Supplementary Material for: Significance of Interdialytic Weight Gain versus Chronic Volume Overload: Consensus Opinion

Predialysis volume overload is the sum of interdialytic weight gain (IDWG) and residual postdialysis volume overload. It results mostly from failure to achieve an adequate volume status at the end of the dialysis session. Recent developments in bioimpedance spectroscopy and possibly relative plasma volume monitoring permit noninvasive volume status assessment in hemodialysis patients. A large proportion of patients have previously been shown to be chronically volume overloaded predialysis (defined as >15% above ‘normal' extracellular fluid volume, equivalent to >2.5 liters on average), and to exhibit a more than twofold increased mortality risk. By contrast, the magnitude of the mortality risk associated with IDWG is much smaller and only evident with very large weight gains. Here we review the available evidence on volume overload and IDWG, and question the use of IDWG as an indicator of ‘nonadherence' by describing its association with postdialysis volume depletion. We also demonstrate the relationship between IDWG, volume overload and predialysis serum sodium concentration, and comment on salt intake. Discriminating between volume overload and IDWG will likely lead to a more appropriate management of fluid withdrawal during dialysis. Consensually, the present authors agree that this discrimination should be among the primary goals for dialysis caretakers today. In consequence, we recommend objective measures of volume status beyond mere evaluations of IDWG.

透析前容量超负荷（Predialysis volume overload）是透析间期体重增长（interdialytic weight gain, IDWG）与透析后残余容量超负荷的总和。其主要诱因是透析疗程结束时未能达成适宜的容量状态。近年来，生物阻抗光谱法（bioimpedance spectroscopy）及潜在的相对血浆容量监测（relative plasma volume monitoring）技术，已可实现血液透析（hemodialysis）患者的无创容量状态评估。既往研究证实，多数患者存在慢性透析前容量超负荷（定义为较“正常”细胞外液容量超出15%以上，平均相当于2.5升以上），且死亡风险升高两倍以上。相较而言，与IDWG相关的死亡风险幅度显著更小，仅在体重增长幅度过大时才会显现。本文综述了目前关于容量超负荷与IDWG的现有证据，并通过阐述IDWG与透析后容量缺失的关联，对将IDWG作为“不依从性”评估指标的做法提出质疑。此外，本文还阐明了IDWG、容量超负荷与透析前血清钠浓度之间的关联，并就食盐摄入问题展开评述。区分容量超负荷与IDWG或可指导透析过程中液体脱除的更优化管理。本文全体作者一致认为，此类区分应成为当前透析护理人员的核心工作目标之一。据此，我们建议除单纯评估IDWG外，还应采用客观的容量状态检测手段。