Volume status and arterial stiffness evaluation in peritoneal dialysis patients

Background: Arterial stiffness represents an independent risk factor for cardiovascular mortality in dialysis patients and is strongly connected to hypervolemia. The aim of the study was to evaluate different methods for fluid status assessment and their association with arterial stiffness parameters in peritoneal dialysis patients. Materials and methods: In 16 peritoneal dialysis patients (53 +/- 18 years, 9/16 men) fluid status was determined by clinical examination, lung ultrasound (number of B-lines, normal up to 4), overhydration degree by bioimpedance monitor device, estimation of central venous pressure by ultrasound measurement of vena cava inferior, measurement of serum N-terminal pro b-type natriuretic peptide (NT-proBNP), and albumin level. Pulse wave velocity and augmentation index were measured non-invasively with an oscillometric device to indirectly assess arterial stiffness, blood pressure (BP) was obtained by the same device. Results: Clinical evaluation (BP 136 +/- 15/93 +/- 15 mmHg, edema in 2/16 patients) and lung ultrasound (on average 3 +/- 6 B-lines) showed mostly normal fluid status of patients. Patients had slightly lower albumin values (37 +/- 4 g/L), slightly elevated central venous pressure (10 +/- 4 mmHg), and elevated NT-proBNP (11,596 +/- 13,635 ng/L). Body composition evaluation showed mild overhydration (1.5 +/- 2 L), which significantly correlated with central venous pressure (p = 0.046) and NT-proBNP (p = 0.004). Lung ultrasound significantly negatively correlated with albumin (r = -0.82, p < 0.001) and positively with NT-proBNP (r = 0.62, p = 0.011). Augmentation index (22 +/- 11%) and augmentation pressure correlated with lung ultrasound (r = 0.54, p = 0.032 and r = 0.67, p = 0.004, respectively), although pulse wave velocity (8.4 +/- 2.5 m/s) showed no significant correlation with fluid status parameters. The multivariate model showed that lung ultrasound B-lines were an independent determinant of augmentation pressure (beta = 0.58, p = 0.043). Conclusion: Fluid status evaluated with lung ultrasound showed good correlation with augmentation index and augmentation pressure, which are markers of arterial stiffness. The lung ultrasound B-lines were found to be an independent determinant of augmentation pressure. Overall arterial stiffness evaluated with pulse wave velocity and augmentation index was not markedly elevated in our patients, which could be due to a good euvolemic status. We conclude that different methods for fluid status evaluation are complementary, with lung ultrasound as a beneficial tool in routine clinical practice in peritoneal dialysis patients.