Hemorrhagic Shock and Resuscitation Causes Glycocalyx Shedding and Endothelial Oxidative Stress Preferentially in the Lung and Intestinal Vasculature

From shortages to solutions: Liquid plasma as a practical alternative to whole blood for prehospital trauma resuscitation

Trauma-induced hemorrhagic shock remains a leading cause of preventable mortality, necessitating timely and effective resuscitation strategies. While low-titer O whole blood (LTOWB) is the preferred choice for prehospital resuscitation due to its balanced composition and ease of use, overall widespread implementation is hindered by persistent supply chain issues and daily logistical challenges of access and deployment. Platelets, containing plasma as a component, are considered the next best alternative to LTOWB but are constrained by their short shelf life and ongoing scarcity, and ongoing storage compliance, rendering their use impractical. This review evaluates plasma-based alternatives, particularly liquid plasma (LP), as a viable and cost-effective substitute therapeutic modality. LP offers a 26-day refrigerated shelf life compared to the 5-day limit of thawed fresh frozen plasma (FFP) and eliminates the challenges associated with freezing and thawing while maintaining clinical efficacy. Preliminary economic analyses further underscore the advantages of LP, demonstrating reduced wastage and lower costs compared to LTOWB, especially when partnering with a hospital system. Acknowledging the barriers in implementing prehospital blood transfusion programs due to blood supply and costs, we advocate for emergency medical service (EMS) adoption of LP, highlighting its availability, comparable efficacy to LTOWB, and cost-effectiveness. Until LTOWB becomes more accessible, LP should be prioritized in prehospital care to optimize outcomes for trauma patients in hemorrhagic shock.

Plasma resuscitation restores glomerular hyaluronic acid and mitigates hemorrhage-induced glomerular dysfunction

BACKGROUND

Acute renal dysfunction following hemorrhagic shock and resuscitation carries significant morbidity and mortality. While shock-induced shedding of the glycocalyx is well described within the pulmonary and splanchnic vasculature, less is known regarding early alterations to the glycocalyx of the renal microcirculation, particularly the glomerulus. We sought to evaluate the impact of hemorrhagic shock and resuscitation modalities on glomerular glycocalyx metabolism and function. We hypothesized that fresh frozen plasma resuscitation would attenuate glomerular glycocalyx shedding and reduce glomerular barrier dysfunction.

METHODS

Male Sprague-Dawley rats were subjected to 60 minutes of hemorrhagic shock to 40% of baseline mean arterial pressure, followed by resuscitation with shed whole blood and either lactated Ringer's or fresh frozen plasma. Experimental groups included the following: (a) baseline, (b) post-hemorrhagic shock, (c) post-lactated Ringer's resuscitation, and (d) post-plasma resuscitation. Enzyme-linked immunosorbent assays and immunohistochemistry were used to evaluate alterations of syndecan-1 and hyaluronic acid within the glomerular glycocalyx. Urine protein concentration was measured as a surrogate for glomerular function, and expression of cubilin and megalin was quantified to evaluate renal tubule protein reabsorptive capacity.

RESULTS

Despite evidence of systemic glycocalyx shedding, hemorrhagic shock and resuscitation did not alter glomerular synedcan-1 expression. However, shock induced shedding of hyaluronic acid from the glomerular glycocalyx. While hyaluronic acid breakdown was exacerbated by crystalloid resuscitation, plasma utilization restored levels back to baseline. Urine protein concentration drastically increased following hemorrhagic shock and resuscitation with lactated Ringer's. By contrast, plasma administration reduced urine protein levels back to normal. Renal cortex cubilin and megalin expression did not differ among the experimental groups, suggesting that alterations in urine protein were driven by changes in glomerular function.

CONCLUSION

Plasma-based resuscitation appears to reverse shock-induced shedding of glomerular hyaluronic acid and attenuates glomerular barrier dysfunction. Differential shedding of the glomerular glycocalyx may represent a novel pathway in acute kidney injury pathophysiology.

Rethinking Balanced Resuscitation in Trauma

Hemorrhagic shock from traumatic injury results in a massive systemic response with activation of the hypothalamic-pituitary-adrenal (HPA) axis, pro-thrombotic and clot-lysis pathways as well as development of an endotheliopathy. With ongoing hemorrhage, these responses become dysregulated and are associated with worsening coagulopathy, microvascular dysfunction, and increased transfusion requirements. Our transfusion practices as well as our understanding of the molecular response to hemorrhage have undergone significant advancement during war. Currently, resuscitation practices address the benefit of the early recognition and management of acute coagulopathy and advocates for balanced resuscitation with either whole blood or a 1:1 ratio of packed red blood cells to fresh frozen plasma (respectively). However, a significant volume of evidence in the last two decades has recognized the importance of the early modulation of traumatic endotheliopathy and the HPA axis via the early administration of plasma, whole blood, and adjunctive treatments such as tranexamic acid (TXA) and calcium. This evidence compels us to rethink our understanding of 'balanced resuscitation' and begin creating a more structured practice to address additional competing priorities beyond coagulopathy. The following manuscript reviews the benefits of addressing the additional interrelated physiologic responses to hemorrhage and seeks to expand beyond our understanding of 'balanced resuscitation'.

THE MITOCHONDRIAL DIVISION INHIBITOR MDIVI-1 PROTECTED ORGAN FUNCTION AND EXTENDED THE TREATMENT WINDOW IN RATS WITH UNCONTROLLED HEMORRHAGIC SHOCK

ABSTRACT

Aim: This study aimed to elucidate whether the application of the mitochondrial division inhibitor Mdivi-1 can protect organ function and prolong the treatment window for traumatic hemorrhagic shock. Methods: Before definitive hemostasis treatment, Mdivi-1 (0.25 mg/kg, 0.5 mg/kg, and 1 mg/kg) was administered to uncontrolled hemorrhagic shock (UHS) model rats. Lactate Ringer's solution plus hydroxyethyl starch (130/0.4) was used as a control. The effects of Mdivi-1 on blood loss; fluid demand; survival time; vital organ function; myocardial mitochondrial structure; mitochondrial function of the heart, liver, kidney, and intestine; and oxidative stress at 1 h after hypotensive resuscitation (50-60 mm Hg) were investigated. In addition, we investigated the effect of varying doses of Mdivi-1 on the maintenance time of hypotensive resuscitation without definitive hemostasis and the beneficial effect of Mdivi-1 after prolonging the duration of hypotensive resuscitation to 2 h. Results: Compared to conventional resuscitative fluid, Mdivi-1 significantly reduced blood loss and fluid demand, improved important organ functions during hypotensive resuscitation, improved animal survival, and reduced the incidence of early death. Mdivi-1 significantly alleviated oxidative stress injury, reduced mitochondrial damage, and restored myocardial mitochondrial structure and mitochondrial function of the heart, liver, kidney, and intestine. In addition, Mdivi-1 increased the maintenance time of hypotensive resuscitation and improved rat survival after the duration of hypotensive resuscitation was prolonged to 2 h. Conclusion: Mdivi-1 significantly prolonged the treatment window for traumatic hemorrhagic shock to 2 h in UHS model rats. The underlying mechanism may be that Mdivi-1 inhibits excessive mitochondrial fission and oxidative stress and improves the structure and function of mitochondria.

Effect on Syndecan-1 and Hyaluronan Levels Depending on Multiple Organ Failure, Coagulopathy and Survival: An Observational Study in Major Trauma Patients

Background: Major trauma, as well as traumatic hemorrhagic shock go along with early damage to the endothelial glycocalyx (EG). Shed glycocalyx constituents can activate the innate immune system and aggravate secondary injury. Subsequently, we investigated the relationship between glycocalyx shedding and the occurrence of coagulopathy, multiple organ failure (MOF) and outcome in our cohort after severe trauma. Methods: We included multiple trauma patients, as defined by Injury Severity Score (ISS). Polytraumatized patients must have arrived in our level 1 trauma center within 60 min after trauma. Retrospectively, patients were assigned to predefined clinical conditions, based on injury severity (ISS ≥ 16 points), multiple organ failure (MOF score ≥ 6 points), need for massive transfusion (≥10 RBC units/first 24 h), coagulopathy (prothrombin time < 70% at 0 h) and survival (90-day survival). Syndecan-1 (Sdc-1) and hyaluronan (HA) plasma concentrations were evaluated immediately (0 h), 6 h and 12 h after trauma. Results: 49 patients (mean ISS 35.7 ± 12.1 SD, mean age 45.78 ± 15.6 SD) were included in this study. A total of 37 patients (75.5%) survived, while 12 patients died within the observation period of 90 days after trauma (24.5%). A total of 77% of all patients suffered multiple organ failure (MOF score ≥ 6, n = 30). Initial prothrombin time at 0 h was <70% in 31 patients. Plasma concentrations of circulating both glycocalyx constituents showed a significant increase over the first 12 h after trauma (p = 0.001; p = 0.008). Patients with multiple organ failure showed significantly increased hyaluronan concentrations at all three time points (p = 0.007/0.006/<0.001), and the syndecan-1 levels were significantly elevated 12 h after trauma in the MOF group (p = 0.01). Patients with coagulopathy on admission exhibited significantly higher hyaluronan levels at 12 h (p = 0.042). Non-survivors showed significantly increased syndecan-1 levels at 12 h after trauma (p = 0.024). Conclusions: Glycocalyx shedding occurs immediately after major trauma. Coagulopathy is associated with significantly increased plasma hyaluronan. Further, significant changes in plasma concentrations within the first 12 h help to identify subgroups at risk for developing MOF and death.

Endothelial dysfunction is dampened by early administration of fresh frozen plasma in a rodent burn shock model

BACKGROUND

Endothelial dysfunction has been implicated in the pathogenesis of burn shock affecting patients with large thermal injury. In response to injury, glycocalyx components like Syndecan-1 (SDC-1) are shed into circulation and have been used as markers of endothelial damage. Previous work in our laboratory has shown that plasma inclusive resuscitation (PIR) with fresh frozen plasma (FFP) ameliorates endothelial damage. However, there remains a paucity of information regarding optimal timing and dosing of PIR as well as organ-specific endothelial responses to shock. We aimed to examine the impact of PIR on endothelial dysfunction using clinically translatable timing and dosing.

METHODS

Sprague-Dawley rats were used to create thermal burns. Rats were subjected to 40% total body surface area scald burns and were resuscitated with lactated Ringer's (LR) only, LR plus albumin, and LR plus early 1 mL boluses of FFP at 0, 2, 4, and 8 hours postinjury. A late group also received LR plus FFP starting at hour 10 postinjury. Syndecan-1 levels were quantified by enzyme-linked immunosorbent assay, and quantitative real-time polymerase chain reaction analysis characterized transcription of glycocalyx components and inflammatory cytokines in the lung and spleen. Evan's blue dye was used to quantify amount of vascular leakage.

RESULTS

Lactated Ringer's plus early FFP reduced Evan's blue dye extravasation when compared with LR only groups, while late FFP did not. When comparing LR only versus LR plus early FFP, SDC-1 levels were reduced in the LR plus early FFP group at hours 8, 12, and 24 (5.23 vs. 2.07, p < 0.001; 4.49 vs. 2.05, p < 0.01; and 3.82 vs. 2.08, p < 0.05, respectively). Lactated Ringer's only groups had upregulation of Exostosin-1 and SDC-1 in the lung compared with LR plus early FFP groups ( p < 0.01 and p < 0.05) and upregulation of cytokines interluekin-10 and interferon γ ( p < 0.001 and p < 0.001).

CONCLUSION

Early administration of LR plus FFP reduces the magnitude of SDC-1 shedding and dampens the cytokine response to injury. The upregulation of glycocalyx components as a response to endothelial injury is also decreased in the lung and spleen by LR plus early FFP administration.

Trauma promotes heparan sulfate modifications and cleavage that disrupt homeostatic gene expression in microvascular endothelial cells

Introduction: Heparan sulfate (HS) in the vascular endothelial glycocalyx (eGC) is a critical regulator of blood vessel homeostasis. Trauma results in HS shedding from the eGC, but the impact of trauma on HS structural modifications that could influence mechanisms of vascular injury and repair has not been evaluated. Moreover, the effect of eGC HS shedding on endothelial cell (EC) homeostasis has not been fully elucidated. The objectives of this work were to characterize the impact of trauma on HS sulfation and determine the effect of eGC HS shedding on the transcriptional landscape of vascular ECs. Methods: Plasma was collected from 25 controls and 49 adults admitted to a level 1 trauma center at arrival and 24 h after hospitalization. Total levels of HS and angiopoietin-2, a marker of pathologic EC activation, were measured at each time point. Enzymatic activity of heparanase, the enzyme responsible for HS shedding, was determined in plasma from hospital arrival. Liquid chromatography-tandem mass spectrometry was used to characterize HS di-/tetrasaccharides in plasma. In vitro work was performed using flow conditioned primary human lung microvascular ECs treated with vehicle or heparinase III to simulate human heparanase activity. Bulk RNA sequencing was performed to determine differentially expressed gene-enriched pathways following heparinase III treatment. Results: We found that heparanase activity was increased in trauma plasma relative to controls, and HS levels at arrival were elevated in a manner proportional to injury severity. Di-/tetrasaccharide analysis revealed lower levels of 3-O-sulfated tetramers with a concomitant increase in ΔIIIS and ΔIIS disaccharides following trauma. Admission levels of total HS and specific HS sulfation motifs correlated with 24-h angiopoietin-2 levels, suggesting an association between HS shedding and persistent, pathological EC activation. In vitro pathway analysis demonstrated downregulation of genes that support cell junction integrity, EC polarity, and EC senescence while upregulating genes that promote cell differentiation and proliferation following HS shedding. Discussion: Taken together, our findings suggest that HS cleavage associated with eGC injury may disrupt homeostatic EC signaling and influence biosynthetic mechanisms governing eGC repair. These results require validation in larger, multicenter trauma populations coupled with in vivo EC-targeted transcriptomic and proteomic analyses.

Magnesium hydride attenuates intestinal barrier injury during hemorrhage shock by regulating neutrophil extracellular trap formation via the ROS/MAPK/PAD4 pathway

Magnesium hydride (MgH2) is a hydrogen storage material that is known for its high capacity and safety and is capable of releasing hydrogen in a controlled manner when administered orally. This release of hydrogen has been associated with a range of biological effects, including anti-inflammatory properties, antioxidant activity, and protection of the intestinal barrier. Previous research has shown that neutrophil extracellular traps (NETs) play a role in the dysfunction of the intestinal barrier in conditions such as sepsis and critical illnesses. However, it remains unclear as to whether MgH2 can protect the intestinal barrier by inhibiting NET formation, and the underlying mechanisms have yet to be elucidated. A rat model of hemorrhagic shock was created, and pretreatment or posttreatment procedures with MgH2 were performed. After 24 h, samples from the small intestine and blood were collected for analysis. In vitro, human neutrophils were incubated with either phorbol-12-myristate-13-acetate (PMA) or MgH2. Reactive oxygen species generation and the expression of key proteins were assessed. The results demonstrated that MgH2 administration led to a decrease in inflammatory cytokines in the serum and mitigated distant organ dysfunction in rats with HS. Furthermore, MgH2 treatment reversed histopathological damage in the intestines, improved intestinal permeability, and enhanced the expression of tight junction proteins (TJPs) during HS. Additionally, MgH2 treatment was found to suppress NET formation in the intestines. In vitro pretreatment with MgH2 alleviated intestinal monolayer barrier disruption that was induced by NETs. Mechanistically, MgH2 pretreatment reduced ROS production and NET formation, inhibited the activation of ERK and p38, and suppressed the expression of the PAD4 protein. These findings indicated that MgH2 may inhibit NET formation in a ROS/MAPK/PAD4-dependent manner, which reduces NET-related intestinal barrier damage, thus offering a novel protective role in preventing intestinal barrier dysfunction during HS.

Involvement of CD44 and MAPK14-mediated ferroptosis in hemorrhagic shock

To elucidate the induction of ferroptotic pathways and the transcriptional modulation of pivotal genes in the context of hemorrhagic shock. The R software was used to analyze the GSE64711 dataset, isolating genes relevant to ferroptosis. Enrichment analyses and protein interaction networks were assembled. Using WGCNA hub genes were identified and intersected with ferroptosis-related genes, highlighting hub genes CD44 and MAPK14. In a rat hemorrhagic shock model, cardiac ROS, Fe2+, MDA, and GSH levels were assessed. Key ferroptotic proteins (SLC7A11/GPX4) in myocardial tissues were examined via western blot. Hub genes, CD44 and MAPK14, expressions were confirmed through immunohistochemistry. Analyzing the GSE64711 dataset revealed 337 differentially expressed genes, including 12 linked to ferroptosis. Enrichment analysis highlighted pathways closely related to ferroptosis. Using Genemania, we found these genes mainly affect ROS metabolism and oxidative stress response. WGCNA identified CD44 and MAPK14 as hub genes. Rat myocardial tissue validation showed significant cardiac damage and elevated ROS and MDA levels, and decreased GSH levels in the hemorrhagic shock model. The ferroptotic pathway SLC7A11/GPX4 was activated, and immunohistochemistry showed a significant increase in the expression levels of CD44 and MAPK14 in the hemorrhagic shock rat model. We demonstrated the presence of tissue ferroptosis in hemorrhagic shock by combining bioinformatics analysis with in vivo experimentation. Specifically, we observed the activation of the SLC7A11/GPX4 ferroptotic pathway. Further, CD44 and MAPK14 were identified as hub genes in hemorrhagic shock.

Shear Stress and Endothelial Mechanotransduction in Trauma Patients with Hemorrhagic Shock: Hidden Coagulopathy Pathways and Novel Therapeutic Strategies

Massive trauma remains a leading cause of death and a global public health burden. Post-traumatic coagulopathy may be present even before the onset of resuscitation, and correlates with severity of trauma. Several mechanisms have been proposed to explain the development of abnormal coagulation processes, but the heterogeneity in injuries and patient profiles makes it difficult to define a dominant mechanism. Regardless of the pattern of death, a significant role in the pathophysiology and pathogenesis of coagulopathy may be attributed to the exposure of endothelial cells to abnormal physical forces and mechanical stimuli in their local environment. In these conditions, the cellular responses are translated into biochemical signals that induce/aggravate oxidative stress, inflammation, and coagulopathy. Microvascular shear stress-induced alterations could be treated or prevented by the development and use of innovative pharmacologic strategies that effectively target shear-mediated endothelial dysfunction, including shear-responsive drug delivery systems and novel antioxidants, and by targeting the venous side of the circulation to exploit the beneficial antithrombogenic profile of venous endothelial cells.

Resuscitating the Endothelial Glycocalyx in Trauma and Hemorrhagic Shock

The endothelium is lined by a protective mesh of proteins and carbohydrates called the endothelial glycocalyx (EG). This layer creates a negatively charged gel-like barrier between the vascular environment and the surface of the endothelial cell. When intact the EG serves multiple functions, including mechanotransduction, cell signaling, regulation of permeability and fluid exchange across the microvasculature, and management of cell-cell interactions. In trauma and/or hemorrhagic shock, the glycocalyx is broken down, resulting in the shedding of its individual components. The shedding of the EG is associated with increased systemic inflammation, microvascular permeability, and flow-induced vasodilation, leading to further physiologic derangements. Animal and human studies have shown that the greater the severity of the injury, the greater the degree of shedding, which is associated with poor patient outcomes. Additional studies have shown that prioritizing certain resuscitation fluids, such as plasma, cryoprecipitate, and whole blood over crystalloid shows improved outcomes in hemorrhaging patients, potentially through a decrease in EG shedding impacting downstream signaling. The purpose of the following paragraphs is to briefly describe the EG, review the impact of EG shedding and hemorrhagic shock, and begin entertaining the notion of directed resuscitation. Directed resuscitation emphasizes transitioning from macroscopic 1:1 resuscitation to efforts that focus on minimizing EG shedding and maximizing its reconstitution.

Succinate metabolism and membrane reorganization drives the endotheliopathy and coagulopathy of traumatic hemorrhage

Acute hemorrhage commonly leads to coagulopathy and organ dysfunction or failure. Recent evidence suggests that damage to the endothelial glycocalyx contributes to these adverse outcomes. The physiological events mediating acute glycocalyx shedding are undefined, however. Here, we show that succinate accumulation within endothelial cells drives glycocalyx degradation through a membrane reorganization-mediated mechanism. We investigated this mechanism in a cultured endothelial cell hypoxia-reoxygenation model, in a rat model of hemorrhage, and in trauma patient plasma samples. We found that succinate metabolism by succinate dehydrogenase mediates glycocalyx damage through lipid oxidation and phospholipase A2-mediated membrane reorganization, promoting the interaction of matrix metalloproteinase 24 (MMP24) and MMP25 with glycocalyx constituents. In a rat hemorrhage model, inhibiting succinate metabolism or membrane reorganization prevented glycocalyx damage and coagulopathy. In patients with trauma, succinate levels were associated with glycocalyx damage and the development of coagulopathy, and the interaction of MMP24 and syndecan-1 was elevated compared to healthy controls.

Implications of the Regulation of Endothelial Glycocalyx Breakdown and Reconstitution in Severe Burn Injury

INTRODUCTION

Effective initial fluid resuscitation is the cornerstone intervention in the setting of severe burn injury. Critically, few major advances in burn resuscitation have been made since the 1970s, and since that time there has been only modest improvement in overall morbidity and mortality. Recently, investigations regarding the dynamic changes of vascular endothelium, and more specifically the vascular endothelial glycocalyx, in the setting of severe burn injury and resuscitation have offered insight into the possibility of more tightly controlling fluid shifts and understanding the consequences thereof during this critical period.

METHODS

We conducted a literature search of the PubMed database using the terms "burn", and "glycocalyx" limited to studies published in the English language over the past 10 y. A total of 31 articles were initially identified. Abstracts and full text were manually reviewed to identify suitable articles. Of the identified articles, 10 were deemed relevant and included within this review, along with additional articles necessary to provide background on glycocalyx structure and function as well as principles of burn injury management.

RESULTS

Glycocalyx shedding is a process known to occur early in the setting of severe burn injury and resuscitation. The degree of shedding tends to increase with age and severity of injury. Though the role and regulation of this shedding is incompletely understood, it has direct consequences on vascular unction and permeability and likely coagulation as well.

CONCLUSIONS

Here in this research review, we examine what is known regarding the dynamic breakdown and reconstitution of the glycocalyx during burn injury and how it may be impacted by fluid resuscitation strategies. We further explore the need to more completely understand this mechanism and the consequences of its manipulation.

Albumin protects the ultrastructure of the endothelial glycocalyx of coronary arteries in myocardial ischemia-reperfusion injury in vivo

Myocardial ischemia-reperfusion (I/R) injury induces endothelial glycocalyx (GCX) degradation. Several candidate GCX-protective factors including albumin have been identified, few have been demonstrated in in vivo studies and most albumins used to date have been heterologous. Albumin is a carrier protein for sphingosine 1-phosphate (S1P), which has protective effects on the cardiovascular system. However, changes inhibited by albumin in the endothelial GCX structure in I/R in vivo via the S1P receptor has not been reported. In this study, we aimed to determine whether albumin prevents the shedding of endothelial GCX in response to I/R in vivo. Rats were divided into four groups: control (CON), I/R, I/R with albumin preload (I/R + ALB), and I/R + ALB with S1P receptor agonist fingolimod (I/R + ALB + FIN). FIN acts as an initial agonist of S1P receptor 1 and downregulates the receptor in an inhibitory manner. The CON and I/R groups received saline and I/R + ALB and I/R + ALB + FIN groups received albumin solution before left anterior descending coronary artery ligation. Our study used rat albumin. Shedding of endothelial GCX was evaluated in the myocardium by electron microscopy, and the concentration of serum syndecan-1 was measured. Thus, albumin administration maintained the structure of endothelial GCX and prevented shedding of endothelial GCX via the S1P receptor in myocardial I/R, and FIN annihilated the protective effect of albumin against I/R injury.

Effect of tranexamic acid on endothelial von Willebrand factor/ADAMTS-13 response to in vitro shock conditions

BACKGROUND

Traumatic/hemorrhagic shock, sepsis and other inflammatory processes lead to endothelial activation and a loss of the endothelial glycocalyx. von Willebrand factor (vWF) is an acute phase reactant that is released from endothelial cells and megakaryocytes. Stimulated but not basal vWF leads to significant formation of ultralarge multimers (ultralarge vWF [ULvWF]) and risk for thrombotic complications. Ultralarge vWF is cleaved by a disintegrin and metalloproteinase with a thrombospondin type motif 13 (ADAMTS 13); alterations in ULvWF/ADAMTS 13 ratio may contribute to trauma-induced coagulopathy. Salutary effects of tranexamic acid (TXA) on trauma-induced coagulopathy have been described. These effects appear apart from antifibrinolytic actions of TXA and include protection of the endothelial glycocalyx. Ultralarge vWF is in part anchored to the glycocalyx layer of the endothelium. Tranexamic acid protected the endothelial glycocalyx layer from degradation using a microfluidic model of the microcirculation subjected to hypoxia-reoxygenation and catecholamine excess. We hypothesized that TXA administration following shock conditions would impact the vWF-ADAMTS-13 axis by protecting the glycocalyx from degradation. This was studied in a endothelial microfluidic flow study.

METHODS

Human umbilical vein endothelial cells were established under flow conditions and subjected to biomimetic shock. Tranexamic acid was added after 90 minutes of perfusion. von Willebrand factor antigen and ADAMTS-13 activity were measured. Western blot analysis was performed for vWF characterization from perfusion media.

RESULTS

Shock conditions increased vWF antigen and decreased ADAMTS 13 activity. Tranexamic acid ameliorated shock induced cleavage in the ADAMTS 13-vWF axis with a reduction of the thrombogenic ULvWF.

CONCLUSION

These results suggest another mechanism whereby administration of TXA early following traumatic/hemorrhagic shock mitigates microvascular perfusion abnormalities and subsequent organ failure. The resultant effects on platelet adhesion and aggregation require further study.

Dimethyl malonate slows succinate accumulation and preserves cardiac function in a swine model of hemorrhagic shock

BACKGROUND

Succinate (SI) is a citric acid cycle metabolite that accumulates in tissues during hemorrhagic shock (HS) due to electron transport chain uncoupling. Dimethyl malonate (DMM) is a competitive inhibitor of SI dehydrogenase, which has been shown to reduce SI accumulation and protect against reperfusion injury. Whether DMM can be therapeutic after severe HS is unknown. We hypothesized that DMM would prevent SI buildup during resuscitation (RES) in a swine model of HS, leading to better physiological recovery after RES.

METHODS

The carotid arteries of Yorkshire pigs were cannulated with a 5-Fr catheter. After placement of a Swan-Ganz catheter and femoral arterial line, the carotid catheters were opened and the animals were exsanguinated to a mean arterial pressure (MAP) of 45 mm. After 30 minutes in the shock state, the animals were resuscitated to a MAP of 60 mm using lactated ringers. A MAP above 60 mm was maintained throughout RES. One group received 10 mg/kg of DMM (n = 6), while the control received sham injections (n = 6). The primary end-point was SI levels. Secondary end-points included cardiac function and lactate.

RESULTS

Succinate levels increased from baseline to the 20-minute RES point in control, while the DMM cohort remained unchanged. The DMM group required less intravenous fluid to maintain a MAP above 60 (450.0 vs. 229.0 mL; p = 0.01). The DMM group had higher pulmonary capillary wedge pressure at the 20-minute and 40-minute RES points. The DMM group had better recovery of cardiac output and index during RES, while the control had no improvement. While lactate levels were similar, DMM may lead to increased ionized calcium levels.

DISCUSSION

Dimethyl malonate slows SI accumulation during HS and helps preserve cardiac filling pressures and function during RES. In addition, DMM may protect against depletion of ionized calcium. Dimethyl malonate may have therapeutic potential during HS.

Targeting repair of the vascular endothelium and glycocalyx after traumatic injury with plasma and platelet resuscitation

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Endothelial glycocalyx shedding is a key instigator of the endotheliopathy of trauma.

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Plasma and platelet transfusions preserve vascular integrity in pre-clinical models.

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However, platelets may be less effective than plasma in preserving the glycocalyx.

Severely injured patients with hemorrhagic shock can develop endothelial dysfunction, systemic inflammation, and coagulation disturbances collectively known as the endotheliopathy of trauma (EOT). Shedding of the endothelial glycocalyx occurs early after injury, contributes to breakdown of the vascular barrier, and plays a critical role in the pathogenesis of multiple organ dysfunction, leading to poor outcomes in trauma patients. In this review we discuss (i) the pathophysiology of endothelial glycocalyx and vascular barrier breakdown following hemorrhagic shock and trauma, and (ii) the role of plasma and platelet transfusion in maintaining the glycocalyx and vascular endothelial integrity.