FP738BODY COMPOSITION ANALYSIS PREDICTS MORTALITY RISK IN HAEMODIALYSIS PATIENTS

Abstract

Introduction and Aims: Haemodialysis patients have a high mortality rate, mainly due to cardiovascular disease and malnutrition. At the end of the Nineties, some observational studies described a paradoxically correlation between elevated body mass index (BMI) values and longer survival in haemodialysis patients: "obesity paradox". BMI cannot give information about the alterations in the different body compartments due to protein energy wasting (PEW). Furthermore, BMI is influenced by the increase in extracellular water, which is frequent in haemodialysis patients. The aim of this study was to evaluate the efficacy of the analysis of body composition by bioimpedence (BIA) to predict the mortality risk in haemodialysis patients. Methods: Observational longitudinal study lasting six years on 78 prevalent haemodialysis patients (68% male, mean age 65 +/- 14 years; dialysis vintage 7 +/- 7 years). Every two years, starting from the baseline, we collected clinical, laboratory and BIA data, including BIVA analysis and hydration scale, that is the hydration as percentage of lean body mass. We compared the BIA data of patients dead during the study period (n = 45; 65%) with those of survivors (n = 24; 35%). The significance of the differences between the mean values of the two groups at the baseline was evaluated. Results: Nine patients underwent renal transplantation or moved to another haemodialysis facility. The group of patients dead at different times during the six years of observation had significantly higher values of BMI (28 +/- 6 vs 24.8 +/- 3.1 kg / m, p <0.01) and fat mass index (11.2 +/- 4.1 vs 8.4 +/- 2.8 kg / m2, p <0.003) compared to the group of survivors, while there were no significant differences regarding the values of body cell mass index (BCMI) (7.1 +/- 1.7 vs 7.9 +/- 1.8 kg / m2), which is a marker of muscle mass, and serum albumin (4.1 +/- 0.4 vs 4.1 +/- 0.1 mg/dl). The group of survivors had significantly higher values of electrical reactance (67.3 +/- 13.7 vs 53.5 +/- 11.7 ohm, p <0.000003), phase angle (5.9 +/- 0.8 vs 5.1 +/- 0.9 degrees, p <0.00003) and the percentage of extracellular water was significantly lower (46.1 +/- 3.6 vs 50.6 +/- 5.2%, p <0.00003). Finally the BIVA analysis indicated that the percentage of hydration, evaluated by the hydration scale, was significantly lower in the group of survivors (71.2 +/- 3.3 vs 73.3 +/- 1.8%, p <0.00006). In summary the group of survivors had normal values of BMI and fat mass, a smaller reduction in BCM and less fluid overload than the group of deceased patients. Conclusions: The survival of haemodialysis patients is influenced by the nutritional status. The fluid overload and decrease in muscle mass play a decisive role on survival. The low values of electrical resistance and of phase angle, measured by BIA, and the high values of hydration scale predict mortality risk in maintenance haemodialysis patients.