EXCHANGE TRANSFUSION WITH VS -101: A NEW PEGYLATED-HB DESIGNED TO RESTORE PERFUSION AND INCREASE O 2 CARRYING CAPACITY.

ABSTRACT: Blood products are the current standard for resuscitation of hemorrhagic shock. However, logistical constraints of perishable blood limit availability and prehospital use, meaning alternatives that provide blood-like responses remain an area of active investigation and development. VS-101 is a new PEGylated human hemoglobin-based oxygen carrier that avoids the logistical hurdles of traditional blood transfusion. This study sought to determine the safety and ability of VS -101 to maintain circulatory function and capillary oxygen delivery in a severe (50%) exchange transfusion (ET) model. Anesthetized, male Sprague Dawley rats were prepared for cardiovascular monitoring and phosphorescence quenching microscopy of interstitial fluid oxygen tension (P ISFo2 ) in the spinotrapezius muscle. Fifty-percent isovolemic ET of estimated total blood volume with either lactated Ringer's solution (LRS, n = 8) or VS -101 (n = 8) at 1 mL/kg/min was performed, and animals were observed for 240 min. VS -101 maintained P ISFo2 at baseline with a transient 18 ± 4 mm Hg decrease ( P < 0.05) in mean arterial pressure (MAP). In contrast, ET with LRS decreased P ISFo2 by approximately 50% ( P < 0.05) and MAP by 74 ± 10 mm Hg ( P < 0.05). All VS -101 animals survived 240 min, the experimental endpoint, while 100% of LRS animals expired by 142 min. VS -101 animals maintained normal tissue oxygenation through 210 min, decreasing by 25% ( P < 0.05 vs. baseline) thereafter, likely from VS -101 vascular clearance. No arteriolar vasoconstriction was observed following VS -101 treatment. In this model of severe ET, VS -101 effectively maintained blood pressure, perfusion, and P ISFo2 with no vasoconstrictive effects. Further elucidation of these beneficial resuscitation effects of VS -101 is warranted to support future clinical trials.

Outcomes of Protocol-Driven Venous Thromboembolic Chemo-Prophylaxis in Trauma Patients: A Trauma Quality Improvement Project Analysis.

INTRODUCTION: Low molecular weight heparin (LMWH) is the standard for venous thromboembolic (VTE) chemo-prophylaxis in trauma patients; however, inconsistencies in the use of LMWH exist. The objective of this study was to assess VTE outcomes in response to a chemo-prophylaxis protocol guided by patient physiology (eg, creatinine clearance) and comorbidities. METHODS: ACS TQIP Benchmark Reports at a level 1 trauma center using a patient physiology and comorbidity directed VTE chemo-prophylaxis protocol were analyzed for Spring 2019 to Fall 2021. Patient demographics, VTE rates and pharmacologic VTE prophylaxis type were collected for "All Patients" and "Elderly" (TQIP: age ≥ 55 years) cohorts. RESULTS: Data was analyzed for 1919183 "All Hospitals" (AH) and 5843 patients single institution (SI) using the physiologic and comorbidity guided VTE chemo-prophylaxis protocol. Elderly subgroup had 701965 (AH) and 2939 (SI) patients. Use of non-LMWH chemo-prophylaxis was significantly higher at SI: All patients = 62.6% SI vs 22.1% (P < .01); Elderly = 68.8% SI vs 28.1% AH (P < .01). VTE, DVT, and PE rates for All Patients and Elderly subgroup were significantly reduced at SI, except Elderly PE which was statistically equivalent. CONCLUSIONS: Protocol-driven VTE chemo-prophylaxis was associated with significantly lower LMWH use accompanied by significant reductions in All VTE, DVT, PE, and Elderly VTE and DVT with no difference in Elderly PE rates. These results may imply that adherence to a physiologic and comorbidity directed chemo-prophylaxis protocol, rather than LMWH, reduces VTE events in trauma patients. Further investigation to elucidate best practice is warranted.

Thoracoscopic-assisted rib plating (TARP): initial single-center case series, including TARP in the super elderly, technical lessons learned, and proposed expanded indications.

Objectives: The application of surgical stabilization of rib fractures (SSRF) remains inconsistent due to evolving indications and perceived associated morbidity. By implementing thoracoscopic-assisted rib plating (TARP), a minimally invasive SSRF approach, we expanded our SSRF application to patients who otherwise might not be offered fixation. This report presents our initial experience, including fixation in super elderly (aged ≥85 years), and technical lessons learned. Methods: This was a retrospective cohort study at a level 1 trauma center of admitted patients who underwent TARP between August 2019 and October 2020. Patient demographics, injury characteristics, surgical indications and outcomes are represented as mean±SD, median or percentage. Results: A total of 2134 patients with rib fractures were admitted. In this group, 39 SSRF procedures were performed, of which 54% (n=21) were TARP. Average age was 68.5±16 years. Patients had a median of 5 fractured ribs, with an average of 1 rib that was bicortically displaced, and 19% presented with 'clicking' on inspiration. Patient outcomes were a mean hospital length of stay (LOS) of 11±3.7 days, mean postoperative LOS of 8 days, and mean intensive care unit LOS of 6.6±2.9 days. Five patients were ≥85 years old with a mean age of 90.8±4.7 years. They presented with an average of 4 rib fractures, of which an average of 2.4 ribs were plated. The procedure was well tolerated in this age group with a hospital LOS of 9.4±2 days, and all five patients were discharged to a rehab facility with no in-hospital mortalities. Conclusion: Our experience incorporating TARP at our institution demonstrated feasibility of the technique and application across a broad range of patients. This approach and its application warrants further evaluation and potentially expands the application of SSRF..

Venous thromboembolism prophylaxis in the trauma intensive care unit: an American Association for the Surgery of Trauma Critical Care Committee Clinical Consensus Document.

Venous thromboembolism (VTE) is a potential sequela of injury, surgery, and critical illness. Patients in the Trauma Intensive Care Unit are at risk for this condition, prompting daily discussions during patient care rounds and routine use of mechanical and/or pharmacologic prophylaxis measures. While VTE rightfully garners much attention in clinical patient care and in the medical literature, optimal strategies for VTE prevention are still evolving. Furthermore, trauma and surgical patients often have real or perceived contraindications to prophylaxis that affect the timing of preventive measures and the consistency with which they can be applied. In this Clinical Consensus Document, the American Association for the Surgery of Trauma Critical Care Committee addresses several practical clinical questions pertaining to specific or unique aspects of VTE prophylaxis in critically ill and injured patients.

Improved Hemodynamic Recovery and 72-Hour Survival Following Low-Volume Resuscitation with a PEGylated Carboxyhemoglobin in a Rat Model of Severe Hemorrhagic Shock.

INTRODUCTION: Hemorrhage is a leading cause of death from potentially survivable civilian and military trauma. As projected conflicts move from settings of tactical and logistical supremacy to hyper-dynamic tactical zones against peer and near-peer adversaries, protracted medical evacuation times are expected. Treatment at the point-of-injury is critical. Although crystalloids like Lactated Ringer's (LR) are ubiquitous, whole blood (WB) is the preferred resuscitation fluid following hemorrhage; however, logistical constraints limit the availability of WB in prehospital settings. Hemoglobin-based oxygen carriers (HBOCs) offer both hemodynamic support and oxygen-carrying capacity while avoiding logistical constraints of WB. We hypothesized that low-volume resuscitation of severe hemorrhagic shock with an HBOC (PEGylated carboxyhemoglobin, [PC]) would improve hemodynamic recovery and 72-hour survival; comparable to WB and superior to LR. MATERIALS AND METHODS: A total of 21 anesthetized male Sprague-Dawley rats underwent severe hemorrhagic shock followed by randomly assigned low-volume resuscitation with LR, WB, or PC, and then recovered from anesthesia for up to 72-hour observation. Mean arterial pressure (MAP) was recorded continuously under anesthesia, and arterial blood gases were measured at baseline (BL), 60 minutes post-hemorrhage (HS1h), and 24 hours post-resuscitation (PR24h). Survival was presented on a Kaplan-Meier plot and significance determined with a log-rank test. Cardiovascular and blood gas data were assessed with one-way analysis of variance and post hoc analysis where appropriate. RESULTS: All measured cardiovascular and blood chemistry parameters were equivalent between groups at BL and HS1h. BL MAP values were 90 ± 3, 86 ± 1, and 89 ± 2 mmHg for LR, PC, and WB, respectively. Immediately following resuscitation, MAP values were 57 ± 4, 74 ± 5, and 62 ± 3 mmHg, with PC equivalent to WB and higher than LR (P < 0.05). WB and LR were both lower than BL (P < 0.0001), whereas PC was not (P = 0.13). The PC group's survival to 72 hours was 57%, which was not different from WB (43%) and higher than LR (14%; P < 0.05). CONCLUSIONS: A single bolus infusion of PC produced superior survival and MAP response compared to LR, which is the standard fluid resuscitant carried by combat medics. PC was not different from WB in terms of survival and MAP, which is encouraging because its reduced logistical constraints make it viable for field deployment. These promising findings warrant further development and investigation of PC as a low-volume, early treatment for hemorrhagic shock in scenarios where blood products may not be available.

Prolonged Cardiopulmonary Bypass is Associated With Endothelial Glycocalyx Degradation.

BACKGROUND: The endothelial glycocalyx (EG) is involved in critical regulatory mechanisms that maintain endothelial vascular integrity. We hypothesized that prolonged cardiopulmonary bypass (CPB) may be associated with EG degradation. We performed an analysis of soluble syndecan-1 levels in relation to duration of CPB, as well as factors associated with cell stress and damage, such as mitochondrial DNA (mtDNA) and inflammation. METHODS: Blood samples from subjects undergoing cardiac surgery with CPB (n = 54) were obtained before and during surgery, 4-8 h and 24 h after completion of CPB, and on postoperative day 4. Flow cytometry was used to determine subpopulations of white blood cells. Plasma levels of mtDNA were determined using quantitative polymerase chain reaction and plasma content of shed syndecan-1 was measured. To determine whether syndecan-1 was signaling white blood cells, the effect of recombinant syndecan-1 on mobilization of neutrophils from bone marrow was tested in mice. RESULTS: CPB is associated with increased mtDNA during surgery, increased syndecan-1 blood levels at 4-8 h, and increased white blood cell count at 4-8 h and 24 h. Correlation analysis revealed significant positive associations between time on CPB and syndecan-1 (rs = 0.488, P < 0.001) and level of syndecan-1 and neutrophil count (rs = 0.351, P = 0.038) at 4-8 h. Intravenous administration of recombinant syndecan-1 in mice resulted in a 2.5-fold increase in the number of circulating neutrophils, concurrent with decreased bone marrow neutrophil number. CONCLUSIONS: Longer duration of CPB is associated with increased plasma levels of soluble syndecan-1, a signal for EG degradation, which can induce neutrophil egress from the bone marrow. Development of therapy targeting EG shedding may be beneficial in patients with prolonged CPB.

Microvascular and Systemic Impact of Resuscitation with PEGylated Carboxyhemoglobin-Based Oxygen Carrier or Hetastarch in a Rat Model of Transient Hemorrhagic Shock.

BACKGROUND: Hemorrhage is the leading cause of preventable, traumatic death. Currently, prehospital resuscitation fluids provide preload but not oxygen-carrying capacity-a critical blood function that mitigates microvascular ischemia and tissue hypoxia during hemorrhagic shock. Solutions containing polymerized hemoglobin have been associated with vasoactive and hypertensive events. A novel hemoglobin-based oxygen carrier, modified with PEGylation and CO moieties (PEG-COHb), may overcome these limitations. OBJECTIVES: To evaluate the systemic and microcirculatory effects of PEG-COHb as compared with the 6% hetastarch in a rat model of hemorrhagic shock. METHODS: Male Sprague Dawley rats (N = 20) were subjected to severe, controlled, hemorrhagic shock. Animals were randomized to 20% estimated blood-volume resuscitation with either 6% hetastarch or PEG-COHb. Continuous, invasive, cardiovascular measurements, and arterial blood gases were measured. Microcirculatory measurements of interstitial oxygenation (PISFO2) and vasoactivity helped model oxygen delivery in the spinotrapezius muscle using intravital and phosphorescence quenching microscopy. RESULTS: Hemorrhage reduced mean arterial pressure (MAP), arteriolar diameter, and PISFO2, and increased lactate 10-fold in both groups. Resuscitation with both PEG-COHb and hetastarch improved cardiovascular parameters. However, PEG-COHb treatment resulted in higher MAP (P < 0.001), improved PISFO2 (14 [PEG-COHb] vs. 5 [hetastarch] mmHg; P < 0.0001), lower lactate post-resuscitation (P < 0.01), and extended survival from 90 to 142 min (P < 0.001) as compared with the hetastarch group. CONCLUSIONS: PEG-COHb improved MAP PISFO2, lactate, and survival time as compared with 6% hetastarch resuscitation. Importantly, hypertension and vasoactivity were not detected in response to PEG-COHb resuscitation supporting further investigation of this resuscitation strategy.

'Step Up' approach to the application of REBOA technology in a rural trauma system.

Our group has developed a 'Step Up' approach to the application of Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) in a rural trauma system. This incorporates viewing REBOA as a spectrum of technology. Examples of REBOA technology use to improve outcomes and provision of our system's clinical practice guideline for the Step-Up application of REBOA technology in the care of trauma patients are presented.

Fibrinolysis Shutdown in Trauma: Historical Review and Clinical Implications.

Despite over a half-century of recognizing fibrinolytic abnormalities after trauma, we remain in our infancy in understanding the underlying mechanisms causing these changes, resulting in ineffective treatment strategies. With the increased utilization of viscoelastic hemostatic assays (VHAs) to measure fibrinolysis in trauma, more questions than answers are emerging. Although it seems certain that low fibrinolytic activity measured by VHA is common after injury and associated with increased mortality, we now recognize subphenotypes within this population and that specific cohorts arise depending on the specific time from injury when samples are collected. Future studies should focus on these subtleties and distinctions, as hypofibrinolysis, acute shutdown, and persistent shutdown appear to represent distinct, unique clinical phenotypes, with different pathophysiology, and warranting different treatment strategies.

Prehospital whole blood resuscitation prevents coagulopathy and improves acid-base status at hospital arrival in a nonhuman primate hemorrhagic shock model.

BACKGROUND: Hemorrhage remains the primary cause of preventable death in civilian and military trauma. The Committee on Tactical Combat Casualty Care recommends prehospital (PH) resuscitation with whole blood (WB). However, 6% hetastarch in lactated electrolyte (HEX) and crystalloids are more commonly available and used for PH resuscitation in military and civilian environments, respectively. The mechanistic benefits of PH WB resuscitation have not been well studied and remain to be elucidated. STUDY DESIGN AND METHODS: The aim of this study was to evaluate the differences in simulated PH WB and HEX resuscitation, specifically with regards to coagulation, physiologic, and metabolic outcomes to better elucidate the mechanistic benefits of WB. In a randomized study, the physiologic, coagulation, and metabolic responses to simulated PH WB (n = 12) or HEX (n = 12) were evaluated in a nonhuman primate model of severe polytraumatic hemorrhagic shock. RESULTS: Notable findings included 1) equivalence of shock reversal between simulated PH WB and HEX treatment groups as determined by hemodynamics and base deficit and 2) prevention of coagulopathy at simulated hospital arrival with initial WB resuscitation as determined by viscoelastic and plasmatic coagulation assays. CONCLUSION: The major benefit of WB, as compared to HEX, in simulated PH resuscitation appears to be prevention of coagulopathy at hospital arrival. Both fluids effectively reversed shock in this model, implying that efficacious provision preload (cardiac output support and hence oxygen delivery) and coagulation proteins (prevention of coagulopathy) are mechanisms underlying WB's effectiveness in early resuscitation of hemorrhagic shock.

Cerebral Blood Flow in Polytrauma: Transcranial Doppler Analysis in a Nonhuman Primate Shock Model.

BACKGROUND: In combat-related trauma, resuscitation goals are to attenuate tissue hypoxia and maintain circulation. During hemorrhagic shock, compensatory and autoregulatory mechanisms are activated to preserve cerebral blood flow. Transcranial Doppler (TCD) ultrasonography may be an ideal noninvasive modality to monitor cerebral hemodynamics. Using a nonhuman primate (NHP) model, we attempted to characterize cerebral hemodynamics during polytraumatic hemorrhagic shock using TCD ultrasonography. MATERIALS AND METHODS: The ophthalmic artery was insonated at multiple time points during varying stages of shock. Hemorrhage was controlled and pressure targeted to 20 mmHg to initiate and maintain the shock period. Mean flow velocity (MFV), peak systolic velocity (PSV), end diastolic velocity (EDV), pulsatility index (PI), and resistance index (RI) were recorded. Results represent mean ± standard deviation; statistical significance is P < 0.05; n = 12. RESULTS: Compared to baseline, MFV, PSV, EDV, and RI show significant changes after 60 min of hemorrhagic shock, (9.81 ± 3.60 cm/s; P < 0.01), (21.15 ± 8.59 cm/s; P < 0.01), (5.15 ± 0.21 cm/s; P < 0.01), (0.70 ± 0.11; P < 0.05), respectively. PI did not change during hemorrhagic shock. At end of prehospital care (T30), cerebral flow recovers for MFV, PSV, and RI while EDV remained decreased at T30 (6.15 ± 1.13 cm/s; P < 0.01) and 1 h of simulated transport (T90) (5.87 ± 0.62 cm/s; P < 0.01). Changes in PI at T30 and T90 were not significant. MFV diminished (16.45 ± 3.85 cm/s; P < 0.05) at T90. CONCLUSIONS: This study establishes baseline and hemorrhagic shock values for NHP cerebral blood flow velocities and cerebrovascular indices. TCD ultrasonography may represent an important area of research for targeted resuscitation investigations using a hemorrhagic shock model in NHPs.

Whole blood mitigates the acute coagulopathy of trauma and avoids the coagulopathy of crystalloid resuscitation.

INTRODUCTION: The contributions of type and timing of fluid resuscitation to coagulopathy in trauma remain controversial. As part of a multifunctional resuscitation fluid research effort, we sought to further characterize the coagulation responses to resuscitation, specifically as compared to whole blood. We hypothesized that early whole blood administration mitigates the acute coagulopathy of trauma by avoiding the coagulopathy of CR resuscitation. METHODS: Anesthetized rhesus macaques underwent polytraumatic, hemorrhagic shock, then a crossover study design resuscitation (n = 6 each) with either whole blood first (WB-1st) followed by crystalloid (CR); or CR-1st followed by WB. Resuscitation strategies were the following: WB-1st received 50% shed blood in 30minutes, followed by twice the shed blood volume (SBV) of CR over 30minutes and one times the SBV CR over 60minutes, where CR-1st received twice the SBV of CR over 30minutes, followed by 50% of shed blood in 30minutes, and one times the SBV CR over 60minutes. Blood samples were collected at baseline, end-of-shock, end-of-first and end-of-second resuscitation stages, and end-of-resuscitation for assessment (thromboelastometry, platelet aggregation, and plasmatic coagulation factors). Statistical analyses were conducted using two-way analysis of variance ANOVA with Bonferroni correction and t-tests; significance was at p < 0.05. RESULTS: Survival, blood loss, hemodynamics, and shock duration were equivalent between the groups. Compared to baseline, parameters measured at first and second resuscitation stage time points directly following CR infusion revealed abnormalities in thromboelastometry (clot formation time, α angle, and maximum clot firmness), platelet aggregation response (to collagen, arachidonic acid, and adenosine diphosphate), and plasmatic coagulation (prothrombin time, anti-thrombin 3, and fibrinogen), while whole blood infusion resulted in stabilization or correction of these parameters following its administration. CONCLUSIONS: These data suggest that in the setting of trauma and hemorrhagic shock, the coagulation alterations begin before intervention/resuscitation; however, these are significantly aggravated by CR resuscitation and could perhaps be best termed acute coagulopathy of resuscitation. STUDY TYPE: Translational animal model.

Nonhuman Primate (Rhesus Macaque) Models of Severe Pressure-Targeted Hemorrhagic and Polytraumatic Hemorrhagic Shock.

BACKGROUND: We endeavored to develop clinically translatable nonhuman primate (NHP) models of severe polytraumatic hemorrhagic shock. METHODS: NHPs were randomized into five severe pressure-targeted hemorrhagic shock (PTHS) ±â€Šadditional injuries scenarios: 30-min PTHS (PTHS-30), 60-min PTHS (PTHS-60), PTHS-60 + soft tissue injury (PTHS-60+ST), PTHS-60+ST + femur fracture (PTHS-60+ST+FF), and decompensated PTHS+ST+FF (PTHS-D). Physiologic parameters were recorded and blood samples collected at five time points with animal observation through T = 24 h. Results presented as mean ±â€ŠSEM; statistics: log transformation followed by two-way ANOVA with Bonferroni multiple comparisons, Wilcoxon nonparametric test for comparisons, and the Friedmans' one-way ANOVA; significance: P < 0.05. RESULTS: Percent blood loss was 40% ±â€Š2, 59% ±â€Š3, 52% ±â€Š3, 49% ±â€Š2, and 54% ±â€Š2 for PTHS-30, PTHS-60, PTHS-60+ST, PTHS-60+ST+FF, and PTHS-D, respectively. All animals survived to T = 24 h except one in each of the PTHS-60 and PTHS-60+ST+FF groups and seven in the PTHS-D group. Physiologic, coagulation, and inflammatory parameters demonstrated increasing derangements with increasing model severity. CONCLUSION: NHPs exhibit a high degree of resilience to hemorrhagic shock and polytrauma as evidenced by moderate perturbations in metabolic, coagulation, and immunologic outcomes with up to 60 min of profound hypotension regardless of injury pattern. Extending the duration of PTHS to the point of decompensation in combination with polytraumatic injury, evoked derangements consistent with those observed in severely injured trauma patients which would require ICU care. Thus, we have successfully established a clinically translatable NHP trauma model for use in testing therapeutic interventions to trauma.

Cryopreservation of human whole blood allows immunophenotyping by flow cytometry up to 30days after cell isolation.

Immunophenotyping of whole blood (WB) by flow cytometry (FC) is used clinically to assess a patient's immune status and also in biomedical research. Current protocols recommend storage of immunolabeled samples at 4°C with FC analysis to be completed within seven days. This data acquisition window can be extended to up to one year post-labeling, but this requires cryopreservation of the samples at ultra-low temperatures (≤-80°C or in liquid nitrogen). In this study we optimized a standardized cryopreservation protocol to enable preservation of immunolabeled, human WB samples at -20°C for FC and tested its effectiveness after 0, 5, 15 or 30days. Analysis of stored samples shows that this protocol effectively preserves immunolabeled WB samples and that the duration of storage has no effect on morphology, viability or frequency of WB cell subpopulations, and that the intensity of fluorescent signal from labeled extracellular markers is fully preserved for at least 15days, and up to 30days for some markers. We demonstrate that using this protocol, we are able to differentiate resting versus activated WB cells as demonstrated by detection of significantly increased expression of CD11b by myeloid cells in WB samples pretreated with LPS (100µg/mL for 12h). Finally, we show that this method allows for labeling and detection of the intracellular cytokine (IL-8) up to 30days following cryopreservation from myeloid cells, in previously labeled and cryopreserved WB samples.

Whole blood and Hextend: Bookends of modern tactical combat casualty care field resuscitation and starting point for multifunctional resuscitation fluid development.

BACKGROUND: Hemorrhage is the leading cause of preventable death in traumatically injured civilian and military populations. Prehospital resuscitation largely relies on crystalloid and colloid intravascular expansion, as whole blood and component blood therapy are logistically arduous. In this experiment, we evaluated the bookends of Tactical Combat Casualty Care Guidelines recommendations of prehospital resuscitation with Hextend and whole blood in a controlled hemorrhagic shock model within non-human primates, as means of a multifunctional resuscitative fluid development. METHODS: In the nonhuman primate, a multiple injuries model was used, consisting of a musculoskeletal injury (femur fracture), soft tissue injury (15-cm laparotomy), and controlled hemorrhage to a mean arterial pressure of 20 mm Hg, demarcating the beginning of the shock period. Animals were randomized to prehospital interventions of whole blood or Hextend at T = 0 minutes, and at T = 90 minutes definitive surgical interventions and balanced sanguineous damage control resuscitation could be implemented. All animals were euthanized at T = 480 minutes. Data are expressed as mean ± SEM; significance, p < 0.05. RESULTS: No significant differences in survival (83% vs. 100%; p = 0.3), tissue perfusion (EtCO2 and StO2) or endpoints of resuscitation (base deficit, lactate, pH) between Hextend and whole blood were identified. Second, whole blood compared with Hextend demonstrated significantly earlier normalization of clot formation time, maximal clot firmness, and α angle. CONCLUSION: A future multifunctional resuscitative fluid including an asanguineous, oncotic, non-oxygen-carrying component to facilitate intravascular volume expansion, and a component with synthetic coagulation factors and fibrinogen to deter coagulopathy may show equivalence to whole blood. LEVEL OF EVIDENCE: N/A: Study type: translational animal model.

All animals are equal but some animals are more equal than others: Plasma lactate and succinate in hemorrhagic shock-A comparison in rodents, swine, nonhuman primates, and injured patients.

BACKGROUND: Plasma levels of lactate and succinate are predictors of mortality in critically injured patients in military and civilian settings. In relative terms, these metabolic derangements have been recapitulated in rodent, swine, and nonhuman primate models of severe hemorrhage. However, no direct absolute quantitative comparison has been evaluated across these species. METHODS: Ultra-high pressure liquid chromatography-mass spectrometry with stable isotope standards was used to determine absolute concentrations of baseline and postshock levels of lactate and succinate in rats, pigs, macaques, and injured patients. RESULTS: Baseline levels of lactate and succinate were most comparable to humans in macaques, followed by pigs and rats. Baseline levels of lactate in pigs and baseline and postshock levels of lactate and succinate in rats were significantly higher than those measured in macaques and humans. Postshock levels of lactate and succinate in pigs and macaques, respectively, were directly comparable to measurements in critically injured patients. CONCLUSION: Acknowledging the caveats associated with the variable degrees of shock in the clinical cohort, our data indicate that larger mammals represent a better model than rodents when investigating metabolic derangements secondary to severe hemorrhage.

A Novel Secretome Biotherapeutic Influences Regeneration in Critical Size Bone Defects.

Severe traumatic injuries often result in critical size bone defects, which are unable to heal without treatment. Autologous grafting is the standard of care but requires additional surgeries for graft procurement. Amnion-derived multipotent progenitor cells release a secretome of biomolecules identified as integral to the process of bone regeneration and angiogenesis. This secretome is currently under development as a biotherapeutic. The efficacy of this secretome biotherapeutic was evaluated in vitro on the proliferation and migration of mesenchymal stem cells and osteoprogenitor cells as well as in vivo using a critical size rat calvarial defect model. The secretome biotherapeutic was loaded onto a collagen scaffold and placed into the defect, which was allowed to heal for 4 and 12 weeks. The secretome biotherapeutic enhanced the proliferation and migration of mesenchymal stem cells and proliferation of osteoprogenitor cells. Further, the secretome biotherapeutic improved new bone volume and connectivity by 12 weeks and significantly improved angiogenesis at 4 weeks and bone density at 4 and 12 weeks with no deleterious effects. The improvement in new bone volume, connectivity, and angiogenesis suggests that the secretome biotherapeutic has beneficial effects for bone healing and a higher dose of the secretome biotherapeutic may further improve regeneration.

Generation of complement molecular complex C5b-9 (C5b-9) in response to poly-traumatic hemorrhagic shock and evaluation of C5 cleavage inhibitors in non-human primates.

Severe trauma initiates a systemic inflammatory cascade and that involves early activation of complement and cleavage of C5 into C5a (anaphylatoxin) and C5b (C5b-9 membrane attack complex). We examined activation of C5 in non-human primate (NHP) models of hemorrhagic shock. Blood plasma concentrations of C5b-9 were significantly increased in NHPs in response to hemorrhage alone and were further increased with the addition of tissue trauma. The onset of increased C5 cleavage was accelerated in NHPs that experienced decompensated poly-traumatic hemorrhagic shock. Next, to identify an effective inhibitor of NHP C5 cleavage in vitro, as a first step in the development of a potential therapy, three inhibitors of human C5 cleavage and hemolysis were tested in vitro. NHP C5 cleavage and complement-mediated hemolysis were successfully inhibited by pre-treatment of serum samples with a small, inhibitory peptide RA101348. Commercially-available C5 inhibitory antibodies were found to exhibit species-specific efficacy in vitro. Quidel's A217 antibody demonstrated dose-dependent inhibition of C5 cleavage and hemolysis in NHP samples, whereas LGM-Eculizumab only inhibited complement-mediated hemolysis in human samples. This study shows that complement activation in NHPs following experimental poly-traumatic hemorrhagic shock is consistent with clinical reports, and that cleavage of C5 and complement-mediated hemolysis can be effectively inhibited in vitro using a small peptide inhibitor. Taken together, these findings offer a clinically-relevant vehicle and a potential strategy for treatment of hemorrhagic shock with poly-traumatic injury.

Fibrinolysis in Trauma: "Myth," "Reality," or "Something in Between".

The emphasis on fibrinolysis as an important contributor to trauma-induced coagulopathy (TIC) has led to a debate regarding the relative clinical significance of fibrinolysis in the setting of trauma. The debate has centered on two camps. The one camp defines fibrinolysis in trauma by standard coagulation tests as well as fibrin split products, D-dimers, and plasmin/antiplasmin levels. This camp favors a more liberal use of tranexamic acid and attributes more significance to hyperfibrinolysis in TIC. The other camp favors a definition of fibrinolysis based on the viscoelastic tests (VET), rotational thromboelastometry (ROTEM), and thromboelastography (TEG). These whole blood assays define hyperfibrinolysis at a higher threshold than plasma-based tests. Therefore, this VET camp reserves antifibrinolytic treatment for patients who demonstrate severe coagulopathy associated with hyperfibrinolysis. This bimodal attribution of the clinical relevance of fibrinolysis in trauma suggests that there may be an underlying "Myth" of the concept of TIC that was historically defined by plasma-based tests and a future "Reality" of the concept of TIC that is grounded on an understanding of TIC based on a VET-defined "fibrinolytic spectrum" of TIC. This narrative review explores this "Myth" and "Reality" of fibrinolysis in TIC and proposes a direction that will allow a "Future" interpretation of TIC that incorporates both the past "Myth" and present "Reality" of fibrinolysis TIC.