Splenectomy is associated with altered leukocyte kinetics after severe trauma.

BACKGROUND: Inadequate activation of the innate immune system after trauma can lead to severe complications such as Acute Respiratory Distress Syndrome and Multiple Organ Dysfunction Syndrome. The spleen is thought to modulate the cellular immune system. Furthermore, splenectomy is associated with improved outcome in severely injured trauma patients. We hypothesized that a splenectomy alters the cellular immune response in polytrauma. METHODS: All adult patients with an ISS ≥ 16 and suffering from splenic or hepatic injuries were selected from our prospective trauma database. Absolute leukocyte numbers in peripheral blood were measured. White blood cell kinetics during the first 14 days were compared between splenectomized patients, patients treated surgically for liver trauma and nonoperatively treated individuals. RESULTS: A total of 129 patients with a mean ISS of 29 were included. Admission characteristics and leukocyte numbers were similar in all groups, except for slightly impaired hemodynamic status in patients with operatively treated liver injuries. On admission, leukocytosis occurred in all groups. During the first 24 h, leukopenia developed gradually, although significantly faster in the operatively treated patients. Thereafter, leukocyte levels normalized in all nonoperatively treated cases whereas leukocytosis persisted in operatively treated patients. This effect was significantly more prominent in splenectomized patients than all other conditions. CONCLUSIONS: This study demonstrates that surgery for intra-abdominal injuries is associated with an early drop in leucocyte numbers in peripheral blood. Moreover, splenectomy in severely injured patients is associated with an altered cellular immune response reflected by a persistent state of prominent leukocytosis after trauma.

Analysis of the Plasma Metabolome after Trauma, Novel Circulating Sphingolipid Signatures, and In-Hospital Outcomes.

BACKGROUND: Trauma is the leading cause of death and disability for individuals under age 55. Many severely injured trauma patients experience complicated clinical courses despite appropriate initial therapy. We sought to identify novel circulating metabolomic signatures associated with clinical outcomes following trauma. STUDY DESIGN: Untargeted metabolomics and circulating plasma immune mediator analysis was performed on plasma collected during 3 post-injury time periods (<6 hours [h], 6 h-24h, day 2-day 5) in critically ill trauma patients enrolled between April 2004 and May 2013 at UPMC Presbyterian Hospital in Pittsburgh, PA. Inclusion criteria were age ≥ 18 years, blunt mechanism, ICU admission, and expected survival ≥ 24 h. Exclusion criteria were isolated head injury, spinal cord injury, and pregnancy. Exploratory endpoints included length of stay (overall and ICU), ventilator requirements, nosocomial infection, and Marshall organ dysfunction (MOD) score. The top 50 metabolites were isolated using repeated measures ANOVA and multivariate empirical Bayesian analysis for further study. RESULTS: Eighty-six patients were included for analysis. Sphingolipids were enriched significantly (chi-square, p < 10-6) among the top 50 metabolites. Clustering of sphingolipid patterns identified 3 patient subclasses: nonresponders (no time-dependent change in sphingolipids, n = 41), sphingosine/sphinganine-enhanced (n = 24), and glycosphingolipid-enhanced (n = 21). Compared with the sphingolipid-enhanced subclasses, nonresponders had longer mean length of stay, more ventilator days, higher MOD scores, and higher circulating levels of proinflammatory immune mediators IL-6, IL-8, IL-10, MCP1/CCL2, IP10/CXCL10, and MIG/CXCL9 (all p < 0.05), despite similar Injury Severity Scores (p = 0.12). CONCLUSIONS: Metabolomic analysis identified broad alterations in circulating plasma sphingolipids after blunt trauma. Circulating sphingolipid signatures and their association with both clinical outcomes and circulating inflammatory mediators suggest a possible link between sphingolipid metabolism and the immune response to trauma.

Distinct immunologic endotypes are associated with clinical trajectory after severe blunt trauma and hemorrhagic shock.

BACKGROUND: The genomic/cytokine "storm" after severe trauma is well described. However, the differing composition, magnitude and resolution of this response, and its relationship to clinical outcomes remain unclear. METHODS: This is a secondary analysis of a prospective longitudinal cohort study of severely injured trauma patients in hemorrhagic shock. Peripheral blood sampling was performed at 0.5, 1, 4, 7, 14, and 28 days after injury for measurement of circulating immune biomarkers. K-means clustering using overall mean and trajectory slope of selected immunologic biomarkers were used to identify distinct temporal immunologic endotypes. Endotypes were compared with known clinical trajectories defined as early death (<14 days), chronic critical illness (CCI) (ICU length of stay of ≥14 days with persistent organ dysfunction), and rapid recovery (RAP) (ICU length of stay of <14 days with organ recovery). RESULTS: The cohort included 102 subjects enrolled across 2 level 1 trauma centers. We identified three distinct immunologic endotypes (iA, iB, and iC), each with unique associations to clinical trajectory. Endotype iA (n = 47) exhibited a moderate initial proinflammatory response followed by a return to immunologic homeostasis, with a primary clinical trajectory of RAP (n = 44, 93.6%). Endotype iB (n = 44) exhibited an early hyperinflammatory response with persistent inflammation and immunosuppression, with the highest incidence of CCI (n = 10, 22.7%). Endotype iC (n = 11) exhibited a similar hyperinflammatory response, but with rapid return to immunologic homeostasis and a predominant trajectory of RAP (n = 9, 81.8%). Patients with endotype iB had the highest severity/duration of organ dysfunction and highest incidence of nosocomial infections (50%, p = 0.001), and endotype iB was the predominant endotype of patients who developed CCI (10 of 13 patients, 76.9%; p = 0.002). CONCLUSION: We identified three distinct immunologic endotypes after severe injury differing the magnitude and duration of the early response. The clinical trajectory of CCI is characterized by an endotype (iB) defined by persistent alteration in inflammation/immunosuppression and is associated with poor clinical outcomes. LEVEL OF EVIDENCE: Prognostic, level III.

May the neutrophil-to-lymphocyte ratio at admission predict the occurrence and the severity of ARDS after blunt chest trauma patients? A retrospective study.

INTRODUCTION: In blunt chest trauma patients, the activation of inflammatory response is thought to be one of the pathophysiological pathways leading to delayed acute respiratory distress syndrome(ARDS). The main objective of the study was to assess the performance of the neutrophil-lymphocyte ratio(NLR) for prediction of delayed ARDS. The secondary objective was to compare NLR in patients with traumarelated focal and non-focal ARDS. METHODS: Over a 2-year period, every adult patient triaged to our level 1 trauma center with multiple rib fractures and PaO 2 /FiO 2 ratio > 200 at admission were retrospectively included. The NLR was recorded at admission in the Emergency Department(ED). The main study outcome was the occurrence of moderate to severe ARDS within 5 days after admission according to Berlin criteria. Two phenotypes (focal and non-focal ARDS) were determined based on the closest chest CT regarding the ARDS onset. RESULTS: 216 patients were included and 42(19%) underwent moderate to severe ARDS within 5 days after ED admission (focal, N = 26 [12%] and non-focal, N = 16 [7%]). The NLR at ED admission was not statistically different between patients who developed or not a delayed ARDS (14 ± 13 vs. 11 ± 8,p = 0.095), although patients with non-focal ARDS presented higher NLR ratio than focal ARDS (21 ± 18 p < 0.0001). The AUC for NLR at ED in predicting delayed ARDS was 0.53. CONCLUSION: In blunt chest trauma patients, the NLR at ED admission was unable to predict delayed ARDS over the five first days post-injury. Although not clinically relevant, the NLR was higher in patients with non focal ARDS.

The Cutaneous Wound Innate Immunological Microenvironment.

The skin represents the first line of defense and innate immune protection against pathogens. Skin normally provides a physical barrier to prevent infection by pathogens; however, wounds, microinjuries, and minor barrier impediments can present open avenues for invasion through the skin. Accordingly, wound repair and protection from invading pathogens are essential processes in successful skin barrier regeneration. To repair and protect wounds, skin promotes the development of a specific and complex immunological microenvironment within and surrounding the disrupted tissue. This immune microenvironment includes both innate and adaptive processes, including immune cell recruitment to the wound and secretion of extracellular factors that can act directly to promote wound closure and wound antimicrobial defense. Recent work has shown that this immune microenvironment also varies according to the specific context of the wound: the microbiome, neuroimmune signaling, environmental effects, and age play roles in altering the innate immune response to wounding. This review will focus on the role of these factors in shaping the cutaneous microenvironment and how this ultimately impacts the immune response to wounding.

An Aging-Related Single-Nucleotide Polymorphism is Associated With Altered Clinical Outcomes and Distinct Inflammatory Profiles in Aged Blunt Trauma Patients.

The contribution of individual genetic determinants of aging to the adverse clinical outcomes and altered inflammation mediator networks characteristic of aged trauma patients is unknown. The AA genotype of the aging-related single-nucleotide polymorphism (SNP) rs2075650 in TOMM40 has been associated with longevity, while the AG and GG genotypes are associated with an increased risk of Alzheimer disease. Here, we studied the effect of rs2075650 on clinical outcomes and dynamic biomarker patterns after traumatic injury. Genomic DNA was obtained from blunt trauma patients admitted to the ICU and examined for 551,839 SNPs using an Illumina microarray kit. Plasma was sampled from each patient three times within the first 24 h and daily from day 1 to 7 then assayed for 31 biomarkers using Luminex. Aged patients (65-90 years) were segregated into AA (n = 77) and AG/GG (n = 17) genotypes. Additional comparisons were made with matched groups of young patients (18-30 years), controlling for injury severity score (ISS) and sex ratio, and also segregated into AA (n = 56) and AG/GG (n = 19) genotypes. Aged patients with the AA genotype had a significantly lower requirement for ventilation and fewer days on mechanical ventilation, as well as significantly higher levels of one mediator and lower levels of two mediators. Dynamic Bayesian Network inference revealed IL-23 as a central node in each network regardless of age or genotype, with MIG and IP-10 also as key mediators in the networks of the aged patients. These findings suggest that an aging-related SNP, rs2075650, may influence clinical outcomes and inflammation networks in aged patients following blunt trauma, and thus may serve as a predictive outcome biomarker in the setting of polytrauma.

Contributing factors in the development of acute lung injury in a murine double hit model.

OBJECTIVES: Blunt chest (thoracic) trauma (TxT) is known to contribute to the development of secondary pulmonary complications. Of these, acute lung injury (ALI) is common especially in multiply injured patients and might not only be due to the direct trauma itself, but seems to be caused by ongoing and multifactorial inflammatory changes. Nevertheless, the exact mechanisms and contributing factors of the development of ALI following blunt chest trauma are still elusive. METHODS: 60 CL57BL/6N mice sustained either blunt chest trauma combined with laparotomy without further interventions or a double hit (DH) including TxT and cecal ligation puncture (CLP) after 24 h to induce ALI. Animals were killed either 6 or 24 h after the second procedure. Pulmonary expression of inflammatory mediators cxcl1, cxcl5, IL-1ß and IL-6, neutrophil infiltration and lung tissue damage using the Lung Injury Score (LIS) were determined. RESULTS: Next to a moderate increase in other inflammatory mediators, a significant increase in CXCL1, neutrophil infiltration and lung injury was observed early after TxT, which returned to baseline levels after 24 h. DH induced significantly increased gene expression of cxcl1, cxcl5, IL-1ß and IL-6 after 6 h, which was followed by the postponed significant increase in the protein expression after 24 h compared to controls. Neutrophil infiltration was significantly enhanced 24 h after DH compared to all other groups, and exerted a slight decline after 24 h. LIS has shown a significant increase after both 6 and 24 h compared to both control groups as well the late TxT group. CONCLUSION: Early observed lung injury with moderate inflammatory changes after blunt chest trauma recovered quickly, and therefore, may be caused by mechanical lung injury. In contrast, lung injury in the ALI group did not undergo recovery and is closely associated with significant changes of inflammatory mediators. This model may be used for further examinations of contributing factors and therapeutic strategies to prevent ALI.

Diurnal Variation in Systemic Acute Inflammation and Clinical Outcomes Following Severe Blunt Trauma.

Animal studies suggest that the time of day is a determinant of the immunological response to both injury and infection. We hypothesized that due to this diurnal variation, time of injury could affect the systemic inflammatory response and outcomes post-trauma and tested this hypothesis by examining the dynamics of circulating inflammatory mediators in blunt trauma patients injured during daytime vs. nighttime. From a cohort of 472 blunt trauma survivors, two stringently matched sub-cohorts of moderately/severely injured patients [injury severity score (ISS) >20] were identified. Fifteen propensity-matched, daytime-inured ("mDay") patients (age 43.6 ± 5.2, M/F 11/4, ISS 22.9 ± 0.7) presented during the shortest local annual period (8:00 am-5:00 pm), and 15 propensity-matched "mNight" patients (age 43 ± 4.3, M/F 11/4, ISS 24.5 ± 2.5) presented during the shortest night period (10:00 pm-5:00 am). Serial blood samples were obtained (3 samples within the first 24 h and daily from days 1-7) from all patients. Thirty-two plasma inflammatory mediators were assayed. Two-way Analysis of Variance (ANOVA) was used to compare groups. Dynamic Network Analysis (DyNA) and Dynamic Bayesian Network (DyBN) inference were utilized to infer dynamic interrelationships among inflammatory mediators. Both total hospital and intensive care unit length of stay were significantly prolonged in the mNight group. Circulating IL-17A was elevated significantly in the mNight group from 24 h to 7 days post-injury. Circulating MIP-1α, IL-7, IL-15, GM-CSF, and sST2 were elevated in the mDay group. DyNA demonstrated elevated network complexity in the mNight vs. the mDay group. DyBN suggested that cortisol and sST2 were central nodes upstream of TGF-ß1, chemokines, and Th17/protective mediators in both groups, with IL-6 being an additional downstream node in the mNight group only. Our results suggest that time of injury affects clinical outcomes in severely injured patients in a manner associated with an altered systemic inflammation program, possibly implying a role for diurnal or circadian variation in the response to traumatic injury.

Cell-free nuclear, but not mitochondrial, DNA concentrations correlate with the early host inflammatory response after severe trauma.

Severe blunt trauma is associated with an early 'genomic storm' which causes simultaneous up- and down-regulation of host protective immunity. Excessive inflammation can lead to organ injury. In the absence of infection, the inflammatory response is presumably driven by release of endogenous alarmins called danger-associated molecular patterns (DAMPs), which initiate immune responses through pattern-recognition receptors (PRR). Here we examined the relationship between concentrations of cell-free (cf) nuclear DNA (ncDNA) and mitochondrial DNA (mtDNA) within 24 hours post trauma with circulating leukocyte transcriptomics and plasma IL-6 concentrations, as well as the patients' clinical trajectories. In 104 patients enrolled from two level-1 trauma centers, ncDNA and mtDNA concentrations were increased within 24 hours of severe trauma, but only ncDNA concentrations correlated with leukocyte gene expression and outcomes. Surprisingly, ncDNA, not mtDNA concentrations, were significantly elevated in trauma patients who developed chronic critical illness versus rapid clinical recovery. Plasma IL-6 and leukocyte transcriptomics were better predictors of outcomes than cfDNA levels. Although mtDNA and ncDNA are significantly increased in the immediate post-trauma period, the dramatic inflammatory and gene expression changes seen after severe trauma are only weakly correlated with ncDNA concentrations, and more importantly, mtDNA concentrations are not associated with adverse clinical trajectories.

Immunostimulatory functions of adoptively transferred MDSCs in experimental blunt chest trauma.

Myeloid-derived suppressor cells (MDSCs) expand during inflammation and exhibit immunomodulatory functions on innate and adaptive immunity. However, their impact on trauma-induced immune responses, characterized by an early pro-inflammatory phase and dysregulated adaptive immunity involving lymphocyte apoptosis, exhaustion and unresponsiveness is less clear. Therefore, we adoptively transferred in vitro-generated MDSCs shortly before experimental blunt chest trauma (TxT). MDSCs preferentially homed into spleen and liver, but were undetectable in the injured lung, although pro-inflammatory mediators transiently increased in the bronchoalveolar lavage (BAL). Surprisingly, MDSC treatment strongly increased splenocyte numbers, however, without altering the percentage of splenic leukocyte populations. T cells of MDSC-treated TxT mice exhibited an activated phenotype characterized by expression of activation markers and elevated proliferative capacity in vitro, which was not accompanied by up-regulated exhaustion markers or unresponsiveness towards in vitro activation. Most importantly, also T cell expansion after staphylococcal enterotoxin B (SEB) stimulation in vivo was unchanged between MDSC-treated or untreated mice. After MDSC transfer, T cells preferentially exhibited a Th1 phenotype, a prerequisite to circumvent post-traumatic infectious complications. Our findings reveal a totally unexpected immunostimulatory role of adoptively transferred MDSCs in TxT and might offer options to interfere with post-traumatic malfunction of the adaptive immune response.

Burn and thoracic trauma alters fracture healing, systemic inflammation, and leukocyte kinetics in a rat model of polytrauma.

BACKGROUND: Singular traumatic insults, such as bone fracture, typically initiate an appropriate immune response necessary to restore the host to pre-insult homeostasis with limited damage to self. However, multiple concurrent insults, such as a combination of fracture, blunt force trauma, and burns (polytrauma), are clinically perceived to result in abnormal immune response leading to inadequate healing and resolution. To investigate this phenomenon, we created a model rat model of polytrauma. METHODS: To investigate relationship between polytrauma and delayed healing, we created a novel model of polytrauma in a rat which encompassed a 3-mm osteotomy, blunt chest trauma, and full-thickness scald burn. Healing outcomes were determined at 5 weeks where the degree of bone formation at the osteotomy site of polytrauma animals was compared to osteotomy only animals (OST). RESULTS: We observed significant differences in the bone volume fraction between polytrauma and OST animals indicating that polytrauma negatively effects wound healing. Polytrauma animals also displayed a significant decrease in their ability to return to pre-injury weight compared to osteotomy animals. Polytrauma animals also exhibited significantly altered gene expression in osteogenic pathways as well as the innate and adaptive immune response. Perturbed inflammation was observed in the polytrauma group compared to the osteotomy group as evidenced by significantly altered white blood cell (WBC) profiles and significantly elevated plasma high-mobility group box 1 protein (HMGB1) at 6 and 24 h post-trauma. Conversely, polytrauma animals exhibited significantly lower concentrations of plasma TNF-alpha (TNF-α) and interleukin 6 (IL-6) at 72 h post-injury compared to OST. CONCLUSIONS: Following polytrauma with burn injury, the local and systemic immune response is divergent from the immune response following a less severe singular injury (osteotomy). This altered immune response that follows was associated with a reduced capacity for wound healing.

Neutralizing Alpha-Toxin Accelerates Healing of Staphylococcus aureus-Infected Wounds in Nondiabetic and Diabetic Mice.

Staphylococcus aureus wound infections delay healing and result in invasive complications such as osteomyelitis, especially in the setting of diabetic foot ulcers. In preclinical animal models of S. aureus skin infection, antibody neutralization of alpha-toxin (AT), an S. aureus-secreted pore-forming cytolytic toxin, reduces disease severity by inhibiting skin necrosis and restoring effective host immune responses. However, whether therapeutic neutralization of alpha-toxin is effective against S. aureus-infected wounds is unclear. Herein, the efficacy of prophylactic treatment with a human neutralizing anti-AT monoclonal antibody (MAb) was evaluated in an S. aureus skin wound infection model in nondiabetic and diabetic mice. In both nondiabetic and diabetic mice, anti-AT MAb treatment decreased wound size and bacterial burden and enhanced reepithelialization and wound resolution compared to control MAb treatment. Anti-AT MAb had distinctive effects on the host immune response, including decreased neutrophil and increased monocyte and macrophage infiltrates in nondiabetic mice and decreased neutrophil extracellular traps (NETs) in diabetic mice. Similar therapeutic efficacy was achieved with an active vaccine targeting AT. Taken together, neutralization of AT had a therapeutic effect against S. aureus-infected wounds in both nondiabetic and diabetic mice that was associated with differential effects on the host immune response.

An Enrichment Strategy Yields Seven Novel Single Nucleotide Polymorphisms Associated With Mortality and Altered Th17 Responses Following Blunt Trauma.

Trauma is the leading cause of death worldwide for individuals under the age of 55. Interpatient genomic differences, in the form of candidate single-nucleotide polymorphisms (SNPs), have been associated previously with adverse outcomes after trauma. However, the utility of these SNPs to predict outcomes based on a meaningful endpoint such as survival is as yet undefined. We hypothesized that specific SNP haplotypes could segregate trauma survivors from non-survivors. Genomic DNA samples were obtained from 453 blunt trauma patients, for whom complete daily clinical and biomarker data were available for 397. Of these, 13 patients were non-survivors and the remaining 384 were survivors. All 397 DNA samples were amplified, fragmented, and examined for 551,839 SNPs using the Illumina Infinium CoreExome-24 v1.1 BeadChip (Illumina). To enrich for likely important SNPs, we initially compared SNPs of the 13 non-survivors versus 13 matched survivors, who were matched algorithmically for injury severity score (ISS), age, and gender ratio. This initial enrichment yielded 126 SNPs; a further comparison to the haplotypes of the remaining 371 survivors yielded a final total of 7 SNPs that distinguished survivors from non-survivors. Furthermore, severely injured survivors with the same seven SNPs as non-survivor exhibited distinct inflammatory responses from similarly injured survivors without those SNPs, and specifically had evidence of altered Th17 cell phenotypes based on computational modeling. These studies suggest an interaction among genetic polymorphism, injury severity, and initial inflammatory responses in driving trauma outcomes.

MDSCs are induced after experimental blunt chest trauma and subsequently alter antigen-specific T cell responses.

Severe blunt chest trauma (TxT) induces a strong inflammatory response with posttraumatic immune suppression pointing to an impaired adaptive immune response. Since CD11b+Gr-1+-expressing myeloid-derived suppressor cells (MDSCs) are induced after inflammation and suppress T cell responses, MDSC induction and their impact on T cell functions was analysed in an experimental TxT model. MDSCs were induced preferentially in the lung until 24 hours after TxT. Although MDSC numbers were only faintly increased in the spleen, splenic MDSCs isolated after TxT strongly inhibited alloantigen-induced T cell proliferation in vitro. Suppressive activity correlated with increased expression of arginase-1 and iNOS. MDSCs also prevented antigen-induced T cell expansion in vivo, since staphylococcus enterotoxin B (SEB)-induced proliferation of vß8+ T cells was impaired in TxT mice in the presence of CD11b+Gr-1+ cells. Surprisingly, MDSCs were not involved in shifting T cells into Th2 cells, characterized by the secretion of cytokines impairing cell-mediated immunity and promoting immunosuppression. Instead, the presence of CD11b+Gr-1+ cells was required for efficient IL-2, IFN-γ and TNFα production after antigenic stimulation, indicating, that elevation of MDSCs early after traumatic injuries might contribute to restrict the initial inflammatory response by alleviating T cell expansion, however, without impeding Th1 functions.

The effect of resuscitation strategy on the longitudinal immuno-inflammatory response to blunt trauma.

INTRODUCTION: Resuscitation strategies following blunt trauma have been linked to immuno-inflammatory complications leading to systemic inflammatory syndrome (SIRS), sepsis and multiple organ failure (MOF). The effect of resuscitation strategy on longitudinal inflammation marker trajectories is, however, unknown. We hypothesized that the effect of resuscitation strategy extends beyond the trauma-related coagulopathy, perhaps affecting the longitudinal immuno-inflammatory response to injury. METHODS: We analyzed data prospectively collected for the Inflammation and Host Response to Injury (Glue Grant) study. Blood sampling for inflammation marker analyses from blunt trauma patients was done on admission days 0, 1, 4, 7, 14, 21 and 28 where applicable. Total volume transfused of packed red blood cells (PRBC), fresh frozen plasma (FFP), platelets (PLT), and crystalloids during the initial 48h was extracted, along with an analysis for an array of cytokines by Enzyme Linked Immunosorbent Assay (ELISA) technique. A within patient concentration change (WPCC) was calculated to quantify longitudinal alterations in cytokine levels, while controlling for potential confounders. To account for the multiple comparisons performed, p-values obtained from the multivariate regression model were post-hoc corrected by the false detection rate (FDR) q-value. RESULTS: No longitudinal trajectories of inflammatory markers were found to be associated with PRBC- or PLT transfusion. Three proinflammatory cytokines (Il-1ß, MIP-1ß, and TNFR2) were negatively associated with volume of FFP transfused (q=0.02, q<0.001 and q=0.007 respectively), and one proinflammatory cytokine (MIP-1ß) was positively associated with crystalloid infusion (q=0.005). CONCLUSIONS: Resuscitation strategy employed following blunt trauma has limited association to longitudinal inflammation marker trajectories, with a potential association between the strategy employed and IL-1ß, TNFR2, and MIP-1ß trajectories, respectively.

Hypercapnic Conditions After Experimental Blunt Chest Trauma Increase Efferocytosis of Alveolar Macrophages and Reduce Local Inflammation.

Blunt chest trauma induces severe local and systemic inflammatory alterations and an accumulation of apoptotic polymorphonuclear granulocytes (aPMN) in the lungs, frequently followed by bacterial infection. Alveolar macrophages (AM) represent one of the main actors for their clearance. However, little is known regarding regulatory and influencing factors of AM efferocytic and phagocytic activities. In this context, we investigated the influence of impaired gas exchange on AM activity.Male rats underwent blunt chest trauma or sham procedure and aPMN or Escherichia coli (E. coli) were instilled. Subsequently, the efferocytic and phagocytic activities were assessed by analyzing AM obtained from bronchoalveolar lavage fluids at three time points. To determine whether efferocytic and phagocytic activities of AM are affected by shifting gas concentrations, AM were subjected in vitro to hypoxic and hypercapnic conditions.Trauma significantly upregulated the capacity of AM to ingest E. coli starting 24 h after trauma, whereas the aPMN uptake rate remained virtually unchanged. In vitro, AM reacted to hypercapnic conditions by enhanced efferocytosis associated with increased release of anti-inflammatory cytokines. Additionally, phagocytosis and the pro-inflammatory reaction of AM after trauma appeared to be impaired. In contrast, hypoxic conditions displayed no regulatory effect on AM.In conclusion, blunt chest trauma enhances phagocytic activity of AM. On the other hand, hypercapnic conditions in the lungs may significantly contribute to the clearance of aPMN. The application of CO2 in clinical settings must be properly assessed, with the benefits of CO2 balanced against the detrimental effects of impaired bacterial clearance.

Clinical Evaluation of "Shock Bowel" Using Intestinal Fatty Acid Binding Protein.

"Shock bowel" is one of the computed tomographic (CT) signs of hypotension, yet its clinical implications remain poorly understood. We evaluated how shock bowel affects clinical outcomes and the extent of intestinal epithelial damage in trauma patients by measuring the level of intestinal fatty acid binding protein (I-FABP). We reviewed the initial CT scans, taken in the emergency room, of 92 patients with severe blunt torso trauma who were consecutively admitted during a 24-month period. The data collected included CT signs of hypotension, I-FABP, feeding intolerance, and other clinical outcomes. Demographic and clinical outcomes were compared in patients with and without hemodynamic shock and shock bowel. Shock bowel was found in 16 patients (17.4%); of them 7 patients (43.8%) did not have hemodynamic shock. Certain CT signs of hypotension, namely free peritoneal fluid, contrast extravasation, small-caliber aorta, and shock bowel, were significantly more common in patients with hemodynamic shock than in patients without (P < 0.05). Injury severity score and the rate of consciousness disturbance were significantly higher in patients with shock bowel than in patients without (P < 0.05). The rate of feeding intolerance and median plasma I-FABP levels were significantly higher in patients with shock bowel than in patients without (75.0% vs. 22.4%, P < 0.001 and 17.0 ng/mL vs. 3.7 ng/mL, P < 0.001, respectively). There was no difference in mortality. In conclusion, shock bowel is not always due to hemodynamic shock. It does, however, indicate severe intestinal mucosal damages and may predict feeding intolerance.

Elevated Admission Base Deficit Is Associated with a Complex Dynamic Network of Systemic Inflammation Which Drives Clinical Trajectories in Blunt Trauma Patients.

We hypothesized that elevated base deficit (BD) ≥ 4 mEq/L upon admission could be associated with an altered inflammatory response, which in turn may impact differential clinical trajectories. Using clinical and biobank data from 472 blunt trauma survivors, 154 patients were identified after excluding patients who received prehospital IV fluids or had alcohol intoxication. From this subcohort, 84 patients had a BD ≥ 4 mEq/L and 70 patients with BD < 4 mEq/L. Three samples within the first 24 h were obtained from all patients and then daily up to day 7 after injury. Twenty-two cytokines and chemokines were assayed using Luminex™ and were analyzed using two-way ANOVA and dynamic network analysis (DyNA). Multiple mediators of the innate and lymphoid immune responses in the BD ≥ 4 group were elevated differentially upon admission and up to 16 h after injury. DyNA revealed a higher, sustained degree of interconnectivity of the inflammatory response in the BD ≥ 4 patients during the initial 16 h after injury. These results suggest that elevated admission BD is associated with differential immune/inflammatory pathways, which subsequently could predispose patients to follow a complicated clinical course.

Sex-based differences in the genomic response, innate immunity, organ dysfunction, and clinical outcomes after severe blunt traumatic injury and hemorrhagic shock.

INTRODUCTION: The effect of sex on posttraumatic pathophysiology and outcomes after severe traumatic injury remains debated. We sought to determine the relationship of sex to the genomic and inflammatory responses, and clinical outcomes after hemorrhagic shock. METHODS: We analyzed blunt trauma patients in hemorrhagic shock from a prospective multi-institutional cohort study to assess for sex-based differences in the genomic response and clinical outcomes. Serially drawn blood samples were analyzed to evaluate peripheral leukocyte genomewide expression and circulating inflammatory mediators at intervals between 0.5 and 28 days after injury. Multivariate logistic regression models were developed to assess the effect of sex on outcomes after controlling for age, injury and shock severity, blood transfusion, and comorbidities. RESULTS: The cohort consisted of 1,285 (67%) male and 643 (33%) female blunt trauma patients. Injury and shock severity were similar between the two groups. There were small but statistically significant differences between males and females regarding their age, body mass index, and 12-hour blood and crystalloid administration. Organ failure was more severe in males, with slower recovery (9.0 vs. 6.5 days) in males compared to females (p < 0.01). However, there were no differences between males and females in plasma levels of IL-6, IL-8, IL-10, IL-1ß, tumor necrosis factor alpha, and monocyte chemoattractant protein 1. Multivariate analysis revealed that sex was not a significant independent risk factor for complicated recovery or 28-day mortality. Transcriptomic analysis revealed 333 genes with significant differential expression patterns between males and females (FDR, <0.001), including genes associated with general inflammation, innate immunity, cell adhesion, and cell signaling. None of the former genes were directly associated with sex hormones or X/Y chromosomes. CONCLUSION: There are sex-specific differences in the leukocyte genomic response to severe injury that are associated with more robust and longer-duration organ dysfunction. However, these expression patterns do not seem to be associated with sex-linked genes or circulating cytokine level differences, and do not translate to worsened sex-specific organ failure outcomes or inpatient mortality. LEVEL OF EVIDENCE: Prognostic/epidemiologic study, level III.