Assessment of the Microcirculation During Extracorporeal Blood Purification in Septic Patients: A Narrative Review

Background and Objectives: Microcirculatory dysfunction is a key feature of septic shock and contributes to organ failure despite the apparent normalization of systemic hemodynamic parameters. Extracorporeal blood purification (EBP) therapies aim to modulate the dysregulated inflammatory response through removal of endotoxins and cytokines. However, their impact on tissue-level perfusion remains unclear. Direct bedside assessment of microcirculation may provide mechanistic insight into the effects of EBP beyond macrohemodynamic stabilization. To date, no structured review has specifically synthesized evidence on direct microcirculatory assessment during EBP therapy in sepsis. Materials and Methods: This structured narrative review summarizes current evidence on direct microcirculatory assessment during EBP therapy in sepsis. A literature search of PubMed, Web of Science, and Scopus was performed using combinations of the terms "microcirculation" and "blood purification" or "hemoadsorption." Studies published between 2015 and 2026 evaluating direct sublingual microcirculation using sidestream dark field (SDF) or incident dark field (IDF) videomicroscopy during EBP were included. Both experimental and clinical studies were considered. Results: Eight studies met the inclusion criteria. Selective endotoxin adsorption with polymyxin B hemoperfusion (PMX-HP) demonstrated improvements in perfused vessel density and small vessel density in both animal and clinical settings. Non-selective cytokine adsorption devices (CytoSorb and HA380) were associated with increases in microvascular flow index (MFI), perfused vessel density (PVD), and proportion of perfused vessels (PPV), although most data derive from small observational studies. Across studies, improvements in microcirculatory parameters were observed during or following hemoadsorption therapy. However, heterogeneity in design, timing, and concomitant treatments limits definitive interpretation. Conclusions: The included studies report improvements in microcirculatory parameters in septic patients during hemoadsorption therapy. However, despite signals suggesting improved perfusion, interpretation is limited by methodological constraints and the use of hemoadsorption within multimodal sepsis treatment. In the absence of adequately powered randomized controlled trials, these changes cannot be directly attributed to mediator removal and should be considered within the broader context of overall therapy.