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Chronic volume overload is pervasive in patients on chronic haemodialysis and substantially increases the risk of cardiovascular death. The rediscovery of the three-compartment model in sodium metabolism revolutionizes our understanding of sodium (patho-)physiology and is an effect modifier that still needs to be understood in the context of hypertension and end-stage kidney disease. Assessment of fluid overload in haemodialysis patients is central yet difficult to achieve, because traditional clinical signs of volume overload lack sensitivity and specificity. The highest all-cause mortality risk may be found in haemodialysis patients presenting with high fluid overload but low blood pressure before haemodialysis treatment. The second highest risk may be found in patients with both high blood pressure and fluid overload, while high blood pressure but normal fluid overload may only relate to moderate risk. Optimization of fluid overload in haemodialysis patients should be guided by combining the traditional clinical evaluation with objective measurements such as bioimpedance spectroscopy in assessing the risk of fluid overload. To overcome the tide of extracellular fluid, the concept of time-averaged fluid overload during the interdialytic period has been established and requires possible readjustment of a negative target post-dialysis weight. 23Na-magnetic resonance imaging studies will help to quantitate sodium accumulation and keep prescribed haemodialytic sodium mass balance on the radar. Cluster-randomization trials (e.g. on sodium removal) are underway to improve our therapeutic approach to cardioprotective haemodialysis management.

Background: Chronic fluid overload is frequent in hemodialysis patients (P) and it associates with hypertension, left ventricular hypertrophy (LVH) and higher mortality. Moreover, echocardiographic data assessing fluid overload is limited. Our aim was to evaluate the relationship between fluid overload measured by bioimpedance spectroscopy (BIS) and different echocardiographic parameters. Methods: Cross-sectional observational study including 76 stable patients. Dry weight was clinically assessed. BIS and echocardiography were performed. Weekly time-averaged fluid overload (TAFO) and relative fluid overload (FO/ECW) were calculated using BIS measurements. Results: Based on TAFO three groups were defined: A- dehydrated, TAFO < -0.25 L 32 P (42%); B- normohydrated, TAFO between -0.25 and 1.5 l: 26 (34%); C- overhydrated, TAFO>1.5 l: 18 (24%). We found significant correlation between TAFO and left atrial volume index (LAVI) (r: 0.29; p = 0.013) but not with FO/ECW (r: 0.06; p = 0.61). TAFO, but not FO/ECW kept a significant relationship with LAVI (p = 0.03) using One-Way ANOVA test and linear regression methods. LVH was present in 73.7% (concentric 63.2%, eccentric in 10.5%). No differences between groups in the presence of LVH or left ventricular mass index were found. Conclusions: We found that left atrial volume index determined by echocardiographic Area-length method, but not left ventricle hypertrophy or dimensions of cavities, are related on hydration status based on bioimpedance measured time-averaged fluid overload (TAFO), and not with FO/ECW. Resumen Introducción: La sobrehidratación es frecuente en pacientes en hemodiálisis (P) y se asocia con hipertensión, hipertrofia ventricular izquierda (LVH) y mayor mortalidad. Los datos ecocardiográficos evaluando sobrecarga hídrica son escasos. Nuestro objetivo fue evaluar la relación entre sobrehidratación medida por Bioimpedancia multifrecuencia (BIS) y parámetros ecocardiográficos. Métodos: Estudio transversal observacional, con 76 P estables; El peso seco fue determinado clínicamente; se realizaron ecocardiograma, BIS y analítica sanguínea. Se calcularon la sobrehidratación promedio semanal (TAFO) y sobrehidratación relativa (FO/ECW). Resultados: 3 grupos: A- deshidratados, TAFO < -0.25 L: 32 P (42,1%); B- normohidratado, TAFO -0.25 - 1.5 L: 26 P (34,2%); C- sobrehidratados TAFO > 1.5 L: 18 P (23,7%). Encontramos correlación significativa entre TAFO e índice de volumen auricular izquierdo (LVAI) (r: 0.29; p = 0.013) y no con FO/ECW (rho 0,06; p = 0,61). TAFO, pero no FO/ ECW, mantuvo una relación significativa con LVAI (p = 0,03) utilizando test de ANOVA y regresión lineal. LVH estuvo presente en 73,7% de P (concéntrica 63,2%, excéntrica 10,5%). No encontramos diferencias entre grupos en cuanto a la presencia de LVH, ni del índice de masa ventricular izquierda. Conclusiones: Nosotros observamos que el índice de volumen auricular izquierdo determinado por longitud de área medida por ecocardiograma y no la hipertrofia ventricular izquierda o dimensión de cavidades se relaciona con el estado de hidratación medido por sobrehidatación semanal y no con FO/ECW.