Volume Status in Patients on Peritoneal Dialysis: The Role of Apelin and Bio-Impedance Spectroscopy

Abstract

One of the main factors determining the survival of peritoneal dialysis (PD) patients is volume status. We aimed to investigate hydration status of PD patients by bio-impedance spectroscopy (BIS) and echocardiography and to study the relation of them with apelin, which has effects related with volume status like vasodilation, positive inotropism, and inhibition of ADH release and RAS antagonism. Chronic PD patients without active cardiac disease or clinically prominent hypervolemia were included. Besides the demographic, clinical, and laboratory data, BIS and echocardiographic findings together with apelin levels were recorded. The study included 21 patients. Of them, eight patients were euvolemic, one patient was hypovolemic, and others have some degree of overhydration (1.1-6.8 L) with BIS, although all were euvolemic clinically. Mean apelin level was 1.49 AE 0.49 ng/mL. Apelin level was positively correlated with ejection fraction and negatively with total body water (TBW), intracellular and extracellular water, lean tissue mass, and left atrium diameter. On linear regression model, TBW was the major determinant of apelin. Although apelin is expected to increase in hypervolemic patients, the negative correlation with body water in this study may be related with yet unknown role of apelin in dialyzed patients. They may have important roles in volume status in future.

The relation between apelin levels, echocardiographic findings and carotid intima media thickness in peritoneal dialysis patients

“…This unexpected result may be due to limited number of patients. 28 In our study, it is detected that LVMI and serum apelin level in patient group was significantly higher than control group. As the patient group was divided into two groups as high and low apelin groups, LVMI is higher in high apelin group than low apelin group, but not statistically significant.…”

Apelin and nutritional status in children on dialysis

“…Likewise, Karadag and Kazancioglu et al reported positive association between apelin and LDL in PD patients. 31,34 However, Malyszko et al found apelin was negatively correlated with TG, total and LDL cholesterol in HD patients. 38 The controversy between those studies might be due to dialysis modality as PD patients are more predisposed to metabolic disturbances, particularly to hyperglycemia and dyslipidemia.…”

“…33,34 However we did not directly analyze body fluid composition by bio-impedance spectroscopy (BIA). Although all measurements were done in euvolemic state, hypervolemia was not actually ruled out because of hypertension and hypoalbuminemia, particularly in PD patients.…”

The superiority of bioimpedance vs. echocardiography and pitting edema in predicting automated office blood pressure in continuous ambulatory peritoneal dialysis patients

“…In other words, edemafree status does not always indicate the state of euvolemia [28]. This is because some pathologic alterations in dialysis patients, including vascular permeability and stiffness, cardiac dysfunctions, and use of vasodilator medications, may interfere with accurately interpreting volume status [29,30]. Second, a study has shown that the severity of pedal edema was not associated with more objective methods of assessing the volume status, including IVC diameter measurement or serum biomarkers [30].…”

“…In line with a previous study [28], we speculate that increments in OH are one of the main contributors to edema formation in PD patients. However, some pathologic alterations in dialysis patients, including vascular permeability and stiffness, cardiac dysfunctions, and use of vasodilator medications, may interfere with accurately interpreting volume status using edema assessment [29,30]. Moreover, the mechanism behind edema formation in dialysis is multifactorial, and some other contributors, like hypoalbuminemia, should be considered in evaluating edematous patients [28].…”