Extracellular Volume Changes and Blood Pressure Levels in Hemodialysis Patients

Background: Despite the use of highly efficient antihypertensive drugs (AHD), blood pressure (BP) is poorly controlled in the vast majority of hemodialysis (HD) patients. Many of them show no reduction in nocturnal BP, a finding that is associated with left ventricular hypertrophy. The aim of the study was to investigate the effect of the removal of a fluid overload on BP by monitoring the ambulatory BP during 48 hours in 16 hypertensive HD patients treated with AHD. Our aim was to obtain a gradual reduction in post‐HD body weight (BW) over a period of 3 to 4 months. Methods: During a period of 3–4 months, the postdialysis BW was reduced as the minimal tolerable BW was gradually achieved by slightly increasing the ultrafiltration volume. The Na concentration in the dialysate was reduced from 143–141 mmol/L to 139–138 mmol/L. Extracellular volume (ECV) was measured with a multiple‐frequency bioimpedance analyzer (Xitron 4000B, Xitron Technologies Inc., San Diego, CA, USA). Based on the change in ECV, the patients were subdivided into two groups: group 1 with a reduction in ECV (n = 10), and group 2 with no reduction (n = 6). At the start of the study, BW, BP, and AHD in group 1 and group 2 were virtually identical. Results: Group 1 showed a significant reduction during the entire 48‐hour period in systolic (156 ± 16 mmHg vs. 140 ± 14 mmHg, P = 0.030) and diastolic BP (97 ± 12 mmHg vs. 87 ± 9 mmHg, P = 0.026) as well as in mean arterial pressure (MAP, 117 ± 13 vs. 105 ± 10 mmHg, P = 0.027). This reduction was more marked during the night (systolic BP 156 ± 15 mmHg vs. 138 ± 14 mmHg, P = 0.007; diastolic BP 97 ± 12 mmHg vs. 85 ± 9 mmHg, P = 0.009) than during the day (157 ± 18 mmHg vs. 142 ± 15 mmHg, P = 0.067; diastolic BP 97 ± 13 mmHg vs. 90 ± 9 mmHg, P = 0.126). A significant reduction in systolic load also occurred during the entire 48‐hour period (76 ± 24% vs. 46 ± 28%, P = 0.043) as well as in night systolic load (75 ± 21% vs. 41 ± 30%, P = 0.015) and night diastolic load (67 ± 32% vs. 39 ± 31%, P = 0.030). AHD were stopped in eight and reduced in two patients. There were no significant reductions in BP and AHD in group 2. Conclusions: The removal of excess fluid is necessary for adequate BP control and especially for the reduction in elevated BP during the night.