Effects of endotoxin absorber hemoperfusion on microcirculation in septic pigs

Large animal models for translational research in acute kidney injury

While extensive research using animal models has improved the understanding of acute kidney injury (AKI), this knowledge has not been translated into effective treatments. Many promising interventions for AKI identified in mice and rats have not been validated in subsequent clinical trials. As a result, the mortality rate of AKI patients remains high. Inflammation plays a fundamental role in the pathogenesis of AKI, and one reason for the failure to translate promising therapeutics may lie in the profound difference between the immune systems of rodents and humans. The immune systems of large animals such as swine, nonhuman primates, sheep, dogs and cats, more closely resemble the human immune system. Therefore, in the absence of a basic understanding of the pathophysiology of human AKI, large animals are attractive models to test novel interventions. However, there is a lack of reviews on large animal models for AKI in the literature. In this review, we will first highlight differences in innate and adaptive immunities among rodents, large animals, and humans in relation to AKI. After illustrating the potential merits of large animals in testing therapies for AKI, we will summarize the current state of the evidence in terms of what therapeutics have been tested in large animal models. The aim of this review is not to suggest that murine models are not valid to study AKI. Instead, our objective is to demonstrate that large animal models can serve as valuable and complementary tools in translating potential therapeutics into clinical practice.

Therapeutic Rationale for Endotoxin Removal with Polymyxin B Immobilized Fiber Column (PMX) for Septic Shock

Endotoxin removal therapy with polymyxin B immobilized fiber column (PMX) has been clinically applied for sepsis and septic shock patients since 1994. The effectiveness and usefulness of this therapy have been demonstrated for more than a quarter of a century. However, a documented survival benefit has not yet been demonstrable in a large, multicenter, randomized and controlled trial. Following the findings derived from a large sepsis clinical trial with PMX in North America, a new trial is ongoing to determine if PMX has a long-term survival benefit when administered to septic patients. Another approach to support a survival benefit from intervention with PMX is to utilize a detailed analysis available from a large clinical data base. The endotoxin adsorption capacity of PMX columns in vitro and the effectiveness of PMX columns can be further demonstrable in animal models. The capability of PMX and details of its mechanism of action to intervene in the sepsis cascade and impede organ dysfunction in septic patients is not fully understood. The surface antigen expression in monocytes and neutrophils are improved after PMX therapy. Immunomodulatory effects as a result of endotoxin removal and/or other mechanisms of action have been suggested. These effects and other potential immune effects may explain some of the improved effects upon organ dysfunction of sepsis and septic shock patients. Endotoxemia may be involved in the pathophysiology of other diseases than sepsis. A rapid diagnostic method to detect and target endotoxemia could allow us to practice precision medicine and expand the clinical indications of endotoxin removal therapy.

Effects of endotoxin adsorber hemoperfusion on sublingual microcirculation in patients with septic shock: a randomized controlled trial

Background

Endotoxins can induce an excessive inflammatory response and result in microcirculatory dysfunction. Polymyxin-B hemoperfusion (PMX-HP) has been recognized to effectively remove endotoxins in patients with sepsis and septic shock, and a rat sepsis model revealed that PMX-HP treatment can maintain a better microcirculation. The primary aim of this study was to investigate the effect of PMX-HP on microcirculation in patients with septic shock.

Methods

Patients with septic shock were enrolled and randomized to control and PMX-HP groups. In the PMX-HP group, patients received the first session of PMX-HP in addition to conventional septic shock management within 24 h after the onset of septic shock; the second session of PMX-HP was provided after another 24 h as needed.

Results

Overall, 28 patients finished the trial and were analyzed. The mean arterial pressure and norepinephrine infusion dose did not differ significantly between the control and PMX-HP groups after PMX-HP treatment. At 48 h after enrollment, total vessel density (TVD) and perfused vessel density (PVD) were higher in the PMX-HP group than in the control group [TVD 24.2 (22.1–24.9) vs. 21.1 (19.9–22.9) mm/mm²; p = 0.007; PVD 22.9 (20.9–24.9) vs. 20.0 (18.9–21.6) mm/mm², p = 0.008].

Conclusions

This preliminary study observed that PMX-HP treatment improved microcirculation but not clinical outcomes in patients with septic shock at a low risk of mortality. Nevertheless, larger multicenter trials are needed to confirm the effect of PMX-HP treatment on microcirculation in patients with septic shock at intermediate- and high-risk of mortality.

Trial registration ClinicalTrials.gov protocol registration ID: NCT01756755. Date of registration: December 27, 2012. First enrollment: October 6, 2013. https://clinicaltrials.gov/ct2/show/NCT01756755

Does the application of Opsite⋄ Flexigrid⋄ occlude the oxygen saturation readings in healthy individuals using the moorVMS-OXY machine?

Background

A proportion of people who have been diagnosed with peripheral arterial disease and diabetes mellitus will be susceptible to chronic wounds. Oxygen is vital for wound healing, so oxygen measurements should to be taken as predictive values for wound healing in patients. When measuring oxygen at the wound bed, there is potentially a risk of cross-infection if no protective barrier is used; and skin stripping if an adhesive barrier is used on the wound bed. This cross sectional within subject repeated measures pilot study, aims to determine if the application of opsite film, as an infection control measure, in one or two layers, impacts on tissue oxygenation readings obtained when using the MoorVMS-OXY.

Methods

Mean oxygen saturation percentages were measured from 29 limbs of 18 healthy participants. Oxygen saturation was measured for 20 s and analysed at the first metatarsophalangeal joint using no film, one and two layers using the MoorVMS-OXY. A one-way repeated ANOVA with a Bonferroni post hoc test was performed to test for statistically significant differences between the values of the three parameters and multiple pairwise comparisons was completed.

Results

Amongst the three layers, there was a statistically significant difference in oxygen saturation between the two layers of Opsite Flexigrid and none; and also between the two layers of Flexigrid and single layer (p < 0.05). It was also established that there was no statistically significant difference between the single layer of Opsite Flexigrid and no Flexigrid layer (p > 0.05).

Conclusions

The results imply that one layer of Opsite Flexigrid is a suitable protective barrier to use when establishing capillary bed oxygen perfusion with the MoorVMS-OXY. However, the application of two Opsite Flexigrid layers, to prevent skin stripping, decreases the recorded values of oxygen saturation percentages significantly, therefore providing inaccurate results. Indicating that a double layer cannot be used over ulceration sites if measuring oxygen levels at the wound bed.

Effect of lipopolysaccharide on the adherence of human umbilical vein endothelial cells (HUVEC) on a natural substrate

 Polymers are often contaminated with lipopolysaccharides also known as endotoxins. Even small amounts of endotoxins can have strong effects on endothelial cell function so that the endothelialisation of cardiovascular implants might be hampered. An open question is how endothelial cells seeded on a body foreign substrate respond to shear load after adding Lipid A (LPA), the domain, which is responsible for much of the toxicity of gram-negative bacteria, and whether morphological changes of endothelial cells occur.LPA supplementation to the culture medium in increasing concentrations (5, 25 and 50μg/ml) resulted in progressive reductions of the density of adherent HUVEC after shear load (p < 0.001). 48% of the HUVEC in control cultures (0μg/ml LPA) were still adherent after 2 hours of shearing at 6 dyne/cm2, while 80 minutes after addition of 50μg/ml LPA, 88% of the HUVEC had already detached from the substrate and after 100 minutes no more HUVEC were attached.The results demonstrate that endotoxins are of extreme importance for the behavior of HUVEC and that in vivo pathologies can be increasingly simulated in vitro.

Characterization and evolution of intestine injury at the anhepatic phase in portal hypertensive rats

The aim of the present study was to investigate the characteristics and progression of intestinal injury at the anhepatic phase in portal hypertensive rats. A total of 120 healthy male Wistar rats were purchased, with 15 rats in the normal control group and 105 rats were assigned to establish a prehepatic portal hypertension model. The 105 model rats were further divided into seven treatment groups following ischemia-reperfusion. Meanwhile, portal vein pressure, the area of lower esophageal mucosal vein, endotoxin levels in portal vein blood and the level of malondialdehyde (MDA) and superoxide dismutase (SOD) were measured. Morphology changes of the intestine were observed using optical microscopy and transmission electron microscopy. A portal hypertension rat model was successfully established. Furthermore, endotoxin, MDA and SOD level reached a peak at 12-24 h following reperfusion and then decreased gradually to normal levels at 1 week following reperfusion. However, cytological damage did not recover to preoperative level within 1 week. These findings suggest that intestinal injury was most severe within 12-24 h following ischemia-reperfusion and most indicators recovered to almost normal levels. Therefore, further study on the intestinal mucosal damage is required, with the aim to reduce the production of intestinal endotoxin.

Peritoneal lavage with povidone-iodine solution in colorectal cancer-induced rats

BACKGROUND

Although peritoneal lavage with povidone-iodine (PVPI) is frequently performed after surgery on the gastrointestinal tract, the effects of PVPI on the intestinal epithelial barrier are unknown. The purpose of this study was to investigate the effects of abdominal irrigation with PVPI on the intestinal epithelial barrier in a colorectal cancer (CRC)-induced rat model.

MATERIALS AND METHODS

The CRC model was induced in rats with azoxymethane and dextran sodium sulfate. Next, a total of 24 male CRC-induced rats were randomly divided into three groups (n = 8): (1) a sham-operated group, (2) an NS group (peritoneal lavage 0.9% NaCl), and (3) a PVPI group (peritoneal lavage with 0.45%-0.55% PVPI). The mean arterial pressure was continuously monitored throughout the experiment. The levels of plasma endotoxin and D-lactate, blood gases, and protein concentration were measured. The ultrastructural changes of the epithelial tight junctions were observed by transmission electron microscopy.

RESULTS

The mean arterial pressure after peritoneal lavage was lower in the PVPI group than that in the NS group. The protein concentration and levels of endotoxin and D-lactate were higher in the PVPI group than they were in the PVPI group. In addition, PVPI treatment resulted in a markedly severe metabolic acidosis and intestinal mucosal injury compared with NS rats.

CONCLUSIONS

Peritoneal lavage with PVPI dramatically compromises the integrity of the intestinal mucosa barrier and causes endotoxin shock in CRC rats. It is unsafe for clinical applications to include peritoneal lavage with PVPI in colorectal operations.