Sorbents have been utilized in the past for intoxication and poisoning, but their spectrum of clinical application is now expanding. Hemoadsorption (HA) is still indicated for toxin and poison removal, but other molecules are considered appropriate targets for this blood purification modality. HA combined with hemodialysis (HA + HD) has been proposed for end-stage kidney disease patients to remove molecules that are not easily removed by classic HD or hemodiafiltration. More recently, a rationale for the use of sorbents in critical illness, sepsis, and acute kidney injury has emerged due to the proposed humoral theory behind these disorders. Pathogenetic circulating molecules in critical illness (damage- and pathogen-associated molecular patterns) cannot be sufficiently removed by classic continuous renal replacement therapies. New sorbent-based extracorporeal therapies have therefore been designed to remove these molecules, offering potential biological and clinical benefits. There is also the possibility of employing selective sorbents to target specific molecules or to perform nonspecific HA for a wide spectrum of molecules. Moreover, there is the possibility of separating plasma from blood and then applying adsorption to plasma or of combining HA with other extracorporeal therapies. Here, we describe a complete appraisal of current available techniques utilizing adsorption.

Sepsis is caused by the host response to an infectious organism. It is common among hospitalized patients and is associated with significant morbidity and mortality. The current standard of care for sepsis is predominantly supportive, with early detection followed by prompt antibiotic administration. While this approach has undoubtedly improved patient outcomes, it has significant limitations. First, mortality from sepsis remains unacceptably high. Second, emerging pathogen resistance to antimicrobial therapies threatens a return to the pre-antimicrobial era of patient care. Lastly, the early stages of a pandemic (e.g., the recent coronavirus 19 pandemic) lack effective therapeutics. Given these limitations, novel treatment strategies are needed to advance the field and care for patients. One potential class of therapy is extracorporeal blood purification (EBP). While EBP is a broad classification, encompassing a wide range of techniques, this article will focus on three emerging EBP therapies that have been shown to bind and remove a wide variety of viral, bacterial, and fungal pathogens directly from circulation. These devices utilize different mechanisms of action for pathogen removal. The Seraph® 100 is composed of heparin coated beads. The Hemopurifier® combines the concept of plasma exchange with mannose-binding lectin (MBL). Lastly, the GARNET® utilizes a MBL fused to an IgG antibody. Via these mechanisms, these devices have been demonstrated to remove pathogens and pathogen-associated molecular patterns. The hope is that by directly removing pathogens, these EBP techniques may result in the biggest breakthrough in the management of sepsis since the advent of antibiotics almost 100 years ago.

The removal of soluble toxins from blood is necessary in patients with severe kidney failure. The majority of blood purification techniques are based on the use of semipermeable membranes, such as for dialysis treatment. But, whenever there is the need to remove small soluble molecules from blood, the use of such purification techniques may exhibit limited efficiency. This leads to a search for better-performing treatments. Hemoperfusion, given the recent strong advances in the sorption media biocompatibility with plasma (or blood), is considered a promising blood purification technique. This introductive chapter aims at briefly presenting the phenomenology of the adsorption process, also providing some basic elements related to how to use equilibrium load data to define an adsorption isotherm, which can be used to size a hemoperfusion cartridge.

Sepsis and multiple organ failure (MOF) are characterized by multiple hemodynamic changes and imbalanced immune response of the patient. Oxiris is a highly adsorptive membrane with the ability to remove cytokines and endotoxins, as well as to perform renal replacement therapy. Here we describe the evolution from previous AN69 to the 3-in-1 Oxiris membrane, and review its characteristics and performance. In clinical practice, Oxiris showed consistent effects in mean arterial pressure recovery, a decrease in vasopressor needs, and reduction of the Sequential Organ Failure Assessment score. These results have been reproduced by several independent studies addressing both sepsis and, to a lesser extent, COVID-19 patients. In addition, more recent studies in sepsis showed improvements in MOF duration and the length of stay in the ICU, as well as some promising results regarding mortality. Finally, we review ongoing clinical trials and discuss its potential significance to clinical practice improvement and to further reinforce knowledge on the use of blood purification in sepsis and acute kidney injury.

After initial tentative steps with bioincompatible sorbents, hemoadsorption is making a comeback. This has been fueled by improved coating technology and improved sorbent technology. Both have markedly increased the safety, biocompatibility, and efficiency of hemoadsorption. Despite such development and an emerging body of evidence, the research agenda for hemoadsorption is substantial and, in most ways, unfulfilled. In this chapter, we highlight the need for more extensive and sophisticated work to understand the biological effect of hemoadsorption in key areas (especially sepsis). We also explain why more technical research needs to be conducted ex vivo and in large animals to understand the performance characteristics of hemoadsorption sorbent cartridge, including optimal blood flow, optimal anticoagulation, and optimal duration of application. Finally, we focus on the need to develop registries of the use of this technique so that more extensive information can be obtained about current use and real-world performance.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused the global emergency outbreak disease that devastatingly affected world public health and the economy. The pathogenesis of severe SARS-CoV-2 infection in humans has been linked to a strong immunological response that leads to a hyperinflammatory state, or “cytokine storm,” which is a sepsis-like state resulting in capillary leakage, microvascular and macrovascular thrombosis, and multiple organ destruction. In recent years, there have been several case series and few randomized controlled trials studying the effectiveness and risk of various hemoperfusion techniques in the context of severe SARS-CoV-2 infection including HA330, CytoSorb, Polymyxin, oXiris, and Seraph 100 cartridges. Because inconsistencies exist between studies, there is currently no consensus regarding the use of hemoperfusion in patients with SARS-CoV-2 infection. Further well-designed research is needed to validate its potential clinical benefits and identify the timing and characteristics of patients who might benefit the most.

In the fields of sepsis and systemic inflammation, endotoxin might be the most studied molecule since the term was coined by Richard Pfeiffer in 1892. Paradoxically measuring endotoxin in humans and finding an effective treatment for endotoxemia have remained challenging. While advances have been made in understanding the mechanisms of how this simple molecule can trigger an intense immune cascade, there is an ever growing need to develop better treatments. Studies measuring endotoxin levels in patients with septic shock have consistently demonstrated that there is a dose-response relationship between endotoxin levels and adverse outcomes. A rapid assay to measure endotoxin activity has been available for more than a decade, but few studies have synergized the assay with a therapeutic. Polymyxin B hemoperfusion (PMX-HP) leverages a molecule with high affinity for endotoxin with a technique to eliminate exposure. Polymyxin is bound and immobilized to fibers within a cartridge and administered as an extracorporeal therapy via veno-venous hemoperfusion. Clinical evidence of its use is plentiful yet inconsistent in studies based on an outcome for mortality at 28 days. Herein, we describe targeted patient selection using the endotoxin activity assay and clinical phenotyping followed by adsorption of endotoxin using the PMX-HP for endotoxemic sepsis.

Sepsis is a life-threatening syndrome initiated by a dysregulated host response to infection. Maladaptive inflammatory burst damages host tissues and causes organ dysfunction, the burden of which has been demonstrated as the paramount predictor of worse clinical outcomes. In this setting, septic shock represents the most lethal complication of sepsis and implies profound alterations of both the cardiovascular system and cellular metabolism with consequent high mortality rate. Although an increasing amount of evidence attempts to characterize this clinical condition, the complexity of multiple interconnections between underlying pathophysiological pathways requires further investigations. Accordingly, most therapeutic interventions remain purely supportive and should be integrated in light of the continuous organ cross-talk, in order to match a patient’s specific needs. In this context, different organ supports may be combined to replace multiple organ dysfunctions through the application of sequential extracorporeal therapy in sepsis (SETS). In this chapter, we provide an overview of sepsis-induced organ dysfunction, focusing on the pathophysiological pathways that are triggered by endotoxin. Based on the need to apply specific blood purification techniques in specific time windows with different targets, we suggest a sequence of extracorporeal therapies. Accordingly, we reported the hypothesis that sepsis-induced organ dysfunction may benefit the most from SETS. Finally, we point out basic principles of this innovative approach and describe a multifunctional platform that allows SETS, in order to make clinicians aware of this new therapeutic frontier for critically ill patients.