The Effect of a Dry-weight Probing Guided by Lung Ultrasound on Ambulatory Blood Pressure and Arterial Stiffness in Hemodialysis Patients. A LUST Sub-study.

The most common co-morbidity accompanying Chronic Kidney Disease (CKD) is hypertension, which appears in approximately 80% of all patients with renal dysfunction, whereas its prevalence in general population is remarkably lower appearing in approximately 30% of adults.Defining hypertension in ESRD patients under maintenance dialysis is a challenging procedure. Ambulatory blood pressure monitoring (ABPM) is considered the "gold standard" for the diagnosis of hypertension in hemodialysis patients over the last years. The major pathophysiologic mechanism underlying hypertension development in patients with ESRD under hemodialysis is water and sodium overload.

Identifying an accurate and objective method of dry weight evaluation has been a matter of intensive nephrology research for more than two decades. Assessment of the water balance in hemodialysis patients on the basis of common clinical criteria (e.g. leg or face swelling or signs of lung congestion) is a subjective method with limited reliability, despite its widespread use. Recently, a novel technique has been developed to quantify water excess by conducting an ultrasound lung scan. Pilot studies have shown significant changes in lung water in hemodialysis patients according to body weight changes during interdialytic days and dialysis sessions. Moreover, results from previous studies indicate significant benefits from dry weight probing with regards to blood pressure (BP).

The clinical application of a lung-ultrasound-based volume control strategy in hemodialysis patients is currently being tested by the randomized study entitled "Lung water by ultrasound guided treatment to prevent death and cardiovascular complications in high risk end stage renal disease patients with cardiomyopathy (The LUST Study)". This clinical trial aims at evaluating whether the use of the number of US-B lines could be used as a biomarker to guide a per-protocol intensification of ultrafiltration (UF) in order to reduce volume overload, improve cardiac function and prolong survival.

Cardiovascular disease in patients with CKD is attributed to a spectrum of structural and functional alterations of the large and the small branches of the arterial tree. The most important process in patients with advanced CKD is that of arteriosclerosis, which is developed in parallel to atherosclerosis and is typically associated with impaired cushioning function of the aorta and the large conduit arteries. Accelerated arterial stiffening is involved in the development of isolated systolic hypertension, left ventricular hypertrophy (LVH) and congestive heart failure (CHF), which predispose to arrhythmias and sudden cardiac death. In the context of the phenomenon of "aortic-to-brachial BP amplification", systolic BP (SBP) and pulse pressure (PP) conventionally measured at the level of brachial artery are higher than the relevant pressures in the ascending aorta. Due to extreme elevation of arterial stiffness, BP amplification is disturbed in patients with ESRD. Prospective cohort studies have demonstrated that elevated central PP, wave reflections and arterial stiffness, as well as, reduced PP amplification represent strong and independent predictors of all-cause and cardiovascular mortality in hemodialysis patients. On this basis, estimation of central BP indices appears as an important tool towards optimisation of cardiovascular risk stratification in ESRD as well as in other diseased populations.

Until recently, available devices for ABPM evaluated BP levels only at the level of brachial artery. The newly developed Mobil-O-Graph NG (IEM, Stolberg, Germany) provides the ability to monitor central aortic pressure and indices of vascular resistance, such as wave reflections (augmentation index, AIx) and arterial stiffness (pulse wave velocity, PWV).This device has recently been validated in hemodialysis patients and showed comparable performance with the widely used tonometric SphygmoCor device (ArtCor, Sydney, Australia). Accumulated evidence over central BP and PWV in hemodialysis patients derives mostly from studies that included only static pre-dialysis and post-dialysis measurements. However, variations of BP levels during intra- and interdialytic intervals combined with the superiority of aortic BP measurements, as analysed above, indicate that ambulatory monitoring of central BP is the best available method.

This study aims for the first time to evaluate the outcome of a treatment strategy for dry weight probing, based on volume overload quantification with lung ultrasound, on 48-hour peripheral systolic BP, aortic BP and arterial stiffness in hemodialysis hypertensive patients.

This is a Lust Sub-Study. Additional information can be found at: NCT02310061.