The endothelial glycocalyx in critical illness: A pediatric perspective

Dysregulated autoantibodies targeting AGTR1 are associated with the accumulation of COVID-19 symptoms

Coronavirus disease 2019 (COVID-19) presents a wide spectrum of symptoms, the causes of which remain poorly understood. This study explored the associations between autoantibodies (AABs), particularly those targeting G protein-coupled receptors (GPCRs) and renin‒angiotensin system (RAS) molecules, and the clinical manifestations of COVID-19. Using a cross-sectional analysis of 244 individuals, we applied multivariate analysis of variance, principal component analysis, and multinomial regression to examine the relationships between AAB levels and key symptoms. Significant correlations were identified between specific AABs and symptoms such as fever, muscle aches, anosmia, and dysgeusia. Notably, anti-AGTR1 antibodies, which contribute to endothelial glycocalyx (eGC) degradation, a process reversed by losartan, have emerged as strong predictors of core symptoms. AAB levels increased with symptom accumulation, peaking in patients exhibiting all four key symptoms. These findings highlight the role of AABs, particularly anti-AGTR1 antibodies, in determining symptom severity and suggest their involvement in the pathophysiology of COVID-19, including vascular complications.

Fluid Management in Critically Ill Children: Single-Center Retrospective Comparison of Trauma and Postoperative Patients, 2020-2022

OBJECTIVE

Injury and surgery both represent well-defined starting points of a predictable inflammatory response, but the consequent response to IV fluids has not been studied. We aimed to review and compare our single-center fluid management strategies in these two populations.

DESIGN

Retrospective cohort study from January 2020 to July 2022. The primary outcome was total IV fluid volume administered. Net fluid balances and select clinical outcomes were also evaluated.

SETTING

Single tertiary academic center and level 1 pediatric trauma center in New York.

PATIENTS

A dataset of critically ill trauma and surgical patients aged 0-18 years who were admitted to the PICU, 2020-2022. Trauma patients had at least moderate traumatic injuries (Injury Severity Score ≥ 9) and surgical patients had at least a 1-hour operation time.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We identified 25 trauma and 115 surgical patients. During the first 5 days of hospitalization, we did not identify an association between grouping and total IV fluids administered and fluid balance in the prehospital, emergency department, and operating room ( p = 0.90 and p = 0.79), even when adjusted for weight ( p = 0.96). Time trend graphs of net fluid balance and IV fluid administered illustrated analogous fluid requirement and response with the transition from net positive to net negative fluid balance between 48 and 72 hours. There was an association between total IV fluid and ventilator requirement ( p = 0.003).

CONCLUSIONS

Critically ill pediatric trauma and postoperative patients seem to have similar fluid management and balance after injury or surgery. In our opinion, these two critically ill populations could be combined in large prospective studies on optimal fluid therapy in critically ill children.

PIGO-CDG: A case study with a new genotype, expansion of the phenotype, literature review, and nosological considerations

The phosphatidylinositol glycan anchor biosynthesis class O protein (PIGO) enzyme is an important step in the biosynthesis of glycosylphosphatidylinositol (GPI), which is essential for the membrane anchoring of several proteins. Bi-allelic pathogenic variants in PIGO lead to a congenital disorder of glycosylation (CDG) characterized by global developmental delay, an increase in serum alkaline phosphatase levels, congenital anomalies including anorectal, genitourinary, and limb malformations in most patients; this phenotype has been alternately called "Mabry syndrome" or "hyperphosphatasia with impaired intellectual development syndrome 2." We report a 22-month-old female with PIGO deficiency caused by novel PIGO variants. In addition to the Mabry syndrome phenotype, our patient's clinical picture was complicated by intermittent hypoglycemia with signs of functional hyperinsulinism, severe secretory diarrhea, and osteopenia with a pathological fracture, thus, potentially expanding the known phenotype of this disorder, although more studies are necessary to confirm these associations. We also provide an updated review of the literature, and propose unifying the nomenclature of PIGO deficiency as "PIGO-CDG," which reflects its pathophysiology and position in the broad scope of metabolic disorders and congenital disorders of glycosylation.

End organ perfusion and pediatric microcirculation assessment

Cardiovascular instability and reduced oxygenation are regular perioperative critical events associated with anesthesia requiring intervention in neonates and young infants. This review article addresses the current modalities of assessing this population's adequate end-organ perfusion in the perioperative period. Assuring adequate tissue oxygenation in critically ill infants is based on parameters that measure acceptable macrocirculatory hemodynamic parameters such as vital signs (mean arterial blood pressure, heart rate, urinary output) and chemical parameters (lactic acidosis, mixed venous oxygen saturation, base deficit). Microcirculation assessment represents a promising candidate for assessing and improving hemodynamic management strategies in perioperative and critically ill populations. Evaluation of the functional state of the microcirculation can parallel improvement in tissue perfusion, a term coined as "hemodynamic coherence". Less information is available to assess microcirculatory disturbances related to higher mortality risk in critically ill adults and pediatric patients with septic shock. Techniques for measuring microcirculation have substantially improved in the past decade and have evolved from methods that are limited in scope, such as velocity-based laser Doppler and near-infrared spectroscopy, to handheld vital microscopy (HVM), also referred to as videomicroscopy. Available technologies to assess microcirculation include sublingual incident dark field (IDF) and sublingual sidestream dark field (SDF) devices. This chapter addresses (1) the physiological basis of microcirculation and its relevance to the neonatal and pediatric populations, (2) the pathophysiology associated with altered microcirculation and endothelium, and (3) the current literature reviewing modalities to detect and quantify the presence of microcirculatory alterations.

ENDOTHELIAL GLYCOCALYX SHEDDING IN INTRA-ABDOMINAL SEPSIS: A FEASIBILITY STUDY

ABSTRACT

Background: The endothelial glycocalyx layer (EGL) is a complex meshwork of glycosaminoglycans and proteoglycans that protect the vascular endothelium. Cleavage or shedding of EGL-specific biomarkers, such as hyaluronic acid (HA) and syndecan-1 (SDC-1, CD138) in plasma, have been shown to be associated with poor clinical outcomes. However, it is unclear whether levels of circulating EGL biomarkers are representative of the EGL injury within the tissues. The objective of the present feasibility study was to describe a pathway for plasma and tissue procurement to quantify EGL components in a cohort of surgical patients with intra-abdominal sepsis. We sought to compare differences between tissue and plasma EGL biomarkers and to determine whether EGL shedding within the circulation and/or tissues correlated with clinical outcomes. Methods: This was a prospective, observational, single-center feasibility study of adult patients (N = 15) with intra-abdominal sepsis, conducted under an approved institutional review boards. Blood and resected tissue (pathologic specimen and unaffected peritoneum) samples were collected from consented subjects at the time of operation and 24-48 hours after surgery. Endothelial glycocalyx layer biomarkers (i.e., HA and SDC-1) were quantified in both tissue and plasma samples using a CD138 stain and ELISA kit, respectively. Pairwise comparisons were made between plasma and tissue levels. In addition, we tested the relationships between measured EGL biomarkers and clinical status and patient outcomes. Results: Fifteen patients with intra-abdominal sepsis were enrolled in the study. Elevations in EGL-specific circulating biomarkers (HA, SDC-1) were positively correlated with postoperative SOFA scores and weakly associated with resuscitative volumes at 24 hours. Syndecan-1 levels from resected pathologic tissue significantly correlated with SOFA scores at all time points ( R = 0.69 and P < 0.0001) and positively correlated with resuscitation volumes at 24 hours ( R = 0.41 and P = 0.15 for t = 24 hours). Tissue and circulating HA and SDC-1 positively correlated with SOFA >6. Conclusions: Elevations in both circulating and tissue EGL biomarkers were positively correlated with postoperative SOFA scores at 24 hours, with resected pathologic tissue EGL levels displaying significant correlations with SOFA scores at all time points. Tissue and circulating EGL biomarkers were positively correlated at higher SOFA scores (SOFA > 6) and could be used as indicators of resuscitative needs within 24 hours of surgery. The present study demonstrates the feasibility of tissue and plasma procurement in the operating room, although larger studies are needed to evaluate the predictive value of these EGL biomarkers for patients with intra-abdominal sepsis.

SHock-INduced Endotheliopathy (SHINE): A mechanistic justification for viscoelastography-guided resuscitation of traumatic and non-traumatic shock

Irrespective of the reason for hypoperfusion, hypocoagulable and/or hyperfibrinolytic hemostatic aberrancies afflict up to one-quarter of critically ill patients in shock. Intensivists and traumatologists have embraced the concept of SHock-INduced Endotheliopathy (SHINE) as a foundational derangement in progressive shock wherein sympatho-adrenal activation may cause systemic endothelial injury. The pro-thrombotic endothelium lends to micro-thrombosis, enacting a cycle of worsening perfusion and increasing catecholamines, endothelial injury, de-endothelialization, and multiple organ failure. The hypocoagulable/hyperfibrinolytic hemostatic phenotype is thought to be driven by endothelial release of anti-thrombogenic mediators to the bloodstream and perivascular sympathetic nerve release of tissue plasminogen activator directly into the microvasculature. In the shock state, this hemostatic phenotype may be a counterbalancing, yet maladaptive, attempt to restore blood flow against a systemically pro-thrombotic endothelium and increased blood viscosity. We therefore review endothelial physiology with emphasis on glycocalyx function, unique biomarkers, and coagulofibrinolytic mediators, setting the stage for understanding the pathophysiology and hemostatic phenotypes of SHINE in various etiologies of shock. We propose that the hyperfibrinolytic phenotype is exemplified in progressive shock whether related to trauma-induced coagulopathy, sepsis-induced coagulopathy, or post-cardiac arrest syndrome-associated coagulopathy. Regardless of the initial insult, SHINE appears to be a catecholamine-driven entity which early in the disease course may manifest as hyper- or hypocoagulopathic and hyper- or hypofibrinolytic hemostatic imbalance. Moreover, these hemostatic derangements may rapidly evolve along the thrombohemorrhagic spectrum depending on the etiology, timing, and methods of resuscitation. Given the intricate hemochemical makeup and changes during these shock states, macroscopic whole blood tests of coagulative kinetics and clot strength serve as clinically useful and simple means for hemostasis phenotyping. We suggest that viscoelastic hemostatic assays such as thromboelastography (TEG) and rotational thromboelastometry (ROTEM) are currently the most applicable clinical tools for assaying global hemostatic function-including fibrinolysis-to enable dynamic resuscitation with blood products and hemostatic adjuncts for those patients with thrombotic and/or hemorrhagic complications in shock states.

Glycocalyx Sensing with a Mathematical Model of Acoustic Shear Wave Biosensor

The article deals with an idea of exploiting an acoustic shear wave biosensor for investigating the glycocalyx, a polysaccharide polymer molecule layer on the endothelium of blood vessels that, according to recent studies, plays an important role in protecting against diseases. To test this idea, a mathematical model of an acoustic shear wave sensor and corresponding software developed earlier for proteomic applications are used. In this case, the glycocalyx is treated as a layer homogenized over the thin polymer "villi". Its material characteristics depend on the density, thickness, and length of the villi and on the viscous properties of the surrounding liquid (blood plasma). It is proved that the model used has a good sensitivity to the above parameters of the villi and blood plasma. Numerical experiments performed using real data collected retrospectively from premature infants show that the use of acoustic shear wave sensors may be a promising approach to investigate properties of glycocalyx-like structures and their role in prematurity.

Vascular Endothelial Glycocalyx Damage and Potential Targeted Therapy in COVID-19

COVID-19 is a highly infectious respiratory disease caused by a new coronavirus known as SARS-CoV-2. COVID-19 is characterized by progressive respiratory failure resulting from diffuse alveolar damage, inflammatory infiltrates, endotheliitis, and pulmonary and systemic coagulopathy forming obstructive microthrombi with multi-organ dysfunction, indicating that endothelial cells (ECs) play a central role in the pathogenesis of COVID-19. The glycocalyx is defined as a complex gel-like layer of glycosylated lipid–protein mixtures, which surrounds all living cells and acts as a buffer between the cell and the extracellular matrix. The endothelial glycocalyx layer (EGL) plays an important role in vascular homeostasis via regulating vascular permeability, cell adhesion, mechanosensing for hemodynamic shear stresses, and antithrombotic and anti-inflammatory functions. Here, we review the new findings that described EGL damage in ARDS, coagulopathy, and the multisystem inflammatory disease associated with COVID-19. Mechanistically, the inflammatory mediators, reactive oxygen species (ROS), matrix metalloproteases (MMPs), the glycocalyx fragments, and the viral proteins may contribute to endothelial glycocalyx damage in COVID-19. In addition, the potential therapeutic strategies targeting the EGL for the treatment of severe COVID-19 are summarized and discussed.

Endothelial dysfunction in preterm infants: The hidden legacy of uteroplacental pathologies

Millions of infants are born prematurely every year worldwide. Prematurity, particularly at lower gestational ages, is associated with high mortality and morbidity and is a significant global health burden. Pregnancy complications and preterm birth syndrome strongly impact neonatal clinical phenotypes and outcomes. The vascular endothelium is a pivotal regulator of fetal growth and development. In recent years, the key role of uteroplacental pathologies impairing endothelial homeostasis is emerging. Conditions leading to very and extremely preterm birth can be classified into two main pathophysiological patterns or endotypes: infection/inflammation and dysfunctional placentation. The first is frequently related to chorioamnionitis, whereas the second is commonly associated with hypertensive disorders of pregnancy and fetal growth restriction. The nature, timing, and extent of prenatal noxa may alter fetal and neonatal endothelial phenotype and functions. Changes in the luminal surface, oxidative stress, growth factors imbalance, and dysregulation of permeability and vascular tone are the leading causes of endothelial dysfunction in preterm infants. However, the available evidence regarding endothelial physiology and damage is limited in neonates compared to adults. Herein, we discuss the current knowledge on endothelial dysfunction in the infectious/inflammatory and dysfunctional placentation endotypes of prematurity, summarizing their molecular features, available biomarkers, and clinical impact. Furthermore, knowledge gaps, shadows, and future research perspectives are highlighted.