Pectoralis Muscle Index as Predictor of Outcomes in Patients With Severe Blunt Chest Wall Injury.

INTRODUCTION: Sarcopenia has been shown to portend worse outcomes in injured patients; however, little is known about the impact of thoracic muscle wasting on outcomes of patients with chest wall injury. We hypothesized that reduced pectoralis muscle mass is associated with poor outcomes in patients with severe blunt chest wall injury. METHODS: All patients admitted to the intensive care unit between 2014 and 2019 with blunt chest wall injury requiring mechanical ventilation were retrospectively identified. Blunt chest wall injury was defined as the presence of one or more rib fractures as a result of blunt injury mechanism. Exclusion criteria included lack of admission computed tomography imaging, penetrating trauma, <18 y of age, and primary neurologic injury. Thoracic musculature was assessed by measuring pectoralis muscle cross-sectional area (cm2) that was obtained at the fourth thoracic vertebral level using Slice-O-Matic software. The area was then divided by the patient height in meters2 to calculate pectoralis muscle index (PMI) (cm2/m2). Patients were divided into two groups, 1) the lowest gender-specific quartile of PMI and 2) second-fourth gender-specific PMI quartiles for comparative analysis. RESULTS: One hundred fifty-three patients met the inclusion criteria with a median (interquartile range) age 48 y (34-60), body mass index of 30.1 kg/m2 (24.9-34.6), and rib score of 3.0 (2.0-4.0). Seventy-five percent of patients (116/153) were male. Fourteen patients (8%) had prior history of chronic lung disease. Median (IQR) intensive care unit length-of-stay and duration of mechanical ventilation (MV) was 18.0 d (13.0-25.0) and 15.0 d (10.0-21.0), respectively. Seventy-three patients (48%) underwent tracheostomy and nine patients (6%) expired during hospitalization. On multivariate linear regression, reduced pectoralis muscle mass was associated with increased MV duration when adjusting for rib score and injury severity score (ß 5.98, 95% confidence interval 1.28-10.68, P = 0.013). CONCLUSIONS: Reduced pectoralis muscle mass is associated with increased duration of MV in patients with severe blunt chest wall injury. Knowledge of this can help guide future research and risk stratification of critically ill chest wall injury patients.

Tranexamic Acid Administration Does Not Alter Inflammation After Traumatic Brain Injury, Regardless of Timing.

INTRODUCTION: Tranexamic acid (TXA) administered early after traumatic brain injury (TBI) can decrease morbidity and mortality. The purpose of this study is to determine if the timing of TXA administration after TBI affects postinjury inflammatory markers or phosphorylated tau (p-tau) levels within the hippocampus. METHODS: Male mice (9-11 wk) were split into six groups based on injury and timing of TXA administration (n = 5 per group): Sham, TBI-only, 100 mg/kg TXA-only, TBI + TXA 10 min, TBI + TXA 1 h, and TBI + TXA 6 h. Moderate concussive TBI was induced via weight drop. Serum and brain homogenates were collected at 6 and 24 h postinjury and analyzed for 14 inflammatory cytokines via multiplex enzyme-linked immunosorbent assay. Serum was analyzed for glial fibrillary acidic protein levels. Additional cohorts were survived to 30 d for hippocampal p-tau quantification using immunohistochemistry. RESULTS: Serum levels of interleukin (IL) 1ß (IL-1ß), IL-3, IL-12, IL-17, monocyte chemoattractant protein-1, granulocyte-macrophage colony-stimulating factor, and regulated on activation, normal T-cell expressed and secreted were elevated in TBI mice compared to sham mice at 24 h. Levels of IL-1ß and monocyte chemoattractant protein-1 were lower in 6-h TXA-treated mice than 1-h TXA-treated mice following TBI. IL-12 and macrophage inflammatory protein-1α levels were decreased in 6-h TXA-treated mice compared to 10-min TXA-treated mice. Administration of TXA at 10 min and 6 h but not 1 h postTBI reduced serum glial fibrillary acidic protein levels compared to TBI-only mice. Hippocampal p-tau accumulation was increased after TBI but not reduced by TXA administration. CONCLUSIONS: Our results demonstrate that neither early nor delayed administration of TXA conveyed significant systemic or cerebral benefit in cytokine levels following TBI. Further research should be conducted to assess blood brain barrier integrity and neurobehavioral recovery following TXA administration postTBI.

Murine Traumatic Brain Injury Model Comparison: Closed Head Injury Versus Controlled Cortical Impact.

INTRODUCTION: Various murine models have been utilized to study TBI, including closed head injury (CHI) and controlled cortical impact (CCI), without direct comparison. The aim of our study was to evaluate these models to determine differences in neurological and behavioral outcomes postinjury. METHODS: Male C57B/6 mice (9-10 wk) were separated into six groups including: untouched, sham craniotomy (4 mm), CCI 0.9 mm depth of impact, CCI 1.6 mm, CCI 2.2 mm, and CHI. CCI was performed using a 3 mm impact tip at a velocity of 5 m/s, dwell time of 250 ms, and depth as noted above. CHI was completed with a centered 400 g weight drop from 1 cm height. Mice were survived to 14-d (n = 5 per group) and 30-d (n = 5 per group) respectively for histological analysis of p-tau within the hippocampus. These mice underwent Morris Water Maze memory testing and Rotarod motor testing. Serum was collected from a separate cohort of mice (n = 5 per group) including untouched, isoflurane only, CCI 1.6 mm, CHI at 1, 4, 6, and 24 h for analysis of neuron specific enolase and glial fibrillary acidic protein (GFAP) via ELISA. Laser speckle contrast imaging was analyzed prior to and after impact in the CHI and CCI 1.6 mm groups. RESULTS: There were no significant differences in Morris Water Maze or Rotarod testing times between groups at 14- or 30-d. P-tau was significantly elevated in all groups except CCI 1.6 mm contralateral and CCI 2.2 mm ipsilateral compared to untouched mice at 30-d. P-tau was also significantly elevated in the CHI group at 30 d compared to CCI 1.6 mm contralateral and CCI 2.2 mm on both sides. GFAP was significantly increased in mice undergoing CHI (9959 ± 91 pg/mL) compared to CCI (2299 ± 1288 pg/mL), isoflurane only (133 ± 75 pg/mL), and sham (86 ± 58 pg/mL) at 1-h post TBI (P < 0.0001). There were no differences in serum neuron specific enolase levels between groups. Laser doppler imaging demonstrated similar decreases in cerebral blood flow between CHI and CCI; however, CCI mice had a reduction in blood flow with craniotomy only that did not significantly decrease further with impact. CONCLUSIONS: Based on our findings, CHI leads to increased serum GFAP levels and increased p-tau within the hippocampus at 30-d postinjury. While CCI allows the comparison of one cerebral hemisphere to the other, CHI may be a better model of TBI as it requires less technical expertise and has similar neurological outcomes in these murine models.

Re-evaluating the Use of High Sensitivity Troponin to Diagnose Blunt Cardiac Injury.

INTRODUCTION: Blunt cardiac injury (BCI) can be challenging diagnostically, and if misdiagnosed, can lead to life-threatening complications. Our institution previously evaluated BCI screening with troponin and electrocardiogram (EKG) during a transition from troponin I to high sensitivity troponin (hsTnI), a more sensitive troponin I assay. The previous study found an hsTnI of 76 ng/L had the highest capability of accurately diagnosing a clinically significant BCI. The aim of this study was to determine the efficacy of the newly implemented protocol. METHODS: Patients diagnosed with a sternal fracture from March 2022 to April 2023 at our urban level-1 trauma center were retrospectively reviewed for EKG findings, hsTnI trend, echocardiogram changes, and clinical outcomes. The BCI cohort and non-BCI cohort ordinal measures were compared using Wilcoxon's two-tailed rank sum test and categorical measures were compared with Fisher's exact test. Youden indices were used to evaluate hsTnI sensitivity and specificity. RESULTS: Sternal fractures were identified in 206 patients, of which 183 underwent BCI screening. Of those screened, 103 underwent echocardiogram, 28 were diagnosed with clinically significant BCIs, and 15 received intervention. The peak hsTnI threshold of 76 ng/L was found to have a Youden index of 0.31. Rather, the Youden index was highest at 0.50 at 40 ng/L (sensitivity 0.79 and specificity 0.71) for clinically significant BCI. CONCLUSIONS: Screening patients with sternal fractures for BCI using hsTnI and EKG remains effective. To optimize the hsTnI threshold, this study determined the hsTnI threshold should be lowered to 40 ng/L. Further improvements to the institutional protocol may be derived from multicenter analysis.

Need for Blood Transfusion Volume Is Associated With Increased Mortality in Severe Traumatic Brain Injury.

INTRODUCTION: Many patients suffering from isolated severe traumatic brain injury (sTBI) receive blood transfusion on hospital arrival due to hypotension. We hypothesized that increasing blood transfusions in isolated sTBI patients would be associated with an increase in mortality. METHODS: We performed a trauma quality improvement program (TQIP) (2017-2019) and single-center (2013-2021) database review filtering for patients with isolated sTBI (Abbreviated Injury Scale head ≥3 and all other areas ≤2). Age, initial Glasgow Coma Score (GCS), Injury Severity Score (ISS), initial systolic blood pressure (SBP), mechanism (blunt/penetrating), packed red blood cells (pRBCs) and fresh frozen plasma (FFP) transfusion volume (units) within the first 4 h, FFP/pRBC ratio (4h), and in-hospital mortality were obtained from the TQIP Public User Files. RESULTS: In the TQIP database, 9257 patients had isolated sTBI and received pRBC transfusion within the first 4 h. The mortality rate within this group was 47.3%. The increase in mortality associated with the first unit of pRBCs was 20%, then increasing approximately 4% per unit transfused to a maximum mortality of 74% for 11 or more units. When adjusted for age, initial GCS, ISS, initial SBP, and mechanism, pRBC volume (1.09 [1.08-1.10], FFP volume (1.08 [1.07-1.09]), and FFP/pRBC ratio (1.18 [1.08-1.28]) were associated with in-hospital mortality. Our single-center study yielded 138 patients with isolated sTBI who received pRBC transfusion. These patients experienced a 60.1% in-hospital mortality rate. Logistic regression corrected for age, initial GCS, ISS, initial SBP, and mechanism demonstrated no significant association between pRBC transfusion volume (1.14 [0.81-1.61]), FFP transfusion volume (1.29 [0.91-1.82]), or FFP/pRBC ratio (6.42 [0.25-164.89]) and in-hospital mortality. CONCLUSIONS: Patients suffering from isolated sTBI have a higher rate of mortality with increasing amount of pRBC or FFP transfusion within the first 4 h of arrival.

Multi-Modal Venous ThromboembolicProphylaxis Aids in Risk Reduction Following Splenectomy in Female and Male Mice.

INTRODUCTION: Splenectomy (SPLN) is associated with elevated risk of venous thromboembolic (VTE) disease. Enoxaparin (ENX) is a low-molecular-weight heparin agent used in VTE chemoprophylaxis. Early aspirin administration ameliorates postSPLN platelet hyperaggregability in male mice. Previous literature has excluded female mice, citing potential effects of estrogen on platelet count and activation as a reason. We hypothesized that multimodal therapy using aspirin and ENX would mitigate postoperative platelet aggregability in mice across sexes. METHODS: Murine models of SPLN included both male and female mice. Treatment groups included placebo gavage, sham laparotomy, SPLN alone, SPLN and aspirin, SPLN and ENX, and SPLN with aspirin and ENX (n = 5 per group). Chemoprophylaxis dosing was initiated before SPLN. Mice were euthanized on post-operative day (POD) 1 or 3; platelet counts were obtained and blood samples were analyzed via electrical impedance aggregometry. RESULTS: Females on POD 3 following SPLN demonstrated increased platelet count compared to female mice with no treatment intervention. Male and female mice demonstrated increased adenosine diphosphate (ADP)-induced platelet aggregability on POD 3 following SPLN compared to the placebo group. Treatment with aspirin and ENX decreased this post-SPLN platelet hyperaggregability in both sexes. Females demonstrated significantly higher ADP-mediated platelet aggregability in placebo, SPLN, and SPLN with aspirin and ENX when compared to males of identical treatment groups on POD 3. CONCLUSIONS: Platelet hyperaggregability following SPLN is mediated primarily by ADP in both males and females, but higher relative aggregability is demonstrated in females. Early administration of dual-agent VTE chemoprophylaxis utilizing aspirin and ENX mitigates this hyperaggregability and may aid in VTE risk reduction across sexes.

Aberrant Oxygen Concentrations Induce Systemic Inflammation in a Murine Model.

INTRODUCTION: Hypoxia is a significant cause of secondary insult in the critically ill trauma or surgical patient. The cause of increased mortality following a brief period of hypoxia is not well understood. The aim of this study is to determine the effect of acute, isolated deviations in oxygen concentration on proinflammatory cytokine release and markers of endothelial stress in a murine model. METHODS: Mice were randomized to either control, hypoxia, or hyperoxia group. The control group was exposed to room air for 60 min, the hyperoxia group was exposed to 70% fraction of inspired oxygen, and the hypoxia group was exposed to 10% fraction of inspired oxygen for 60 min. Whole blood collection was completed via cardiac puncture. Serum concentrations of proinflammatory cytokines and endothelial stress markers were analyzed via enzyme-linked immunosorbent assay. RESULTS: Following exposure to hypoxic conditions, there was a significant increase in interleukin (IL)-1α (IL-1 α), IL-1 ß, IL-3, IL-4, IL-6, IL-10, tumor necrosis factor α . Following exposure to hyperoxic conditions, there was a significant increase in monocyte chemoattractant protein-1 and regulated upon activation normal T cell expressed and presumably secreted, as well as a significant decrease in IL-12, and IL-17. No clinically significant difference was noted in serum concentration of endothelial stress markers between the treatment groups. DISCUSSION: Exposure to oxygen extremes induces systemic inflammation as measured by proinflammatory cytokines in a murine model. Hyperoxia also demonstrates the ability to downregulate certain inflammatory pathways while inducing others. No effect on serum concentration of endothelial stress markers is observed following acute, isolated hypoxic or hyperoxic conditions.

Syndecan-1 as the Effect or Effector of the Endothelial Inflammatory Response?

INTRODUCTION: Syndecan-1 is a heparan sulfate proteoglycan found in the glycocalyx of vascular endothelial cells. Serum levels of syndecan-1 have repeatedly been demonstrated to increase following traumatic injury and shock, but it is unclear whether syndecan-1 plays an active role in the inflammatory response or is simply a biomarker of a state of hypoperfusion. The aim of this study was to identify the role of syndecan-1 role in the inflammatory process in the absence of trauma. METHODS: Male mice were randomized into five groups (n = 3). Four groups received increasing concentrations of syndecan-1 (1, 10, 100, and 1000pg/mL per blood volume) and a fifth group was given normal saline as a control via intravenous injection. These concentrations were selected based on previous syndecan-1 enzyme-linked immunosorbent assay data acquired following induced hemorrhagic shock in mice resulting in serum levels of 10-6000 pg/mL. Mice from each group were sacrificed at 1-, 4-, and 24-h time points for serum biomarker evaluation. A multiplex enzyme-linked immunosorbent assay was performed to analyze proinflammatory cytokines and chemokines including interleukin (IL)-1a, IL-1b, IL-2, IL-3, IL-4, IL-6, IL-10, IL-12, IL-17, monocyte chemoattractant protein-1, TNF-α, macrophage inflammatory protein-1α, granulocyte-macrophage colony-stimulating factor, and normal T cell expressed and presumably secreted levels. Whole blood was analyzed via rotational thromboelastometry in a separate group of mice dosed with syndecan-1 at 1000 pg/mL and compared to sham mice at 1 h. RESULTS: Tumor necrosis factor-α was significantly elevated in the 1000 pg/mL group compared to sham animals. There were no significant changes in IL-1a, IL-1b, IL-2, IL-3, IL-4, IL-6, IL-10, IL-12, monocyte chemoattractant protein--1, macrophage inflammatory protein-1α, granulocyte-macrophage colony-stimulating factor, or normal T cell expressed and presumably secretedat 1, 4, and 24 h for any group when compared to mice receiving saline alone. No significant differences were noted in coagulability between the 1000 pg/mL syndecan-1 group and shams at 1 h CONCLUSIONS: Inflammatory cytokine concentrations did not change with increasing dosage of syndecan-1 within mice at any timepoint, except for an acute change in tumor necrosis factor-α which was transient. Based on our results, syndecan-1 appears to be a biomarker for inflammation rather than an active participant in eliciting an inflammatory response. Further research will focus on the role of syndecan-1 following hemorrhagic shock.

Validation of Preload Assessment Technologies at Altitude in a Porcine Model of Hemorrhage.

INTRODUCTION: Dynamic preload assessment measures including pulse pressure variation (PPV), stroke volume variation (SVV), pleth variability index (PVI), and hypotension prediction index (HPI) have been utilized clinically to guide fluid management decisions in critically ill patients. These values aid in the balance of correcting hypotension while avoiding over-resuscitation leading to respiratory failure and increased mortality. However, these measures have not been previously validated at altitude or in those with temporary abdominal closure (TAC). METHODS: Forty-eight female swine (39 ± 2 kg) were separated into eight groups (n = 6) including all combinations of flight versus ground, hemorrhage versus no hemorrhage, and TAC versus no TAC. Flight animals underwent simulated aeromedical evacuation via an altitude chamber at 8000 ft. Hemorrhagic shock was induced via stepwise hemorrhage removing 10% blood volume in 15-min increments to a total blood loss of 40% or a mean arterial pressure of 35 mmHg. Animals were then stepwise transfused with citrated shed blood with 10% volume every 15 min back to full blood volume. PPV, SVV, PVI, and HPI were monitored every 15 min throughout the simulated aeromedical evacuation or ground control. Blood samples were collected and analyzed for serum levels of serum IL-1ß, IL-6, IL-8, and TNF-α. RESULTS: Hemorrhage groups demonstrated significant increases in PPV, SVV, PVI, and HPI at each step compared to nonhemorrhage groups. Flight increased PPV (P = 0.004) and SVV (P = 0.003) in hemorrhaged animals. TAC at ground level increased PPV (P < 0.0001), SVV (P = 0.0003), and PVI (P < 0.0001). When TAC was present during flight, PPV (P = 0.004), SVV (P = 0.003), and PVI (P < 0.0001) values were decreased suggesting a dependent effect between altitude and TAC. There were no significant differences in serum IL-1ß, IL-6, IL-8, or TNF-α concentration between injury groups. CONCLUSIONS: Based on our study, PPV and SVV are increased during flight and in the presence of TAC. Pleth variability index is slightly increased with TAC at ground level. Hypotension prediction index demonstrated no significant changes regardless of altitude or TAC status, however this measure was less reliable once the resuscitation phase was initiated. Pleth variability index may be the most useful predictor of preload during aeromedical evacuation as it is a noninvasive modality.

Just Say NO: Inhaled Nitric Oxide Effect on Respiratory Parameters Following Traumatic Brain Injury in Humans and a Porcine Model.

INTRODUCTION: The mechanism of post-traumatic brain injury (TBI) hypoxemia involves ventilation/perfusion mismatch and loss of pulmonary hypoxic vasoconstriction. Inhaled nitric oxide (iNO) has been studied as an adjunct treatment to avoid the use of high positive end-expiratory pressure and inspired oxygen in treatment-refractory hypoxia. We hypothesized that iNO treatment following TBI would improve systemic and cerebral oxygenation via improved matching of pulmonary perfusion and ventilation. METHODS: Thirteen human patients with isolated TBI were enrolled and randomized to receive either placebo or iNO with measured outcomes including pulmonary parameters, blood gas data, and intracranial pressure (ICP) /perfusion. To complement this study, a porcine model of TBI (including 10 swine) was utilized with measured outcomes of brain tissue blood flow and oxygenation, ventilator parameters, and blood gas data both after administration and following drug removal and clearance. RESULTS: There were no clinically significant changes in pulmonary parameters in either the human or porcine arm following administration of iNO when compared to either the placebo group (human arm) or the internal control (porcine arm). Analysis of pooled human data demonstrated the preservation of alveolar recruitment in TBI patients. There were no clinically significant changes in human ICP or cerebral perfusion pressure following iNO administration compared to controls. CONCLUSIONS: iNO had no significant effect on clinically relevant pulmonary parameters or ICPs following TBI in both human patients and a porcine model. The pressure-based recruitment of the human lungs following TBI was preserved. Further investigation will be needed to determine the degree of utility of iNO in the setting of hypoxia after polytrauma.

Desmopressin, Misoprostol, nor Carboprost Affect Platelet Aggregability Following Traumatic Brain Injury and Aspirin.

INTRODUCTION: Desmopressin (DDAVP) has been utilized clinically in patients taking aspirin (ASA) to improve drug-induced platelet dysfunction. Misoprostol and carboprost, prostaglandin analogs commonly used for postpartum hemorrhage, may also induce platelet aggregation. The aim of this study was to determine the effects of DDAVP, misoprostol, and carboprost administration on platelet aggregability following traumatic brain injury (TBI) in mice treated with ASA. METHODS: Male C57BL/6 mice were randomized into seven groups (n = 5 each): untouched, ASA only, Saline/TBI, ASA/TBI, ASA/TBI/DDAVP 0.4 µg/kg, ASA/TBI/misoprostol 1 mg/kg, and ASA/TBI/carboprost 100 µg/kg. TBI was induced via a weight drop model 4-h after ASA (50 mg/kg) gavage. Mice were given an intraperitoneal injection of DDAVP, misoprostol, or carboprost 10 minutes after TBI. In vivo testing was completed utilizing tail vein bleed. Mice were sacrificed 30-min posttreatment and blood was collected via cardiac puncture. Whole blood was analyzed via Multiplate impedance aggregometry, rotational thromboelastometry, and TEG6s. RESULTS: Mice receiving misoprostol after ASA/TBI demonstrated decreased tail vein bleeding times compared to ASA only treated mice. However, mice treated with misoprostol following ASA and TBI demonstrated decreased platelet aggregability compared to untouched mice and TBI only mice within the arachidonic acid agonist pathway. By contrast, DDAVP and carboprost did not significantly change platelet aggregability via adenosine diphosphate or arachidonic acid following ASA and TBI. However, DDAVP did decrease the platelet contribution to clot via rotational thromboelastometry. CONCLUSIONS: Reversal of medication-induced platelet inhibition has become increasingly controversial after TBI. Based on these results, DDAVP, misoprostol, nor carboprost consistently improve platelet aggregability following TBI in those also treated with ASA.

Evaluating the Utility of High Sensitivity Troponin in Blunt Cardiac Injury.

INTRODUCTION: Screening for blunt cardiac injury (BCI) includes obtaining a serum troponin level and an electrocardiogram for patients diagnosed with a sternal fracture. Our institution has transitioned to the use of a high sensitivity troponin I (hsTnI). The aim of this study was to determine whether hsTnI is comparable to troponin I (TnI) in identifying clinically significant BCI. MATERIALS AND METHODS: Trauma patients presenting to a level I trauma center over a 24-mo period with the diagnosis of sternal fracture were screened for BCI. Any initial TnI more than 0.04 ng/mL or hsTnI more than 18 ng/L was considered positive for potential BCI. Clinically significant BCI was defined as a new-bundle branch block, ST wave change, echocardiogram change, or need for cardiac catheterization. RESULTS: Two hundred sixty five patients with a sternal fracture were identified, 161 underwent screening with TnI and 104 with hsTnI. For TnI, the sensitivity and specificity for detection of clinically significant BCI was 0.80 and 0.79, respectively. For hsTnI, the sensitivity and specificity for detection of clinically significant BCI was 0.71 and 0.69, respectively. A multivariate analysis demonstrated the odds ratio for significant BCI with a positive TnI was 14.4 (95% confidence interval, 3.9-55.8, P < 0.0001) versus an odds ratio of 5.48 (95% confidence interval 1.9-15.7, P = 0.002) in the hsTnI group. CONCLUSIONS: The sensitivity of hsTnI is comparable to TnI for detection of significant BCI. Additional investigation is needed to determine the necessity and interval for repeat testing and the need for additional diagnostic testing.

Predictive Value of Early Inflammatory Markers in Trauma Patients Based on Transfusion Status.

INTRODUCTION: Seven key inflammatory biomarkers were recently found to be associated with the risk of mortality in a multicenter study of massively transfused patients. The aim of this prospective single-center study was to determine which of these early inflammatory markers could predict 30-d mortality among all critically injured trauma patients. METHODS: Serum samples were collected at 6, 24, and 72 h from 238 consecutive patients admitted to the intensive care unit following traumatic injury. Inflammatory markers syndecan-1, eotaxin, IL-1ra, IL-6, IL-8, IL-10, IP-10, and MCP-1 were analyzed via multiplex enzyme-linked immunosorbent assay. Subgroup analysis was performed for patients undergoing massive transfusion (≥5 red blood cells), submassive transfusion (1-4 red blood cells), or no transfusion during the first 4 h postinjury. The primary outcome of 30-d survival was modeled as a function of each biomarker and confounders using repeat measures logistic regression. RESULTS: Patients had a median age of 51.3 y [33.7, 70.2], 70.6% were male, 17.4% experienced penetrating trauma, and had a median injury severity score of 22 [14, 33]. IL-1ra, IL-8, IL-10, and MCP-1 were significantly increased during the first 72 h in nonsurvivors (n = 31). Elevated IL-1ra, IL-8, IL-10, and MCP-1 at 6 h postinjury were associated with 30-d mortality. By contrast, serum syndecan-1 and eotaxin levels were not associated with mortality at any time point. IL-8 and lactate were increased at 6 h in 30-d nonsurvivors for patients receiving submassive transfusion (n = 78). CONCLUSIONS: Early evaluations of IL-1ra, IL-8, IL-10, and IP-10 within 6 h of injury are useful predictors of 30-d mortality. Subgroup analysis suggests that transfusion status does not significantly affect early inflammatory markers. LEVEL OF EVIDENCE: Level III, prognostic/epidemiological.

Aspirin Administration Mitigates Platelet Hyperaggregability After Splenectomy in a Murine Model.

INTRODUCTION: Patients who undergo splenectomy (SPLN) have an estimated 10%-35% risk of venous thromboembolic events; however, the underlying mechanism and strategy for prevention have yet to be identified. The goals of this study were to 1) investigate platelet aggregation after SPLN, 2) examine if aspirin administration could mitigate this effect, and 3) determine if concomitant hemorrhage would affect post-SPLN platelet function and response to aspirin. METHODS: Murine models of operative SPLN and submandibular bleed (SMB) were utilized. Mice were randomized to eight groups as follows: untouched, SPLN, sham (laparotomy only), SMB, SPLN + SMB, SPLN + aspirin (ASA), SMB + ASA, and SPLN + SMB + ASA. Aspirin (50 mg/kg) was administered on postoperative days (PODs) one and two via oral gavage. Mice were euthanized on POD 3, platelet counts were obtained, and blood samples were analyzed via rotational thromboelastometry and impedance aggregometry with adenosine diphosphate (ADP) and arachidonic acid (AA) as agonists. RESULTS: By POD 3, SPLN mice displayed a significant thrombocytosis compared to untouched, SMB, and sham SPLN mice. Clotting time and clot formation time were significantly decreased in SPLN and SPLN + SMB cohorts compared to untouched and sham controls with elevated mean clot firmness. SPLN mice also displayed a significant increase in ADP- and AA-mediated platelet aggregability compared to untouched controls, SMB, and SPLN + SMB. ASA significantly decreased platelet aggregation via both ADP and AA signaling in SPLN and SPLN + SMB cohorts without affecting viscoelastic coagulation testing. CONCLUSIONS: Platelet hyperaggregability after SPLN is mediated by both ADP and AA signaling. Early aspirin administration may prevent increased platelet aggregation exacerbated after polytrauma.

Postinjury Treatment to Mitigate the Effects of Aeromedical Evacuation After Traumatic Brain Injury in a Porcine Model.

INTRODUCTION: Early aeromedical evacuation after traumatic brain injury (TBI) has been associated with worse neurologic outcomes in murine studies and military populations. The goal of this study was to determine if commonly utilized medications, including allopurinol, propranolol, or tranexamic acid (TXA), could mitigate the secondary traumatic brain injury experienced during the hypobaric and hypoxic environment of aeromedical evacuation. METHODS: Porcine TBI was induced via controlled cortical injury. Twenty nonsurvival pigs were separated into four groups (n = 5 each): TBI+25 mL normal saline (NS), TBI+4 mg propranolol, TBI+100 mg allopurinol, and TBI+1g TXA. The pigs then underwent simulated AE to an altitude of 8000 ft for 4 h with an SpO2 of 82-85% and were sacrificed 4 h later. Hemodynamics, serum cytokines, and hippocampal p-tau accumulation were assessed. An additional survival cohort was partially completed with TBI/NS (n = 5), TBI/propranolol (n = 2) and TBI/allopurinol groups (n = 2) survived to postinjury day 7. RESULTS: There were no significant differences in hemodynamics, tissue oxygenation, cerebral blood flow, or physiologic markers between treatment groups and saline controls. Transient differences in IL-1b and IL-6 were noted but did not persist. Neurological Severity Score (NSS) was significantly lower in the TBI + allopurinol group on POD one compared to NS and propranolol groups. P-tau accumulation was decreased in the nonsurvival animals treated with allopurinol and TXA compared to the TBI/NS group. CONCLUSIONS: Allopurinol, propranolol, and TXA, following TBI, do not induce adverse changes in systemic or cerebral hemodynamics during or after a simulated postinjury flight. While transient changes were noted in systemic cytokines and p-tau accumulation, further investigation will be needed to determine any persistent neurological effects of injury, flight, and pharmacologic treatment.

Direct red blood cell effect on thrombosis is dependent on the interaction of tissue factor and calcium with membrane phosphatidylserine.

BACKGROUND: Prior literature has implicated red blood cells (RBCs) in the initiation of thrombosis and suggests that posttransfusion hypercoagulability may occur secondary to the effects of RBCs. Elevated serum tissue factor is a known sequelae of acute trauma. Phosphatidylserine (PS) is a prothrombotic phospholipid present within the RBC cell membrane. We hypothesized that RBC aggregation is dependent on the interaction between RBC membrane bound (exposed) PS, extracellular calcium, and tissue factor. METHODS: Human whole blood (WB) was separated into components, including RBCs and platelet-rich plasma (PRP). Whole blood, PRP, and RBCs underwent impedance aggregometry utilizing arachidonic acid (AA), ADP, collagen, calcium, and tissue factor (TF)-based agonists. Red blood cells then underwent impedance aggregometry utilizing combined calcium and TF agonists. Red blood cells were pretreated with Annexin V, a known PS blocking agent, and underwent impedance aggregometry with combined calcium and TF agonists to determine if the mechanism of calcium/TF-induced RBC aggregability is dependent on PS. Red blood cells treated with calcium, TF, calcium+TF, and pre-treated with Annexin V followed by calcium+TF were perfused through an in vitro model of pulmonary microcirculatory flow. RESULTS: Red blood cell aggregation was significantly higher than that of WB and PRP when utilizing a TF agonist, an effect unique to TF. The combination of calcium and TF demonstrated significantly higher RBC aggregation than either agonist alone. Pretreatment with Annexin V resulted in a significantly reduced aggregability of RBC following treatment with TF + calcium. Red blood cells aged to 42 days did not exhibit significant change in aggregation. Exposure to calcium and TF significantly reduced time to thrombosis of RBCs perfused through a pulmonary microcirculatory model. CONCLUSION: Treatment with both TF and calcium synergistically induces RBC aggregation. Phosphatidylserine appears to play an integral role in the TF/calcium-based, age-independent RBC aggregation response. Red blood cells treated with TF + calcium exhibit more rapid thrombus formation in an in vitro model of pulmonary microcirculatory perfusion.

Hypobaria During Aeromedical Evacuation and Systemic Inflammation after Porcine Traumatic Brain Injury.

BACKGROUND: Traumatic brain injury (TBI)-related morbidity is caused largely by secondary injury resulting from hypoxia, excessive sympathetic drive, and uncontrolled inflammation. Aeromedical evacuation (AE) is utilized by the military for transport of wounded soldiers to higher levels of care. We hypothesized that the hypobaric, hypoxic conditions of AE may exacerbate uncontrolled inflammation following TBI that could contribute to more severe TBI-related secondary injury. STUDY DESIGN: Thirty-six female pigs were used to test TBI vs. TBI sham, hypoxia vs. normoxia, and hypobaria vs. ground conditions. TBI was induced by controlled cortical injury, hypobaric conditions of 12,000 feet were established in an altitude chamber, and hypoxic exposure was titrated to 85% SpO2 while at altitude. Serum cytokines, UCH-L1 and TBI biomarkers were analyzed via ELISA. Gross analysis and staining of cortex and hippocampus tissue was completed for glial fibrillary acidic protein (GFAP) and phosphorylated tau (p-tau). RESULTS: Serum IL-1b, IL-6, and TNFα were significantly elevated following TBI in pigs exposed to altitude-induced hypobaria/hypoxia, as well as hypobaria alone, compared to ground level/normoxia. No difference in TBI biomarkers following TBI or hypobaric, hypoxic exposure was noted. No difference in brain tissue GFAP or p-tau when comparing the most different conditions of sham TBI+ground/normoxia to the TBI+hypobaria/hypoxia group was noted. CONCLUSION: The hypobaric environment of AE induces systemic inflammation following TBI. Severe inflammation may play a role in exacerbating secondary injury associated with TBI and contribute to worse neurocognitive outcomes. Measures should be taken to minimize barometric and oxygenation changes during AE following TBI.

Blood component resuscitative strategies to mitigate endotheliopathy in a murine hemorrhagic shock model.

BACKGROUND: Resuscitation with plasma components has been shown to improve endotheliopathy induced by hemorrhagic shock, but the optimal resuscitation strategy to preserve the endothelial glycocalyx has yet to be defined. The aim of this study was to determine if resuscitation with lactated Ringer's (LR), whole blood (WB), packed red blood cells (RBCs), platelet-rich plasma (PRP), platelet poor plasma, balanced RBC:PRP (1:1), or day 14 (d14) RBC would best minimize endothelial damage following shock. METHODS: Male C57BL/6 mice were hemorrhaged to a goal mean arterial pressure of 25 mm Hg for 1 hour. Unshocked sham mice served as controls. Mice were then resuscitated with equal volumes of LR, WB, RBC, PRP, platelet poor plasma, 1:1, or d14 RBC and then sacrificed at 1, 4, or 24 hours (n = 5). Serum was analyzed for syndecan-1, ubiquitin C-terminal hydrolase L1, and cytokine concentrations. Lungs underwent syndecan-1 immunostaining, and lung injury scores were calculated after hematoxylin and eosin. Proteolytic cleavage of the endothelial glycocalyx was assessed by serum matrix metalloprotease 9 levels. RESULTS: Serum syndecan-1 and ubiquitin C-terminal hydrolase L1 levels were significantly increased following resuscitation with d14 RBC compared with other groups. Early elevation in lung syndecan-1 staining was noted in LR-treated mice, while d14 mice showed decreased staining compared with sham mice following shock. Lung injury scores were significantly elevated 4 hours after resuscitation with LR and d14 RBC compared with WB. Serum matrix metalloprotease 9 levels were significantly increased at 1 and 4 hours in d14 mice compared with sham mice. Systemic inflammation was increased in animals receiving LR, 1:1, or d14 RBC. CONCLUSION: Resuscitation with WB following hemorrhagic shock reduces endothelial syndecan-1 shedding and mitigates lung injury. Aged RBC and LR fail to attenuate endothelial injury following hemorrhagic shock. Further research will be necessary to determine the effect of each of these resuscitative fluids in a hemorrhagic shock model with the addition of tissue injury.

Platelet dysfunction persists after trauma despite balanced blood product resuscitation.

BACKGROUND: Platelet activation and aggregation are critical to the initiation of hemostasis after trauma with hemorrhage. Platelet dysfunction is a well-recognized phenomenon contributing to trauma-induced coagulopathy. The goal of this study was to evaluate the timing and severity of platelet dysfunction in massively transfused, traumatically injured patients during the first 72 hours after injury and its association with 30-day survival. METHODS: A retrospective secondary cohort study of platelet count and function was performed using samples from the Pragmatic Randomized Optimal Platelet and Plasma Ratios trial. Platelet characteristics were measured at 8 timepoints during the first 72 hours of hospitalization and compared between 30-day survivors and nonsurvivors. Platelet counts were assessed via flow cytometry. Platelet function was analyzed with the use of serial thrombelastography and impedance aggregometry with agonists arachidonic acid, adenosine diphosphate, collagen, thrombin receptor activating peptide, and ristocetin. RESULTS: In total, 680 patients were included for analysis. Platelet counts were significantly lower from baseline to 72 hours after hospital admission with further 1.3 to 2-fold reductions noted in nonsurvivors compared to survivor patients. Platelet aggregation via adenosine diphosphate, arachidonic acid, collagen, thrombin receptor activating peptide, and ristocetin was significantly lower in nonsurvivors at all time points. The nadir of platelet aggregation was 2 to 6 hours after admission with significant improvements in viscoelastic maximum clot formation and agonist-induced aggregation by 12 hours without concomitant improvement in platelet count. CONCLUSION: Platelet aggregability recovers 12 hours after injury independent of worsening thrombocytopenia. Failure of platelet function to recover portends a poor prognosis.

Effectiveness of Negative Pressure Wound Therapy During Aeromedical Evacuation Following Soft Tissue Injury and Infection.

INTRODUCTION: Negative pressure wound therapy (NPWT) is utilized early after soft tissue injury to promote tissue granulation and wound contraction. Early post-injury transfers via aeromedical evacuation (AE) to definitive care centers may actually induce wound bacterial proliferation. However, the effectiveness of NPWT or instillation NPWT in limiting bacterial proliferation during post-injury AE has not been studied. We hypothesized that instillation NPWT during simulated AE would decrease bacterial colonization within simple and complex soft tissue wounds. METHODS: The porcine models were anesthetized before any experiments. For the simple tissue wound model, two 4-cm dorsal wounds were created in 34.9 ± 0.6 kg pigs and were inoculated with Acinetobacter baumannii (AB) or Staphylococcus aureus 24 hours before a 4-hour simulated AE or ground control. During AE, animals were randomized to one of the five groups: wet-to-dry (WTD) dressing, NPWT, instillation NPWT with normal saline (NS-NPWT), instillation NPWT with Normosol-R® (NM-NPWT), and RX-4-NPWT with the RX-4 system. For the complex musculoskeletal wound, hind-limb wounds in the skin, subcutaneous tissue, peroneus tertius muscle, and tibia were created and inoculated with AB 24 hours before simulated AE with WTD or RX-4-NPWT dressings. Blood samples were collected at baseline, pre-flight, and 72 hours post-flight for inflammatory cytokines interleukin (IL)-1ß, IL-6, IL-8 and tumor necrosis factor alpha. Wound biopsies were obtained at 24 hours and 72 hours post-flight, and the bacteria were quantified. Vital signs were measured continuously during simulated AE and at each wound reassessment. RESULTS: No significant differences in hemodynamics or serum cytokines were noted between ground or simulated flight groups or over time in either wound model. Simulated AE alone did not affect bacterial proliferation compared to ground controls. The simple tissue wound arm demonstrated a significant decrease in Staphylococcus aureus and AB colony-forming units at 72 hours after simulated AE using RX-4-NPWT. NS-NPWT during AE more effectively prevented bacterial proliferation than the WTD dressing. There was no difference in colony-forming units among the various treatment groups at the ground level. CONCLUSION: The hypoxic, hypobaric environment of AE did not independently affect the bacterial growth after simple tissue wound or complex musculoskeletal wound. RX-4-NPWT provided the most effective bacterial reduction following simulated AE, followed by NS-NPWT. Future research will be necessary to determine ideal instillation fluids, negative pressure settings, and dressing change frequency before and during AE.