Utility of bioimpedance spectroscopy (BIS) in the management of refractory hypertension in patients with chronic kidney disease (CKD)

Abstract

Expansion of extracellular volume (ECV) is a frequent cause of resistant hypertension (RHT) in patients with chronic kidney disease (CKD). The aim of this exploratory study was that of applying bioimpedance spectroscopy (BIS) for the identification of CKD patients with RHT and expansion of ECV, while trying to control blood pressure (BP) using an intensification of diuretic treatment. We included 50 patients with RHT and CKD who underwent BIS. In order to control BP, diuretic treatment was intensified in those patients with expansion of the ECV. In all other cases, another antihypertensive drug was added. The mean age was 68.2 ± 10.4 years, 68% were male and 58% were diabetic. The mean estimated glomerular filtration rate (eGFR) was 50.7 ± 22.4 mL/min/1.72 m(2). Baseline systolic BP was 167.2 ± 8.6 mmHg and diastolic BP was 84.8 ± 9.5 mmHg. The mean number of antihypertensive drugs received was 3.8 ± 0.9. Expansion of ECV was recorded in 30 (60%) patients and was more frequent in diabetics and in patients with more albuminuria. At 6 months of follow-up, a decline of 21.4 ± 7.1 mmHg was observed in systolic BP in the patients with expansion of ECV, compared with a decrease of 9.4 ± 3.4 mmHg in the normal ECV group (P < 0.01). We did not find differences in the decrease in diastolic BP between the groups. Nine patients (30%) with ECV expansion who increased diuretic therapy reached the target blood pressure (BP) of <140/90 mmHg, when compared with only two patients (10%) who had normal ECV and in whom other antihypertensive drug was added. A total decrease in body water of 1.9 ± 1.1 L was observed in patients with ECV expansion who intensified diuretic treatment at the expense of a decline in ECV of 1.1 ± 1 L. eGFR remained stable in both groups (47.1 ± 21.1 versus 54.1 ± 25.2 mL/min/1.73 m(2); P = 0.37). An increase in ECV as measured by BIS frequently occurs in RHT in patients with CKD. Diabetic and severe proteinuric patients are more exposed to expansion of ECV. BIS is a potentially useful method for identifying and treating patients with RHT and expansion of ECV. The hypothesis generated by this exploratory study needs to be tested in a randomized clinical trial.