评价血液透析患者容量状态的新参量:峰值阻抗

目的本研究初步总结血液透析患者在血液透析前后阻抗-频率曲线变化的规律,提出评价血液透析患者容量状况的新参量。方法本研究随机抽取20例健康人(对照组)与20例血液透析患者(透析组),在100Hz到50kHz频率范围内对其全身阻抗进行扫频测量,描绘并比较两组的阻抗曲线。结果阻抗曲线与ECFC模型相吻合,透析组透析前后阻抗曲线变化明显,透析后阻抗曲线更接近对照组阻抗曲线。透析组患者透析前后峰值阻抗分别为(415±106)Ω和(566±74)Ω,峰值频率分别为(5.16±1.49)kHz和(3.94±0.91)kHz,差异均有统计学意义(P0.01);透析前峰值频率、峰值阻抗分别与对照组健康人的峰值频率[(4.03±0.50)kHz]、峰值阻抗[(502±38)Ω]相比差异有统计学意义(P0.01),而透析后峰值频率、阻抗与对照组峰值频率、阻抗相比差异无统计学意义(P0.05)。透析组患者透析前后的峰值阻抗差与体质量差呈显著相关(r=0.574,P0.01);在控制变量年龄和身高体质量比进行偏相关分析后,透析前后的体质量差和峰值阻抗差仍呈显著正相关(r=0.631,P0.01)。结论生物阻抗曲线可以较好地反映血液透析患者的容量状况;峰值阻抗可作为评价血液透析患者容量状况的新参量。     

血浆脑钠肽水平预测维持性血液透析患者容量超负荷的价值

目的利用生物电阻抗分析(bioimpedance analysis,BIA)测量将患者容量状态定量化,同期检测血浆脑钠肽(brain natriuretic peptide,BNP),探讨BNP在评价维持性血液透析(maitaining hemodialysis dialysis,MHD)患者容量超负荷的价值。方法选择北京大学国际医院透析中心MHD患者共74人,BIA测算化验BNP当日患者的多余水分(overhydration in the day of measuring plasma BNP,OH_(bnp)),在BIA测量2周内进行超声心动图检查;依据OHb_(bnp)是否大于2.5L将患者分为2组,正常容量负荷组(OH_(bnp)≤2.5L)和容量超负荷组(OH_(bnp)2.5L),比较2组血浆BNP及相关指标差异;多重线性回归分析BNP影响因素;ROC曲线分析血浆BNP对容量超负荷的诊断价值。结果容量超负荷组的BNP显著高于正常容量负荷组[209(116,395)pg/ml比339(172,843)pg/ml,t=-2.197,P=0.028]。多重线性回归分析显示血浆BNP受OH_(bnp)(β=0.107±0.037,P=0.005)、血红蛋白(β=-0.012±0.004,P=0.005)、瘦体质量指数(β=-0.046±0.019,P=0.016)影响;ROC曲线显示取BNP为309pg/ml时,诊断容量超负荷敏感性为0.548,特异性为0.698。结论容量负荷、血红蛋白及瘦体质量指数均影响MHD患者血浆BNP,血浆BNP大于309pg/ml提示存在容量超负荷。     

多频生物电阻抗法评价血液透析患者体液分布

目的利用多频生物电阻抗测量法了解维持性血液透析（HD）患者体液分布情况。方法选择透析龄大于3个月的维持性HD患者119名,应用多频生物电阻抗频谱分析法分别于透析前、后测定细胞外液（ECW）、细胞内液（ICW）,并分别计算占体重的百分比（ECW%、ICW%）。选择性别、年龄和体重相匹配个体82例作为正常对照。结果男性和女性维持性HD患者ECW%较同性别正常对照组明显增高（男P〈0.01,女P〈0.05）,透析后较透析前显著降低（P〈0.01）;ICW%与同性别正常对照组无显著性差异（P〉0.05）,且透析前、后无明显变化;男女患者ECW/ICW比值透析前均显著高于同性别正常对照组（P〈0.01）,透析后虽较透析前显著降低（P〈0.01）,但仍高于同性别正常对照组（P〈0.05）。HD患者透析过程ECW下降值与实际超滤量呈显著正相关（男r=0.572,P〈0.01;女r=0.556,P〈0.01）。同性别透析高血压组的ECW%透析前后均高于正常血压组和正常对照组（P〈0.05）;正常血压组透后ECW%与对照组无明显差异。高血压组和正常血压组ICW%在透析前、透析后与正常对照均无差别。结论①透析前HD患者存在体液分布异常,主要表现为ECW%显著增加;②HD脱水主要来自细胞外液,对细胞内液无明显影响;③利用多频生物电阻抗测量透后ECW%可能是评价HD患者干体重的有效指标。     

联机血液透析滤过纠正尿毒症血液透析患者钙磷代谢紊乱临床观察

目的 探讨联机血液透析滤过(HDF)、综合血液透析(HD)对患者钙、磷、甲状旁腺激素(PTH)清除效果.方法 取本血液净化中心维持性血液透析患者40例,随机分为两组,联机HDF组(n=20)和HD组(n=20).维持透析6个月后检测透析前、透析后钙、磷、PTH.结果 联机HDF组透析前后血钙水平为(1.90±0.35) mmol/L vs(2.20±0.67)mmol/L,HD组分别为(2.02±0.22)mmol/L vs (2.30±0.18) mmol/L,两组透析后血钙均有轻度升高,但两组透析后差异无统计学意义(P＞0.05);联机HDF组透析前后血磷水平为(2.45±0.41) mmol/L vs (1.70±0.15)mmol/L;而HD组分别为(2.52±0.60) mmol/L vs(1.82±0.20)mmol/L,两组患者接受透析后较透析前其血磷浓度均有明显的降低,并且两组透析后差异有统计学意义(P＜0.05).联机HDF组透析前后血PTH为(702.0±14.3)ng/L vs(345.0±16.8)ng/L; HD组分别为(697.2±13.2)ng/L vs(391.7±19.4)ng/L,两组患者在接受治疗后均有明显的降低,而联机组患者其治疗后含量明显低于HD组(P＜0.05).结论 联机HDF可以有效清除维持性血液透析患者血液中钙、磷PTH,改善患者预后.     

腹膜透析患者血清CHI3L1、FABP4水平和容量超负荷及蛋白质能量消耗的相关性研究

目的探讨腹膜透析患者血清CHI3L1、FABP4、容量超负荷及蛋白质能量消耗的相关性。方法本研究纳入160例临床状况稳定、在北京大学第三医院腹膜透析中心规律随访的腹膜透析患者。通过ELISA方法测定血清CHI3L1及FABP4浓度。根据多频生物电阻抗原理测定患者体成分,以水负荷(overdydration,OH)值来评估腹膜透析患者的容量负荷状态,OH值≥2L为容量超负荷,OH值2L为容量正常。纳入分析的生化指标包括血清白蛋白、尿毒氮、血肌酐、三酰甘油、总胆固醇、低密度脂蛋白胆固醇、高密度脂蛋白胆固醇等。根据蛋白质能量消耗(protein energy wasting,PEW)诊断标准,将入组腹膜透析患者分为蛋白质能量消耗组(PEW组)和非蛋白质能量消耗组(非PEW组)。结果腹膜透析患者血清CHI3L1和FABP4水平呈正相关(r=0.273,P=0.001)。血清CHI3L1水平与容量超负荷呈负相关(r=-0.191,P=0.020),与肌肉重量呈负相关(r=-0.443,P=0.000)。血清FABP4水平与容量超负荷呈负相关(r=-0.172,P=0.040),与肌肉重量呈负相关(r=-0.188,P=0.025)。与容量正常组相比,容量超负荷组的血清CHI3L1水平更低(289.6±117.9ng/ml比335.3±119.3ng/ml,t=2.349,P=0.020),FABP4水平也更低[152.0(131.6,194.6)ng/ml比170.0(132.0,374.9)ng/ml,z=-2.051,P=0.040]。容量超负荷患者的PEW发生率更高(61.7%比42.3%,χ~2=5.756,P=0.013),但是PEW组和非PEW组的CHI3L1、FABP4水平无显著性差异。Logistic回归分析提示PEW的独立危险因素是容量负荷(OR=2.744,95%CI 1.190~6.327,P=0.018)、血清白蛋白(OR=0.837,95%CI 0.734~0.955,P=0.008)和肌肉重量(OR=0.936,95%CI0.891~0.982,P=0.007)。结论腹膜透析患者的血清CHI3L1、FABP4水平显著升高,首次发现两者呈正相关且均与容量超负荷呈负相关,并与肌肉量负相关;PEW发生的独立危险因素是低白蛋白血症、低肌肉量及容量超负荷,而与CHI3L1、FABP4水平无关。     

人尾加压素Ⅱ和花生四烯酸乙醇胺在腹膜透析患者容量抵抗和高血压中的作用

目的人尾加压素Ⅱ(human urotensinⅡ,hUⅡ)和花生四烯酸乙醇胺(arachidonoylet-hanolamine,AEA)是近年来新发现的舒张血管的降压物质。我们既往研究发现有一定比例的腹膜透析患者尽管出现容量超负荷,但却能维持正常血压,提示这部分患者具有容量抵抗。本研究探讨AEA、hUⅡ在腹膜透析患者高血压中的作用,并初步探讨其是否在容量抵抗中发挥作用。方法回顾性研究纳入2009年7月至2010年1月年在北京大学第三医院肾内科腹膜透析门诊随诊的腹膜透析患者105例,患者均采用标准的持续不卧床腹膜透析(continuous ambulatory peritoneal dialysis,CAPD)方式。应用生物电阻抗测定出的OH值为衡量患者容量负荷的主要指标。患者在随访过程中多次测量OH取平均值。OH2为正常容量组,OH≥2为高容量组;收缩压130mm Hg(1mm Hg=0.133kPa)为正常收缩压组,收缩压≥130mm Hg为高收缩压组。将患者分为4组:①正常收缩压正常容量组(NT-NV组);②正常收缩压高容量组(NT-HV组);③高收缩压正常容量组(HT-NV组);④高收缩压高容量组(HT-HV组)。血浆hUⅡ水平采用放射免疫测定法,AEA水平采用高效液相色谱-串联质谱(UPLC-MS)测定。结果收缩压组130mm Hg患者血浆hUⅡ水平显著高于高收缩压组(P0.05),AEA水平也有高于收缩压组的趋势,但差异无统计学意义(P=0.13)。NT-HV组hUⅡ水平高于HT-HV组(P0.05),NT-HV组AEA水平高于HT-NV组(P0.05)。结论 hUⅡ水平高可能是腹膜透析患者容量抵抗的原因之一,而AEA亦可能参与容量抵抗腹膜透析患者的血压调节。     

实时剪切波超声弹性成像技术评估帕金森病患者骨骼肌弹性模量的研究

目的研究帕金森病患者肱二头肌、肱桡肌、股直肌及小腿三头肌长轴杨氏模量值特征,探讨实时剪切波超声弹性成像技术评估帕金森病患者肌肉状态的应用价值。方法选取46例帕金森病患者(病变组)和健康志愿者31例(对照组),应用实时定量剪切波超声弹性成像技术获取病变组双侧、对照组右侧的肱二头肌、肱桡肌、股直肌及小腿三头肌松弛状态下长轴杨氏模量值,并进行对比分析。结果放松状态下病变组患者症状明显侧、症状较轻侧及对照组肱二头肌长轴杨氏模量值分别为(59.94±20.91)k Pa、(47.77±24.00)k Pa及(24.44±5.09)k Pa;肱桡肌长轴杨氏模量值分别为(32.18±17.19)k Pa、(28.41±13.19)k Pa及(21.71±7.45)k Pa;股直肌长轴杨氏模量值分别为(15.74±12.16)k Pa、(16.13±11.61)k Pa及(10.25±7.89)k Pa;小腿三头肌长轴杨氏模量值分别为(20.77±10.18)k Pa,(20.63±11.83)k Pa及(9.32±4.75)k Pa。病变组患者双侧肱二头肌、肱桡肌、股直肌及小腿三头肌长轴杨氏模量均高于对照组(均P0.05);症状明显侧肱二头肌长轴杨氏模量高于症状较轻侧(P0.05),病变组患者双侧肱桡肌、股直肌及小腿三头肌长轴杨氏模量比较差异无统计学意义。结论实时定量剪切波弹性成像技术可检测帕金森病患者较大骨骼肌杨氏模量值差异,为评估帕金森病患者肌肉状态提供了一种新的检测方法。     

生物电阻抗分析法评估血液透析患者干体重

目的利用生物电阻抗频谱分析法（bioimpedence analysis,BIA）了解维持性血液透析（hemodialysis,HD）患者的体液分布,同时了解其对血压的影响。方法选择苏州大学附属第一医院血透中心维持性血液透析患者85例,透析时间均大于3个月,应用BIA分别测定透析前后细胞内液（intra—cellular water,ICW）、细胞外液（extra—cellular water,ECW）,并分别计算占体重的百分比（ECW％、ICW％）。另外选取83名性别、年龄、体重匹配的正常个体作为对照组。结果HD患者透前ECW％明显高于同性别正常对照（P〈0．01）,透后较透前明显降低（P〈0．05）,透后接近正常人群水平（P〉0．05）。HD患者ICW％透析后降低,但与透前相比无明显差异,且与同性别正常对照组亦无明显差异（P〉0．05）;HD患者高血压组透前、透后均高于正常对照（P〈0．05）;HD患者正常血压组透前高于正常对照（P〈0．05）。透后与正常对照组无显著差异;HD患者低血压组透前与正常对照无差异（P〉0．05）,透后低于正常对照组（P〈0．05）。结论透析患者的体液分布存在明显异常,主要表现为透析前ECW％增加。透析脱水主要来自ECW,对ICW无明显影响。利用多频生物电阻抗测定透析后ECW％可用于评价HD患者干体重,但仍需进一步研究。     

腹膜透析和血液透析患者心脏负荷的临床分析

目的初步评估行腹膜透析（PD）和血液透析（HD）的终末期肾病（ESRD）患者心脏负荷的状况;并比较PD、HD患者心脏负荷的差异。方法对上述两组患者通过测定平均动脉压（MAP）、血浆B型利钠肽（BNP）、超声心动图、心胸比（CTR）等进行比较。结果两组患者的MAP、BNP、超声心动图、CTR改变均高于正常对照组（P〈0．05）而PD组MAP、BNP、超声心动图、CTR改变轻于HD组（P〈0．05）。结论ESRD透析患者普遍存在心脏负荷过重,PD患者心脏超负荷状态较HD患者轻。     

非对称性二甲基精氨酸与血液透析中血压变化的研究

目的研究血液透析(Hemodialysis,HD)患者血浆非对称性二甲基精氨酸(Asymmetric dimethylarginine,ADMA)与透析中血压变化的关系。方法经生物电阻抗检测干体质量达标且符合入选标准的维持性血液透析(Maintenance Hemodialysis,MHD)患者31名进入研究,根据血液透析过程中血压波动情况分为年龄相匹配的3组:透析中高血压组(n=11)、低血压组(n=12)和血压平稳组(n=8)。用酶联免疫吸附(Enzyme linked immunosorbent assay,ELISA)法检测患者透析前、后血浆ADMA水平,探讨ADMA与透析中血压变化的关系,并进行组间矿物质骨代谢指标、电解质、营养指标、炎性标记物、血脂水平、脉压差和降压治疗等的比较。结果 31例MHD患者透析前血ADMA均值为3.37±1.48μmol/L,透析后降至1.71±0.80μmol/L(P0.001),均显著高于国外正常参考值。透析中低血压组透析前、后血ADMA值(4.38±1.56μmol/L,2.25±0.83μmol/L)均高于透析中高血压组和血压平稳组,差异有统计学意义(2.70±1.18μmol/L,1.32±0.60μmol/L和2.78±0.88μmol/L,1.43±0.56μmol/L;P=0.006和0.006)。透析中高血压组患者透析中的平均脉压差高于透析中低血压组和血压平稳组(62.41±11.57mmHg,48.80±12.88 mmHg和44.56±8.30 mmHg,P=0.004)。高血压组碱性磷酸酶(ALP)、总胆固醇(TC)、低密度脂蛋白胆固醇(LDL-C)和高敏C-反应蛋白(high-sensitivity c-reactive protein,Hs-CRP)均高于血压平稳组(P值分别为0.036、0.039、0.046、0.046),低血压组同样指标也高于血压平稳组(P值分别为0.046、0.035、0.040、0.004),上述指标在高血压组和低血压组间差异无统计学意义(P0.05)。结论在干体质量达标的MHD患者中,血ADMA水平显著高于正常,透析过程中的血压波动与内皮功能不良、血管僵硬、微炎症状态等密切相关。     

Use of single-frequency bioimpedance at 50 kHz to estimate total body water in patients with multiple organ failure and fluid overload.

OBJECTIVE: To investigate the relationship between single-frequency bioimpedance at 50 kHz (both total body impedance and segmental impedance) and total body water, measured using tritiated water in the presence of the severe fluid retention seen in multiple organ failure. DESIGN: Prospective, controlled study. SETTING: General intensive care unit. SUBJECTS: Twenty patients with multiple organ failure and 30 normal volunteers, of whom a subgroup of ten had total body water measured. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Total body water and total and segmental bioimpedance values at 50 kHz were measured using tritiated water and a Holtain body composition analyzer in 20 patients with multiple organ failure and in ten normal volunteers. An additional 20 normal volunteers also had segmental and total body impedance measured. There was no difference in the linear regression lines constructed for the patients and the volunteers, but the SEM in the patients (7.6 L) was four times that seen in the normal subjects (1.9 L). In a further seven patients, the impedance technique overestimated the change in total body water, deduced from acute changes in weight, by between 0% and 46% (median, 12%). In the patients, who were supine, the knee-ankle segment contributed significantly more to total body impedance than it did in the normal volunteers (42.5% vs. 34.4%; p < .001), who were upright and mobile immediately before the measurement. CONCLUSIONS: Although single-frequency bioimpedance does give an indication of total body water and change in total body water, it is neither precise nor accurate enough to be the sole guide to fluid therapy. The proportion of total impedance contributed by the knee-ankle segment, which contains relatively little water, was significantly greater in the patients than in the controls, probably reflecting better drainage of fluid from the lower limb in the supine position.     

Evaluation of algorithms for calculating bioimpedance phase angle values from measured whole-body impedance modulus

This paper addresses the problem of calculating the bioimpedance phase angle from measurements of impedance modulus. A complete impedance measurement was performed on altogether 20 healthy persons using a Solatron 1260/1294 system. The obtained impedance modulus (absolute impedance value) values were used to calculate the Cole parameters and from them the phase angles. In addition, the phase angles were also calculated using a Kramers-Kronig approach. A correlation analysis for all subjects at each frequency (5, 50, 100 and 200 kHz) for both methods gave R(2) values ranging from 0.7 to 0.96 for the Cole approach and from 0.83 to 0.96 for the Kramers-Kronig approach; thus, both methods gave good results compared with the complete measurement results. From further statistical significance testing of the absolute value of the difference between measured and calculated phase angles, it was found that the Cole equation method gave significantly better agreement for the 50 and 100 kHz frequencies. In addition, the Cole equation method gives the four Cole parameters (R(0), R(∞), τ(z) and α) using measurements at frequencies up to 200 kHz while the Kramers-Kronig method used frequencies up to 500 kHz to reduce the effect of truncation on the calculated results. Both methods gave results that can be used for further bioimpedance calculations, thus improving the application potential of bioimpedance measurement results obtained using relatively inexpensive and portable measurement equipment.     

An instrumentation amplifier as a front-end for a four-electrode bioimpedance measurement

The performance of a monolithic instrumentation amplifier used as an interface for a four-electrode bioimpedance measurement is examined with a commercially available impedance meter based on an auto-balancing bridge. The errors due to particularities in the input stage of the impedance meter, when used without a front-end, were several orders of magnitude higher than the measured quantity. The analysis was performed on an electrical circuit model of the skin and electrodes over a frequency range of 20 Hz to 1 MHz. The achieved accuracy with balanced electrode impedances for the frequencies up to 100 kHz can be below 0.2% for impedance magnitude and 0.1 degrees for impedance phase, which is within the specified basic accuracy range of the LCR-meter used for the measurements. At frequencies above 100 kHz the errors are increasing and are higher than the LCR-meter's basic accuracy. This study indicates that use of an instrumentation amplifier as a front-end with the particular LCR-meter can significantly improve the measurement accuracy of the four-electrode bioimpedance measurement at low frequencies.     

生物电阻抗矢量分析法评价维持性血液透析患者干体重初探

目的探索生物电阻抗矢量分析法（bioelectrical impedance vector analysis,BIVA）在评价维持性血液透析（maintenance hemodialysis,MHD）患者干体重（dryweight,DW）中的应用。方法选择北京大学第一医院肾脏内科血液透析室临床评价DW合适的MHD患者,透析前和透析后分别进行单频（50KHz）、全身生物电阻抗测量。收集北京石景山地区的健康查体人群作为对照。在电阻-电抗矢量图（RXc图）上分别绘制健康人群和MHD患者矢量的95%可信区间和健康人群的容受区间。根据透析前患者在健康人群容受区间图上的位置将MHD患者分为A（水负荷过重）、B（水负荷正常）两组,比较两组患者透析前高血压患病情况。根据透析后患者的矢量在容受区间图上的位置将患者分为水负荷过重（OH）组、水负荷正常（NH）组和脱水（DH）组,从而预测干体重调整方向,并比较三组患者透析前和透析后的血压变化。结果共测量290例健康成人,男∶女=149∶141;血液透析患者37例,男∶女=13∶24。相比健康对照,透析患者透析前的矢量较短,相角较小;透析后矢量均较透析前变长,相角变大,水合状态改善。A组高血压出现率为39.3%,而B组为22.2%。DH组血压平均水平较OH和NH组低,但没有统计学差异。BIVA方法评价干体重合适的患者与临床评价一致性为70.3%;BIVA预测11例患者需要调整DW,经过两周的观察,5人调整了干体重,调整方向与BIVA预测方向一致。结论在临床评估干体重合适的患者中,仍然有部分患者的透析前水负荷较重。BIVA方法能先于临床经验发现不合适的干体重,可以作为较为敏感的估计干体重的辅助工具。     

Effect of body mass index (BMI) on estimation of extracellular volume (ECV) in hemodialysis (HD) patients using segmental and whole body bioimpedance analysis

The aim of the study was to investigate whether body mass index (BMI) influences the estimation of extracellular volume (ECV) in hemodialysis (HD) patients when using segmental bioimpedance analysis (SBIA) compared to wrist-to-ankle bioimpedance analysis (WBIA) during HD with ultrafiltration (UF). Twenty five HD patients (M:F 19:6,) were studied, and further subdivided into two groups of patients, one group with a high BMI (25 kg m-2) and the other with a low BMI (<25 kg m-2). Segmental (arm, trunk, leg) and wrist-to-ankle bioimpedance measurements on each patient were performed using a modified Xitron 4000B system (Xitron Technologies, San Diego, CA). No differences in extracellular resistance (R(E), ohms) between wrist-to-ankle (R(W)) and sum of segments (R(S)) were noted for either the high BMI (489.2+/-82 ohm versus 491.6+/-82 ohm, p=ns) or low BMI groups (560.8+/-77 ohm versus 557.5+/-75 ohm, p=ns). UF volume (UFV, liters) did not differ significantly between the groups (4.0+/-0.9 L versus 3.3+/-1.0 L, p=ns), but change in ECV (DeltaECV) differed not only between methods: WBIA versus SBIA in the high BMI group (2.74+/-1.1 L versus 3.64+/-1.4 L, p<0.001) and in the low BMI group (1.86+/-0.9 L versus 2.91+/-1.0 L, p<0.05) but also between the high and lower BMI groups with WBIA (2.74+/-1.1 L versus 1.86+/-0.9 L, p<0.01). However, there was no significant difference in SBIA between BMI groups. This study suggests that the segmental bioimpedance approach may more accurately reflect changes in ECV during HD with UF than whole body impedance measurements.     

A method for the estimation of hydration state during hemodialysis using a calf bioimpedance technique

Although many methods have been utilized to measure degrees of body hydration, and in particular to estimate normal hydration states (dry weight, DW) in hemodialysis (HD) patients, no accurate methods are currently available for clinical use. Biochemcial measurements are not sufficiently precise and vena cava diameter estimation is impractical. Several bioimpedance methods have been suggested to provide information to estimate clinical hydration and nutritional status, such as phase angle measurement and ratio of body fluid compartment volumes to body weight. In this study, we present a calf bioimpedance spectroscopy (cBIS) technique to monitor calf resistance and resistivity continuously during HD. Attainment of DW is defined by two criteria: (1) the primary criterion is flattening of the change in the resistance curve during dialysis so that at DW little further change is observed and (2) normalized resistivity is in the range of observation of healthy subjects. Twenty maintenance HD patients (12 M/8 F) were studied on 220 occasions. After three baseline (BL) measurements, with patients at their DW prescribed on clinical grounds (DW(Clin)), the target post-dialysis weight was gradually decreased in the course of several treatments until the two dry weight criteria outlined above were met (DW(cBIS)). Post-dialysis weight was reduced from 78.3 +/- 28 to 77.1 +/- 27 kg (p < 0.01), normalized resistivity increased from 17.9 +/- 3 to 19.1 +/- 2.3 x 10(-2) Omega m(3) kg(-1) (p < 0.01). The average coefficient of variation (CV) in three repeat measurements of DW(cBIS) was 0.3 +/- 0.2%. The results indicate that cBIS utilizing a dynamic technique continuously during dialysis is an accurate and precise approach to specific end points for the estimation of body hydration status. Since no current techniques have been developed to detect DW as precisely, it is suggested as a standard to be evaluated clinically.     

Stroke volume measurements by electrical bioimpedance and echocardiography in healthy volunteers

To evaluate the validity of three equations for estimation of thoracic electrical field size in a new bioimpedance algorithm, stroke volume (SV) as calculated by these equations was compared with that calculated by Doppler echocardiography in 48 healthy volunteers, both lean and obese. When the volume of electrically participating tissue was estimated from body height (modified Sramek) or body height corrected for body habitus (Sramek-Bernstein), there was considerable variation between bioimpedance and Doppler stroke volumes. When the volume of electrically participating tissue was estimated from the actual measurement of the height of the thorax and the circumference at the base of the thorax, the variation in SV differences decreased substantially (Sramek equation), although still considerable for clinical use, and there was no relationship between SV thus obtained and body habitus. Analysis of calculated stroke indices derived by our Doppler echocardiographic standard, as compared with values in the literature, revealed a systematic underestimation. We conclude that the original Sramek equation systematically underestimates SV by 15% to 20%, and the modified Sramek and Sramek-Bernstein equations systematically underestimates SV by 15% to 20%, and the modified Sramek and Sramek-Bernstein equations systematically overestimate SV in females by about 15%, but provide SV values in males in the predicted range. Further studies on the current assumption that the electrical field size is a truncated cone may improve precision of the bioimpedance method.     

低钠透析对血液透析患者大动脉僵硬度的影响

目的大动脉僵硬度的金标准--腹主动脉脉搏波传导速度(pulse wave velocity,PWV)是终末期肾脏病患者全因死亡和心血管死亡的独立危险因素。在非透析人群,饮食钠摄入增多可升高PWV;反之,限盐可降低PWV。本研究旨在观察应用低钠透析液增加透析钠清除对血液透析患者大动脉僵硬度的影响。方法选择处于干体质量的稳定血液透析患者16名。先应用标准透析液(钠浓度138mmol/L)透析一1个月,再将透析液钠浓度降为136mmol/L透析4个月(低钠透析)。研究期间未对饮食钠进行限制和干预,并且每个月应用生物电阻抗仪对干体质量进行调节,以保持透析后容量状态稳定。同时测量PWV、44h动态血压,记录透析间期体质量增长、每月透析中低血压和肌肉痉挛的发生率。结果随着低钠透析,腹主动脉PWV显著下降(12.61±2.30比11.74±2.65m/s,P=0.005);44h动态收缩压和舒张压分别较基线水平下降10mmHg和6mmHg(1mmHg=0.133kpa),而透析后容量状态无明显变化;透析间期体重增长轻度下降(2.89±0.66比2.67±0.63kg,P=0.051)。低血压和肌肉痉挛的发生率无明显变化。结论降低透析液钠浓度可显著改善透析患者的大动脉僵硬度。