Free Water Transport and its Association with Cardiovascular Status in Children on Peritoneal Dialysis

Abstract

Background Volume overload is one of the most important factors associated with left ventricular hypertrophy (LVH) and cardiovascular disease in chronic peritoneal dialysis (PD) patients. MiniPET is a reliable tool to evaluate free water transport (FWT). In a clinical setting, the significance of FWT has not been evaluated in terms of outcome in children on PD. The objective was to define a FWT value of clinical significance in children on PD, fixing its relationship to left ventricular mass index (LVMI) as a well-known outcome parameter. Methods MiniPET was performed with 3.86% glucose, 1-h long, to measure FWT in PD patients > 6 years old. An echocardiogram (ECG) was performed within 2 months of the MiniPET. Left ventricular hypertrophy was defined as LVMI ≥ 38.6 g/height2.7 (95th percentile). Receiver operating characteristic curve (ROC) analysis was used to determine the cut-off value of FWT searching the highest sensitivity and specificity to differentiate patients with normal/abnormal LVMI. A p < 0.05 was considered significant. Results Forty-six studies were performed on 32 patients, 16 males; mean age 11.59 ± 3.07 years. Mean normalized FWT (nFWT) was 144.4 ± 84.8 mL/m2, corresponding to 46.7% of total ultrafiltration. Mean LVMI was 42 ± 11.3 g/m2.7 with a negative correlation to nFWT ( p < 0.01). Eighteen out of 32 patients had LVH. The ROC analysis (nFWT vs LVMI) showed an area under the curve of 0.71 (95% confidence interval [CI], 0.53 – 0.89; p = 0.04), allowing a cut-off nFWT value of 110 mL/m2 to be defined, dividing the population into 2 groups of patients according to the LVMI cut-off value of 38,6 g/m2.7. Conclusions The nFWT showed an inverse correlation to LVMI. A nFWT value < 110 mL/m2 was significantly associated with LVH. The negative relationship observed between nFWT and LVMI, and the cut-off level for nFWT according to the 95th percentile of LVMI, suggest that the regular evaluation of nFWT could become a useful tool in assessing the capacity of PD treatment to keep patients’ volume status under control, avoiding cardiovascular impairment.

ABC de la diálisis peritoneal en pediatría

“…El transporte de agua libre evita la sobrecarga de volumen, y se ha relacionado al pronóstico cardiovascular 25 . El PET no evalúa el transporte de agua por los USP 32 , en cambio el miniPET permite esta evaluación administrando una solución hipertónica de glucosa 3,86% en el peritoneo y midiendo la caída de la concentración de sodio en la solución a Promedio bajo (media a < 1 ds) 0,26-0,38 0,43-0,57 0,73-0,83 0,5-0,61…”

“…La UF de USP se obtiene restando de la UF total la UF de poros pequeños, calculada dividiendo la remoción de sodio por la concentración de sodio plasmático; el valor final se normaliza por superficie corporal 33 . En un estudio local se identificó un valor de 110 ml/m² como punto de corte para el transporte de agua libre en función del impacto cardiovascular, correlacionando valores menores a este con hipertrofia de ventrículo izquierdo 32 . El protocolo miniPET se encuentra detallado en publicaciones previas 12,33 .…”