Relevance of hydration status on the interpretation of nutritional parameters in peritoneal dialysis

Objective This study identified determinants of the hydration status of chronic peritoneal dialysis patients and investigated the effects of fluid overload on their nutritional status. Methods A cross-sectional study was conducted in 2006 to evaluate 27 chronic peritoneal dialysis patients from the Dialysis Center of the Medical School Hospital of Botucatu (SP), considering clinical, dialytic, laboratory, anthropometric and bioimpedance parameters. A linear multiple regression model was used to evaluate the influence of these parameters on hydration status. The sample was stratified according to hydration status, given by the ratio between extracellular water and total body water (0.47 for males and 0.52 for females), obtained by bioelectrical impedance. Analysis of covariance, Mann-Whitney test, chi-square test, and Fisher's exact test were used for making comparisons. The significance level was set at 5% (p <= 0.05). Results Patients with greater urine volume and receiving automatic dialysis presented better hydration status. Patients with higher fluid overload, compared with those with lower overload, presented lower phase angle (M=4.2, SD=0.9 vs. M=5.7, SD=0.7 degrees; p=0.006), lower albumin levels (M=3.06, SD=0.46 vs. M=3.55, SD=0.52g/dL; p=0.05), and higher percentage of triceps skinfold thickness (M=75.3, SD=36.9 vs. M=92.1, SD=56.9; p=0.058). No other anthropometric differences were observed. Conclusion Low levels of albumin and phase angle in patients with higher fluid overload were not related to worse nutritional status. This result suggests that one must consider the set of variables obtained by many methods and relate and interpret them comprehensively in order to obtain a reliable nutritional diagnosis of patients with fluid overload.