Endotoxemia Correlates with Kidney Function and Length of Stay in Critically Ill Patients

INTRODUCTION

Endotoxin is a key driver of sepsis, which frequently causes acute kidney injury (AKI). However, endotoxins may also be found in non-bacteremic critically ill patients, likely from intestinal translocation. Preclinical models show that endotoxins can directly injure the kidneys, and in COVID-19 patients, endotoxemia correlated with AKI. We sought to determine correlations between endotoxemia and kidney and hospital outcomes in a broad group of critically ill patients.

METHODS

In this single-center, serial prospective study, 124 predominantly Caucasian adult patients were recruited within 48 h of admission to Stony Brook University Hospital Intensive Care Unit (ICU). Demographics, vital signs, laboratory data, and outcomes were collected. Circulating endotoxin was measured on days 1, 4, and 8 using the endotoxin activity assay (EAA). The association of EAA with outcomes was examined with EAA: (1) categorized as <0.6, ≥0.6, and nonresponders (NRs); and (2) used as a continuous variable.

RESULTS

Patients with EAA ≥0.6 had a higher prevalence of proteinuria, and lower arterial oxygen saturation (SaO2) to fraction of inspired oxygen (FiO2) (SaO2/FiO2) ratio versus patients with EAA <0.6. EAA levels positively correlated with serum creatinine (sCr) levels on day 1. Patients whose EAA level stayed ≥0.6 had a slower decline in sCr compared to those whose EAA started at ≥0.6 and subsequently declined. Patients with AKI stage 1 and EAA ≥0.6 on day 1 showed slower decline in sCr compared to patients with stage 1 AKI and EAA <0.6. EAA ≥0.6 and NR patients had longer hospital stay and delayed ICU discharge versus EAA <0.6.

CONCLUSIONS

High EAA levels correlated with worse kidney function and outcomes. Patients whose EAA levels fell, and those with AKI stage I and day 1 EAA <0.6 recovered more quickly compared to those with EAA ≥0.6, suggesting that removal of circulating endotoxins may be beneficial in critically ill patients.

Endotoxemia in Critically Ill Patients with COVID-19

Introduction

Mechanism(s) mediating critical illness in coronavirus disease 2019 (COVID-19) remain unclear. Previous reports demonstrate the existence of endotoxemia in viral infections without superimposed gram-negative bacteremia, but the rate and severity of endotoxemia in critically ill patients with COVID-19 requires further exploration.

Materials and Methods

This is a single-center cross-sectional study of 92 intensive care unit patients diagnosed with COVID-19 pneumonia. Endotoxin activity (EA) was measured in patients that met the following criteria: (1) age ≥18 years and (2) multi-organ dysfunction score >9 from March 24, 2020, to June 20, 2020.

Results

A total of 32 patients met the inclusion/exclusion criteria for measurement of EA. The median age of the study cohort was 60 years with a majority male (21/32, 65%) with hypertension (50%). A significant proportion of the patients exhibited either elevated EA in the intermediate range (0.40–0.59 EA units) (10/32, 31%) or high range (≥0.60 EA units) (14/32, 44%) or were nonresponders (NRs, low neutrophil response) to EA (6/32, 19%), with the presence of gram-negative bacteremia only in 2/32 (6%) patients. Low EA was reported in 2/32 patients. NRs (5/6, 83%) and patients with high EA (7/14, 50%) exhibited higher acute kidney injury (AKI) as compared to patients with low/intermediate EA level (1/12, 8.3%).

Discussion/Conclusion

Elevated EA was observed in a large majority of critically ill patients with COVID-19 and multi-organ dysfunction despite a low incidence of concurrent gram-negative bacteremia. While we observed that elevated EA and nonresponsiveness to EA were associated with AKI in critically ill patients with COVID-19, these findings require further validation in larger longitudinal cohorts.

Association between endotoxemia and enterocyte injury and clinical course in patients with gram-positive septic shock: A posthoc analysis of a prospective observational study

Endotoxemia often occurs in patients with gram-positive infections. The possible mechanism is thought to be bacterial translocation after enterocyte hypoperfusion injury. However, the association between endotoxemia and enterocyte injury among patients with gram-positive septic shock has never been assessed. The aim of this study was to evaluate the association between endotoxemia and enterocyte injury in gram-positive septic shock patients and to evaluate the association among endotoxemia, subsequent clinical course, and other related factors.This was a posthoc analysis of a prospective observational study that evaluated the capability of intestinal fatty acid-binding protein (I-FABP), an indicator of enterocyte injury, to predict mortality. Among 57 patients in septic shock, those whose causative microorganisms were gram positive were included. The correlation between endotoxin activity (EA), which indicates endotoxemia, and I-FABP levels upon admission to the intensive care unit (ICU), the clinical course, and other related factors were evaluated.A total of 21 patients were examined. One-third of the patients presented with high EA levels at the time of ICU admission. However, there was no significant correlation between EA and I-FABP levels (Spearman ρ = 0.002, P = .993). Additionally, high EA levels were not associated with abdominal complications after ICU admission or mortality. Similarly, high EA levels were not associated with severity scores, inotropic scores, or lactate levels upon ICU admission, which were previously reported to be factors related to high EA levels.In this posthoc analysis, no correlation was observed between endotoxemia and enterocyte injury among patients in gram-positive septic shock. Additionally, high EA levels were not associated with the clinical course and reported factors related to endotoxemia. Although our results need to be validated in a large prospective cohort study, hypoperfusion enterocyte injury might not be a cause of endotoxemia in these patients. Thus, if there is no correlation between EA and I-FABP levels, other mechanisms that induce high EA levels among patients with gram-positive septic shock should be elucidated.

Effects of endotoxin absorber hemoperfusion on microcirculation in septic pigs

BACKGROUND

Endotoxins contribute to systemic inflammatory response and microcirculatory dysfunctions under conditions of sepsis. Polymyxin B hemoperfusion (PMX-HP) is used to remove circulating endotoxins and improve clinical outcomes. This study aims to investigate the effect of PMX-HP on microcirculation in septic pigs.

MATERIALS AND METHODS

By using a septic pig model, we tested the hypothesis that PMX-HP can correct intestinal microcirculation, tissue oxygenation saturation, and histopathologic alterations. A total of 18 male pigs were divided into three groups: (1) sham; (2) sepsis (fecal peritonitis); and (3) sepsis + PMX-HP groups. A sidestream dark field video microscope was used to record microcirculation throughout the terminal ileal mucosa, colon mucosa, kidney surface, and sublingual area. A superficial tissue oxygenation monitor employing the light reflectance spectroscopy technique was used to measure the tissue oxygen saturation. Hematoxylin and eosin staining was used for histologic examination.

RESULTS

The perfused small vessel density and tissue oxygen saturation of the ileal mucosa at 6 h were higher in the sepsis + PMX-HP group than those in the sepsis group. The fluid amount and norepinephrine infusion rate between the sepsis group and sepsis + PMX-HP groups did not differ significantly. The histologic score for the ileal mucosa was lower in the sepsis + PMX-HP group than that in the sepsis group. Finally, the urine output was higher in the sepsis + PMX-HP group than it was in the sepsis group.

CONCLUSIONS

This study demonstrates that PMX-HP attenuates microcirculatory dysfunction, tissue desaturation, and histopathologic alterations in the ileal mucosa in septic pigs.

Evaluation of Endotoxemia After Pediatric Cardiac Surgery With the Endotoxin Activity Assay: An Exploratory Prospective Cohort Study

OBJECTIVE

Children with congenital heart diseases undergoing surgery with cardiopulmonary bypass are exposed to a high risk of perioperative endotoxemia. The aim of our study was to prospectively evaluate endotoxin assay activity reference levels during the postoperative phase of infants undergoing cardiac surgery for congenital heart disease and to assess their association with perioperative variables and postoperative infections.

DESIGN

Prospective exploratory single-center cohort study.

SETTING

Tertiary pediatric cardiac ICU.

PATIENTS

Infants undergoing cardiac surgery with cardiopulmonary bypass were enrolled. Exclusion criteria were preoperative suspected or confirmed infection, the need for extracorporeal membrane oxygenation or a ventricular assist device in any perioperative phase, surgery for heart transplantation, and/or urgent surgery.

INTERVENTIONS

Serial measurements of endotoxin assay activity were performed at baseline, pediatric cardiac ICU arrival, postoperative day 1 and 2.

MEASUREMENTS AND MAIN RESULTS

Twenty-five patients were enrolled. Overall, 14 of 25 patients (58%) presented at least one endotoxin assay activity level greater than 0.4 during the study period (normal level is < 0.4). Endotoxin assay activity levels tended to significantly increase from baseline to postoperative day 1 and 2 and from pediatric cardiac ICU arrival to postoperative day 2 (p < 0.0001). Endotoxin assay activity greater than 0.6 predicted Gram-negative infections with a sensitivity of 0.40, a specificity of 0.95, a positive predictive value of 0.66, and a negative predictive value of 0.86. At multivariable regression, endotoxin assay activity on postoperative day 1 resulted independently associated with cardiopulmonary bypass duration, lactate, temperature peak, and vasoactive inotropic score at pediatric cardiac ICU arrival. Children with endotoxin assay activity levels greater than 0.6 (vs all the others) showed a significantly higher median (interquartile) number of ventilation days: 8 (2-39) versus 1.5 (1-3 (p = 0.02).

CONCLUSIONS

This exploratory study showed that endotoxin assay activity levels in infants undergoing cardiopulmonary bypass are frequently above 0.4 and peak 24-48 hours after surgery and appear to be associated with perioperative impaired organ perfusion. Endotoxin assay activity is not useful to predict Gram-negative infections.