Update on the role of endothelial cells in trauma

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.

Enhanced in vivo and ex vivo thrombin generation after lower-leg trauma, but not after knee arthroscopy

BACKGROUND

There is room for improvement of prevention of venous thromboembolism (VTE) after lower-leg cast application or knee arthroscopy. Information about the mechanism of clot formation in these patients may be useful to identify new prophylaxis targets. We aimed to study the effect of 1) lower-leg injury and 2) knee arthroscopy on thrombin generation.

METHODS

A cross-sectional study was conducted using plasma samples of POT-(K)CAST trials to measure ex vivo thrombin generation (Calibrated Automated Thrombography [CAT]) and plasma levels of prothrombin fragment 1 + 2 (F1 + 2), thrombin-antithrombin (TAT), fibrinopeptide A (FPA). Plasma was obtained shortly after lower-leg trauma or before and after (< 4 h) knee arthroscopy. Participants were randomly selected from those who did not develop VTE. For aim 1, samples of 88 patients with lower-leg injury were compared with 89 control samples (i.e., preoperative samples of arthroscopy patients). Linear regression was used to obtain mean differences (or ratios if ln-retransformed because of skewedness) adjusted for age, sex, body mass index, comorbidities. For aim 2, pre- and postoperative samples of 85 arthroscopy patients were compared, for which mean changes were obtained.

RESULTS

In patients with lower-leg injury (aim 1), endogenous thrombin potential, thrombin peak, velocity index, FPA and TAT were increased as compared with controls. In arthroscopy patients (aim 2), pre- and postoperative levels were similar for all parameters.

CONCLUSION

Lower-leg trauma increases thrombin generation both ex vivo and in vivo, in contrast to knee arthroscopy. This may imply that the pathogenesis of VTE is different in both situations.

Haemostasis and Inflammatory Parameters as Potential Diagnostic Biomarkers for VTE in Trauma-Immobilized Patients

Venous thromboembolism (VTE), which encompasses deep venous thrombosis (DVT) and pulmonary embolism (PE), is a major public health concern due to its high incidences of morbidity and mortality. Patients who have experienced trauma with prolonged immobilization are at an increased risk of developing VTE. Plasma D-dimer levels have been known to be elevated in trauma patients, and they were closely correlated with the number of fractures. In other words, plasma D-dimer levels cannot be used as the only indicator of VTE in trauma cases. Given the limitations, further study is needed to explore other potential biomarkers for diagnosing VTE. To date, various established and novel VTE biomarkers have been studied in terms of their potential for predicting VTE, diagnostic performance, and improving clinical therapy for VTE. Therefore, this review aims to provide information regarding classic and essential haemostasis (including prothrombin time (PT), activated partial thromboplastin time (aPTT), D-dimer, fibrinogen, thrombin generation, protein C, protein S, antithrombin, tissue factor pathway inhibitor, and platelet count) and inflammatory biomarkers (C-reactive protein, erythrocyte sedimentation rate, and soluble P-selectin) as potential diagnostic biomarkers that can predict the risk of VTE development among trauma patients with prolonged immobilization. Thus, further advancement in risk stratification using these biomarkers would allow for a better diagnosis of patients with VTE, especially in areas with limited resources.

Lower-leg injury and knee arthroscopy have distinct effects on coagulation

Unlike knee arthroscopy, lower-leg injury is associated with increased plasma levels of factor VIII, von Willebrand factor, and D-dimer.

In both situations, coagulation is affected differently, which suggests that there are different pathways toward venous thromboembolism.

It is unknown how lower-leg injury and knee arthroscopy, both associated with venous thromboembolism (VTE), affect coagulation. To study the effect of (1) lower-leg trauma and (2) knee arthroscopy on coagulation, plasma samples of the Prevention of Thrombosis following CAST immobilization (POT-CAST, #NCT01542762) and Prevention of Thrombosis following Knee Arthroscopy (POT-KAST, #NCT01542723) trials were used, which were collected shortly after lower-leg trauma and before/after (<4 hours) knee arthroscopy. For aim 1, 1204 lower-leg injury patients were compared with preoperative samples of 1001 controls. Mean differences/ratios (if ln-retransformed because of skewedness) were adjusted for sex, age, body mass index, comorbidity, malignancy, and oral contraceptives using linear regression. For aim 2, perioperative mean changes of 715 arthroscopy patients were calculated. Plasma levels of fibrinogen, factor (F)VIII, FIX, FXI, von Willebrand Factor (VWF), and D-dimer were measured in all individuals. Parameters of underlying mechanisms (tissue factor, interleukin-6 [IL-6], myeloperoxidase DNA, cell-free DNA) were measured in random subsets. In lower-leg injury patients, coagulation parameter levels increased, especially FVIII, VWF, and D-dimer, that is, adjusted mean differences: FVIII 26.8% (95% confidence interval [CI], 23.7-29.9), FIX 13.8% (95% CI, 11.9-15.6), FXI 5.1% (95% CI, 3.3-7.0), VWF 29.8% (95% CI, 26.0-33.6), fibrinogen 32.5 mg/dL (95% CI, 25.8-39.2), and D-dimer (mean ratio) 3.3 (95% CI, 3.1-3.6). Remaining parameters were unchanged, except for increased IL-6 levels. After arthroscopy, all parameters decreased. Lower-leg trauma is associated with increased procoagulant factor levels in contrast to knee arthroscopy. This suggests that, in both situations, different pathways are involved in development of VTE.

The Impact of Anticoagulant Activity of Tissue Factor Pathway Inhibitor Measured by a Novel Functional Assay for Predicting Deep Venous Thrombosis in Trauma Patients: A Prospective Nested Case-Control Study

Deep venous thrombosis (DVT) is a common complication in patients with traumatic injury. Tissue factor pathway inhibitor (TFPI) is a natural anticoagulant protein in the extrinsic coagulation pathway. However, the relationship between DVT after trauma and the anticoagulant activity of TFPI remains unclear. In this prospective study, we investigated the role of TFPI in trauma patients with DVT to evaluate whether the anticoagulant activity of TFPI measured by a new functional assay can be used to help predict the risk of DVT. Patients and methods: This prospective nested case-control study enrolled trauma patients and healthy volunteers. Forty-eight trauma patients diagnosed with DVT and forty-eight matched trauma patients without DVT were included in the study. 120 healthy volunteers were also included as controls. Blood samples and case information were collected at admission. Patients accepted angiography before surgery to diagnose DVT. The parameters examined included TFPI anticoagulant activity, free-TFPI antigen, blood cell counts, and routine clinical coagulation tests. Results: For the parameters of TFPI anticoagulant activity, three were markedly increased in the DVT group compared to the non-DVT group (TFPI initial anticoagulant time ratio, P  =  .022; TFPI whole anticoagulant time ratio, P  =  .048; and TFPI anticoagulant rate, P  =  .034). The free-TFPI antigen concentration also showed a significant increasing trend in trauma patients with DVT compared with trauma patients without DVT (P  =  .035). Multivariate logistic regression analysis identified four independent factors for the development of DVT (TFPI initial anticoagulant time ratio, free-TFPI antigen, prothrombin time, and red blood cell count). We calculated the TFPI correlation coefficient and found that the area under the receiver operating characteristic curve was .821. Conclusions: A novel functional assay was developed to measure the anticoagulant activity of TFPI. The anticoagulant activity of TFPI can be used as a potential biomarker for diagnosing DVT in trauma patients.

Inhalation Injury is Associated with Endotheliopathy and Abnormal Fibrinolytic Phenotypes in Burn Patients: A Cohort Study

Burn injury is associated with endothelial dysfunction and coagulopathy and concomitant inhalation injury increases morbidity and mortality. The aim of this work is to identify associations between inhalation injury (IHI), coagulation homeostasis, vascular endothelium, and clinical outcomes in burn patients. One-hundred and twelve patients presenting to a regional burn center were included in this retrospective cohort study. Whole blood was collected at set intervals from admission through 24 hours and underwent viscoelastic assay with rapid TEG (rTEG). Syndecan-1 (SDC-1) on admission was quantified by ELISA. Patients were grouped by the presence (n=28) or absence (n=84) of concomitant IHI and rTEG parameters, fibrinolytic phenotypes, SDC-1, and clinical outcomes were compared. Of the 112 thermally injured patients, 28 (25%) had IHI. Most patients were male (68.8%) with a median age of 40 (IQR, 29-57) years. Patients with IHI had higher overall mortality (42.68% vs. 8.3%; p<0.0001). rTEG LY30 was lower in patients with IHI at hours 4 and 12 (p<0.05). There was a pattern of increased abnormal fibrinolytic phenotypes among IHI patients. There was a greater proportion of IHI patients with endotheliopathy (SDC-1 > 34 ng/mL) (64.7% vs. 26.4%; p=0.008). There was a pattern of increased mortality among patients with inhalation injury and endotheliopathy (0% vs. 72.7%; p=0.004). Significant differences between patients with and without IHI were found in measures assessing fibrinolytic potential and endotheliopathy. Mortality was associated with abnormal fibrinolysis, endotheliopathy, and inhalation injury. However, the extent to which IHI associated dysfunction is independent of TBSA burn size remains to be elucidated.

Alarming Cargo: The Role of Exosomes in Trauma-Induced Inflammation

Severe polytraumatic injury initiates a robust immune response. Broad immune dysfunction in patients with such injuries has been well-documented; however, early biomarkers of immune dysfunction post-injury, which are critical for comprehensive intervention and can predict the clinical course of patients, have not been reported. Current circulating markers such as IL-6 and IL-10 are broad, non-specific, and lag behind the clinical course of patients. General blockade of the inflammatory response is detrimental to patients, as a certain degree of regulated inflammation is critical and necessary following trauma. Exosomes, small membrane-bound extracellular vesicles, found in a variety of biofluids, carry within them a complex functional cargo, comprised of coding and non-coding RNAs, proteins, and metabolites. Composition of circulating exosomal cargo is modulated by changes in the intra- and extracellular microenvironment, thereby serving as a homeostasis sensor. With its extensively documented involvement in immune regulation in multiple pathologies, study of exosomal cargo in polytrauma patients can provide critical insights on trauma-specific, temporal immune dysregulation, with tremendous potential to serve as unique biomarkers and therapeutic targets for timely and precise intervention.

Damage-associated molecular patterns in trauma

In 1994, the "danger model" argued that adaptive immune responses are driven rather by molecules released upon tissue damage than by the recognition of "strange" molecules. Thus, an alternative to the "self versus non-self recognition model" has been provided. The model, which suggests that the immune system discriminates dangerous from safe molecules, has established the basis for the future designation of damage-associated molecular patterns (DAMPs), a term that was coined by Walter G. Land, Seong, and Matzinger. The pathological importance of DAMPs is barely somewhere else evident as in the posttraumatic or post-surgical inflammation and regeneration. Since DAMPs have been identified to trigger specific immune responses and inflammation, which is not necessarily detrimental but also regenerative, it still remains difficult to describe their "friend or foe" role in the posttraumatic immunogenicity and healing process. DAMPs can be used as biomarkers to indicate and/or to monitor a disease or injury severity, but they also may serve as clinically applicable parameters for optimized indication of the timing for, i.e., secondary surgeries. While experimental studies allow the detection of these biomarkers on different levels including cellular, tissue, and circulatory milieu, this is not always easily transferable to the human situation. Thus, in this review, we focus on the recent literature dealing with the pathophysiological importance of DAMPs after traumatic injury. Since dysregulated inflammation in traumatized patients always implies disturbed resolution of inflammation, so-called model of suppressing/inhibiting inducible DAMPs (SAMPs) will be very briefly introduced. Thus, an update on this topic in the field of trauma will be provided.

Apoptotic exosome-like vesicles regulate endothelial gene expression, inflammatory signaling, and function through the NF-κB signaling pathway

Persistent endothelial injury promotes maladaptive responses by favoring the release of factors leading to perturbation in vascular homeostasis and tissue architecture. Caspase-3 dependent death of microvascular endothelial cells leads to the release of unique apoptotic exosome-like vesicles (ApoExo). Here, we evaluate the impact of ApoExo on endothelial gene expression and function in the context of a pro-apoptotic stimulus. Endothelial cells exposed to ApoExo differentially express genes involved in cell death, inflammation, differentiation, and cell movement. Endothelial cells exposed to ApoExo showed inhibition of apoptosis, improved wound closure along with reduced angiogenic activity and reduced expression of endothelial markers consistent with the first phase of endothelial-to-mesenchymal transition (endoMT). ApoExo interaction with endothelial cells also led to NF-κB activation. NF-κB is known to participate in endothelial dysfunction in numerous diseases. Silencing NF-κB reversed the anti-apoptotic effect and the pro-migratory state and prevented angiostatic properties and CD31 downregulation in endothelial cells exposed to ApoExo. This study identifies vascular injury-derived extracellular vesicles (ApoExo) as novel drivers of NF-κB activation in endothelial cells and demonstrates the pivotal role of this signaling pathway in coordinating ApoExo-induced functional changes in endothelial cells. Hence, targeting ApoExo-mediated NF-κB activation in endothelial cells opens new avenues to prevent endothelial dysfunction.

Insight on the endothelialization of small silk-based tissue-engineered vascular grafts

Along with an increased incidence of cardiovascular diseases, there is a strong need for small-diameter vascular grafts. Silk has been investigated as a biomaterial to develop such grafts thanks to different processing options. Endothelialization was shown to be extremely important to ensure graft patency and there is ongoing research on the development and behavior of endothelial cells on vascular tissue-engineered scaffolds. This article reviews the endothelialization of silk-based scaffolds processed throughout the years as silk non-woven nets, films, gel spun, electrospun, or woven scaffolds. Encouraging results were reported with these scaffolds both in vitro and in vivo when implanted in small- to middle-sized animals. The use of coatings and heparin or sulfur to enhance, respectively, cell adhesion and scaffold hemocompatibility is further presented. Bioreactors also showed their interest to improve cell adhesion and thus promoting in vitro pre-endothelialization of grafts even though they are still not systematically used. Finally, the importance of the animal models used to study the right mechanism of endothelialization is discussed.

Inflammatory response in trauma patients: are there ways to decrease the inflammatory reaction?

PURPOSE OF REVIEW

Trauma patients are considered a complex population of patients in emergency medicine and need extensive, specialized therapy. One major part is the prevention and treatment of the inflammatory response, which occurs in patients after severe injury resulting in complications like endotheliopathy. Likely as a consequence, coagulopathy occurs. Sterile inflammation is hard to address, especially because of the lack of a single activator. Moreover, it is a complex composition of factors that lead to a pathologic immune response. Our understanding of these patterns is increasing, but the complete pathophysiologic changes have yet to be investigated. Therefore, there is no specific target to treat inflammatory response in trauma patients at the moment.

RECENT FINDINGS

There is increasing knowledge of the pathways and mediators that are responsible for the inflammatory response in patients after severe trauma. The endothelial glycocalyx has been identified to be an integral part of these mechanisms. There have been several new therapeutic approaches to diminish the inflammatory response.

SUMMARY

Our increasing understanding of the immune system have led to new potential therapeutic perspectives. All of these approaches need further research to be validated. As the current therapies are based on empirical strategies and have not changed much over the years, new treatment options would be an important progress.

The effect of red blood cell transfusion on platelet function in critically ill patients

INTRODUCTION

Red blood cell (RBC) transfusion is associated with an increased risk of pro-thrombotic events, but the underlying mechanism is poorly understood. We hypothesized that RBC transfusion modulates platelet activity in critically ill patients with and without sepsis.

METHODS

In a prospective cohort study, 37 critically ill patients receiving a single RBC unit to correct for anemia were sampled prior to and 1 h after transfusion. Platelet exposure of P-selectin, CD63 and binding of PAC-1 as well as formation of platelet-leukocyte complexes were measured by flow cytometry. The ability of plasma from critically ill patients to induce ex vivo platelet aggregation was assessed by flow cytometry after incubation with platelets from a healthy donor.

RESULTS

RBC transfusion neither triggered the expression of platelet activation markers nor the formation of platelet-leukocyte complexes. Plasma from critically ill patients induced more spontaneous platelet aggregation prior to RBC transfusion compared to healthy controls, which was further augmented following RBC transfusion. Also collagen-induced platelet aggregation was already increased prior to RBC transfusion compared to healthy controls, and this response was unaffected by RBC transfusion. In contrast, ristocetin-induced platelet agglutination was decreased when compared to controls, suggesting impaired vWF-dependent platelet agglutination, even in the presence of high vWF levels. Following RBC transfusion, ristocetin-induced platelet agglutination further decreased. There were no differences between septic and non-septic recipients in all assays.

CONCLUSION

Ex vivo platelet aggregation is disturbed in the critically ill. Transfusion of a RBC unit may further increase the spontaneous platelet aggregatory response.

A review of hyperfibrinolysis in cats and dogs

The fibrinolytic system is activated concurrently with coagulation; it regulates haemostasis and prevents thrombosis by restricting clot formation to the area of vascular injury and dismantling the clot as healing occurs. Dysregulation of the fibrinolytic system, which results in hyperfibrinolysis, may manifest as clinically important haemorrhage. Hyperfibrinolysis occurs in cats and dogs secondary to a variety of congenital and acquired disorders. Acquired disorders associated with hyperfibrinolysis, such as trauma, cavitary effusions, liver disease and Angiostrongylus vasorum infection, are commonly encountered in primary care practice. In addition, delayed haemorrhage reported in greyhounds following trauma and routine surgical procedures has been attributed to a hyperfibrinolytic disorder, although this has yet to be characterised. The diagnosis of hyperfibrinolysis is challenging and, until recently, has relied on techniques that are not readily available outside referral hospitals. With the recent development of point-of-care viscoelastic techniques, assessment of fibrinolysis is now possible in referral practice. This will provide the opportunity to target haemorrhage due to hyperfibrinolysis with antifibrinolytic drugs and thereby reduce associated morbidity and mortality. The fibrinolytic system and the conditions associated with increased fibrinolytic activity in cats and dogs are the focus of this review article. In addition, laboratory and point-of-care techniques for assessing hyperfibrinolysis and antifibrinolytic treatment for patients with haemorrhage are reviewed.

Inflammasomes in Tissue Damages and Immune Disorders After Trauma

Trauma remains a leading cause of death worldwide. Hemorrhagic shock and direct injury to vital organs are responsible for early mortality whereas most delayed deaths are secondary to complex pathophysiological processes. These processes result from imbalanced systemic reactions to the multiple aggressions associated with trauma. Trauma results in the uncontrolled local and systemic release of endogenous mediators acting as danger signals [damage-associated molecular patterns (DAMPs)]. Their recognition by the innate immune system triggers a pro-inflammatory immune response paradoxically associated with concomitant immunosuppression. These responses, ranging in intensity from inappropriate to overwhelming, promote the propagation of injuries to remote organs, leading to multiple organ failure and death. Some of the numerous DAMPs released after trauma trigger the assembly of intracellular multiprotein complexes named inflammasomes. Once activated by a ligand, inflammasomes lead to the activation of a caspase. Activated caspases allow the release of mature forms of interleukin-1β and interleukin-18 and trigger a specific pro-inflammatory cell death termed pyroptosis. Accumulating data suggest that inflammasomes, mainly NLRP3, NLRP1, and AIM2, are involved in the generation of tissue damage and immune dysfunction after trauma. Following trauma-induced DAMP(s) recognition, inflammasomes participate in multiple ways in the development of exaggerated systemic and organ-specific inflammatory response, contributing to organ damage. Inflammasomes are involved in the innate responses to traumatic brain injury and contribute to the development of acute respiratory distress syndrome. Inflammasomes may also play a role in post-trauma immunosuppression mediated by dysregulated monocyte functions. Characterizing the involvement of inflammasomes in the pathogenesis of post-trauma syndrome is a key issue as they may be potential therapeutic targets. This review summarizes the current knowledge on the roles of inflammasomes in trauma.

Danger signals in trauma

This review summarizes a short list of currently discussed trauma-induced danger-associated molecular patterns (DAMP). Due to the bivalent character and often pleiotropic effects of a DAMP, it is difficult to describe its "friend or foe" role in post-traumatic inflammation and regeneration, both systemically as well locally in tissues. DAMP can be used as biomarkers to indicate or monitor disease or injury severity, but also may serve as clinically applicable parameters for better indication and timing of surgery. Due to the inflammatory processes at the local tissue level or the systemic level, the precise role of DAMP is not always clear to define. While in vitro and experimental studies allow for the detection of these biomarkers at the different levels of an organism-cellular, tissue, circulation-this is not always easily transferable to the human setting. Increased knowledge exploring the dual role of DAMP after trauma, and concentrating on their nuclear functions, transcriptional targets, release mechanisms, cellular sources, multiple functions, their interactions and potential therapeutic targeting is warranted.