Is adsorption an important characteristic of dialysis membranes?

Population Pharmacokinetics of Vancomycin Under Continuous Renal Replacement Therapy Using a Polymethylmethacrylate Hemofilter

BACKGROUND

Although continuous hemodiafiltration (CHDF) is often performed in critically ill patients during sepsis treatment, the pharmacokinetics of vancomycin (VCM) during CHDF with a polymethylmethacrylate hemofilter (PMMA-CHDF) have not been revealed. In this study, the authors aimed to describe the population pharmacokinetics of VCM in critically ill patients undergoing PMMA-CHDF and clarify its hemofilter clearance (CLhemofilter).

METHODS

This single-center, retrospective study enrolled patients who underwent intravenous VCM therapy during PMMA-CHDF at the intensive care unit of Chiba University Hospital between 2008 and 2016. A population analysis was performed, and CLhemofilter was assessed.

RESULTS

Twenty-five patients were enrolled. Median body weight (BW) and Sequential Organ Failure Assessment (SOFA) score were 63 kg and 15, respectively. Mean conditions for CHDF were 107.5 ± 18.3 mL/min for blood flow rate and 26.3 ± 6.3 mL/kg/h for effluent flow rate. The mean parameter estimates were distribution volume of the central compartment (V1), 59.1 L; clearance of the central compartment (CL1), 1.35 L/h; distribution volume of the peripheral compartment (V2), 56.1 L; and clearance of the peripheral compartment (CL2), 3.65 L/h. BW and SOFA score were significantly associated with V1 (P < 0.05) and CL1 (P < 0.05), respectively, and were thus selected as covariates in the final model. The estimated dosage of VCM to achieve a target area under the concentration-time curve/minimum inhibitory concentration ≥400 was 27.1 mg/kg for loading and 9.7 mg/kg every 24 hours for maintenance; these dosages were affected by BW and SOFA score. Mean CLhemofilter obtained from 8 patients was 1.35 L/h, which was similar to CL1.

CONCLUSIONS

The authors clarified the pharmacokinetics and CLhemofilter of VCM in PMMA-CHDF patients. The PK of VCM in patients undergoing CHDF appeared to vary not only with the CHDF setting and BW but also with SOFA score.

Peptides in Plasma, Urine, and Dialysate: Toward Unravelling Renal Peptide Handling

PURPOSE

The peptidomes of spent hemodialysate, urine, and plasma are investigated, to shed light on peptide handling in the kidney.

EXPERIMENTAL DESIGN

Fifteen plasma, 15 urine, and 13 spent hemodialysate samples are collected from age- and sex-matched subjects with chronic kidney disease. Peptide identification and quantification are performed with capillary electrophoresis-coupled mass spectrometry.

RESULTS

A total of 6278 urinary peptides, 1743 plasma peptides, and 1727 peptides from spent hemodialysate are detected. Of these, sequences can be assigned to 1580, 419, and 352 peptides, respectively. A strong correlation in peptide abundance between urine and spent hemodialysate (p = 3 × 10-21 , Rho = 0.52), a moderately strong correlation between spent hemodialysate and plasma (p = 4.5 × 10-5 , Rho = 0.30), and no significant correlation between urine and plasma (p = 0.11, Rho = 0.094) are found. Collagen and fibrinogen alpha peptides are highly abundant in all three body fluids. In spent hemodialysate, thymosin ß4 is one of the most abundant peptides, which is shown to be negatively associated with the estimated glomerular filtration rate (Rho = -0.39, p-value = 3.9 × 10-81 ).

CONCLUSION AND CLINICAL RELEVANCE

The correlation of peptide abundance in these three body fluids is lower than expected, supporting the hypothesis that tubular reabsorption has a major impact on urinary peptide content. Further investigation of thymosin ß4 in hemodialysis is thus warranted.

Current approaches to middle molecule removal: room for innovation

Aggressive removal of middle molecules or larger low-molecular-weight proteins (LMWPs) has been a growing concern following studies on their harmful effects on the mortality and morbidity of chronic dialysis patients. To remove larger LMWPs and some protein-bound uremic toxins (PBUTs), high- and medium-cutoff (HCOs and MCOs, respectively) membranes, convective therapy and protein adsorptive membranes are available. When we use HCO or MCO membranes for convective therapy, we have to take care to avoid massive albumin leakage during a dialysis session. Convection volume is an important element to increase middle molecule removal; however, a larger convection volume has a risk of larger leakage of albumin. Predilution hemodiafiltration is a useful measurement to increase larger LMWPs without massive albumin leakage. β2-microglobulin (B2M), α1-microglobulin (A1M) and albumin leakage during a dialysis session are useful parameters for assessing middle-molecule removal. Reduction ratios of B2M >80% and of A1M >35% are favorable to improve severe dialysis-related symptoms. The efficacy of middle molecule removal should be evaluated in comparison with clinical outcomes, mortality, morbidity and the improvement of dialysis-related symptoms. Recently some dialysis-related symptoms such as sleep disturbance, skin itchiness and dialysis hypotension have been recognized as good surrogate makers for mortality. Further studies to evaluate the relationship between middle molecule or PBUTs removal and the improvement of patient symptoms should be performed in well-designed randomized controlled trials.

Leukocyte Adhesion Molecules and Leukocyte-Platelet Interactions during Hemodialysis: Effects of Different Synthetic Membranes

Membranes made from synthetic polymers, in general, are considered as being biocompatible membranes and tend to be treated as a homogeneous group. However, all of these membranes have multiple and different characteristics that may contribute to interactions with blood components. As a consequence, the biocompatibility profile of synthetic membranes may vary. In the present cross-over study, we examined by flow cytometry the effects (expressed as % change from predialysis values) of three different synthetic polymers (polysulfone, PSF; polyacrylonitrile-co-sodium methallyl sulfonate, AN69; ethylenevinylalcohol, EVAL) on the expression of leukocyte adhesion molecules (CD11b/CD18, CD15s) and the interactions between leukocytes and platelets under conditions of routine clinical use.

For neutrophils, a statistically significant difference was found in CD15s expression for EVAL as compared to AN69 (p<0.05) and in CD11b/CD18 expression for PSF as compared to both EVAL (p<0.01) and AN69 (p<0.05). No difference between membranes was found on the expression of such adhesive molecules on monocytes. Significant differences in platelet-neutrophil (but not in platelet-monocyte) coaggregate formation were observed between PSF and both EVAL (p<0.001) and AN69 (p<0.01). Reactive oxygen species production by neutrophil population during hemodialysis was significantly different between each pair of synthetic polymers (PSF vs EVAL, p<0.001; PSF vs AN69, p<0.001; AN69 vs EVAL, p<0.05).

Our data demonstrate that in terms of leukocyte adhesion receptors and platelet-leukocyte interactions, the biocompatibility profile of the synthetic membranes polysulphone, AN69 and EVAL shows many similarities but also several significant differences. Our results support the concept that biocompatibility evaluation of each membrane should be based exclusively on data generated by that membrane in order to avoid errors based on assumptions about group characteristics.

A Clinical Study to Assess the Effect of Heparin in Dialyzer Rinsing Solutions

The solution usually recommended for rinsing the blood side, which is an indispensable step in preparing a dialyzer for hemodialysis (HD), contains saline and heparin. The heparin used for rinsing is said to reduce the thrombogenic properties of the dialysis membrane and, hence, also the need for systemic heparinization during the whole procedure. The aim of our study was to establish whether this postulate also applies to polysulphone steam-sterilized dialyzers. To do so, 16 patients on long-term dialysis were randomized into two groups of eight. One group was subsequently treated with polysulphone low-flux dialyzers (F6HPS), the other with polysulphone high-flux dialyzers (F60S). Both groups were examined, in a crossover manner during HD using a dialyzer previously rinsed with 1000 ml of saline plus 2,000 IU of heparin, and during HD using a dialyzer previously rinsed with 500 ml of saline without heparin. Except for the rinsing, HD conditions were completely identical. Blood obtained before HD, and at 15, 60 and 240 min of HD at the dialyzer inlet, was used to determine the activated partial thromboplastin time (to test heparinization control), the thrombin-antithrombin III complex (ELISA, to evaluate coagulation system activation), platelet factor 4 (ELISA, a substance with antiheparin activity), and platelet count. None of the above parameters showed, at any of the collecting intervals, a statistically significant difference between HD with and without heparin with a reduced volume of rinsing solution, or between HD using low- and high-flux dialyzers. It is concluded that heparin used to rinse polysulphone dialyzers before HD has no effect on blood coagulation or on the need for heparin during the procedure.

Quantitating Dialysis using two Dialysate Samples: A Simple, Practical and Accurate Approach for Evaluating Urea Kinetics

Urea kinetics is now widely used to determine the adequacy of dialysis. Several simplified formulae are currently in use but only a few have been accepted into clinical practice because of their simplicity and ease of calculation. A recent analysis of these formulae showed that for the same set of blood urea values the calculated Kt/V can range from 1.0 to 1.5. We have developed a new dialysate-based method (2DSM) to estimate the urea kinetic parameters using dialysate and blood samples taken at the beginning and at the end of dialysis. The total urea removed (TUR) was calculated from the geometric mean of the two dialysate samples, dialysate flow rate and the duration of dialysis. The Watson formula was used to determine the volume of distribution of urea. A comparison of the 2DSM and the direct dialysate quantification (DDQ) method showed the following results (mean ± sd, n = 52): for total urea removal (TUR) 697 ± 32 vs 722 ± 37 mmol (p = 0.6, r2 = 0.928, y = 101 + 0.83 ×, mean difference 25 ± 76 mmol, see Bland-Altman plot), dialysate urea concentration (Durea) 5.55 ± 0.25 vs 5.75 ± 0.29 mmol/l (p = 0.6, r2 = 0.928, y = 0.8 + 0.82 x, mean difference 0.2 ± 0.6 mmol, see Bland-Altman plot), dialyser clearance (K) 232 ± 4.4 vs 235 ± 5.6 ml/min (p - 0.54), Kt/V 1.42 ± 0.04 vs 1.51 ± 0.04 (p = 0.21), volume of distribution of urea (Vd) 40.14 ± 1.04 vs 38.74 ± 1.2 L, (p = 0.38), and PCR 64.6 ± 2.6 vs 68.1 ± 3.1 g/day. We have developed a simple method of determining dialysate-based urea kinetics which requires two dialysate samples, one at the beginning and one at the end of dialysis and a blood sample at the midpoint of dialysis. TUR can be calculated using the dialysate flow rate and the dialysis duration and once this is known all the other kinetic parameters can be calculated.

Examining hemodialyzer membrane performance using proteomic technologies

The success and the quality of hemodialysis therapy are mainly related to both clearance and biocompatibility properties of the artificial membrane packed in the hemodialyzer. Performance of a membrane is strongly influenced by its interaction with the plasma protein repertoire during the extracorporeal procedure. Recognition that a number of medium-high molecular weight solutes, including proteins and protein-bound molecules, are potentially toxic has prompted the development of more permeable membranes. Such membrane engineering, however, may cause loss of vital proteins, with membrane removal being nonspecific. In addition, plasma proteins can be adsorbed onto the membrane surface upon blood contact during dialysis. Adsorption can contribute to the removal of toxic compounds and governs the biocompatibility of a membrane, since surface-adsorbed proteins may trigger a variety of biologic blood pathways with pathophysiologic consequences. Over the last years, use of proteomic approaches has allowed polypeptide spectrum involved in the process of hemodialysis, a key issue previously hampered by lack of suitable technology, to be assessed in an unbiased manner and in its full complexity. Proteomics has been successfully applied to identify and quantify proteins in complex mixtures such as dialysis outflow fluid and fluid desorbed from dialysis membrane containing adsorbed proteins. The identified proteins can also be characterized by their involvement in metabolic and signaling pathways, molecular networks, and biologic processes through application of bioinformatics tools. Proteomics may thus provide an actual functional definition as to the effect of a membrane material on plasma proteins during hemodialysis. Here, we review the results of proteomic studies on the performance of hemodialysis membranes, as evaluated in terms of solute removal efficiency and blood-membrane interactions. The evidence collected indicates that the information provided by proteomic investigations yields improved molecular and functional knowledge and may lead to the development of more efficient membranes for the potential benefit of the patient.

Assessment of hemodialysis adequacy in patients with chronic kidney disease in the hemodialysis unit at Tanta University Hospital in Egypt

Worldwide, hemodialysis (HD) constitutes the most common form of renal replacement therapy. Many studies have shown strong correlation between HD dose and clinical outcome. The cross-sectional study was conducted on 100 patients in Hemodialysis Unit at Tanta University Hospital, Egypt. Data were collected using a reliable questionnaire (including clinical, demographic, dialysis, laboratory, and radiological data). SpKt/V was used to assess the adequacy of HD. The results revealed inadequate HD dose among 60% of the study population. The results also showed that increasing time and frequency of dialysis, blood flow rates, low recirculation percentages, reduction of intradialytic complaints, and well-functioning vascular access are associated with better HD adequacy. Our findings showed a positive correlation between dialysis dose and hemoglobin, serum albumin, normalized protein catabolic rate, and physical health. A great percentage of patients had inadequate HD. HD adequacy was influenced by several factors such as duration and frequency of dialysis session, patients' complaints, and well-functioning vascular access.

Proteomic Investigations into Hemodialysis Therapy

The retention of a number of solutes that may cause adverse biochemical/biological effects, called uremic toxins, characterizes uremic syndrome. Uremia therapy is based on renal replacement therapy, hemodialysis being the most commonly used modality. The membrane contained in the hemodialyzer represents the ultimate determinant of the success and quality of hemodialysis therapy. Membrane's performance can be evaluated in terms of removal efficiency for unwanted solutes and excess fluid, and minimization of negative interactions between the membrane material and blood components that define the membrane's bio(in)compatibility. Given the high concentration of plasma proteins and the complexity of structural functional relationships of this class of molecules, the performance of a membrane is highly influenced by its interaction with the plasma protein repertoire. Proteomic investigations have been increasingly applied to describe the protein uremic milieu, to compare the blood purification efficiency of different dialyzer membranes or different extracorporeal techniques, and to evaluate the adsorption of plasma proteins onto hemodialysis membranes. In this article, we aim to highlight investigations in the hemodialysis setting making use of recent developments in proteomic technologies. Examples are presented of why proteomics may be helpful to nephrology and may possibly affect future directions in renal research.

Evaluation of the effects of pulse high-volume hemofiltration in patients with severe sepsis: a preliminary study

OBJECTIVES

The aim of this study was to evaluate the effects of pulse high-volume hemofiltration (PHVHF) in patients with severe sepsis.

METHODS

Twenty-two patients with severe sepsis admitted to XiJing hospital between January 2009 and January 2010 were included in the present study. Patients were randomly divided into the control group (conventional treatment) and the PHVHF group. Patients in the PHVHF group received 72 h of PHVHF treatment in addition to conventional treatment after admission. PHVHF was conducted as follows: HVHF 85 ml/kg per hour for 6 h followed by continuous venovenous hemofiltration 35 ml/kg per hour for 18 h with an AN69 membrane. The hemofilter was replaced every 24 h and PHVHF was performed with 250 to 300 ml/min blood flow rate. The blood samples were taken to measure the changes of plasma cytokines (TNF-α, IL-1, IL-4, IL-6 and IL-10).

RESULTS

With 72 h of PHVHF treatment, there was an improvement in clinical features and hemodynamics variables in PHVHF-treated patients. All plasma cytokines after PHVHF treatment were significantly lower than those at the start of PHVHF treatment (p<0.05). In contrast, there was no significant change in control patients.

CONCLUSIONS

Our findings suggest that PHVHF is a feasible adjuvant modality in the treatment of patients with severe sepsis. With the application of PHVHF treatment, plasma cytokines are effectively removed. Considering the lower cost and better feasibility than continuous high-volume hemofiltration (CHVF), PHVHF shows promising prospects for the future.

Proteomics Characterization of Protein Adsorption onto Hemodialysis Membranes

Protein-adsorptive properties are a key feature of membranes used for hemodialysis treatment. Protein adsorption is vital to the biocompatibility of a membrane material and influences membrane's performance. The object of the present study is to investigate membrane biocompatibility by correlating the adsorbed proteome repertoire with structural feature of the membrane surfaces. Minidialyzers of identical structural characteristics composed of either cellulose diacetate or ethylenevinyl alcohol materials were employed to develop an ex vivo apparatus to investigate protein adsorption. Adsorbed proteins were eluted by a strong chaotropic buffer condition and investigated by 2-DE coupled to both MALDI-TOF mass spectrometry (MS) mass fingerprinting and fragmentation analysis on a nanoLC-MS/MS hybrid instrument. Membrane surface characterization included evaluation of roughness (atomic force microscopy), elemental chemical composition (X-ray-photoelectron-spectroscopy), and hydrophilicity (pulsed nuclear magnetic resonance). The present study identifies a number of different proteins as common or characteristic of filter material interaction, showing that proteomic techniques are a promising approach for the investigation of proteins surface-adsorbed onto hemodialysis membrane. Proteomic analysis enables the characterization of protein layers of unknown composition.

uPAR (CD87) as a biocompatibility marker of dialysis membrane

BACKGROUND/AIMS

Hemodialysis (HD) therapy may lead to functional changes in patient leukocytes. For example, the upregulation of inflammatory cytokines, such as IL-1beta and TNFalpha, has been well characterized. However, these findings do not explain the entire response of leukocytes in HD. In this study, we carried out a comprehensive gene expression analysis in leukocytes treated with various dialysis membranes using DNA microarrays. The identified gene has the potential to be a new marker for testing dialysis membrane biocompatibility.

METHODS

Gene expression profiles were compared between a group of leukocytes treated with various dialysis membranes and an untreated group by using DNA microarray analysis. Expression was confirmed by quantitative RT-PCR. The expression of the gene product (leukocyte surface protein) was examined in 20 chronic HD patients by flow cytometry.

RESULTS

In addition to the inflammatory cytokines, the urokinase plasminogen activator receptor (uPAR or CD87) gene was induced in leukocytes treated with each dialysis membrane. The extent of induction depended on the membrane's material composition. The expression of the uPAR (CD87) protein on leukocytes was markedly increased in patients undergoing dialysis therapy. The magnitude of uPAR (CD87) protein expression was correlated with clinical findings, i.e., the degree of leukopenia and the expression of adhesion molecules.

CONCLUSIONS

The gene and protein expression of uPAR (CD87) depended on the dialysis membrane material and correlated closely with clinical findings. These results suggest that uPAR has the potential to serve as a marker not only for clinical use but also for the development of new dialysis membranes.

A case of severe acute pancreatitis treated with CTR-001 direct hemoperfusion for cytokine apheresis

Severe acute pancreatitis is a clinical entity that can develop into multiple organ failure (MOF), and still has a poor prognosis. It is generally agreed that excessive humoral mediators such as pro-inflammatory cytokines play important roles in the pathogenesis of organ failure in patients with severe acute pancreatitis (SAP). Furthermore, it has been reported that continuous hemodiafiltration (CHDF) can remove the excess humoral mediators during the hypercytokinemic state of systemic inflammatory response syndrome (SIRS). We experienced a case of severe acute pancreatitis induced by alcohol abuse, on whom we performed cytokine apheresis. The patient was a 46 year-old male. He received 14 cytokine apheresis procedures, for about 4 hours in each session, using a CTR-001 direct hemoperfusion (DHP) cartridge. His serum levels of pro-inflammatory cytokines such as interleukin-6 (IL-6; 1649.1+/-667.1-1257.1+/-489.4 pg/mL, P=0.013) decreased significantly after the CTR-001 procedures. However tumor necrosis factor-alpha (TNF-alpha) (26.2+/-1.7-24.3+/-1.9 pg/mL, P=0.087), IL-1beta (6.1+/-2.9-3.49+/-1.1 pg/mL, P=0.477), IL-8 (192.5+/-33.4-229.5+/-51.8 pg/mL, P=0.754) and IL-10 (14.4+/-2.7-14.0+/-1.9 pg/mL, P=0.726) did not decrease statistically. Therefore, we conclude that in this case, cytokine apheresis using a CTR-001 cartridge was effective for reducing the pro-inflammatory cytokines during severe acute pancreatitis.

Kinetics of adsorption, desorption, and exchange of alpha-chymotrypsin and lysozyme on poly(ethyleneterephthalate) tracked film and track-etched membrane

Adsorption kinetics of (125)I-radiolabeled alpha-chymotrypsin at pH 8.6 was studied in a laminar regime between two walls of poly(ethyleneterephthalate) tracked films and membranes. Adsorption kinetics in the presence of solution (10 microg/mL), desorption by rinsing with buffer, and the following exchange of proteins by flowing unlabeled solution were measured. At pH 8.6, alpha-chymotrypsin is almost neutral and can be mostly removed from the film surface, contrary to positive lysozyme adsorbed at pH 7.4. Results suggest that alpha-chymotrypsin is irreversibly adsorbed in pores, while desorption and exchange occur on membrane flat faces. A method is proposed to determine adsorption kinetics in the pores. Kinetics of desorption and exchange of alpha-chymotrypsin from the film surface can be described by stretched exponential functions in the examined time domain with the same exponent, beta approximately 0.62, which does not depend also on the former adsorption duration. However, the mean residence time at the interface is about 2.5 times greater in the presence of only the buffer than that in the presence of solution. This effect could be explained by a fast exchange at the arrival of unlabeled solution for a part of the adsorbed population.

Cytokine removal by plasma exchange with continuous hemodiafiltration in critically ill patients

The effectiveness of plasma exchange (PE) with continuous hemodiafiltration (CHDF) in the treatment of critically ill patients was evaluated based on changes in cytokine levels. Twenty-six patients with acute hepatic failure were treated with PE (PE group) or PE and CHDF (PE+CHDF group), and the levels of cytokines such as tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, and IL-8 were determined before and after treatment. Bilirubin levels were significantly lower after treatment in both the PE and PE+CHDF groups. There were no significant differences in TNF-alpha levels before and after treatment in the PE group, but the TNF-alpha level was significantly lower after treatment in the PE+CHDF group. There were no significant differences in the IL-6 levels before and after treatment in both the PE and PE+CHDF groups. There were no significant differences in IL-8 levels before and after treatment in the PE group, but the IL-8 level was significantly lower after treatment in the PE+CHDF group. PE with CHDF therapy was given to 5 patients with acutely aggravated autoimmune diseases, 2 patients with hemorrhagic shock and encephalopathy syndrome, and 3 patients with thrombotic microangiopathy. The results suggested that PE with CHDF therapy are useful in critically ill patients with suspected hypercytokinemia.

Activation and control of complement, inflammation, and infection associated with the use of biomedical polymers

It is generally acknowledged that artificial biomaterials are much less immunologically active than transplants or tissue derived biomaterials. However, activation of both the coagulation cascade and the complement system is a common occurrence when human blood is exposed to biomaterial surfaces during extracorporeal procedures, such as renal hemodialysis or cardiopulmonary bypass. Both individual and collective activation of these cascades often produce local and systemic effects. A number of complement activation products function as the mediators of inflammation. They serve as ligands for specific receptors on polymorphonuclear leukocytes, monocytes, macrophages, mast cells, and other cells. Such an interaction leads to induction of cellular responses in adhered cells, including release of oxidative products, lysosomal enzymes, or both, which often contribute to a number of pathologic conditions. Most pathogens invading the human body are attacked by the immune system directly following entry, especially when they are in contact with blood. However, bacteria and parasites have developed a large number of specific strategies to overcome immune defense among others by avoiding either recognition or eradication by complement. In this aspect, of concern are several microorganisms responsible for formation of antibiotic resistant biofilms on biomaterial surfaces, namely Staphylococcus epidermidis, Staphylococcus aureus, and Pseudomonas aeruginosa.

Plasma concentrations of alpha-melanocyte-stimulating hormone are elevated in patients on chronic haemodialysis

BACKGROUND

Clinical and/or laboratory signs of systemic inflammation occur frequently in patients undergoing long-term haemodialysis. It is likely, therefore, that a compensatory release of endogenous anti-inflammatory molecules occurs to limit host reactions. The aim of the present research was to determine if the potent anti-inflammatory peptide alpha-melanocyte-stimulating hormone (alpha-MSH), a pro-opiomelanocortin derivative, is increased in plasma of haemodialysis patients. Because endotoxin and cytokines induce alpha-MSH in vivo and in vitro, we also measured plasma concentrations of endotoxin, interleukin-6 (IL-6), and tumour necrosis factor alpha (TNF-alpha), and the two circulating products of activated monocytes, nitric oxide (NO) and neopterin.

METHODS

Thirty-five chronic haemodialysis patients, 20 patients with chronic renal failure not yet on dialysis, and 35 normal controls were included in the study. In the haemodialysis group, blood samples were obtained before and at the end of a dialysis session. Plasma alpha-MSH was measured using a double antibody radioimmunoassay, and IL-6, TNF-alpha, and neopterin using specific enzyme-linked immunosorbent assays. Plasma nitrites were determined by a colorimetric method, and endotoxin with the quantitative chromogenic LAL (limulus amoebocyte lysate) method.

RESULTS

Mean plasma alpha-MSH was higher in haemodialysis patients than in control subjects, with the peptide concentrations being particularly elevated in dialysed patients with detectable endotoxin. High alpha-MSH concentrations were observed in the pre-dialysis samples, with no substantial change at the end of the dialysis session. Plasma concentrations of IL-6, TNF-alpha, neopterin, and NO were generally elevated in chronic haemodialysis patients and there was a negative correlation between circulating alpha-MSH and IL-6. In patients with renal failure not yet on dialysis, mean plasma alpha-MSH was similar to that of normal subjects.

CONCLUSIONS

alpha-MSH is increased in the circulation of chronic haemodialysis patients and particularly so in case of detectable endotoxaemia. Reduction of renal clearance is unlikely to contribute to the observed rise of the peptide because alpha-MSH concentration is not increased in patients with chronic renal failure who are not yet on dialysis. It is likely that dialysis-associated endotoxaemia, directly and/or through cytokine release, enhances the production of the anti-inflammatory mediator alpha-MSH that limits host reactions.

Effect of uremia and dialysis modality on mononuclear cell apoptosis

The aim of this study was to evaluate the effect of both uremia itself and hemodialysis (HD) membranes on the induction of apoptosis. Four groups of subjects were evaluated: 21 nondialyzed (Non-D) patients, 10 continuous ambulatory peritoneal dialysis (CAPD) patients, and 53 HD patients who were on hemophan, cuprophan, cellulose acetate, AN69, and polysulfone; control subjects were nine healthy volunteers. Circulating mononuclear cells were obtained before dialysis and cultured for 48 h. Mean percentage of apoptosis was analyzed by a FACScan flow cytometer using Annexin V-FITC. Cell apoptosis was increased in Non-D patients (11.5 +/- 5.5%) compared with control subjects (2.1 +/- 0.7%, P < 0.001) and CAPD patients (7. 0 +/- 5.8%, P < 0.05). In patients on HD with cuprophan, apoptosis was higher than in control subjects and Non-D and CAPD patients. In Non-D patients, apoptosis was inversely correlated with renal creatinine clearance (r = -0.62, P = 0.003). Cell apoptosis was higher in hemophan than the other HD membranes. In seven patients on hemophan, switching to polysulfone resulted in decreased apoptosis (P < 0.01). Mononuclear cell circulation through mini-dialyzers made of different types of membranes (cuprophan, hemophan, cellulose acetate, AN69, and polysulfone) prouced a significant increase in apoptosis. However, there was a marked difference in the percentage of apoptosis induced by these five membranes, being significantly increased in hemophan and cuprohan compared with the other three membranes. Similar results were obtained when whole blood from healthy donors was circulated through the mini-dialyzers, showing that mononuclear cell apoptosis was increased in hemophan and cuprophan compared with polysulfone. In conclusion, uremia and membrane characteristics may independently affect the mononuclear cell apoptosis.

Impact of chronic dialysis on serum PSA, free PSA, and free/total PSA ratio: is prostate cancer detection compromised in patients receiving long-term dialysis?

OBJECTIVES

The increased incidence of malignancy (ie, prostate cancer) in patients with end-stage renal failure is well known. However, little is known of the impact of hemodialysis and various membrane types on total and free prostate-specific antigen (PSA). We prospectively studied the impact of high- and low-flux dialysis membranes and kidney function on total PSA (tPSA), free PSA (fPSA), and free/total PSA ratio (f/t PSA).

METHODS

A total of 149 men were included. tPSA, fPSA, and f/t PSA were measured before and immediately after dialysis with high-flux (n = 101) and low-flux (n = 48) membranes in the serum and in the dialysis ultrafiltrate. A multivariate analysis of the impact of kidney function and age on the rate of change of all parameters was performed.

RESULTS

Overall, a significant decrease of fPSA (from 0.49 +/- 0.3 to 0.35 +/- 0.3 ng/mL, P <0.0001) and f/t PSA (from 45 +/- 19% to 38 +/- 13%, P <0.0001) and a nonsignificant decrease in serum tPSA were observed. However, fPSA (from 0.51 +/- 0.5 to 0.27 +/- 0.3 ng/mL, P <0.0001) and f/t PSA (from 47 +/- 19% to 31 +/- 18%, P <0.0001) decreased significantly in high-flux membranes only. The ultrafiltrate contained 100% fPSA in high-flux membranes and no fPSA in low-flux membranes. Age, serum creatinine, blood urea nitrogen, and dialysis evaluation parameters (Kt/V) had no impact on correlation with changes in tPSA and fPSA.

CONCLUSIONS

tPSA molecules do not pass high- and low-flux membranes; fPSA passes high-flux membranes only. The nonsignificant decrease of tPSA is due to adsorption to both dialysis membranes. Although tPSA can safely be used to screen patients on dialysis, independently from the dialysis procedure and membrane, fPSA and f/t PSA are only reliable with low-flux membranes. Finally, we can state that the fPSA is most probably cleared through the kidneys by glomerular filtration.

Cytokine removal during continuous hemofiltration in septic patients

A potential application of the continuous renal replacement therapies is the extracorporeal removal of inflammatory mediators in septic patients. Cytokine elimination with continuous renal replacement therapies has been demonstrated in several clinical studies, but so far without important effects on their serum concentrations. Improved knowledge of the cytokine removal mechanisms could lead to the development of more efficient treatment strategies. In the present study, 15 patients with septic shock and acute renal failure were observed during the first 24 h of treatment with continuous venovenous hemofiltration (CVVH) with an AN69 membrane. After 12 h, the hemofilter was replaced and the blood flow rate (QB) was switched from 100 ml/min to 200 ml/min or vice versa. Pre- and postfilter plasma and ultrafiltrate concentrations of selected inflammatory and anti-inflammatory cytokines were measured at several time points allowing the calculation of a mass balance. Cytokine removal was highest 1 h after the start of CVVH and after the change of the membrane (ranging from 25 to 43% of the prefilter amount), corresponding with a significant fall in the serum concentration of all cytokines. The inhibitors of inflammation were removed to the same extent as the inflammatory cytokines. Adsorption to the AN69 membrane appeared to be the main clearance mechanism, being most pronounced immediately after installation of a new membrane and decreasing steadily thereafter, indicating rapid saturation of the membrane. A QB of 200 ml/min was associated with a 75% increase of the ultrafiltration rate and a significantly higher convective elimination and membrane adsorption than at a QB of 100 ml/min. The results indicate that optimal cytokine removal with CVVH with an AN69 membrane could be achieved with a combination of a high QB/ultrafiltration rate and frequent membrane changes.

In vivo generation of C4d, Bb, iC3b, and SC5b-9 after OKT3 administration in kidney and lung transplant recipients

BACKGROUND

OKT3 monoclonal antibody therapy results in an acute clinical syndrome (ACS) associated with the release of tumor necrosis factor and sequestration of neutrophils in the lungs. We have previously shown that inhibition of tumor necrosis factor does not completely eliminate OKT3-ACS, suggesting that other factors also contribute to the ACS. The current studies analyzed complement activation in vivo during the first hour after OKT3 administration.

METHODS

Renal (n=4) and lung (n=4) transplant recipients received OKT3 as treatment for rejection and induction therapy, respectively. Complement activation products C4d, Bb, iC3b, and SC5b-9 were measured by ELISA. Hemodynamic parameters were also monitored in the lung transplant recipients. Neutrophil expression of CD11a, CD11b, and CD18 was monitored by flow cytometry. Controls included patients receiving methylprednisolone for rejection (n=4), two adults with adult respiratory distress syndrome who received extracorporeal membrane oxygenation, and normal volunteers (n=5). P values less than 0.05 (*) were considered significant.

RESULTS

Increases in the plasma levels of C4d, Bb, iC3b, and SC5b-9 were observed in seven of eight patients after OKT3 administration. Mean values (n=8) at 0, 15, and 60 min (in microg/ml) were as follows-C4d: 1.865, 2.644*, and 2.607*; Bb: 0.245, 0.411, and 0.385; iC3b: 10.881, 17.242*, and 15.145*; and SC5b-9: 0.232, 0.269, and 0.302*. An increase in CD11b and CD18 and a decrease of CD11a on neutrophils in parallel with complement activation was observed. In lung transplant recipients, C3 activation correlated with increases in mean pulmonary and central venous pressures (P<0.05). As compared with extracorporeal membrane oxygenation, which activated classical and alternative pathways, OKT3 predominantly activated complement by the classical pathway. Methylprednisolone pulses did not activate complement.

CONCLUSIONS

Complement activation is an early event after OKT3 administration and is associated with the increased expression of adhesion molecules on neutrophils and with pulmonary hemodynamic changes. Effective therapeutic approaches to the control of early monoclonal antibody side effects may require measures that limit complement activation in addition to reducing cytokine activity.

Dialysis membrane adsorption during CRRT

Experimental and clinical studies have suggested that dialysis membrane biocompatibility may influence the morbidity and mortality of patients with acute renal failure. Complement activation by dialysis membranes may also prolong the recovery from acute renal failure. In this article, we review the concept of dialysis membrane adsorption, with particular attention to adsorption/inhibition of factor D, a highly specific serine protease of the alternative pathway of complement. The adsorptive properties of some dialysis membranes may be useful during continuous renal replacement therapies (CRRT) in critically ill patients.

Acute renal failure: role of dialysis membrane biocompatibility

Recent clinical studies of acute renal failure in adults have focused attention on the biocompatibility of the dialysis membrane as a possible factor influencing patient morbidity and mortality. In this article, we review the concept of dialysis membrane biocompatibility and highlight the difficulty of finding an ideal definition. We then expand on the possible roles of complement and neutrophil activation by dialysis membranes, which may prolong the recovery from acute renal failure. The results of several clinical studies analyzing the impact of dialysis membranes on the course and outcome of acute renal failure are discussed. Finally, the possible relevance of biocompatibility in continuous renal replacement therapies is emphasized.