Bioimpedance Spectroscopy for the Detection of Hypervolemia in Hemodialysis Patients

INTRODUCTION: A practical, inexpensive and reliable method is needed for assessment of volume status in hemodialysis (HD) patients. In this study the effi ciency of bioimpedance spectroscopy (BIS) for detection of hypervolemia was investigated.

MATERIAL and METHODS: A total of 172 prevalent HD patients were enrolled from 2 centers. Echocardiography, 48-hours ambulatory blood pressure (BP) measurement, and body composition analysis using the BIS technique (50 frequencies) (Body Composition Monitor) were performed. Overhydration (OH) and extracellular water (ECW) in liters, and the OH/ECW ratio were used as volume indices.

RESULTS: The mean age was 52±13 years and HD duration 60±43 months. Of the cases, 41% were female, 17% were diabetic. The mean left ventricular mass index (LVMi) was 159±42 gr/m2 and 77% of the patients had left ventricular hypertrophy (LVH). The mean OH and OH/ECW ratio were 2.1±1.6 L and 11±8%, respectively. OH/ECW ratio was correlated with day-time systolic BP (r:0.383, p<0.0001), night-time systolic BP (r:0.380, p<0.0001), pulse pressure-48h (r:0.413, p<0.0001), left atrium index (LAi) (r:0.301, p<0.0001), LVMi (r:0.378, p<0.0001) and ejection fraction (EF) (r:-0.239, p:0.002). Patients with OH/ECW ratio lower than 5% had favorable cardiovascular risk profi le. On linear regression analysis, the OH/ECW ratio was an independent risk factor for LAi (t:3.00, p:0.003), LVMi (t:2.77, p:0.006) and EF (t:-2.34, p:0.02).

CONCLUSION: Bioimpedance spectroscopy is a reliable method to evaluate volume status in HD patients. OH/ECW measured by BIS is a major determinant of left atrial diameter, left ventricular mass and ejection fraction. An OH/ECW value less than 5% is associated with acceptable blood pressure control and better cardiac condition.