a 20% or 40% higher mortality risk, respectively. Low ultrafiltration rates were associated with subsequent weight loss. Ultrafiltration rates associated with a given mortality risk were lower in high-body weight older patients and higher in patients on dialysis for more than 3 years. CONCLUSIONS: Ultrafiltration rates associated with various levels of higher mortality risk depend on body weight, but not in a 1:1 ratio, and are different in men versus women, in high-body weight older patients, and in high-vintage patients.

Peritoneal Dialysis in Advanced Heart Failure Patients with Chronic Severe Congestion Resistant to Optimal Pharmacological Treatment.

Resistant congestion is a difficult clinical picture in advanced heart failure with poor quality of life, worse functional capacity, and frequent hospitalizations. Optimal medical treatment is the first-line therapy. However, diuretic resistance, comorbid conditions such as chronic kidney disease, and obstacles in drug up-titration make it difficult to control congestion. In some of these cases, hemodialysis or peritoneal dialysis is required for short or long-term ultrafiltration therapy. Peritoneal dialysis is a more comfortable treatment option for this group of patients because of the slower and longer duration of ultrafiltration, better preservation of residual renal function, ability to be performed at home, and mobility of the patient during the procedure. In this review, home peritoneal dialysis/ultrafiltration methods have been addressed as an alternative treatment option in advanced heart failure patients with chronic severe congestion resistant to optimal pharmacological treatment.

Cardiorenal syndrome: classification, pathophysiology, diagnosis and management. Literature review / Síndrome cardiorrenal: clasificación, fisiopatología, diagnóstico y tratamiento. Una revisión de las publicaciones médicas.

The cardiorenal syndrome is a complex entity in which a primary heart dysfunction causes kidney injury (Types 1 and 2) and vice versa (Types 3 and 4), being either acute or chronic events, or maybe the result of a systemic disease that involves both organs (Type 5). Approximately 49% of heart failure cases present some grade of kidney dysfunction, significantly increasing morbidity and mortality rates. Its pathogenesis involves a variety of hemodynamic, hormonal and immunological factors that in the majority of cases produce fluid overload; the diagnosis and treatment of such constitutes the disease's management basis. Currently, a clinical based diagnosis is insufficient and the use of biochemical markers, such as natriuretic peptides, or lung and heart ultrasound is required. These tools, along with urinary sodium levels, allow the evaluation of therapy effectiveness. The preferred initial decongestive strategy is based on a continuous infusion of a loop diuretic with a step-up dosing regimen, aiming for a minimal daily urine volume of 3 liters, with the possibility to sequentially add potassium sparing diuretics, thiazide diuretics and carbonic anhydrase inhibitors to reach the diuresis goal, leaving ultrafiltration as a last resource due to its higher rate of complications. Finally, evidence-based therapy should be given to improve quality of life, decrease mortality, and delay the deterioration of kidney and heart function over the long term.

El síndrome cardiorrenal es una entidad compleja en la que la disfunción primaria cardíaca produce daño renal (tipos 1 y 2) y viceversa (tipos 3 y 4) y los episodios pueden ser agudos o crónicos o bien efecto de una enfermedad sistémica que afecta a ambos órganos (tipo 5). Hasta 49% de los pacientes con insuficiencia cardíaca muestra algún grado de disfunción renal, lo que aumenta de manera significativa la morbilidad y mortalidad. Su patogenia incluye diversos factores hemodinámicos, hormonales e inmunológicos que en la mayor parte de los casos producen sobrecarga hídrica, y cuyo diagnóstico y tratamiento son la base de su atención. En la actualidad, el diagnóstico clínico es insuficiente y se requieren marcadores bioquímicos, como péptidos natriuréticos, o el uso de ultrasonido pulmonar y cardíaco; estas herramientas, junto con la medición del sodio urinario, también permiten vigilar la efectividad terapéutica. De modo inicial se prefieren las medidas descongestivas con diuréticos de asa en infusión continua a dosis escalonadas para alcanzar una diuresis mínima de 3 L por día, con la posibilidad de agregar diuréticos ahorradores de potasio, tiazidas e inhibidores de la anhidrasa carbónica de modo secuencial para alcanzar el objetivo; como último recurso se recurre a la ultrafiltración en virtud de su mayor tasa de complicaciones. Por último, se debe indicar tratamiento con base en la evidencia para mejorar la calidad de vida, reducir la mortalidad y retrasar el deterioro de la función renal y cardíaca a largo plazo.

Extracorporeal veno-venous ultrafiltration in patients with acute heart failure.

Hospitalization for congestive heart failure represents a growing burden for health care systems. Heart failure is characterized by extracellular fluid overload and loop diuretics have been for decades the cornerstone of therapy in these patients. However, extensive use of intra-venous diuretics is characterised by several limitations: risk of worsening renal function and electrolyte imbalance, symptomatic hypotension and development of diuretic resistance. Extracorporealveno-venous ultrafiltration (UF) represents an interesting adjunctive therapy to target congestion in patients with heart failure and fluid overload. UF consists of the mechanical removal of iso-tonic plasma water from the blood through a semipermeable membrane using a pressure gradient generated by a pump. Fluid removal through UF presents several advantages such as removal of higher amount of sodium, predictable effect, limited neuro-hormonal activation, and enhanced spontaneous diuresis and diuretic response. After twenty years of "early" studies, since 2000 some pilot studies and randomized clinical trials with modern devices have been carried out with somehow conflicting results, as discussed in this review. In addition, some practical aspects of UF are addressed.

High ultrafiltration rate induced intradialytic hypotension is a predictor for cardiac remodeling: a 5-year cohort study.

BACKGROUND: Intradialytic-hypotension (IDH) is a common complication of hemodialysis. High ultrafiltration rate (UFR) might lead to IDH. However, the relationships between UFR, IDH, and cardiac remodeling among hemodialysis patients in the long-term have not been deeply explored. METHODS: This retrospective cohort study collected clinical and echocardiographic data. Patients were enrolled from 1 January 2014 to 31 March 2014 and were followed-up for 5-year. Those who suffered from more than four hypotensive events during three months (10% of dialysis treatments) were defined as the IDH group. Subgroup analysis was done according to the UFR of 10 ml/h/kg. Associations between UFR, IDH, and alterations of cardiac structure/function were analyzed. RESULTS: Among 209 patients, 96 were identified with IDH (45.9%). The survival rate of IDH patients was lower than that of no-IDH patients (65.5% vs. 81.4%, p = .005). In IDH group, decreased ejection fraction (EF), larger left atrium diameter index (LADI), and left ventricular mass index (LVMI) (p < .05) were observed at the end of the follow-up. In multivariate logistic model, the interaction between UFR and IDH was notably associated with LVMI variation (OR = 1.37). After adjusting covariates, UFR was still an independent risk factor of LVMI variation (OR = 1.52) in IDH group. In subsequent analysis, we divided patients according to UFR 10 ml/h/kg. For IDH-prone patients, decreased EF, larger LADI, and LVMI (p < .05) were observed at the end of the study only in high-UFR group. CONCLUSIONS: UFR and IDH have interactions on cardiac remodeling. High ultrafiltration rate induced IDH is a predictor for cardiac remodeling in long-term follow-up.

Preserved peritoneal function by short-term two-day peritoneal rest in hemodialysis combination therapy patients.

Several reports have demonstrated that peritoneal rest (PR) is considered to preserve the peritoneal function in peritoneal dialysis (PD) patients. However, there has been no report that examines the peritoneal permeability before and after a short-term PR of two days. We examined the effect of the two-day PR on peritoneal permeability. We observed and compared the daily PD ultrafiltration changes in the four PD and hemodialysis (HD) combination patients from the start of dialysis therapy throughout the total observation period of each case. Next, 6 months after the initiation of dialysis therapy we performed a set of peritoneal equilibrium tests (PET) before and after the 2-day PR. D/P creatinine, daily urine volume, daily ultrafiltration volume in PD, weekly residual renal creatinine clearance, and weekly PD creatinine clearance were measured. The daily PD ultrafiltration volume increased significantly after the 2-day PR, and gradually decreased over the last four days throughout the observation period in each patient. In the PET results, D/P creatinine in all patients decreased after the short-term PR, and accordingly the peritoneal ultrafiltration volume increased. However, urine volume, residual renal creatinine clearance, and peritoneal creatinine clearance did not change. The peritoneal permeability clearly decreased after the short-term PR. The repeated improvement in the PD ultrafiltration volume after the short-term PR implies that the peritoneal permeability alteration might be due to a reversible functional change in the initial dialysis period. These results suggest that a short-term PR may preserve the peritoneal function.

Ultrafiltration in Acute Heart Failure: Implications of Ejection Fraction and Early Response to Treatment From CARRESS-HF.

Background Ultrafiltration is not commonly used because of higher incidence of worsening renal function without improved decongestion. We examined differential outcomes of high versus low fluid removal and preserved versus reduced ejection fraction (EF) in CARRESS-HF (Cardiorenal Rescue Study in Acute Decompensated Heart Failure). Methods and Results Baseline characteristics in the ultrafiltration arm were compared according to 24-hour ultrafiltration-based fluid removal above versus below the median. Patients were stratified by EF (≤40% or >40%). We compared clinical parameters of clinical decongestion during the hospitalization based on initial (≤24 hours) response to ultrafiltration. Cox-proportional hazards models were used to identify associations between fluid removal <24 hours and composite of death, hospitalization, or unscheduled outpatient/emergency department visit during study follow-up. The intention-to-treat analysis included 93 patients. Within 24 hours, median fluid removal was 1.89 L (Q1, Q3: 1.22, 3.16). The high fluid removal group had a greater urine output (9.08 versus 6.23 L, P=0.027) after 96 hours. Creatinine change from baseline to 96 hours was similar in both groups (0.10 mg/dL increase, P=0.610). The EF >40% group demonstrated larger increases of change in creatinine (P=0.023) and aldosterone (P=0.038) from baseline to 96 hours. Among patients with EF >40%, those with above median fluid removal (n=17) when compared with below median (n=17) had an increased rate of the combined end point (87.5% versus 47.1%, P=0.014). Conclusions In patients with acute heart failure, higher initial fluid removal with ultrafiltration had no association with worsening renal function. In patients with EF >40%, ultrafiltration was associated with worsening renal function irrespective of fluid removal rate and higher initial fluid removal was associated with higher rates of adverse clinical outcomes, highlighting variable responses to decongestive therapy.

Efficacy and safety of early ultrafiltration in patients with acute decompensated heart failure with volume overload: a prospective, randomized, controlled clinical trial.

BACKGROUND: Ultrafiltration decreases total body water and improves the alveolar to arterial oxygen gradient. The aims of the study were to investigate the efficacy and safety of early ultrafiltration in acute decompensated heart failure (ADHF) patients. METHODS: 100 patients with ADHF within 24 h of admission were randomly assigned into early ultrafiltration (n = 40) or torasemide plus tolvaptan (n = 60) groups. The primary outcomes were weight loss and an increase in urine output on days 4 and 8 of treatment. RESULTS: Patients who received early ultrafiltration for 3 days achieved a greater weight loss (kg) (- 2.94 ± 3.76 vs - 0.64 ± 0.91, P < 0.001) and urine increase (mL) (198.00 ± 170.70 vs 61.77 ± 4.67, P < 0.001) than the torasemide plus tolvaptan group on day 4. From days 4 to 7, patients in the early ultrafiltration group received sequential therapy of torasemide and tolvaptan. Better control of volume was reflected in a greater weight loss (- 3.72 ± 3.81 vs - 1.34 ± 1.32, P < 0.001) and urine increase (373.80 ± 120.90 vs 79.5 ± 52.35, P < 0.001), greater reduction of B-type natriuretic peptide (BNP) (pg/mL) (- 1144 ± 1435 vs - 654.02 ± 889.65, P = 0.037), NYHA (New York Heart Association) functional class (- 1.45 ± 0.50 vs - 1.17 ± 0.62, P = 0.018), jugular venous pulse (JVP) score (points) (- 1.9 ± 1.13 vs - 0.78 ± 0.69, P < 0.001), inferior vena cava (IVC) diameter (mm) (- 15.35 ± 11.03 vs - 4.98 ± 6.00, P < 0.001) and an increase in the dyspnea score (points) (4.08 ± 3.44 vs 2.77 ± 2.03, P = 0.035) in the early ultrafiltration group on day 8. No significant differences were found in the readmission and mortality rates in the 2 patient groups at the 1-month and 3-month follow-ups. Both groups had a similar stable renal profile. CONCLUSION: Early ultrafiltration is superior to diuretics for volume overload treatment initiation of ADHF patients. Trial registration Chinese Clinical Trial Registry, ChiCTR2000030696, Registered 10 March 2020-Retrospectively registered, https://www.chictr.org.cn/showproj.aspx?proj=29099 .

Management of Cardiogenic Shock in a Cardiac Intensive Care Unit.

Cardiogenic shock (CS) is a complex condition characterized by end-organ hypoperfusion and requiring pharmacologic and/or mechanical circulatory support. It is caused by a decline in cardiac output due to a primary cardiac disorder. CS is frequently complicated by multiorgan system dysfunction that requires a multidisciplinary approach in a critical care setting. Appropriate use of diagnostic data using tools available in a modern cardiac intensive care unit should guide optimal management incorporating both pharmacologic and nonpharmacologic therapies to minimize morbidity and mortality.

Formation and interdependence of disinfection byproducts during chlorination of natural organic matter in a conventional drinking water treatment plant.

It is crucial to explore the source, formation process and interdependence of disinfection byproducts (DBPs) to reduce their risk on public health. In this investigation, a source water was chlorinated to evaluate the initial formation rates and the maximum yields of trichloromethane (TCM), dichloroacetic acid (DCAA), and trichloroacetic acid (TCAA) based on a hyperbola model. The results showed that TCM achieved the highest initial formation rate and maximum theoretical concentration compared with DCAA and TCAA. The TCM yield can be used to forecast the yields of DCAA and TCAA throughout the whole reaction process, and the yields of chloral hydrate (CH), dichloroacetonitrile (DCAN) and 1,1,1-trichloropropanone (1,1,1-TCP) within the initial reaction stage. Besides, the raw water, settled water and filtered water collected from a drinking water treatment plant were divided into five fractions, respectively, by ultrafiltration membranes to evaluate their DBP formation after chlorination. Compared with the medium molecular weight species, high and low molecular weight organic matters exhibited relatively high specific regulated and unregulated DBP yields (expressed as µg/mg C), respectively. Humic acid-like compositions predominantly contributed to regulated DBP yields, while soluble microbial by-product-like compounds preferentially generated DCAN. The correlation study revealed that the TCM could also serve as an indicator for the measured DBPs from chlorination of sample fractions with different molecular weight. Finally, it was found that the theoretical cytotoxicity was enhanced during chlorination of filtered water compared with chlorination of settled water.

Tidal peritoneal dialysis versus ultrafiltration in type 1 cardiorenal syndrome: A prospective randomized study.

BACKGROUND: Ultrafiltration is an alternative strategy to diuretic therapy for the treatment of patients with acute decompensated heart failure. Little is known about the efficacy and safety of peritoneal dialysis in patients with acute decompensated heart failure complicated by acute cardiorenal syndrome. METHODS: We randomly assigned a total of 88 patients with type 1 acute cardiorenal syndrome to a strategy of ultrafiltration therapy (44 patients) or tidal peritoneal dialysis (44 patients). The primary endpoint was the change from baseline in the serum creatinine level and left ventricular function represented as ejection fraction, as assessed 72 and 120 h after random assignment. Patients were followed for 90 days after discharge from the hospital. RESULTS: Ultrafiltration therapy was inferior to tidal peritoneal dialysis therapy with respect to the primary endpoint of the change in the serum creatinine levels at 72 and 120 h (p = 0.041) and ejection fraction at 72 and 120 h after enrollment (p = 0.044 and p = 0.032), owing to both an increase in the creatinine level in the ultrafiltration therapy group and a decrease in its level in the tidal peritoneal dialysis group. At 120 h, the mean change in the creatinine level was 1.4 ± 0.5 mg/dL in the ultrafiltration therapy group, as compared with 2.4 ± 1.3 mg/dL in the tidal peritoneal dialysis group (p = 0.023). At 72 and 120 h, there was a significant difference in weight loss between patients in the ultrafiltration therapy group and those in the tidal peritoneal dialysis group (p = 0.025). Net fluid loss was also greater in tidal peritoneal dialysis patients (p = 0.018). Adverse events were more observed in the ultrafiltration therapy group (p = 0.007). At 90 days post-discharge, tidal peritoneal dialysis patients had fewer rehospitalization for heart failure (14.3% vs 32.5%, p = 0.022). CONCLUSION: Tidal peritoneal dialysis is a safe and effective means for removing toxins and large quantities of excess fluid from patients with intractable heart failure. In patients with cardiorenal syndrome type 1, the use of tidal peritoneal dialysis was superior to ultrafiltration therapy for the preservation of renal function, improvement of cardiac function, and net fluid loss. Ultrafiltration therapy was associated with a higher rate of adverse events.

Patients with high-dose diuretics should get ultrafiltration in the management of decompensated heart failure: a meta-analysis.

The identification of specific patients with decompensated heart failure (DHF) who may benefit from ultrafiltration (UF) is important in clinical practice. We undertook a meta-analysis to compare the effects of ultrafiltration and diuretics on major clinical outcomes. The outcomes included weight change, length of hospital stay, rehospitalization for HF, mortality, change in serum creatinine, dialysis dependence, and adverse outcomes. We identified 14 trials including 975 patients with HF, met the eligibility criteria. There was a reduction in heart failure-related rehospitalization in ultrafiltration group when compared with the diuretic group. Subgroup analyses revealed a trend toward the decreased HF readmissions in ultrafiltration plus diuretic therapy group but did not reach statistical significance compared with ultrafiltration alone therapy. Overall, UF treatment did not produce apparent beneficial effects for weight loss, lengths of hospitalization, total mortality, the change of serum creatinine, and dialysis rate. Subgroup analyses showed increase in the serum creatinine were significantly higher for a higher dose regimen (> 200 mg/day) when compared with lower dose diuretic therapy (< 200 mg/day). As for adverse events, UF patients were associated with an increased risk of hypotension and lower risk of neurologic symptoms. The current results revealed ultrafiltration was associated with significant reduction in the rate of rehospitalization. Increase in the serum creatinine was observed in patients with high-dose diuretic regimen. Patients with high-dose diuretics should get ultrafiltration therapy.

Ultrafiltration versus diuretics for the treatment of fluid overload in patients with heart failure: a hospital cost analysis.

Background: Heart failure (HF) is a common, serious disease in the US and Europe. Patients with HF often require treatment for fluid overload, resulting in costly inpatient visits; however, limited evidence exists on the costs of alternative treatments. This study performed a cost-analysis of ultrafiltration (UF) vs diuretic therapy (DIUR-T) for patients with HF from the hospital perspective. Methods: The model used clinical data from the literature and hospital data from the Healthcare Cost and Utilization Project to follow a decision-analytic framework reflecting treatment decisions, probabilistic outcomes, and associated costs for treating patients with HF and hypervolemia with veno-venous UF or intravenous DIUR-T. A 90-day timeframe was considered to account for hospital readmissions beyond 30 days. Sensitivity and scenario analyses were performed to gauge the robustness of the results. Results: Although initial hospitalization costs were higher, fluid removal by UF reduced hospital readmission days, leading to cost savings of $3,975 (14.4%) at the 90-day follow-up (UF costs, $23,633; DIUR-T costs, $27,608). Conclusions: UF is a viable alternative to DIUR-T when treating fluid overload in HF patients because it reduces hospital readmission rates and durations, which substantially lowers costs over a 90-day period compared to DIUR-T.

Alterations of peritoneal transport characteristics in dialysis patients with ultrafiltration failure: tissue and capillary components.

BACKGROUND: Ultrafiltration failure (UFF) in peritoneal dialysis (PD) patients is due to altered peritoneal transport properties leading to reduced capacity to remove excess water. Here, with the aim to establish the role of local alterations of the two major transport barriers, peritoneal tissue and capillary wall, we investigate changes in overall peritoneal transport characteristics in UFF patients in relation to corresponding local alterations of peritoneal tissue and capillary wall transport properties. METHODS: Six-hour dwell studies using 3.86% glucose solutions and radioisotopically labelled serum albumin added to dialysate as a volume marker were analysed in 31 continuous ambulatory PD patients, 20 with normal ultrafiltration (NUF) and 11 with UFF. For each patient, the physiologically based parameters were evaluated for both transport barriers using the spatially distributed approach based on the individual intraperitoneal profiles of volume and concentrations of glucose, sodium, urea and creatinine. RESULTS: UFF patients as compared with NUF patients had increased solute diffusivity in both barriers, peritoneal tissue and capillary wall, decreased tissue hydraulic conductivity and increased local lymphatic absorption and functional decrease in the fraction of the ultra-small pores. This resulted in altered distribution of fluid and solutes in the peritoneal tissue, and decreased penetration depths of fluid and solutes into the tissue in UFF patients. CONCLUSIONS: Mathematical modelling using a spatially distributed approach for the description of clinical data suggests that alterations both in the capillary wall and in the tissue barrier contribute to UFF through their effect on transport and distribution of solutes and fluid within the tissue.

Peritoneal vasculopathy in the pathophysiology of long-term ultrafiltration failure: A hypothesis based on clinical observations
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Ultrafiltration failure in long-term peritoneal dialysis patients is a well-known and important, but poorly-explained complication of the treatment. Transcapillary ultrafiltration consists mainly of small-pore fluid transport and partly of free-water transport. The former is to a large extent dependent on the hydrostatic pressure gradient and on the number of perfused peritoneal microvessels. Free-water transport depends mainly on the crystalloid osmotic gradient. A longitudinal analysis of peritoneal transport has shown a dramatic decrease of net ultrafiltration and small-pore fluid transport after 4 years of peritoneal dialysis. It will be argued that in contrast to common belief, a decrease of osmotically induced water transport cannot be the major contributor to long-term ultrafiltration failure. By exclusion of potential alternatives, the presence of vasculopathy in the peritoneal microcirculation is the most likely explanation. The resulting narrowing of vascular lumina will decrease the hydrostatic pressure gradient and thereby small-pore fluid transport and net ultrafiltration. Deposition of advanced glycosylation end products in peritoneal vessels may be important in the development of vasculopathy. This hypothesis is supported by morphological and functional results of dialysis with "biocompatible" solutions.
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Surface coating of UF membranes to improve antifouling properties: A comparison study between cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs).

The inherent properties of hydrophilicity and environmental preferability of cellulose nanocrystals (CNCs) and cellulose nanofibers (CNFs) make them great candidates for application in water-treatment membranes. In this study, the antifouling properties of CNCs and CNFs, modified ultrafiltration (UF) membranes, were directly compared. A facile modification method was conducted by coating CNCs and CNFs on the surface of polyethersulfone (PES) membranes to prepare CNC-coating membranes and the CNF-coating membranes. Membrane surface morphology was characterized by atomic force microscopy (AFM), and the results showed that the CNF-coating membranes exhibited greater surface roughness than the CNC-coating membranes. Pure water flux measurements demonstrated that the flux of the CNC-coating membranes was slightly lower than that of the CNF-coating membranes. Antifouling properties were evaluated and compared for the two types of membranes by filtration of NOM foulant models, humic acid (HA) and bovine serum albumin (BSA). The results showed that the antifouling properties of the modified membranes were enhanced through the coating of either CNCs or CNFs to a control PES membrane. The CNC-coating membranes outperformed the CNF-coating membranes in alleviating both reversible fouling and irreversible fouling caused by HA and BSA. In addition, the antifouling performance of the coating membranes was enhanced with increased coating content.

Investigation of the mechanisms of membrane fouling by intracellular organic matter under different iron treatments during ultrafiltration.

Iron is an important trace element in algal growth and water eutrophication. This study focused on the ultrafiltration (UF) membrane fouling mechanism by the intracellular organic matter (IOM) of Microcystis aeruginosa under different iron treatments. The results indicated that the membranes experienced faster flux decline and worse fouling reversibility when the IOM formed under low iron concentrations. In contrast, less IOM membrane fouling was found under normal and high iron concentrations. The mass balances of the dissolved organic carbon (DOC) content implied that the IOM in the low-iron treatment was associated with higher IOM retention and a higher capacity of reversibly deposited organics, whereas more IOM in the high-iron treatment passed through the UF membrane. The IOM in the low-iron treatment was composed of more biopolymer macromolecules, whereas the IOM in the high-iron treatment contained more UV-absorbing hydrophobic organics. The fluorescence excitation-emission matrix (EEM) spectra coupled with peak-fitting analysis implied that the fouling associated with protein-like components was more irreversible in the low-iron treatment than those in the normal- and high-iron treatments. Cake formation combined with intermediate blocking was identified as the main membrane fouling mechanism responsible for the flux decline caused by IOM solutions in the three iron treatments in this study.

Effect of isolated ultrafiltration and isovolemic dialysis on myocardial perfusion and left ventricular function assessed with 13N-NH3 positron emission tomography and echocardiography.

Hemodialysis is associated with a fall in myocardial perfusion and may induce regional left ventricular (LV) systolic dysfunction. The pathophysiology of this entity is incompletely understood, and the contribution of ultrafiltration and diffusive dialysis has not been studied. We investigated the effect of isolated ultrafiltration and isovolemic dialysis on myocardial perfusion and LV function. Eight patients (7 male, aged 55 ± 18 yr) underwent 60 min of isolated ultrafiltration and 60 min of isovolemic dialysis in randomized order. Myocardial perfusion was assessed by 13N-NH3 positron emission tomography before and at the end of treatment. LV systolic function was assessed by echocardiography. Regional LV systolic dysfunction was defined as an increase in wall motion score in ≥2 segments. Isolated ultrafiltration (ultrafiltration rate 13.6 ± 3.9 ml·kg-1·h-1) induced hypovolemia, whereas isovolemic dialysis did not (blood volume change -6.4 ± 2.2 vs. +1.3 ± 3.6%). Courses of blood pressure, heart rate, and tympanic temperature were comparable for both treatments. Global and regional myocardial perfusion did not change significantly during either isolated ultrafiltration or isovolemic dialysis and did not differ between treatments. LV ejection fraction and the wall motion score index did not change significantly during either treatment. Regional LV systolic dysfunction developed in one patient during isolated ultrafiltration and in three patients during isovolemic dialysis. In conclusion, global and regional myocardial perfusion was not compromised by 60 min of isolated ultrafiltration or isovolemic dialysis. Regional LV systolic dysfunction developed during isolated ultrafiltration and isovolemic dialysis, suggesting that, besides hypovolemia, dialysis-associated factors may be involved in the pathogenesis of hemodialysis-induced regional LV dysfunction.

The effect of treatment time, dialysis frequency, and ultrafiltration rate on intradialytic hypotension.

Dialysis treatment time, the frequency of dialysis treatments, and the rate of fluid ultrafiltration-each impacts the incidence of intradialytic hypotension. These factors influence blood pressure independently and together. The strongest evidence supports that rapid ultrafiltration increases the likelihood of intradialytic hypotension and that combined strategies leading to a reduction in ultrafiltration rate have the greatest impact on reducing intradialytic hypotension. A practical approach to avoiding the effects of ultrafiltration on systemic hemodynamics would be to set a maximum ultrafiltration rate needed to achieve the desired fluid removal and vary the duration of the treatment to achieve that target volume. Randomized, controlled clinical trials of such strategies are warranted.

Interplay of volume, blood pressure, organ ischemia, residual renal function, and diet: certainties and uncertainties with dialytic management.

Extracellular fluid volume overload and its inevitable consequence, hypertension, increases cardiovascular mortality in the long term by leading to left ventricular hypertrophy, heart failure, and ischemic heart disease in dialysis patients. Unlike antihypertensive medications, a strict volume control strategy provides optimal blood pressure control without need for antihypertensive drugs. However, utilization of this strategy has remained limited because of several factors, including the absence of a gold standard method to assess volume status, difficulties in reducing extracellular fluid volume, and safety concerns associated with reduction of extracellular volume. These include intradialytic hypotension; ischemia of heart, brain, and gut; loss of residual renal function; and vascular access thrombosis. Comprehensibly, physicians are hesitant to follow strict volume control policy because of these safety concerns. Current data, however, suggest that a high ultrafiltration rate rather than the reduction in excess volume is related to these complications. Restriction of dietary salt intake, increased frequency, and/or duration of hemodialysis sessions or addition of temporary extra sessions during the process of gradually reducing postdialysis body weight in conventional hemodialysis and discontinuation of antihypertensive medications may prevent these complications. We believe that even if an unwanted effect occurs while gradually reaching euvolemia, this is likely to be counterbalanced by favorable cardiovascular outcomes such as regression of left ventricular hypertrophy, prevention of heart failure, and, ultimately, cardiovascular mortality as a result of the eventual achievement of normal extracellular fluid volume and blood pressure over the long term.