Hemorrhagic Shock and the Microvasculature

Comparing the effects of various fluid resuscitative strategies on Glycocalyx damage in a canine hemorrhage model

Hemorrhagic shock and subsequent resuscitation can cause significant dysregulation of critical systems, including the vascular endothelium. Following hemorrhage, the endothelial lining (glycocalyx) can shed, causing release of glycocalyx components, endothelial activation, and systemic inflammation. A canine model of hemorrhagic shock was used to evaluate five resuscitation fluids, including Lactated Ringers+Hetastarch, Whole Blood (WB), Fresh Frozen Plasma+packed Red Blood Cells (FFP+pRBC), and two hemoglobin-based oxygen carrier (HBOC) fluids, for their impact on glycocalyx shedding. Under anesthesia, purpose-bred adult canines were instrumented and subjected to a controlled hemorrhage with blood being drawn until a mean arterial pressure of <50 mmHg was reached or 40 % of the estimated blood volume was removed. Canines were left in shock for 45 mins before being resuscitated with one of the resuscitation fluids over 30 mins. Following resuscitation, the dogs were monitored up to 2 weeks. Following an additional 3-4 weeks for washout, the canines repeated the protocol, undergoing each resuscitation fluid individually. Blood samples were collected during each round at various timepoints for serum isolation, which was used for detection of glycocalyx biomarker. Comparison of baseline and post-hemorrhage alone showed a significant reduction in serum protein (p<0.0001), heparan sulfate (p<0.001), and syndecan-1 (p<0.0001) concentrations, and a significant increase in hyaluronan (p<0.0001) concentration. Intercomparisons of resuscitation fluids indicated minimal differences in glycocalyx markers over time. Comparisons within each fluid showed dynamic responses in glycocalyx biomarkers over time. Relative to individual baselines, syndecan-1 was significantly reduced after resuscitation in most cases (p<0.0001), excluding WB and FFP+pRBC. In all cases, VE-cadherin was significantly elevated at 24 hr compared to baseline (p<0.001). Hyaluronan was significantly elevated by 3 hr in all cases (p<0.01), except for HBOC fluids. Total glycosaminoglycans were significantly reduced only at 3 hr (p<0.001) for non-HBOC fluids. Similarly, heparan sulfate was significantly reduced with all fluids between resuscitation and 24 hr (p<0.01), except WB. The temporal changes in canine glycocalyx biomarkers were atypical of hemorrhage response in other species. This suggests that the hemorrhage lacked severity and/or typical glycocalyx biomarkers do not reflect the canine endothelium compared to other species. Further research is needed to characterize the canine endothelium and the response to resuscitation fluids.

Protective Effects and Mechanisms of Inhibiting Endoplasmic Reticulum Stress on Cold Seawater Immersion Combined with Hemorrhagic Shock

Purpose

Cold seawater immersion aggravates hemorrhagic shock-induced homeostasis imbalance and organ dysfunction, leading to increased mortality. Previous studies have shown that treatments targeting oxidative stress and mitochondrial dysfunction have limited efficacy for cold seawater immersion combined with hemorrhagic shock (SIHS). Thus, the mechanisms responsible for SIHS need further investigation.

Methods and Results

Data from the hemorrhagic shock transcriptome and cold seawater immersion targets used for bioinformatics analysis revealed the involvement of endoplasmic reticulum stress (ERS) in SIHS occurrence and progression. Based on these findings, the effects and possible mechanism of inhibiting ERS in SIHS rats were investigated. SIHS causes a lethal triad and impairment of vital organ function, leading to death. Compared to lactated Ringer's solution, the ERS inhibitor 4-phenylbutyric acid (PBA)significantly ameliorated acidosis and coagulopathy and protected vital organ function while prolonging survival and the golden treatment time. Through target screening and validation, 7 targets were identified for the ERS inhibitor PBA for the treatment of SIHS, among which S1PR1, MMP8 and CFTR may play more important roles.

Conclusion

ERS plays a crucial role in the progression of SIHS. Inhibition of ERS caused by SIHS alleviates the lethal triad, protects organ function, and prolongs survival and the golden treatment time. The ERS inhibitor PBA may be an effective therapeutic measure for treating SIHS.

[Damage Control Resuscitation and Damage Control Surgery]

Trauma triggers complex physiological responses with primary and secondary effects vital to understanding and managing trauma impact. "Damage Control" (DC), a concept adapted from naval practices, refers to abbreviated initial surgical care focused on controlling bleeding and contamination, critical for the survival of severely compromised patients. This impacts anaesthesia procedures and intensive care. "Damage Control Resuscitation" (DCR) is an interdisciplinary approach aimed at reducing mortality in severely injured patients, despite potentially increasing morbidity and ICU duration. Current medical guidelines incorporate DC strategies.DC is most beneficial for patients with severe physiological injury, where surgical trauma ("second hit") poses greater risks than delayed treatment. Patient assessment for DC includes evaluating injury severity, physiological reserves, and anticipated surgical and treatment strain. Inadequate intervention can worsen trauma-induced complications like coagulopathy, acidosis, hypothermia, and hypocalcaemia.DCR focuses on rapidly restoring homeostasis with minimal additional burden. It includes rapid haemostasis, controlled permissive hypotension, early blood transfusion, haemostasis optimization, and temperature normalization, tailored to individual patient needs."Damage Control Surgery" (DCS) involves phases like rapid haemostasis, contamination control, temporary wound closure, intensive stabilization, planned reoperations, and final wound closure. Each phase is crucial for managing severely injured patients, balancing immediate life-saving procedures and preparing for subsequent surgeries.Intensive care post-DCS emphasizes stabilizing patients hemodynamically, metabolically, and coagulopathically while restoring normothermia. Decision-making in trauma care is complex, involving precise patient assessment, treatment prioritization, and team coordination. The potential of AI-based decision support systems is noted for their ability to analyse patient data in real-time, aiding in decision-making through evidence-based recommendations.

Plasma resuscitation improves and restores intestinal microcirculatory physiology following haemorrhagic shock

BACKGROUND AND OBJECTIVES

Intestinal ischaemia-reperfusion injury following resuscitated haemorrhagic shock (HS) leads to endothelial and microcirculatory dysfunction and intestinal barrier breakdown. Although vascular smooth muscle machinery remains intact, microvascular vasoconstriction occurs secondary to endothelial cell dysfunction, resulting in further ischaemia and organ injury. Resuscitation with fresh frozen plasma (FFP) improves blood flow, stabilizes the endothelial glycocalyx and alleviates organ injury. We postulate these improvements correlate with decreased tissue CO2 concentrations, improved microvascular oxygenation and attenuation of intestinal microvascular endothelial dysfunction.

MATERIALS AND METHODS

Male Sprague-Dawley rats were randomly assigned to groups (n = 8/group): (1) sham, (2) HS (40% mean arterial blood pressure [MAP], 60 min) + crystalloid resuscitation (CR) (shed blood saline) and (3) HS + FFP (shed blood + FFP). MAP, heart rate (HR), ileal perfusion, pO2 and pCO2 were measured at intervals until 4 h post-resuscitation (post-RES). At 4 h post-RES, the ileum was rinsed in situ with Krebs solution. Topical acetylcholine and then nitroprusside were applied for 10 min each. Serum was obtained, and after euthanasia, tissues were harvested and snap-frozen in liquid N2 and stored at -80°C.

RESULTS

FFP resuscitation resulted in sustained ileal perfusion as well as rapid sustained return to baseline microvascular pO2 and pCO2 values when compared to CR (p < 0.05). Endothelial function was preserved relative to sham in the FFP group but not in the CR group (p < 0.05).

CONCLUSION

FFP-based resuscitation improves intestinal perfusion immediately following resuscitation, which correlates with improved tissue oxygenation and decreased tissue CO2 levels. CR resulted in significant damage to endothelial vasodilation response to acetylcholine, while FFP preserved this function.

Therapeutic implication of Sonic Hedgehog as a potential modulator in ischemic injury

Sonic Hedgehog (SHh) is a homology protein that is involved in the modeling and development of embryonic tissues. As SHh plays both protective and harmful roles in ischemia, any disruption in the transduction and regulation of the SHh signaling pathway causes ischemia to worsen. The SHh signal activation occurs when SHh binds to the receptor complex of Ptc-mediated Smoothened (Smo) (Ptc-smo), which initiates the downstream signaling cascade. This article will shed light on how pharmacological modifications to the SHh signaling pathway transduction mechanism alter ischemic conditions via canonical and non-canonical pathways by activating certain downstream signaling cascades with respect to protein kinase pathways, angiogenic cytokines, inflammatory mediators, oxidative parameters, and apoptotic pathways. The canonical pathway includes direct activation of interleukins (ILs), angiogenic cytokines like hepatocyte growth factor (HGF), platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF), epidermal growth factor (EGF), and hypoxia-inducible factor alpha (HIF-), which modulate ischemia. The non-canonical pathway includes indirect activation of certain pathways like mTOR, PI3K/Akt, MAPK, RhoA/ROCK, Wnt/-catenin, NOTCH, Forkhead box protein (FOXF), Toll-like receptors (TLR), oxidative parameters such as GSH, SOD, and CAT, and some apoptotic parameters such as Bcl2. This review provides comprehensive insights that contribute to our knowledge of how SHh impacts the progression and outcomes of ischemic injuries.

Efficacy and Safety of Early Administration of 4-Factor Prothrombin Complex Concentrate in Patients With Trauma at Risk of Massive Transfusion: The PROCOAG Randomized Clinical Trial

Importance

Optimal transfusion strategies in traumatic hemorrhage are unknown. Reports suggest a beneficial effect of 4-factor prothrombin complex concentrate (4F-PCC) on blood product consumption.

Objective

To investigate the efficacy and safety of 4F-PCC administration in patients at risk of massive transfusion.

Design, Setting, and Participants

Double-blind, randomized, placebo-controlled superiority trial in 12 French designated level I trauma centers from December 29, 2017, to August 31, 2021, involving consecutive patients with trauma at risk of massive transfusion. Follow-up was completed on August 31, 2021.

Interventions

Intravenous administration of 1 mL/kg of 4F-PCC (25 IU of factor IX/kg) vs 1 mL/kg of saline solution (placebo). Patients, investigators, and data analysts were blinded to treatment assignment. All patients received early ratio-based transfusion (packed red blood cells:fresh frozen plasma ratio of 1:1 to 2:1) and were treated according to European traumatic hemorrhage guidelines.

Main Outcomes and Measures

The primary outcome was 24-hour all blood product consumption (efficacy); arterial or venous thromboembolic events were a secondary outcome (safety).

Results

Of 4313 patients with the highest trauma level activation, 350 were eligible for emergency inclusion, 327 were randomized, and 324 were analyzed (164 in the 4F-PCC group and 160 in the placebo group). The median (IQR) age of participants was 39 (27-56) years, Injury Severity Score was 36 (26-50 [major trauma]), and admission blood lactate level was 4.6 (2.8-7.4) mmol/L; prehospital arterial systolic blood pressure was less than 90 mm Hg in 179 of 324 patients (59%), 233 patients (73%) were men, and 226 (69%) required expedient hemorrhage control. There was no statistically or clinically significant between-group difference in median (IQR) total 24-hour blood product consumption (12 [5-19] U in the 4F-PCC group vs 11 [6-19] U in the placebo group; absolute difference, 0.2 U [95% CI, -2.99 to 3.33]; P = .72). In the 4F-PCC group, 56 patients (35%) presented with at least 1 thromboembolic event vs 37 patients (24%) in the placebo group (absolute difference, 11% [95% CI, 1%-21%]; relative risk, 1.48 [95% CI, 1.04-2.10]; P = .03).

Conclusions and Relevance

Among patients with trauma at risk of massive transfusion, there was no significant reduction of 24-hour blood product consumption after administration of 4F-PCC, but thromboembolic events were more common. These findings do not support systematic use of 4F-PCC in patients at risk of massive transfusion.

Trial Registration

ClinicalTrials.gov Identifier: NCT03218722.

Association of Early Norepinephrine Administration With 24-Hour Mortality Among Patients With Blunt Trauma and Hemorrhagic Shock

IMPORTANCE

Hemorrhagic shock is a common cause of preventable death after injury. Vasopressor administration for patients with blunt trauma and hemorrhagic shock is often discouraged.

OBJECTIVE

To evaluate the association of early norepinephrine administration with 24-hour mortality among patients with blunt trauma and hemorrhagic shock.

DESIGN, SETTING, AND PARTICIPANTS

This retrospective, multicenter, observational cohort study used data from 3 registries in the US and France on all consecutive patients with blunt trauma from January 1, 2013, to December 31, 2018. Patients were alive on admission with hemorrhagic shock, defined by prehospital or admission systolic blood pressure less than 100 mm Hg and evidence of hemorrhage (ie, prehospital or resuscitation room transfusion of packed red blood cells, receipt of emergency treatment for hemorrhage control, transfusion of >10 units of packed red blood cells in the first 24 hours, or death from hemorrhage). Blunt trauma was defined as any exposure to nonpenetrating kinetic energy, collision, or deceleration. Statistical analysis was performed from January 15, 2021, to February 22, 2022.

EXPOSURE

Continuous administration of norepinephrine in the prehospital environment or resuscitation room prior to hemorrhage control, according to European guidelines.

MAIN OUTCOMES AND MEASURES

The primary outcome was 24-hour mortality, and the secondary outcome was in-hospital mortality. The average treatment effect (ATE) of early norepinephrine administration on 24-hour mortality was estimated according to the Rubin causal model. Inverse propensity score weighting and the doubly robust approach with 5 distinct analytical strategies were used to determine the ATE.

RESULTS

A total of 52 568 patients were screened for inclusion, and 2164 patients (1508 men [70%]; mean [SD] age, 46 [19] years; median Injury Severity Score, 29 [IQR, 17-36]) presented with acute hemorrhage and were included. A total of 1497 patients (69.1%) required emergency hemorrhage control, 128 (5.9%) received a prehospital transfusion of packed red blood cells, and 543 (25.0%) received a massive transfusion. Norepinephrine was administered to 1498 patients (69.2%). The 24-hour mortality rate was 17.8% (385 of 2164), and the in-hospital mortality rate was 35.6% (770 of 2164). None of the 5 analytical strategies suggested any statistically significant association between norepinephrine administration and 24-hour mortality, with ATEs ranging from -4.6 (95% CI, -11.9 to 2.7) to 2.1 (95% CI, -2.1 to 6.3), or between norepinephrine administration and in-hospital mortality, with ATEs ranging from -1.3 (95% CI, -9.5 to 6.9) to 5.3 (95% CI, -2.1 to 12.8).

CONCLUSIONS AND RELEVANCE

The findings of this study suggest that early norepinephrine infusion was not associated with 24-hour or in-hospital mortality among patients with blunt trauma and hemorrhagic shock. Randomized clinical trials that study the effect of early norepinephrine administration among patients with trauma and hypotension are warranted to further assess whether norepinephrine is safe for patients with hemorrhagic shock.

Direct Peritoneal Resuscitation for Trauma

Direct peritoneal resuscitation (DPR) has been found to be a useful adjunct in the management of critically ill trauma patients. DPR is performed following damage control surgery by leaving a surgical drain in the mesentery, placing a temporary abdominal closure, and postoperatively running peritoneal dialysis solution through the surgical drain with removal through the temporary closure. In the original animal models, the peritoneal dialysate infusion was found to augment visceral microcirculatory blood flow reducing the ischemic insult that occurs following hemorrhagic shock. DPR was also found to minimize the aberrant immune response that occurs secondary to shock and contributes to multisystem organ dysfunction. In the subsequent human trials, performing DPR had significant effects in several key categories. Traumatically injured patients who received DPR had a significantly shorter time to definitive fascial closure, had a higher likelihood of achieving primary fascial closure, and experienced fewer abdominal complications. The use of DPR has been further expanded as a useful adjunct for emergency general surgery patients and in the pretransplant care of human cadaver organ donors.

Hyperspectral Wide-Field-Of-View Imaging to Study Dynamic Microcirculatory Changes During Hypoxia

OBJECTIVE

Hyperspectral imaging (HSI) provides a fast, reliable, and non-invasive way the study vascular microcirculation in animal models. Rapid hyperspectral imaging of large portions of the microcirculatory preparation is critical for understanding the function and regulation of vascular microcirculatory networks.

METHODS

This report presents the application of an off-the-shelf, benchtop, HSI linear scanning system to acquire larger field-of-view images of microcirculatory preparations. The HSI line detector was displaced perpendicular to the scanning direction to map larger areas, with a rate of displacement determined by the scanning rate and the exposure time. The collected image was analyzed to determine dynamic changes in the microcirculation.

RESULTS

The system records dynamic changes in microvascular hemoglobin (Hb) oxygen (O₂) saturation and vascular morphology during hypoxia and reoxygenation and has similar acquisition speeds to commonly referenced spectral-scanning HSI systems. Additionally, the HbO₂ saturations collected via HSI closely correlate with those collected by phosphorescence quenching microscopy.

CONCLUSION

The reported system enables dynamic functional microcirculation imaging for broad experimental and clinical applications.

TLR2/TLR4-Enhanced TIPE2 Expression Is Involved in Post-Hemorrhagic Shock Mesenteric Lymph-Induced Activation of CD4+T Cells

Purpose

Post hemorrhagic shock mesenteric lymph (PHSML) return contributes to CD4+ T cell dysfunction, which leads to immune dysfunction and uncontrolled inflammatory response. Tumor necrosis factor α induced protein 8 like-2 (TIPE2) is one of the essential proteins to maintain the immune homeostasis. This study investigated the role of TIPE2 in regulation of CD4+ T lymphocyte function in interaction of PHSML and TLR2/TLR4.

Methods

The splenic CD4+ T cells were isolated from various mice (WT, TLR2-/-, TLR4-/-) by immunomagnetic beads, and stimulated with PHSML, normal lymphatic fluid (NML), respectively. Application of TIPE2-carrying interfering fragments of lentivirus were transfected to WT, TLR4-/-, and TLR2-/- CD4+ T cells, respectively. After interference of TIPE2, they were stimulated with PHSML and NML for the examinations of TIPE2, TLR2, and TLR4 mRNA expressions, proliferation, activation molecules on surface, and cytokine secretion function.

Results

PHSML stimulation significantly upregulated TIPE2, TLR2, and TLR4 mRNA expressions, decreased proliferation, CD25 expression, and IFN-γ secretion, and increased the secretion ability of IL-4 in WT CD4+ T cells. TIPE2 silencing enhanced proliferative capacity, upregulated CD25 expression, and increased IFNγ secretion in CD4+ T cells. PHSML stimulated TLR2-/-CD4+ T or TLR4-/-CD4+ T cells of which TIPE2 were silenced. TLR2 or TLR4 knockout attenuated PHSML-induced CD4+ T cells dysfunction; PHSML stimulation of silent TIPE2-expressing TLR2-/-CD4+ T or TLR4-/-CD4+ T revealed that the coexistence of low TIPE2 expression with lack of TLR2 or TLR4 eliminated this beneficial effect.

Conclusion

TIPE2 improves the PHSML-mediated CD4+T cells dysfunction by regulating TLR2/TLR4 pathway, providing a new intervention target following hemorrhagic shock-induced immune dysfunction.

Protective Effect of Moderate Hypotonic Fluid on Organ Dysfunction via Alleviating Lethal Triad Following Seawater Immersion With Hemorrhagic Shock in Rats

Previous studies found that seawater immersion combined with hemorrhagic shock (SIHS) induced serious organ function disorder, and lethal triad was a critical sign. There were no effective treatments of SIHS. Fluid resuscitation was the initial measurement for early aid following hemorrhagic shock, while the proper fluid for SIHS is not clear. Effects of different osmotic pressures [lactated Ringer’s (LR) solution, 0.3% saline, 0.6% saline, and 0.9% normal saline] on the lethal triad, mitochondrial function, vital organ functions, and survival were observed following SIHS in rats. The results showed that SIHS led to an obvious lethal triad, which presented the decrease of the body temperature, acidosis, and coagulation functions disorder in rats. Fluid resuscitation with different osmotic pressures recovered the body temperature and corrected acidosis with different levels; effects of 0.6% normal saline were the best; especially for the coagulation function, 0.6% normal saline alleviated the lethal triad significantly. Further studies showed that SIHS resulted in the damage of the mitochondrial function of vital organs, the increase of the vascular permeability, and, at the same time, the organ function including cardiac, liver, and kidney was disordered. Conventional fluid such as LR or 0.9% normal saline could not improve the mitochondrial function and vascular leakage and alleviate the damage of the organ function. While moderate hypotonic fluid, the 0.6% normal saline, could lighten organ function damage via protecting mitochondrial function. The 0.6% normal saline increased the left ventricular fractional shortening and the left ventricular ejection fraction, and decreased the levels of aspartate transaminase, alanine transferase, blood urea nitrogen, and creatinine in the blood. The effects of fluids with different osmotic pressures on the mean arterial pressure (MAP) had a similar trend as above parameters. The survival results showed that the 0.6% normal saline group improved the survival rate and prolonged the survival time, the 72 h survival rate was 7/16, as compared with the LR group (3/16). The results indicate that appropriate hypotonic fluid is suitable after SIHS, which alleviates the lethal triad, protects the mitochondrial function and organ functions, and prolongs the survival time.

Pathophysiology of Hemorrhage as It Relates to the Warfighter

Saving lives of wounded military Warfighters often depends on the ability to resolve or mitigate the pathophysiology of hemorrhage, specifically diminished oxygen delivery to vital organs that leads to multi-organ failure and death. However, caring for hemorrhaging patients on the battlefield presents unique challenges that extend beyond applying a tourniquet and giving a blood transfusion, especially when battlefield care must be provided for a prolonged period. This review will describe these challenges and potential strategies for treating hemorrhage on the battlefield in a prolonged casualty care situation.

Therapeutically Targeting Microvascular Leakage in Experimental Hemorrhagic SHOCK: A Systematic Review and Meta-Analysis

BACKGROUND

Microvascular leakage is proposed as main contributor to disturbed microcirculatory perfusion following hemorrhagic shock and fluid resuscitation, leading to organ dysfunction and unfavorable outcome. Currently, no drugs are available to reduce or prevent microvascular leakage in clinical practice. We therefore aimed to provide an overview of therapeutic agents targeting microvascular leakage following experimental hemorrhagic shock and fluid resuscitation.

METHODS

PubMed, EMBASE.com, and Cochrane Library were searched in January 2021 for preclinical studies of hemorrhagic shock using any therapeutic agent on top of standard fluid resuscitation. Primary outcome was vascular leakage, defined as edema, macromolecule extravasation, or glycocalyx degradation. Drugs were classified by targeting pathways and subgroup analyses were performed per organ.

RESULTS

Forty-five studies, published between 1973 and 2020, fulfilled eligibility criteria. The included studies tested 54 different therapeutics mainly in pulmonary and intestinal vascular beds. Most studies induced trauma besides hemorrhagic shock. Forty-four therapeutics (81%) were found effective to reduce microvascular leakage, edema formation, or glycocalyx degradation in at least one organ. Targeting oxidative stress and apoptosis was the predominantly effective strategy (SMD: -2.18, CI [-3.21, -1.16], P < 0.0001). Vasoactive agents were found noneffective in reducing microvascular leakage (SMD: -0.86, CI [-3.07, 1.36], P = 0.45).

CONCLUSION

Pharmacological modulation of pathways involved in cell metabolism, inflammation, endothelial barrier regulation, sex hormones and especially oxidative stress and apoptosis were effective in reducing microvascular leakage in experimental hemorrhagic shock with fluid resuscitation. Future studies should investigate whether targeting these pathways can restore microcirculatory perfusion and reduce organ injury following hemorrhagic shock.

SYSTEMATIC REVIEW REGISTRATION NUMBER

CRD42018095432.

Massive Transfusion in trauma: an evolving paradigm

A considerable amount of literature has nurtured the idea that massive transfusion is an independent trauma disease and therapeutic tool. In this opinion paper, the authors expose the evolution and challenge the classic paradigm and historic definition of massive transfusion. Based on current evidence the elements of an evolving strategy in transfusion management and bleeding control are exposed such as use of tranexamic acid, combination and ratios of blood products, use of fluids and viscoelastic testing. The synergy of these elements provides the basis to develop updated strategies and perspectives for transfusion management after trauma and to consider a classic definition of massive transfusion as outdated or the need for massive transfusion as failure. An alternative concept, Time Critical Transfusion may be better placed to take into account modern transfusion management after trauma.

The effect of targeting Tie2 on hemorrhagic shock-induced renal perfusion disturbances in rats

BACKGROUND

Hemorrhagic shock is associated with acute kidney injury and increased mortality. Targeting the endothelial angiopoietin/Tie2 system, which regulates endothelial permeability, previously reduced hemorrhagic shock-induced vascular leakage. We hypothesized that as a consequence of vascular leakage, renal perfusion and function is impaired and that activating Tie2 restores renal perfusion and function.

METHODS

Rats underwent 1 h of hemorrhagic shock and were treated with either vasculotide or PBS as control, followed by fluid resuscitation for 4 h. Microcirculatory perfusion was measured in the renal cortex and cremaster muscle using contrast echography and intravital microscopy, respectively. Changes in the angiopoietin/Tie2 system and renal injury markers were measured in plasma and on protein and mRNA level in renal tissue. Renal edema formation was determined by wet/dry weight ratios and renal structure by histological analysis.

RESULTS

Hemorrhagic shock significantly decreased renal perfusion (240 ± 138 to 51 ± 40, p < 0.0001) and cremaster perfusion (12 ± 2 to 5 ± 2 perfused vessels, p < 0.0001) compared to baseline values. Fluid resuscitation partially restored both perfusion parameters, but both remained below baseline values (renal perfusion 120 ± 58, p = 0.08, cremaster perfusion 7 ± 2 perfused vessels, p < 0.0001 compared to baseline). Hemorrhagic shock increased circulating angiopoietin-1 (p < 0.0001), angiopoietin-2 (p < 0.0001) and soluble Tie2 (p = 0.05), of which angiopoietin-2 elevation was associated with renal edema formation (r = 0.81, p < 0.0001). Hemorrhagic shock induced renal injury, as assessed by increased levels of plasma neutrophil gelatinase-associated lipocalin (NGAL: p < 0.05), kidney injury marker-1 (KIM-1; p < 0.01) and creatinine (p < 0.05). Vasculotide did not improve renal perfusion (p > 0.9 at all time points) or reduce renal injury (NGAL p = 0.26, KIM-1 p = 0.78, creatinine p > 0.9, renal edema p = 0.08), but temporarily improved cremaster perfusion at 3 h following start of fluid resuscitation compared to untreated rats (resuscitation + 3 h: 11 ± 3 vs 8 ± 3 perfused vessels, p < 0.05).

CONCLUSION

Hemorrhagic shock-induced renal impairment cannot be restored by standard fluid resuscitation, nor by activation of Tie2. Future treatment strategies should focus on reducing angiopoietin-2 levels or on activating Tie2 via an alternative strategy.

Cardiovascular Responses During Sepsis

Sepsis is the life-threatening organ dysfunction arising from a dysregulated host response to infection. Although the specific mechanisms leading to organ dysfunction are still debated, impaired tissue oxygenation appears to play a major role, and concomitant hemodynamic alterations are invariably present. The hemodynamic phenotype of affected individuals is highly variable for reasons that have been partially elucidated. Indeed, each patient's circulatory condition is shaped by the complex interplay between the medical history, the volemic status, the interval from disease onset, the pathogen, the site of infection, and the attempted resuscitation. Moreover, the same hemodynamic pattern can be generated by different combinations of various pathophysiological processes, so the presence of a given hemodynamic pattern cannot be directly related to a unique cluster of alterations. Research based on endotoxin administration to healthy volunteers and animal models compensate, to an extent, for the scarcity of clinical studies on the evolution of sepsis hemodynamics. Their results, however, cannot be directly extrapolated to the clinical setting, due to fundamental differences between the septic patient, the healthy volunteer, and the experimental model. Numerous microcirculatory derangements might exist in the septic host, even in the presence of a preserved macrocirculation. This dissociation between the macro- and the microcirculation might account for the limited success of therapeutic interventions targeting typical hemodynamic parameters, such as arterial and cardiac filling pressures, and cardiac output. Finally, physiological studies point to an early contribution of cardiac dysfunction to the septic phenotype, however, our defective diagnostic tools preclude its clinical recognition. © 2021 American Physiological Society. Compr Physiol 11:1605-1652, 2021.

In vitro endothelial hyperpermeability occurs early following traumatic hemorrhagic shock

BACKGROUND

Endothelial hyperpermeability is suggested to play a role in the development of microcirculatory perfusion disturbances and organ failure following hemorrhagic shock, but evidence is limited.

OBJECTIVE

To study the effect of plasma from traumatic hemorrhagic shock patients on in vitro endothelial barrier function.

METHODS

Plasma from traumatic hemorrhagic shock patients was obtained at the emergency department (ED), the intensive care unit (ICU), 24 h after ICU admission and from controls (n = 8). Sublingual microcirculatory perfusion was measured using incident dark field videomicroscopy at matching time points. Using electric cell-substrate impedance sensing, the effects of plasma exposure on in vitro endothelial barrier function of human endothelial cells were assessed.

RESULTS

Plasma from traumatic hemorrhagic shock patients collected at ED admission induced a 19% loss of in vitro endothelial resistance compared to plasma from controls (p < 0.001). This loss was due to reduced cell-cell contacts (p < 0.01). Plasma withdrawn at later time points did not affect endothelial barrier function (p > 0.99). Interestingly, in vitro endothelial resistance showed a positive association with in vivo microcirculatory perfusion (r = 0.56, p < 0.01).

CONCLUSIONS

Plasma from traumatic hemorrhagic shock patients obtained following ED admission, but not at later stages, induced in vitro endothelial hyperpermeability. This coincided with in vivo microcirculatory perfusion disturbances.

Therapeutic interventions to restore microcirculatory perfusion following experimental hemorrhagic shock and fluid resuscitation: A systematic review

Objective

Microcirculatory perfusion disturbances following hemorrhagic shock and fluid resuscitation contribute to multiple organ dysfunction and mortality. Standard fluid resuscitation is insufficient to restore microcirculatory perfusion; however, additional therapies are lacking. We conducted a systematic search to provide an overview of potential non‐fluid‐based therapeutic interventions to restore microcirculatory perfusion following hemorrhagic shock.

Methods

A structured search of PubMed, EMBASE, and Cochrane Library was performed in March 2020. Animal studies needed to report at least one parameter of microcirculatory flow (perfusion, red blood cell velocity, functional capillary density).

Results

The search identified 1269 records of which 48 fulfilled all eligibility criteria. In total, 62 drugs were tested of which 29 were able to restore microcirculatory perfusion. Particularly, complement inhibitors (75% of drugs tested successfully restored blood flow), endothelial barrier modulators (100% successful), antioxidants (66% successful), drugs targeting cell metabolism (83% successful), and sex hormones (75% successful) restored microcirculatory perfusion. Other drugs consisted of attenuation of inflammation (100% not successful), vasoactive agents (68% not successful), and steroid hormones (75% not successful).

Conclusion

Improving mitochondrial function, inhibition of complement inhibition, and reducing microvascular leakage via restoration of endothelial barrier function seem beneficial to restore microcirculatory perfusion following hemorrhagic shock and fluid resuscitation.

A Machine Learning-Based Model to Predict Acute Traumatic Coagulopathy in Trauma Patients Upon Emergency Hospitalization

Acute traumatic coagulopathy (ATC) is an extremely common but silent murderer; this condition presents early after trauma and impacts approximately 30% of severely injured patients who are admitted to emergency departments (EDs). Given that conventional coagulation indicators usually require more than 1 hour after admission to yield results—a limitation that frequently prevents the ability for clinicians to make appropriate interventions during the optimal therapeutic window—it is clearly of vital importance to develop prediction models that can rapidly identify ATC; such models would also facilitate ancillary resource management and clinical decision support. Using the critical care Emergency Rescue Database and further collected data in ED, a total of 1385 patients were analyzed and cases with initial international normalized ratio (INR) values >1.5 upon admission to the ED met the defined diagnostic criteria for ATC; nontraumatic conditions with potentially disordered coagulation systems were excluded. A total of 818 individuals were collected from Emergency Rescue Database as derivation cohorts, then were split 7:3 into training and test data sets. A Pearson correlation matrix was used to initially identify likely key clinical features associated with ATC, and analysis of data distributions was undertaken prior to the selection of suitable modeling tools. Both machine learning (random forest) and traditional logistic regression were deployed for prediction modeling of ATC. After the model was built, another 587 patients were further collected in ED as validation cohorts. The ATC prediction models incorporated red blood cell count, Shock Index, base excess, lactate, diastolic blood pressure, and potential of hydrogen. Of 818 trauma patients filtered from the database, 747 (91.3%) patients did not present ATC (INR ≤ 1.5) and 71 (8.7%) patients had ATC (INR > 1.5) upon admission to the ED. Compared to the logistic regression model, the model based on the random forest algorithm showed better accuracy (94.0%, 95% confidence interval [CI]: 0.922-0.954 to 93.5%, 95% CI: 0.916-0.95), precision (93.3%, 95% CI: 0.914-0.948 to 93.1%, 95% CI: 0.912-0.946), F1 score (93.4%, 95% CI: 0.915-0.949 to 92%, 95% CI: 0.9-0.937), and recall score (94.0%, 95% CI: 0.922-0.954 to 93.5%, 95% CI: 0.916-0.95) but yielded lower area under the receiver operating characteristic curve (AU-ROC) (0.810, 95% CI: 0.673-0.918 to 0.849, 95% CI: 0.732-0.944) for predicting ATC in the trauma patients. The result is similar in the validation cohort. The values for classification accuracy, precision, F1 score, and recall score of random forest model were 0.916, 0.907, 0.901, and 0.917, while the AU-ROC was 0.830. The values for classification accuracy, precision, F1 score, and recall score of logistic regression model were 0.905, 0.887, 0.883, and 0.905, while the AU-ROC was 0.858. We developed and validated a prediction model based on objective and rapidly accessible clinical data that very confidently identify trauma patients at risk for ATC upon their arrival to the ED. Beyond highlighting the value of ED initial laboratory tests and vital signs when used in combination with data analysis and modeling, our study illustrates a practical method that should greatly facilitates both warning and guided target intervention for ATC.

Superior Survival Outcomes of a Polyethylene Glycol-20k Based Resuscitation Solution in a Preclinical Porcine Model of Lethal Hemorrhagic Shock

OBJECTIVE

To compare early outcomes and 24-hour survival after LVR with the novel polyethylene glycol-20k-based crystalloid (PEG-20k), WB, or hextend in a preclinical model of lethal HS.

BACKGROUND

Posttraumatic HS is a major cause of preventable death. Current resuscitation strategies focus on restoring oxygen-carrying capacity (OCC) and coagulation with blood products. Our lab shows that PEG-20k is an effective non-sanguineous, LVR solution in acute models of HS through mechanisms targeting cell swelling-induced microcirculatory failure.

METHODS

Male pigs underwent splenectomy followed by controlled hemorrhage until lactate reached 7.5-8.5 mmol/L. They were randomized to receive LVR with PEG-20k, WB, or Hextend. Surviving animals were recovered 4 hours post-LVR. Outcomes included 24-hour survival rates, mean arterial pressure, lactate, hemoglobin, and estimated intravascular volume changes.

RESULTS

Twenty-four-hour survival rates were 100%, 16.7%, and 0% in the PEG-20k, WB, and Hextend groups, respectively (P = 0.001). PEG-20k significantly restored mean arterial press, intravascular volume, and capillary perfusion to baseline, compared to other groups. This caused complete lactate clearance despite decreased OCC. Neurological function was normal after next-day recovery in PEG-20k resuscitated pigs.

CONCLUSION

Superior early and 24-hour outcomes were observed with PEG-20k LVR compared to WB and Hextend in a preclinical porcine model of lethal HS, despite decreased OCC from substantial volume-expansion. These findings demonstrate the importance of enhancing microcirculatory perfusion in early resuscitation strategies.

Temporal Dysregulation of the Angiopoietin-2/-1 Ratio After Trauma and Associations With Injury Characteristics and Outcomes

Traumatic injury and hemorrhagic shock result in endothelial cell activation and vascular dysfunction that, if not corrected, can propagate multiorgan failure. Angiopoietin-1 and angiopoietin-2 are important regulators of endothelial cell function, and the ratio of plasma angiopoietin-2-to-1 is a useful indicator of overall vascular health. We therefore characterized plasma angiopoietin-2/-1 ratios over time after trauma in adults in an effort to gain insight into the pathophysiology that may drive post-traumatic vasculopathy and organ injury. We performed a single-center prospective observational study to measure plasma angiopoietin-1 and -2 levels and determine angiopoietin-2/-1 ratios in adult trauma patients upon hospital arrival and after 12, 24, and 48 h. Compared with levels in healthy adults, angiopoietin-1 levels were significantly elevated at hospital arrival, and angiopoietin-2 levels were significantly elevated at 12, 24, and 48 h. These kinetics translated in angiopoietin-2/-1 ratios that were significantly greater than controls at 24 and 48 h. After regression analysis, elevated angiopoietin-2 levels were independently associated with blunt injuries at admission, with coagulopathy at admission and 12 h, and with hemorrhagic shock at 24 and 48 h. Significant correlations were observed between both angiopoietins and 24-h transfusion requirements. Angiopoietin-2/-1 ratios correlated with mechanical ventilation duration and intensive care unit and hospital lengths of stay. In this study, we demonstrate novel temporal associations between angiopoietin dysregulation and blunt injuries, acute coagulopathy, and hemorrhagic shock. Moreover, our findings highlight the presence of endothelial activation following traumatic insults in adults that may contribute to worse clinical outcomes.

Effect of oxygen supplement during targeted temperature management on acute lung injury in the early stage of traumatic hemorrhagic shock

Ideal concentrations of inhaled oxygen with regard to lung protection during early traumatic hemorrhagic shock (THS) remain unknown especially in the era of targeted temperature management (TTM). We speculated that a significant increase in oxygen supply in early stage of THS would magnify the protecting role of hypothermia in acute lung injury. Forty male New Zealand rabbits were randomly divided into four groups (n = 10): sham group, control group, group 1, and group 2. Except for sham group, all other animals were submitted to 30 min of uncontrolled THS and received limited fluid resuscitation for 60 min. During resuscitation, in addition to 34°C of TTM, animals in group 1 inhaled 21% oxygen while animals in group 2 inhaled 50% oxygen. Animals in control group inhaled room air and were kept normothermia. Oxidative stress, inflammation, and apoptosis parameters in the lung tissues were determined. THS induced higher expression of malondialdehyde, surfactant protein A, nuclear factor kappa B, and caspase 3 as well as lower expression of Bcl-2 mRNA and superoxide dismutase activity. Compared with inhalation of 21% oxygen, inhalation of 50% oxygen during TTM significantly improves oxidative stress, inflammation, apoptosis, and acute lung injury. Oxygen supplement during TTM therapy alleviated acute lung injury in the early stage of THS. Further studies are required to explore the ideal combination forms of TTM and oxygen supplement with the purpose of maximizing therapeutic effect while minimizing adverse effects.

Effectiveness and safety of hypotensive resuscitation in traumatic hemorrhagic shock: A protocol for meta-analysis

BACKGROUND

Hypotensive resuscitation is an old study. But its benefits and losses are still controversial. In clinic, the method of fluid resuscitation needs more reliable experimental evidence. This study's objective is to systematically evaluate the efficacy of hypotensive resuscitation in patients with traumatic hemorrhagic shock.

METHODS AND ANALYSIS

Through October 2019, Web of Science, PubMed, the Cochrane Library, EMBASE, and Clinical Trials will be systematically searched to identify randomized controlled trials exploring the efficacy of hypotensive resuscitation in traumatic hemorrhagic shock. Strict screening and quality evaluation will be independently performed on the obtained literature by 2 researchers; outcome indexes will be extracted, and a meta-analysis will be performed on the data using Revman 5.3 software.

ETHICS AND DISSEMINATION

The stronger evidence about the efficacy of hypotensive resuscitation in traumatic hemorrhagic shock will be provided for clinicians.

TRIAL REGISTRATION NUMBER

PROSPERO CRD42019133169.

STRENGTHS OF THIS STUDY

This study is not only a simple combination of data, but also to verify and discuss the reliability of the results, and provide more convincing evidence for clinicians.

LIMITATIONS OF THIS STUDY

Firstly, according to the previous literature researching, it is found that the number of relevant randomized controlled trials is small and the quality level of the literature is uneven. Secondly, the efficacy of hypotensive resuscitation is discussed for a long time, different trials may take place at different times. Comparability between different trials is reduced.

Cremaster muscle perfusion, oxygenation, and heterogeneity revealed by a new automated acquisition system in a rodent model of prolonged hemorrhagic shock

Local blood flow/oxygen partial pressure (Po₂) distributions and flow-Po₂ relationships are physiologically relevant. They affect the pathophysiology and treatment of conditions like hemorrhagic shock (HS), but direct noninvasive measures of flow, Po₂, and their heterogeneity during prolonged HS are infrequently presented. To fill this void, we report the first quantitative evaluation of flow-Po₂ relationships and heterogeneities in normovolemia and during several hours of HS using noninvasive, unbiased, automated acquisition. Anesthetized rats were subjected to tracheostomy, arterial/venous catheterizations, cremaster muscle exteriorization, hemorrhage (40% total blood volume), and laparotomy. Control animals equally instrumented were not subjected to hemorrhage/laparotomy. Every 0.5 h for 4.5 h, noninvasive laser speckle contrast imaging and phosphorescence quenching were employed for nearly 7,000 flow/Po₂ measurements in muscles from eight animals, using an automated system. Precise alignment of 16 muscle areas allowed overlapping between flow and oxygenation measurements to evaluate spatial heterogeneity, and repeated measurements were used to estimate temporal heterogeneity. Systemic physiological parameters and blood chemistry were simultaneously assessed by blood samplings replaced with crystalloids. Hemodilution was associated with local hypoxia, but increased flow prevented major oxygen delivery decline. Adding laparotomy and prolonged HS resulted in hypoxia, ischemia, decreased tissue oxygen delivery, and logarithmic flow/Po₂ relationships in most regions. Flow and Po₂ spatial heterogeneities were higher than their respective temporal heterogeneities, although this did not change significantly over the studied period. This quantitative framework establishes a basis for evaluating therapies aimed at restoring muscle homeostasis, positively impacting outcomes of civilian and military trauma/HS victims.NEW & NOTEWORTHY This is the first study on flow-Po₂ relationships during normovolemia, hemodilution, and prolonged hemorrhagic shock using noninvasive methods in multiple skeletal muscle areas of monitored animals. Automated flow/Po₂ measurements revealed temporal/spatial heterogeneities, hypoxia, ischemia, and decreased tissue oxygen delivery after trauma/severe hemorrhage. Hemodilution was associated with local hypoxia, but hyperemia prevented a major decline in oxygen delivery. This framework provides a quantitative basis for testing therapeutics that positively impacts muscle homeostasis and outcomes of trauma/hemorrhagic shock victims.

Modeling trauma in rats: similarities to humans and potential pitfalls to consider

Trauma is the leading cause of mortality in humans below the age of 40. Patients injured by accidents frequently suffer severe multiple trauma, which is life-threatening and leads to death in many cases. In multiply injured patients, thoracic trauma constitutes the third most common cause of mortality after abdominal injury and head trauma. Furthermore, 40-50% of all trauma-related deaths within the first 48 h after hospital admission result from uncontrolled hemorrhage. Physical trauma and hemorrhage are frequently associated with complex pathophysiological and immunological responses. To develop a greater understanding of the mechanisms of single and/or multiple trauma, reliable and reproducible animal models, fulfilling the ethical 3 R's criteria (Replacement, Reduction and Refinement), established by Russell and Burch in 'The Principles of Human Experimental Technique' (published 1959), are required. These should reflect both the complex pathophysiological and the immunological alterations induced by trauma, with the objective to translate the findings to the human situation, providing new clinical treatment approaches for patients affected by severe trauma. Small animal models are the most frequently used in trauma research. Rattus norvegicus was the first mammalian species domesticated for scientific research, dating back to 1830. To date, there exist numerous well-established procedures to mimic different forms of injury patterns in rats, animals that are uncomplicated in handling and housing. Nevertheless, there are some physiological and genetic differences between humans and rats, which should be carefully considered when rats are chosen as a model organism. The aim of this review is to illustrate the advantages as well as the disadvantages of rat models, which should be considered in trauma research when selecting an appropriate in vivo model. Being the most common and important models in trauma research, this review focuses on hemorrhagic shock, blunt chest trauma, bone fracture, skin and soft-tissue trauma, burns, traumatic brain injury and polytrauma.

Deficiency of metabolite sensing receptor HCA2 impairs the salutary effect of niacin in hemorrhagic shock

Inflammation and cellular energetics play critical roles in organ dysfunction following hemorrhagic shock. Recent studies suggest a putative role for sirtuin 1 (SIRT1) in potentiating mitochondrial function and improving organ function following hemorrhagic shock in animal models. SIRT1 is an NAD⁺ dependent protein deacetylase and increased availability of NAD⁺ has been shown to augment SIRT1 activity. As niacin is a precursor of NAD⁺, in this study, we tested whether niacin can improve survival following hemorrhagic shock. However niacin also mediates its biological action by binding to its receptor, hydroxyl-carboxylic acid receptor 2 (HCA2 or Gpr109a); so we examined whether the effect of niacin is mediated by binding to Gpr109a or by increasing NAD⁺ availability. We found that niacin administered intravenously to rats subjected to hemorrhagic injury (HI) in the absence of fluid resuscitation resulted in a significantly prolonged duration of survival. However, treatment of rats with similar doses of nicotinamide mononucleotide (NMN), a precursor to NAD⁺ that does not bind Gpr109a, did not extend survival following HI. The duration of survival due to niacin treatment was significantly reduced in Gpr109a^-/- mice subjected to HI. These experiments demonstrated that the Gpr109a receptor-mediated pathway contributed significantly to niacin mediated salutary effect. Further studies showed improvement in markers of cellular energetics and attenuation of inflammatory response with niacin treatment. In conclusion, we report that Gpr109a-dependent signalling is important in restoring cellular energetics and immunometabolism following hemorrhagic shock.