*3.2.2 Diffusion vs. convection*

Given that both clearance methods are efficient at clearing small solutes, the question is mainly about the added benefit (or harm) of removing medium-sized proinflammatory molecules such as cytokines, endotoxins, or exotoxins. In ESRD patients, for those treated with HDF compared to IHD, some benefits were demonstrated in large RCTs on reducing intradialytic hypotension and use of erythropoietinstimulating agents, but more importantly, an all-cause mortality benefit (HR 0.78, 95%CI 0.62–0.98) and cardiovascular mortality (HR0.69, 95%CI 0.47–1.0) were obtained when optimal convective volumes were delivered [27]. However, in AKI no such benefits have been demonstrated with certainty. A 2012 meta-analysis of 19 RCTs, comparing hemofiltration (CVVH) to hemodialysis (mostly CVVHD) found no effect on mortality (RR 0.96, 95%CI 0.71–1.15), or other clinical outcomes (RRT dependence in survivors, vasopressor use, organ dysfunction) despite increased clearance of medium to larger molecules, including inflammatory cytokines [28]. Despite fewer studies, similar results have been shown when comparing intermittent modalities offering diffusion only (IHD) to convection (HDF) in ICUs [8].
