Endotoxic Septic Shock: Diagnosis and Treatment

Abstract

Endotoxin, also referred to as lipopolysaccharide (LPS), is a potent stimulator of the inflammatory cascade which may progress to sepsis and septic shock. The term endotoxic septic shock has been used for patients who have a clinical phenotype that is characterized by high endotoxin activity in addition to a high burden of organ failure; especially a pattern of organ failure including hepatic dysfunction, acute kidney injury, and various forms of endothelial dysfunction. Endotoxic septic shock has been a target for drug therapy for decades with no success. A likely barrier to their success was the inability to quantify endotoxin in the bloodstream. The Endotoxin Activity Assay (EAA) is positioned to change this landscape. In addition, medical devices using adsorptive technology in an extra-corporeal circulation has been shown to remove large quantities of endotoxin from the bloodstream. Focusing on the use of EAA to determine high concentrations of endotoxin will allow patients with endotoxic septic shock to be identified quickly and these patients may benefit most from removal of endotoxin using extracorporeal methods.

Keywords: diagnosis of endotoxemia; endotoxic septic shock; endotoxin; sepsis.

Figure 1

The EAA is a homogenous assay where the antigen-antibody immune complex reacts with the zymosan primed polymorphonuclear leukocyte to produce oxyradicals, that in the presence of a luminol, produce a photon of light. Reproduced from Romaschin et al. [9] Crit. Care 2012, 16, 248.

Figure 2

Whole blood from the patient is pipetted into 3 tubes and run in duplicate. Tube 1 is a “blank” and provides information on the baseline activation state of the patients polymorphonuclear leukocytes (PMN). In the example above, the Tube 1 (red line) has a very low reactivity. Tube 3 is a 1-point calibrator and contains an excess of Anti-LPS antibody. The graph above indicates the maximum reactivity for that patients PMNs. Tube 2 is the sample tube with a fixed concentration of anti-LPS antibody. In the graph above, the sample contains a large amount of LPS such that the Tube 2 reactivity is close to the maximum. This sample indicated a high level of endotoxin activity. The unitless results are expressed as from 0 to 1.0 based on the formula T2 − T1/T3 − T1.

Figure 3

This representative dose response curve is logarithmic with a y-asymptote. Low EAA results (<0.04) are approximately equivalent to an LPS concentration of <50 pg/mL. Intermediate levels (0.4–0.6) are approximately equivalent to an LPS concentration of <2000 pg/mL. A high EAA level (0.6–0.9), is approximately equivalent to 2000–4000 pg/mL. For EAA results that are >0.9, it is beyond the limits of the assay to accurately determine a LPS concentration equivalent; however, it may be substantially higher than 4000 pg/mL. Adapted from Romaschin, A.D. et al. [31] Blood Purif. 2017, 44, 193–197.

Figure 4

Provides a vertical timeline for clinical milestones associated with use of the PMX cartridge. It was approved for clinical use in Japan in 1994 under the trade name Toraymyxin. The device achieved CE marking in 1998 then underwent a series of clinical studies in Europe that were published in 2005 [41], 2009 [42] and 2015 [43] with a meta-analysis published in 2007 [40]. The PMX cartridge underwent a North American study, EUPHRATES, published in 2016 [16] and is currently undergoing a randomized clinical study, Tigris, in the US that began in 2019.