溶质清除指数的简易计算方法

目的 :探求简易溶质清除指数 (SRI)计算方法在临床应用的可行性。方法 :选取 2 0例稳定血透患者 6 0次血透用标准方法和简易方法分别计算其SRI。简易方法即是在标准计算SRI公式中 ,用干体重 超滤量代替透前尿素分布容积 ,用超滤液的尿素浓度代替透前血浆尿素浓度 ,整个计算无需抽血获取生化检验值。两种SRI计算结果进行等效分析。结果 :标准公式计算的SRI为 (70 .2 1± 7.0 8) % ,简易方法测得的结果 (简称SRI简)为 (6 9.78±8.2 1) % ,等效分析 (△ =7.0 8× 0 .5 )t=- 3.5 6 9,P <0 .0 1。结论 :简易方法与标准计算公式计算结果相同 ,且前者整个公式计算无需抽取血化验 ,简单易行 ,值得推广。     

前稀释高容量联机血液滤过与低通量血液透析清除效果的前瞻性交叉研究

目的:比较前稀释高容量联机血液滤过(HF)与低通量血液透析(HD)清除的效果.方法:对10例维持性HD患者采用前瞻性、随机、交叉研究,观察两种血液净化治疗前后血清肌酐(Scr)、血尿素氮(BUN)、血磷、β2微球蛋白(β2-MG)、瘦素(leptin)水平变化及评价尿素清除指数.结果:HF组β2-MG、瘦素下降率明显高于HD组(P＜0.01),而BUN、Scr下降率及一室尿素清除指数、二室尿素清除指数低于HD组(P＜0.05).两组血磷下降率差异无显著性.结论:前稀释高容量联机HF清除较大分子量尿毒症毒素明显优于低通量HD.     

联机尿素监测仪检测Kt/V的临床应用

尿素清除分数Kt/V是评价血液透析充分性的一个重要指标,通常由Daugirdas公式,即Kt/V=-ln(R-0.008t)+(4-3.5R)×UF/W计算而得.在临床应用过程中,需抽取患者透析前、透析后血标本检测血尿素氮,患者不易接受.且计算公式复杂,限制了该公式的普及运用,导致临床上对患者透析充分性评估缺少实质性的依据.本中心运用Biotrack HM3000尿素监测仪检测患者的Kt/V,结果发现:使用尿素监测仪检测的患者的Kt/V值与Daugirdas公式计算的结果相关性好,而且不需抽血,值得推广.     

对透析充分性的认识更新

spKt/Vurea是指用第二代单室可变体积尿素动力学模型估计的尿素清除指数,它只能用来表示单次透析对小分子非蛋白结合毒素的清除是否充分。要表示这类毒素的清除是否充分,需要计算std Kt/Vurea。可以用增加透析次数的手段提高std Kt/Vurea,以改善患者长期存活。当前还没有评价蛋白结合溶质、中大分子溶质、在体液不均匀分布溶质的透析充分性,的公认方法。     

腹膜透析充分性指标探讨

目的在氮平衡的基础上评价Kt/V这一经典的透析充分性评估指标在腹膜透析中的价值,探讨腹膜透析充分性的最佳评估指标.方法在氮平衡的基础上推算持续性不卧床腹膜透析(CAPD)患者的理论透析剂量及透析指数(DI),并进一步推算氮平衡状态下的Kt/V计算公式;计算溶质转运指数(SRI).比较透析指数(DI)、溶质清除指数(Kt/V)、溶质转运指数(SRI)三者在评估透析充分性方面的优缺点.结果溶质清除指数(Kt/V)受饮食蛋白的摄入量及体重的影响,我们不能用同一个Kt/V值标准来评估不同条件下CAPD患者的透析充分状况.在CAPD状态下,溶质转运指数(SRI)与Kt/V反映的数据是相同的,它反映的是溶质的清除量与该溶质在身体中总的含量之比.透析指数(DI)可以反映在达到目标血尿素氮(BUN)水平时不同体重、不同蛋白质摄入(DPI)患者达到氮平衡状态时所需要的透析剂量,当不存在蛋白质摄入不足的情况下,它可以从氮平衡的角度反映透析的充分性.结论对于临床处于稳定状态的CAPD患者,用透析指数(DI)综合蛋白摄入量(DPI)来评估其透析充分性较单纯目标尿素溶质清除指数Kt/V值及溶质转运指数(SRI)更为客观可靠.     

运动疗法对尿毒症血液透析患者透析充分性的影响

目的 探讨运动训练对维持性血液透析充分性的影响.方法 将120例尿毒症血液透析患者随机分为实验组和对照组.实验组在常规护理的基础上进行每周3次的运动训练,对照组按常规护理,干预时间为12周.测定干预前后透析中两组患者尿素下降率、尿素清除指数.结果 干预后,实验组患者尿素下降率、尿素清除指数较对照组明显增加(P＜0.05).结论 患者进行运动训练可提高透析充分性和透析效果.     

降低透析液钾离子浓度对血清钾离子清除及透析效率的影响

目的评估不同钾浓度透析液透析过程中血清钾离子清除程度和对尿素氮清除的影响。方法前瞻性、随机对照分析,32例稳定的维持性血液透析患者参与试验,在5周稳定的血液透析间期(使用1.5m2三醋酸纤维膜透析器,透析时间240min,血流量250ml/min,透析液流量500ml/min,无糖透析液,碳酸氢钠浓度为35mmol/L),使用透析液包括0(0K),1(1mmol/LK),和2(2mmol/LK),在每周中间1次透析治疗后收集部分透析液并计算钾离子的清除量MK和尿素氮的清除量MU,计算尿素氮降解率URR和尿素氮清除指数Kt/V。结果 3组患者在透析过程中,血清钾离子浓度持续稳定下降,在180min左右达到一稳定的浓度。0K、1K和2K透析液组分别达到108.5mmol,84.5mmol和60.3mmol(P<0.05),尿素氮的清除量MU不受钾离子的清除量MK的影响(r=0.49),3组患者尿素氮的清除、尿素氮降解率URR和尿素氮清除指数Kt/V均无明显的变化。结论低钾透析液能显著性增加钾离子的清除量,透析钾离子的清除量并不影响尿素氮的清除水平及透析效率。     

腹膜透析小分子溶质清除评估研究进展

小分子溶质清除是腹膜透析患者透析充分性评估的重要组成部分,本研究主要从其主要指标—尿素清除指数的定义、测定方法、与患者预后的相关研究及进展以及其可能的影响因素等方面进行阐述。尿素清除指数被认为与患者的体质量指数、性别、能量代谢率、种族等因素相关,其对腹膜透析患者预后的独立影响作用仍存在争议。在此基础上,本研究对尿素清除指数在腹膜透析小分子溶质清除评估中的作用及其局限性进行深入分析。     

腹膜透析充分性的评估的新认识

长期以来小分子溶质清除率作为肾脏替代治疗充分性的一个重要指标,应用于持续性不卧床腹膜透析(CAPD)是在20世纪80年代后期。小分子物质的清除的指标尿素清除指数Kt/V和肌酐清除率CrCl是建立在尿素动力学模型基础上,并认为腹膜和残余。肾溶质清除相等,两者可以相加,并影响着透析患者的预后。     

可穿戴透析设备尿素去除技术进展CSCD

可穿戴人工肾(wearable artificial kidney,WAK)是透析设备的进化产物,发展WAK的关键是从废透析液中去除尿毒症溶质,其中尿素是最难去除的尿毒症溶质。通过调研国内外WAK尿素去除技术进展,分别对脲酶去除尿素技术、电氧化技术和尿素吸附技术进行综述,首先简要介绍其原理,然后分析其在WAK临床试验中的应用及尿素去除效果,最后对3种技术进行优缺点评价并进行展望,期望对WAK尿素去除技术研究者给予相关信息支持和参考。     

New enzymatic assay for serum urea nitrogen using urea amidolyase

We established an enzymatic assay for measurement of serum urea nitrogen using urea amidolyase (EC 3.5.1.45) from yeast species. The method is based on hydrolysis of urea by the enzyme. In this assay, we eliminated endogenous ammonium ion by use of glutamate dehydrogenase (EC 1.4.1.4). Then in the presence of urea amido-lyase, ATP, bicarbonate, magnesium, and potassium ions, ammonium ion was produced proportionally to urea concentration in serum. The concentra-tion of ammonium ion formed was determined by adding GLDH to produce NADP(+) in the presence of 2-oxoglutarate and NADPH. We then monitored the change of absorbance at 340 nm. The inhibitory effect of calcium ion on this assay was eliminated by adding glyco-letherdiamine-N, N, N', N'-tetraacetic acid to the reaction system. The with-in-assay coefficient of variations (CVs) of the present method were 1.80-3.76% (n = 10) at 2.8-19.0 mmol/L, respectively. The day-to-day CVs were 2.23-4.59%. Analytical recovery was 92-115%. The presence of ascorbic acid, bilirubin, hemoglobin, lipemic material, ammo-nium ion, or calcium ion did not affect this assay system. The correlation be-tween values obtained with the present method (y) and those by another enzy-matic method (x) was 0.997 (y = 1.02x - 0.10 mmol/L, Sy/x = 0.841, n = 100), with a mean difference of -0.18 +/- 0.86 mmol/L [(values by reference method - that of present method) +/- SD] using the Bland-Altman technique. J. Clin. Lab. Anal. 17:52-56, 2003.     

Blood urea nitrogen and creatinine

The determination of serum creatinine and serum urea nitrogen levels is of great value in helping to ascertain the renal function in the clinical setting. These two serum determinations are best viewed in concert, observing their absolute levels as well as their relation to one another. The serum creatinine level is less influenced by extra-renal factors than is the serum urea nitrogen level, and is the more accurate test. Reproducibility of measurement is within 2 per cent. When the test results return, there are a number of questions to be asked: What is the normal range for the laboratory which analyzed the serum? Are the levels real; i.e., could the elevated levels be factitious? Are there extrarenal etiologies for the abnormal levels? What is the BUN to creatinine ratio? If the abnormal findings are secondary to intrinsic renal disease, what other tests will help to determine the etiology of the renal disease? The laboratory assessments of BUN levels and blood creatinine levels are "standard fare" in the assessment of renal function. They are relatively low-cost tests, are available in any standard hospital laboratory, and are relatively easy to run. They are essential in the assessment of renal function in the Emergency Department.     

The Helicobacter pylori VacA toxin is a urea permease that promotes urea diffusion across epithelia

Urease and the cytotoxin VacA are two major virulence factors of the human pathogen Helicobacter pylori, which is responsible for severe gastroduodenal diseases. Diffusion of urea, the substrate of urease, into the stomach is critically required for the survival of infecting H. pylori. We now show that VacA increases the transepithelial flux of urea across model epithelia by inducing an unsaturable permeation pathway. This transcellular pathway is selective, as it conducts thiourea, but not glycerol and mannitol, demonstrating that it is not due to a loosening of intercellular junctions. Experiments performed with different cell lines, grown in a nonpolarized state, confirm that VacA permeabilizes the cell plasma membrane to urea. Inhibition studies indicate that transmembrane pores formed by VacA act as passive urea transporters. Thus, their inhibition by the anion channel blocker 5-nitro-2-(3-phenylpropylamino) benzoic acid significantly decreases toxin-induced urea fluxes in both polarized and nonpolarized cells. Moreover, phloretin, a well-known inhibitor of eukaryotic urea transporters, blocks VacA-mediated urea and ion transport and the toxin's main biologic effects. These data show that VacA behaves as a low-pH activated, passive urea transporter potentially capable of permeabilizing the gastric epithelium to urea. This opens the novel possibility that in vivo VacA may favor H. pylori infectivity by optimizing urease activity.