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。

Estimation of dry body weight using bioelectrical impedance vector analysis in maintenance hemodialysis patients

Object To probe the possibility of bioelectrical impedance vector analysis （BIVA） as a tool to estimate dry weight （DW） in maintenance hemodialysis patients. Methods Maintenance hemodiaiysis patients with adequate DW appreciated based on clinical experience in the Hemodialysis Center of Peking University First Hospital were included in this study. Single frequency （50kHz） and whole-body impedance vector were measured before and after hemodialysis （HD） sessions. Vector distribution was compared with that of healthy subjects living in the Shijingshan District in Peking. The 95% confidence ellipses for MHD patients and healthy subjects and the tolerance ellipses for healthy subjects were drawn on the resistance-reactance vector graph. Before HD session, the patients were divided into group A （overhydration） and group B （normohydration） according to their vector tolerance analysis, and the occurrence of hypertension was compared between the two groups. After HD session, the patients were divided into overhydration, normohydration and dehydration groups according to their vector tolerance analysis. The prediction of DW adjustment was then made based on hydration status, and their blood pressure levels before and after HD session were compared. Results In this study, 290 healthy subjects （male ： female = 149：141） and 37 adult maintenance hemodialysis patients （male ： female = 13：24） were included. Compared with those of healthy subjects, the vector was shorter and the phase angle was smaller in patients before HD, and the vector became longer and the phase angle became larger after HD. The vector displacement after HD indicates the improvement of hydration status in patients. Before HD, hypertension was found in 39.3% patients in group A, and in 22.2% patients in group B. Blood pressure was lower in dehydration group than in overhydration and normohydration groups, but the differences had no statistical significance. The consistent rate between DW assessed by BIVA and that by clinical assessment was 70.3%. By BIVA, 11 patients were suggested to have DW readjusted. After observation for 2 weeks, DW was readjusted with the same direction based on BIVA prediction in 5 of the 11 patients. Conclusion Over hydration occurred before HD in some patients clinically assessed with proper DW. BIVA can discriminate oatients with improper DW before clinical symptoms and thus can be a sensitive tool to assist physician to evaluate DW.