Hemodynamic Monitoring During Hemodialysis Using Bioimpedance: A Comparison of Changes in Resistance Between Different Body Segments

INTRODUCTION: Prevention of hemodynamic complications during hemodialysis remains challenging. Although whole body bioimpedance is well established in fluid status assessment, its use for dynamic or continuous recordings is limited. A segmental approach may serve this purpose better. This study investigates which body segment is best targeted to measure bioimpedance for hemodynamic monitoring. METHODS: In this observational study, serial bioimpedance measurements were conducted on the whole body, lower leg, upper arm, and thorax of 15 patients during two hemodialysis sessions. The resistance component of bioimpedance was used to investigate the relationship with changes in volume and systolic blood pressure (SBP). FINDINGS: Predialysis to postdialysis changes in relative resistance between the two sessions revealed the lowest intraclass correlation coefficient for upper arm (0.023) and the highest for thoracic resistance (0.728). Correlation between ultrafiltration volume and relative resistance was comparable between upper arm and thoracic segment (0.538 [0.447-0.618] and 0.537 [0.446-0.617], both p < 0.001, respectively) and the highest for whole-body and lower leg (0.697 [0.63-0.754] and 0.670 [0.598-0.731], both p < 0.001, respectively). In contrast, the correlation between changes in SBP and relative resistance was the highest in the thoracic segment (-0.33 [-0.432 to -0.219], p < 0.001) and the lowest for whole body measurements (-0.154 [-0.269 to -0.036], p = 0.01). In addition, multiple regression analysis indicated thoracic resistance as the best predictor for changes in SBP (ß = -0.261 [-0.353 to -0.126], p < 0.001). DISCUSSION: These findings suggest that the thorax is the most suitable region for segmental bioimpedance measurements to assess hemodynamic parameters. Thoracic bioimpedance may innovate the hemodynamic monitoring of hemodialysis patients.