Bioimpedance Analysis Evaluating Fluid Distribution In Patients On Maintenance Hemodialysis And The Effect Of Adjusting The Dry Weight

Objective: To evaluate fluid distribution in patients on maintenance hemodialysis(HD)by bioimpedance analysis, and to evaluate bioimpedance analysis on the effect ofadjusting the dry weight in hemodialysis patients.Methods: Forty maintenance HD patients from the Dialysis Center of the SecondAffiliated Hospital of Dalian Medical University were enrolled as the case group. Onehundred and two individuals who were examined in the Center of Health Examinationin the same hospital were enrolled as the control group. Sex and age of the two groupswere recorded. Body weight, blood pressure, bioimpedance of HD patients (pre-dialysisand post-dialysis) and controls were measured. Bioimpedance was measured bymultifrequency segmental bioimpedance analysis, including right arm (RA)bioimpedance, trunk (TR) bioimpedance and right leg (RL) bioimpedance.Bioimpedance ratio (BIR) of three parts was calculated as BIR=bioimpedance of100kHz/bioimpedance of20kHz and they were RA-BIR, TR-BIR and RL-BIR. Theneihgt HD patients who had high RA-BIA or TR-BIA according to the reference rangewhich were obtained from102controls were chosen for dry weight adjustment.Post-dialysis body weight, blood pressure, and bioimpedance of the eight HD patientswere measured again after adjusting the dry weight. Statistical analysis was performedusing SPSS version13.0. For continuous variables, data were expressed asmean±standard deviation(for Gaussian distribution) or median(the25thand75thpercentile)(for non-Gaussian distribution). For categorical variables, data wereexpressed as ratio or percentage. The Independent-Samples T-test was used forcomparison between groups for continuous variables and chi-squared test was used forcomparison between groups for categorical variables. The Paired-Samples T-test wasused for comparisons between pre-dialysis and post-dialysis HD patients and also for comparisons between pre-adjusted dry-weight and post-adjusted dry-weight HDpatients. P-values of <0.05were considered significant.Results:1. BIR of three parts of pre-dialysis HD patients were RA-BIR (0.9124±0.0210),TR-BIR(0.9249±0.0356), and RL-BIR(0.9124±0.0255). BIR of three parts of thecontrols were RA-BIR(0.8977±0.0124), TR-BIR (0.8805±0.0202), and RL-BIR(0.8917±0.0136). BIR of three parts were all significantly higher in pre-dialysis HDpatients than in the control group (P0.05). BIR of three parts of the post-dialysis HDpatients were RA-BIR(0.9066±0.0218), TR-BIR(0.9185±0.0385), and RL-BIR(0.8972±0.0276) which were still higher than the control group, but RL-BIR was notsignificantly higher than controls. BIR of three parts of the post-dialysis HD patientswere lower than BIR of three parts of the pre-dialysis HD patients, and there wassignificant diffferent (P0.05) with RA-BIR and RL-BIR. The biggest lower-part wasRL-BIR（lower2.27±0.20%）.2. After adjusting the dry weight, BIR of three parts of the post-dialysis HDpatients were RA-BIR(0.9095±0.0267), TR-BIR(0.9046±0.0475), and RL-BIR(0.8836±0.0286) which were still higher than the control group, but none of them wassignificantly higher the controls (P0.05). BIR of three parts of the HD patients afteradjusting the dry weight were lower than BIR of three parts of the HD patients beforeadjusting the dry weight, but there was no significant diffferent with TR-BIR.Conclusions:1.Extracellular fluid is increased in HD patients between dialysis sessions.Hemodialysis patients show fluid loss from extracellular fluid during dialysis. Hightestfluid loss occurs from the legs and no obvious fluid loss occurs from the trunk.2.Bioimpedance analysis may be an effective method for adjusting thedry weight in hemodialysis patients, and the bioimpedance of arms is the most effectivemethod.3. The bioimpedance reference range of hemodialysis patients can beaccording to the reference range of normal individuals.