不同透析膜对血透患者血清C-反应蛋白及白细胞介素-6水平的影响

目的:探讨不同透析膜对维持性血液透析患者血清C-反应蛋白(CRP)及白细胞介素-6(IL-6)水平的影响。方法:选取尿毒症透析患者54例,分为醋酸纤维素膜(CA130)组、低通量聚砜膜(F6)组及高通量聚砜膜(F60)组,另选取30例尿毒症非透析患者作为非透析组,30例健康体检者作为正常对照组,监测透析前后患者炎症指标水平的变化。结果:透析组患者透析前及非透析组患者CRP、IL-6水平均较正常对照组显著升高(P<0.01)。F6组及F60组透析后CRP、IL-6水平与透析前相比差异均无统计学意义(P>0.05),CA130组透析后CRP、IL-6水平与透析前相比明显升高(P<0.01)。结论:尿毒症患者存在着微炎症状态,这种炎症状态与透析膜的生物相容性有关,而采用高通量透析器透析并不增加这种炎症反应。     

Update on dialytic management of acute renal failure

The potential impact of renal replacement therapy on clinical outcomes in acute renal failure (ARF) remains a subject of ongoing investigation and controversy. This article reviews in depth the clinical trials to date that have examined the effect of dialysis-related variables on outcomes of patients with hospital-acquired ARF. In particular, the role of the dialysis modality, dialyzer characteristics, and dosing strategies are discussed. Clinical trials comparing intermittent hemodialysis (HD) to continuous renal replacement therapies (CRRT) have failed to demonstrate a survival difference when adjusting for disease severity. Similarly, studies evaluating dialyzer membrane biocompatibility and flux properties had no impact on survival. Efforts aimed at measuring dialysis adequacy in patients with ARF receiving HD using urea kinetic modeling are hindered by a lack of understanding of solute kinetics in this setting. However, dosing strategies during CRRT are promising. Finally, the application of cell therapy to the successful substitution of renal function shows promise for the future.     

高通量透析膜对维持性血液透析过程中溶质清除及皮肤瘙痒的作用

背景:如何有效地清除尿毒症毒素,以减少透析患者的并发症,改善维持性血液透析患者生活质量及长期预后,一直是人们研究的热点.目的:观察高通量和低通量聚砜膜血液透析器对维持性血液透析患者溶质清除及皮肤瘙痒的作用.方法:选择皮肤瘙痒的维持性血液透析患者38例,随机分为高通量透析组和低通量透析组,每组19例.高通量透析组使用高通量透析器FX60,低通量透析组使用低通量透析器F6,均每周透析3次,每次透析4 h,观察1年;检测血尿素氮、肌酐、磷、β2微球蛋白及甲状旁腺素;观察透析前后各种溶质含量的变化,计算溶质清除率和尿素清除指数(Kt/V值);用目测类比评分法评估瘙痒程度.结果与结论:两组患者透析后尿素氮、肌酐下降率差异无显著性意义(P > 0.05),磷和β2微球蛋白的下降率高通量透析组均高于低通量透析组(P < 0.05),两组Kt/V相比差异无显著性意义(P > 0.05);治疗1年后高通量透析组甲状旁腺素显著低于低通量透析组(P < 0.05),皮肤瘙痒与治疗前相比两组均有减轻(P < 0.05),高通量透析组瘙痒程度评分显著低于低通量透析组(P < 0.05).提示采用高通量FX60聚砜膜透析器进行透析,不仅充分清除小分子毒素,而且增加了对于大、中分子毒素的清除,能改善维持性透析患者顽固性皮肤瘙痒症状.     

浅谈高通量透析的优势及护理体会

目的评价高通量透析治疗维持性血液透析患者的疗效。方法将60例规律血液透析患者随机分为普通PMMA膜透析器组、普通聚砜膜透析器组及高通量透析器组各20例。比较单次血液透析前后,3组患者血清β2-微球蛋白（β2-microglobulin,β2-MG）清除效果,以及6个月后的胆固醇、三酰甘油、低密度脂蛋白的变化情况。结果高通量透析器组以及应用PMMA膜的透析器组,透析后均能降低β2-MG的浓度,其中高通量透析器组更为显著。脂代谢方面,高通量透析器组患者透析后的血总胆固醇、三酰甘油及低密度脂蛋白水平明显下降,而普通透析器组无明显变化。结论高通量透析提高患者透析效率、生活质量,透析并发症明显减少。     

血液透析对终末期肾病患者体内IL-13水平的影响

目的探讨终末期肾病（End stage renal disease ESRD）患者血浆白细胞介素13（Interleukin 13 IL-13）水平以及血液透析（Hemodialysis HD）对其的影响，并判断其能否作为评价透析膜生物相容性的指标。方法选择同济大学附属东方医院肾内科30例ESRD患者分为未透析组和维持性血液透析、（Maintenance hemodialysiS MHD）组，MHD组随机分为纤维素生物膜组（650）和聚砜膜组（F6）各10例，同时设立健康正常者10例为对照组。应用酶联免疫吸附（ELISA）法测定MHD患者透析前、后血浆中IL-13水平，以及外周血单个核细胞（Peripherial blood mononuclear cell SPBMC）经及未经植物凝集素（Phytohemagglutinin PHA）干预的培养上清中IL-13的水平，同时以半定量逆转录多聚酶链反应（RT-PCR）法检测PBMC中IL-13mRNA的表达。结果ESRD未透析组及MHD组透析前血浆IL-13水平较正常对照明显升高，MHD组经透析后血浆IL-13水平下降。ESRD未透析患者的PBMc经PHA刺激后IL-13培养上清水平及mRNA表达量均明显降低，650组PBMC经PHA刺激后IL-13培养上清水平及mRNA表达量无明显变化，F6组PBMC经PHA刺激后IL-13培养上清水平及mRNA表达量明显升高。结论①ESRD患者体内处于微炎症状态；②血液透析可改善其炎症状态，从而使IL-13水平下调；③聚砜膜较纤维素生物膜能更好的改善患者的T细胞对抗原的反应能力；④IL-13可作为评价透析膜生物相容性的指标之一。     

Removal of vancomycin by high-flux hemodialysis membranes.

Levels of vancomycin in serum are traditionally believed to be unaffected by hemodialysis. By both in vivo and in vitro techniques, the effects of a newer, more permeable dialyzer membrane on vancomycin concentrations were investigated. Six patients who were receiving vancomycin and undergoing maintenance hemodialysis with polyacrylonitrile dialyzer membranes had postdialysis levels in serum that were 63% of predialysis levels; the intradialytic half-life was 5.7 h. Vancomycin concentrations in serum exiting the dialyzer were 68% of those simultaneously entering the dialyzer at the beginning of dialysis. When polyacrylonitrile and conventional cellulose membranes were perfused in vitro with a recirculating solution of vancomycin, vancomycin concentrations fell to 39 and 91%, respectively, of the original concentration. The vancomycin concentration in the ultrafiltrate collected from the polyacrylonitrile membranes was only 23% of the original perfusate concentration. A significant decrease in the serum vancomycin concentration may occur during hemodialysis with newer high-flux dialyzer membranes. It appears that vancomycin binds to polyacrylonitrile membranes; this binding does not require the presence of protein and is affected by the pH of the perfusate.     

Application of nanotechnology to hemodialysis membrane

Almost forty years have passed from the start of hemodialysis therapy in Japan. A lot of numbers of dialysis patient have received the benefits from this therapy. In hemodialysis therapy, effective removal of uremic toxins and biocompatibility are required. Hemodialysis membrane plays the most important roles to achieve these requirements. Removal of uremic toxins and biocompatibility are influenced by solute permeability through hemodialysis membrane and characteristics of hemodialysis membrane surface keeping in contact with blood. This paper summarized nanostructure of hemodialysis membrane made from polysulfone adding polyvinylpyrrolidone from some reports, and process of membrane formation from polymer solution. Solute permeability has relation to pore size penetrating hemodialysis membrane, and biocompatibility has relation to swell of polymer particles on surface of hemodialysis membrane immersed in water.     

使用不同透析膜时IL-8表达的改变

目的 了解不同透析膜对血液透析患者IL-8表达的影响。方法 采用酶联免疫吸附试验(ELISA)测定IL-8血浆水平及外周血单个核细胞(PBMC)培养上清液IL-8水平,逆转录多聚酶链反应(RT-PCR)检测基因表达。结果 聚砜膜组的IL-8血浆水平及mRNA表达低于铜仿膜组及铜氨膜组,而铜仿膜组及铜氨膜组之间无显著差异。各组透析后的IL-8血浆水平及mRNA表达均较透析前升高。铜仿膜组透析前PBMC受LPS刺激后产生的IL-8多于聚砜膜组,血透后聚砜膜组产生的IL-8较透析前升高,而铜仿膜组较透析前无明显改变。结论 再生纤维素膜(尤其是铜仿膜)导致IL-8表达改变的能力强于聚砜膜,测量IL-8表达有助于评价不同透析膜的生物相容性。     

不同种类透析膜对维持性血液透析患者P选择素的影响

目的 观察不同种类透析膜对维持性血液透析患者血小板活化程度的影响。方法 尿毒症维持性血液透析患者采用醋酸纤维素膜(CA)、血仿膜(HE)、聚砜膜(PS)透析器进行透析,采用双抗体夹心ELISA法检测患者初用、复用透析器透析过程中不同时间点(0min、270min)血清P-选择素水平的变化,同时选择尿毒症非透析患者、正常健康者作为对照组检测血清P-选择素水平。结果 尿毒症非透析患者与维持性血液透析患者透析前P-选择素水平较正常对照组增高但无显著性差异(P>0.05)。尿毒症透析患者透析开始15分钟后,P-选择素水平升高,与透前相比有显著差异(P<0.05),随着透析的进行,血清P选择素水平继续呈上升趋势,透析270分钟与透析前相比差异更显著(P<0.001)。不同种类透析膜中,CA对血清P-选择素的影响显著大于HE和PS,三种透析器复用对血透患者血清P-选择素水平影响与初用相比显著下降(P<0.06),三种透析器复用组间比较无显著性差异。结论 HID过程中P-选择素显著升高是导致血透患者凝血功能障碍原因之一,HE和PS对血小板的活化程度弱于CA。     

高通量透析膜对维持性血液透析过程中溶质清除及皮肤瘙痒的作用

背景：如何有效地清除尿毒症毒素,以减少透析患者的并发症,改善维持性血液透析患者生活质量及长期预后,一直是人们研究的热点。目的：观察高通量和低通量聚砜膜血液透析器对维持性血液透析患者溶质清除及皮肤瘙痒的作用。方法：选择皮肤瘙痒的维持性血液透析患者38例,随机分为高通量透析组和低通量透析组,每组19例。高通量透析组使用高通量透析器FX60,低通量透析组使用低通量透析器F6,均每周透析3次,每次透析4h,观察1年;检测血尿素氮、肌酐、磷、β2微球蛋白及甲状旁腺素;观察透析前后各种溶质含量的变化,计算溶质清除率和尿素清除指数（Kt/V值）;用目测类比评分法评估瘙痒程度。结果与结论：两组患者透析后尿素氮、肌酐下降率差异无显著性意义（P〉0.05）,磷和β2微球蛋白的下降率高通量透析组均高于低通量透析组（P〈0.05）,两组Kt/V相比差异无显著性意义（P〉0.05）;治疗1年后高通量透析组甲状旁腺素显著低于低通量透析组（P〈0.05）,皮肤瘙痒与治疗前相比两组均有减轻（P〈0.05）,高通量透析组瘙痒程度评分显著低于低通量透析组（P〈0.05）。提示采用高通量FX60聚砜膜透析器进行透析,不仅充分清除小分子毒素,而且增加了对于大、中分子毒素的清除,能改善维持性透析患者顽固性皮肤瘙痒症状。     

CAHPl70透析器复用对血透患者血清补体C3、IL-2、TNF-α、NO的影响

【目的】探讨CAHPl70透析器复用对透析膜生物相容性的影响。【方法】观察10例维持性血液透析患者在透析器初用和复用时,透前、透析15、120min、透后血清白介素-2（IL-2）、肿瘤坏死因子-α（TNF-α）、补体C3、一氧化氮（NO）的水平。【结果】在透析15min,透析器初用血清IL-2、TNF-α、NO水平较各点显著升高（P〈0．05）,复用较初用显著降低（P〈0．05）;血清C3水平则较各点显著降低（P〈0．05）,复用较初用显著升高（P〈O．05）;IL-2、TNF-α、NO水平互相呈正相关（P〈0．05）,补体C3与IL-2、TNF-α、NO均呈负相关（P〈0．05）。透后血清N0水平较透前显著降低（P〈0．05）。【结论】透析15min时血清IL-2、TNF-α、NO、补体C3水平可作为判断透析器生物相容性的良好指标。透析器复用后透析膜生物相容性得到明显改善。     

吸附法无肝素血液透析的临床研究

目的 研究吸附法无肝素透析在临床的应用,探讨其可行性。方法 对10例慢性维持性血液透析患者前后行全身肝素化与吸附法无肝素透析各20次,观察比较两种方法对透析器凝血、透析器容量下降率、透析器对尿素氮及肌酐清除效力的影响。结果 两种方法对透析器的凝血,对透析器容量下降率无显著差异,对尿素氮及肌酐的清除效力,吸附法无肝素透析稍逊于全身肝素化。结论 对有出血倾向的,尤其是活动性出血的患者,吸附法无肝素透析不失为血液透析中可选用的一种抗凝方法。     

Preservation of residual renal function in dialysis patients: effects of dialysis-technique-related factors.

OBJECTIVES: Residual renal function (RRF) is of paramount importance to dialysis adequacy, morbidity, and mortality, particularly for long-term continuous ambulatory peritoneal dialysis (CAPD) patients. Residual renal function seems to be better preserved in patients on CAPD than in hemodialysis (HD) patients. We analyzed RRF in 45 patients with end-stage renal disease (ESRD), commencing either CAPD or HD, to prospectively define the time course of the decline in RRF, and to evaluate dialysis-technique-related factors such as cardiovascular stability and bioincompatibility. STUDY DESIGN: Single-center prospective investigation in parallel design with matched pairs. MATERIALS: Fifteen patients starting CAPD and 15 matched pairs of patients commencing HD were matched according to cause of renal failure and RRF. Hemodialysis patients were assigned to two dialyzer membranes differing markedly in their potential to activate complement and cells (bioincompatibility). Fifteen patients were treated exclusively with the cuprophane membrane (bioincompatible) and the other 15 patients received HD with the high-flux polysulfone membrane (biocompatible). MEASUREMENTS: Residual renal function was determined at initiation of dialytic therapy and after 6, 12, and 24 months. Dry weight (by chest x ray and diameter of the vena cava) was closely recorded throughout the study, and the number of hypotensive episodes counted. RESULTS: Residual renal function declined in both CAPD and HD patients, although this decline was faster in HD patients (2.8 mL/minute after 6 months and 3.7 mL/min after 12 months) than in CAPD patients (0.6 mL/min and 1.4 mL/min after 6 and 12 months respectively). It declined faster in patients with bioincompatible than with biocompatible HD membranes (3.6 mL/min vs 1.9 mL/min after 6 months). Eleven percent of the HD sessions were complicated by clinically relevant blood pressure reductions, but there were no differences between the two dialyzer membrane groups. None of the CAPD patients had documented hypotensive episodes. None of the study patients suffered severe illness or received nephrotoxic antibiotics or radiocontrast media. CONCLUSIONS: The better preservation of RRF in stable CAPD patients corresponded with greater cardiovascular stability compared to HD patients, independently of the membrane used. Furthermore, there was a significantly higher preservation of RRF in HD patients on polysulfone versus cuprophane membranes, indicating an additional effect of biocompatibility, such as less generation of nephrotoxic substances by the membrane. Thus, starting ESRD patients on HD prior to elective CAPD should be avoided for better preservation of RRF.     

Studies on the ability of hemodialysis membranes to induce, bind, and clear human interleukin-1

Interleukin-1 (IL-1) is a polypeptide cytokine predominantly produced by monocytes in response to injury or infection. Effects of IL-1 such as fever, acute phase protein synthesis, hypotension, and loss of body mass are complications of hemodialysis. Endotoxin-contaminated dialysate fluid, sodium acetate as a dialysate buffer, and activated complement can induce IL-1 during hemodialysis. In the present study, we investigated the intrinsic property of hemodialysis membranes to stimulate human blood mononuclear cells (MNC) to produce IL-1. Incubation of MNC on sheets of two commonly used hemodialysis membranes, regenerated cellulose (RC) and polyacrylonitrile (PAN) resulted in significant induction of IL-1 in the absence of endotoxin or complement. Production of intracellular and extracellular IL-1 was greater in MNC exposed to PAN compared with RC (p less than 0.01). Similar results were obtained when MNC were exposed to strips of hemodialysis membranes in rotating tubes. However, compared with RC, PAN binds significant amounts of human IL-1. In a model of in vitro hemodialysis, radiolabeled recombinant human IL-1 was added to the blood compartment of a PAN and a RC dialyzer. Forty percent of radiolabeled IL-1 bound to the PAN dialyzer membrane compared with 10% to the membrane of a RC dialyzer. In addition, 22% of radiolabeled IL-1 was found in the dialysate compartment of a PAN dialyzer after 1 hour whereas 1% was found in the dialysate side of a RC dialyzer; these results were confirmed by measuring bioactivity of IL-1. These studies demonstrate the intrinsic property of hemodialysis membranes to stimulate human IL-1 production; in addition they establish that dialysis membranes differ in their ability to bind and clear IL-1.     

Hemodialysis raises oxidative stress through carbon-centered radicals despite improved biocompatibility

Leukocyte activation and the resulting oxidative stress induced by bioincompatible materials during hemodialysis impact the prognosis of patients. Despite multiple advances in hemodialysis dialyzers, the prognosis of hemodialysis patients with complications deeply related to oxidative stress, such as diabetes mellitus, remains poor. Thus, we re-evaluated the effects of hemodialysis on multiple reactive oxygen species using electron spin resonance-based methods for further improvement of biocompatibility in hemodialysis. We enrolled 31 patients in a stable condition undergoing hemodialysis using high-flux polysulfone dialyzers. The effects of hemodialysis on reactive oxygen species were evaluated by two methods: MULTIS, which evaluates serum scavenging activities against multiple hydrophilic reactive oxygen species, and i-STrap, which detects lipophilic carbon-center radicals. Similar to previous studies, we found that serum hydroxyl radical scavenging activity significantly improved after hemodialysis. Unlike previous studies, we discovered that scavenging activity against alkoxyl radical was significantly reduced after hemodialysis. Moreover, patients with diabetes mellitus showed a decrease in serum scavenging activity against alkyl peroxyl radicals and an increase in lipophilic carbon-center radicals after hemodialysis. These results suggest that despite extensive improvements in dialyzer membranes, the forms of reactive oxygen species that can be eliminated during dialysis are limited, and multiple reactive oxygen species still remain at increased levels during hemodialysis.     

Hemodialysis of phenytoin in a uremic patient.

Removal of phenytoin by hemodialysis was determined in a uremic patient. The rate of appearance of the drug in dialysate, the plasma concentration with time, and the plasma clearance by dialysis were measured. Plasma protein binding of phenytoin was also determined. In spite of greatly reduced plasma protein binding in the uremic patient, removal rate was observed to be less than 10% of the rate of presentation of the dialyzer. During the 6-hr period of dialysis, the plasma concentration showed little change. The amount collected in the dialyase, 43.6 mg, was only a small fraction of drug in the body. These results indicate that replacement of phenytoin based on the amount of drug removed by dialysis is unnecessary in chronically dialyzed uremic patients. In addition, the utility of hemodialysis in phenytoin overdose is questioned.     

Effect of hemodialysis on the oxidative stress and antioxidants.

Oxidative stress plays a role in many disease states. These diseases have an increased incidence in uremia, and particularly in hemodialysis (HD) patients. This suggests an increased exposure to oxidative stress. An imbalance between oxidants and antioxidants has been suggested in uremic patients on HD. However, the respective influence of uremia and dialysis procedure has not been evaluated. It is postulated that antioxidant capacity in uremic patients is reduced, yet the mechanism remains unclear. We have determined the levels of lipid peroxidation expressed as thiobarbituric acid-reactive substances. We assessed oxidative protein damage by carbonyl content and activities of antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) in predialysis uremic patients and in end-stage renal disease (ESRD) patients before and after hemodialysis. Vitamin E and vitamin C levels, reduced glutathione and sulfhydryl content were also studied. We found enhanced oxidative stress in ESRD patients undergoing HD and in predialysis uremic patients. This was mostly due to defective antioxidant enzyme levels. Preventive modalities, including use of biocompatible membranes, ultrapure dialysate, exogenous supplementation of antioxidant vitamins, extracorporeal removal of reactive oxygen species (ROS) and oxidatively modified substances, would appear highly desirable to reduce complications in the long-term dialysis patients.     

Patient survival and renal recovery in acute renal failure: randomized comparison of cellulose acetate and polysulfone membrane dialyzers

OBJECTIVE: To investigate survival and renal recovery after dialysis in patients with acute renal failure with use of synthetic membranes compared with substituted cellulose membranes. PATIENTS AND METHODS: We prospectively studied survival and recovery of renal function of 66 patients with acute renal failure who required intermittent hemodialysis. Patients were randomized to exclusive treatment with either cellulose acetate (CA) or polysulfone (PS) hemodialysis membranes. Additionally, markers of biocompatibility (complement, leukocyte counts, cytokine concentration) were measured at initiation and 1 hour after initiation of dialysis among 10 patients equally distributed between the CA and PS groups. RESULTS: The cohorts were indistinguishable with respect to age, sex, presence of diabetes mellitus, Acute Physiology and Chronic Health Evaluation II scores, percentage in the intensive care unit (ICU), and adequacy of dialysis. Survival (76% CA, 73% PS; P=.78) and recovery of renal function at 30 days (58% CA, 39% PS; P=.14) were not statistically different in the 2 groups. Among 26 CA patients and 27 PS patients treated in the ICU, survival was not statistically different (73% CA, 67% PS; P=.61); however, the proportion of patients recovering renal function suggested a benefit favoring CA membranes (65% CA, 37% PS; P=.04). Additionally, markers of biocompatibility were not significantly different between groups among the 10 patients equally distributed between the CA and PS groups. CONCLUSIONS: Overall clinical outcomes among patients with acute renal failure treated with CA hemodialysis membranes and those treated with PS membranes were not significantly different. The observed advantage favoring renal recovery among this ICU population treated with CA hemodialysis membranes warrants further investigation.     

不同透析膜对维持性血液透析患者血磷清除效果的研究

目的　了解不同的透析膜对维持性血液透析患者血磷的清除情况。方法　将2 6例进行维持性血液透析的高磷血症患者分为3组,分别使用聚砜膜(1.3m2 )、三醋酸纤维膜(1.5m2 )和血仿膜(1.7m2 )透析,比较透析前后血磷的下降率(单位膜面积)以及透析2个月后血磷及钙磷乘积的变化。结果　去除膜面积因素后,聚砜膜和三醋酸纤维膜与血仿膜比较,单次透析血磷的下降率(单位膜面积)差异均有显著性(P<0 .0 5 ) ,但聚砜膜和三醋酸纤维膜比较差异无显著性(P >0 .0 5 )。使用2个月后比较血磷水平及钙磷乘积,三醋酸纤维膜组透析前血磷及钙磷乘积均较前显著下降(P <0 .0 5 ) ,而聚砜膜组和血仿膜组均较前无明显改善(P >0 .0 5 )。结论　膜面积相等的情况下,聚砜膜和三醋酸纤维膜对磷的清除优于血仿膜,前两者之间差异无显著性。使用聚砜膜和三醋酸纤维膜并适当增大膜面积可更大程度地清除血磷,同时可降低钙磷乘积。     

Effect of dialyzer reuse on complement activation and neutropenia in hemodialysis

A prospective study of 10 patients undergoing hemodialysis showed that less neutropenia and complement activation occurred with dialyzer reuse. Neutrophil counts fell 95% +/- 5% (SEM) with first use and 66% +/- 8% and 48% +/- 10% with second and third uses, respectively (p less than 0.05). The production of complement component C5a-desarg, as measured by the bioassay granulocyte aggregation, was decreased by 96% +/- 1% and 93% +/- 2% with second and third uses, respectively (p less than 0.05). We investigated the role of the dialyzer disinfectant formaldehyde in decreased neutropenia. In vitro, formaldehyde inhibited granulocyte aggregation and chemotaxis and the dialyzer membrane's ability to generate granulocyte aggregating activity; however, this occurred only at concentrations higher than those likely to obtain in patients. The ability of dialysis membranes to generate granulocyte aggregating activity in plasma was decreased 55% +/- 5% by their prior sequential preincubation in plasma and then formalin (p less than 0.05) and extensive rinsing, which is similar to the circumstances obtaining with dialyzer reuse. Preincubation of membranes in plasma or formalin alone resulted in no change in the membrane's ability to generate granulocyte aggregating activity. We conclude that the exposure of membranes to both plasma and formalin during dialysis and storage is responsible for the decreased C5a-desarg production with reuse, probably because plasma proteins are fixed to the membrane in such a way that interrupts free interaction between the membrane and plasma complement components.