Blood Purification in Sepsis and Acute Kidney Injury in Critically III Patients

Despite major advances in blood purification therapies, numerous questions remain. As a result, clinicians may still have some hesitation regarding the real efficacy of these techniques in sepsis as well as the best mode of hemofiltration therapy when treating patients with septic shock plus acute kidney injury (AKI) [1]. However, despite major recent therapeutic improvements, septic shock remains a leading cause of mortality in intensive care patients [2]. In addition, according to the latest available literature, it is of paramount importance to realize that the mortality rate of patients with septic AKI is much higher compared to that of patients with non-septic AKI [3], [4]. In the last decade, several milestone studies [5], [6] have shown that dose of therapy is important in terms of mortality, although recent so-called negative trials have challenged this concept. Nevertheless, a critical dose is still desirable and beyond that dose, mortality will be affected [7], [8]. We should not forget, however, that these studies carry some very important limitations [9], [10]. Regarding specifically rationale, it seems at least theoretically reasonable that effectively removing mediators from the tissue, where they are harmful, and transporting them to the central circulation must be effective. Effectiveness through only a passive transportation mechanism remains elusive. Indeed, the surface of the central blood compartment is about 30 m2, which is much smaller than the surface of the capillary blood compartment, which is about 300 m2 [11], so that passive transport between these two asymmetric compartments will not yield the same elimination rate on both sides.