Systemic Inflammatory Response Syndrome and Nosocomial Infection in Trauma

Impact of withholding early antibiotic therapy in nonseptic surgical patients with suspected nosocomial infection: a retrospective cohort analysis

BACKGROUND

Systemic inflammatory responses mimicking infectious complications are often present in surgical patients.

METHODS

The objective was to assess the association between withholding early antimicrobial therapy while investigating alternative diagnoses and worse outcomes in nonseptic patients with suspected nosocomial infection in a retrospective cohort of critically ill surgical patients. The initiation of antibiotic therapy within 24 h of the suspicion of infection was defined as the Early Empirical Antibiotic strategy (EEA) group and the initiation after 24 h of suspicion or not prescribed was defined as the Conservative Antibiotic strategy (CA) group. Primary outcome was composite: death, sepsis, or septic shock within 14 days. Main exclusion criteria were sepsis or an evident source of infection at inclusion.

RESULTS

Three hundred and forty patients were eligible for inclusion (74% trauma patients). Age, sex, reason for hospital admission, SAPS3 score, SOFA score, and use of vasopressors or mechanical ventilation were not different between the groups. Within 14 days of inclusion, 100% (130/130) of EEA patients received antibiotics compared to 57% (120/210) of CA patients. After adjusting for confounding variables, there was no association between primary outcome and the groups. In a post hoc subgroup analysis including only patients with a posteriori confirmed infection (by microbiological cultures), delay in initiation of adequate antimicrobial therapy was independently associated with the primary outcome (Odds Ratio = 1.19 per day of delay; 95% CI 1.05-1.37).

CONCLUSIONS

Withholding early empiric antibiotic therapy was not associated with progression of organ dysfunction within 14 days in nonseptic surgical patients with suspected nosocomial infection without an obvious source.

Association of antimicrobial use and incidence of hospital-acquired pneumonia in critically ill trauma patients with pulmonary contusion: an observational study

BACKGROUND

Pneumonia occurs in about 20% of trauma patients with pulmonary contusions. This study aims to evaluate the association between empirical antibiotic therapy and nosocomial pneumonia in this population.

METHODS

Retrospective cohort of adult patients admitted to a trauma-surgical ICU. The Antibiotic Therapy Group (ATG) was defined by intravenous antibiotic use for more than 48 h starting on hospital admission, while the Conservative Group (CG) was determined by antibiotic use no longer than 48 h. Primary outcome was microbiologically documented nosocomial pneumonia within 14 days after hospital admission. Logistic regression was used to estimate the association between group allocation and primary outcome. Exploratory analyses evaluating the association between resistant strains in pneumonia and antibiotic use were performed.

RESULTS

The study included 177 patients with chest trauma and pulmonary contusion on CT scan. ATG were more severely ill than CG, as shown by higher Injury Severity Score, SAPS3, SOFA score, higher rates, and longer duration of mechanical ventilation. In the multivariate analysis, ATG was associated with a lower incidence of primary outcome (OR = 0.25, 95% CI 0.09-0.64; p < 0.01). Similar results were found in the sensitivity analysis with another set of variables. However, each day of antibiotic use was associated with an increased risk of pneumonia by resistant bacteria (OR = 1.18 per day, 95% CI 1.05-1.36; p < 0.01).

CONCLUSIONS

Empiric antibiotic therapy was independently associated with lower incidence of nosocomial pneumonia in critically ill patients with pulmonary contusion. However, each day of antibiotic use was associated with increased resistant strains in infected patients.

Systemic immune response of burns from the acute to chronic phase

Immune responses that occur following burn injury comprise a series of reactions that are activated in response to damaged autologous tissues, followed by removal of damaged tissues and foreign pathogens such as invading bacteria, and tissue repair. These immune responses are considered to be programmed in living organisms. Developments of modern medicine have led to the saving of burned patients who could not be cured previously; however, the programmed response is no longer able to keep up, and various problems have arisen. This paper describes the mechanism of immune response specific to burn injury and the emerging concept of persistent inflammation, immunosuppression, and catabolism syndrome.

Therapeutic Applications of Essential Oils from Native and Cultivated Ecuadorian Plants: Cutaneous Candidiasis and Dermal Anti-Inflammatory Activity

Essential oils are a complex mixture of aromatic substances whose pharmacological actions, including antimicrobial, antioxidant, anticancer, and anti-inflammatory activities, have been widely reported. This study aimed to evaluate the anti-Candida and dermal anti-inflammatory activity of essential oils from native and cultivated Ecuadorian plants. Essential oils from Bursera graveolens, Dacryodes peruviana, Mespilodaphne quixos, and Melaleuca armillaris were isolated by hydrodistillation and were characterized physically and chemically. Its tolerance was analyzed by in vitro and in vivo studies. The antifungal activity was studied against Candida albicans, Candida glabrata, and Candida parapsilosis, whereas the anti-inflammatory effect was evaluated by a mouse ear edema model. The main compounds were limonene, α-phellandrene, (E)-methyl cinnamate, and 1,8-cineole, respectively. All essential oils showed high tolerability for skin application, antifungal activity against the three Candida strains, and anti-inflammatory efficacy by decreasing edema and overexpression of pro-inflammatory cytokines. Dacryodes peruviana essential oil showed the highest antifungal activity. On the other hand, Dacryodes peruviana and Melaleuca armillaris showed the greatest anti-inflammatory potential, decreasing edema by 53.3% and 65.25%, respectively, and inhibiting the overexpression of TNF-α, IL-8, IL-17A, and IL-23. The results suggest that these essential oils could be used as alternative therapies in the treatment of both cutaneous candidiasis and dermal inflammation.

Evaluation of critical care burden following traumatic injury from two randomized controlled trials

Trauma resuscitation practices have continued to improve with new advances targeting prehospital interventions. The critical care burden associated with severely injured patients at risk of hemorrhage has been poorly characterized. We aim to describe the individual and additive effects of multiorgan failure (MOF) and nosocomial infection (NI) on delayed mortality and resource utilization. A secondary analysis of harmonized data from two large prehospital randomized controlled trials (Prehospital Air Medical Plasma (PAMPer) Trial and Study of Tranexamic Acid during Air and Ground Medical Prehospital Transport (STAAMP) Trial) was conducted. Only those patients who survived beyond the first 24 hours post-injury and spent at least one day in the ICU were included. Patients were stratified by development of MOF only, NI only, both, or neither and diagnosis of early (≤ 3 days) versus late MOF (> 3 days). Risk factors of NI and MOF, time course of these ICU complications, associated mortality, and hospital resource utilization were evaluated. Of the 869 patients who were enrolled in PAMPer and STAAMP and who met study criteria, 27.4% developed MOF only (n = 238), 10.9% developed NI only (n = 95), and 15.3% were diagnosed with both MOF and NI (n = 133). Patients developing NI and/or MOF compared to those who had an uncomplicated ICU course had greater injury severity, lower GCS, and greater shock indexes. Early MOF occurred in isolation, while late MOF more often followed NI. MOF was associated with 65% higher independent risk of 30-day mortality when adjusting for cofounders (OR 1.65; 95% CI 1.04-2.6; p = 0.03), however NI did not significantly affect odds of mortality. NI was individually associated with longer mechanical ventilation, ICU stay, hospital stay, and rehabilitation requirements, and the addition of MOF further increased the burden of inpatient and post-discharge care. MOF and NI remain common complications for those who survive traumatic injury. MOF is a robust independent predictor of mortality following injury in this cohort, and NI is associated with higher resource utilization. Timing of these ICU complications may reveal differences in pathophysiology and offer targets for continued advancements in treatment.

Investigating the potential of a prematurely aged immune phenotype in severely injured patients as predictor of risk of sepsis

BACKGROUND

Traumatic injury elicits a hyperinflammatory response and remodelling of the immune system leading to immuneparesis. This study aimed to evaluate whether traumatic injury results in a state of prematurely aged immune phenotype to relate this to clinical outcomes and a greater risk of developing additional morbidities post-injury.

METHODS AND FINDINGS

Blood samples were collected from 57 critically injured patients with a mean Injury Severity Score (ISS) of 26 (range 15-75 years), mean age of 39.67 years (range 20-84 years), and 80.7% males, at days 3, 14, 28 and 60 post-hospital admission. 55 healthy controls (HC), mean age 40.57 years (range 20-85 years), 89.7% males were also recruited. The phenotype and frequency of adaptive immune cells were used to calculate the IMM-AGE score, an indicator of the degree of phenotypic ageing of the immune system. IMM-AGE was elevated in trauma patients at an early timepoint (day 3) in comparison with healthy controls (p < 0.001), driven by an increase in senescent CD8 T cells (p < 0.0001), memory CD8 T cells (p < 0.0001) and regulatory T cells (p < 0.0001) and a reduction in naïve CD8 T cells (p < 0.001) and overall T cell lymphopenia (p < 0 .0001). These changes persisted to day 60. Furthermore, the IMM-AGE scores were significantly higher in trauma patients (mean score 0.72) that developed sepsis (p = 0.05) in comparison with those (mean score 0.61) that did not.

CONCLUSIONS

The profoundly altered peripheral adaptive immune compartment after critical injury can be used as a potential biomarker to identify individuals at a high risk of developing sepsis and this state of prematurely aged immune phenotype in biologically young individuals persists for up to two months post-hospitalisation, compromising the host immune response to infections. Reversing this aged immune system is likely to have a beneficial impact on short- and longer-term outcomes of trauma survivors.

Traumatic Brain Injury Induces a Differential Immune Response in Polytrauma Patients; Prospective Analysis of CD69 Expression on T Cells and Platelet Expansion

Background: Accidents and injuries are the leading causes of mortality in young people. CD4+ regulatory T cells (CD4+ Tregs), Th17 cells and platelets could be identified as key players in post-traumatic immunological dysfunction, which is a common cause of late mortality in trauma patients. The mechanisms of activation of these cell types and their interaction remain mostly unclear. Since CD69 is not only a leukocyte marker but has also immunoregulatory functions, we postulate a role for CD69 after trauma. The present study investigates the expression of CD69 on CD4+ Tregs and Th17 cells, as well as the posttraumatic expansion of platelets and hemostatic function. Subgroup analysis was performed to assess the differences between polytrauma patients with and without severe traumatic brain injury (TBI). Methods: In this non-interventional prospective clinical trial, we analyzed sequential blood samples over a period of 10 days from 30 patients after multiple traumas with an ISS ≥ 16. Platelet function was assessed by rotational thromboelastometry (ROTEM analysis). CD4+ Tregs and Th17 cells were stained with surface markers and analyzed by flow cytometry. Results: We were able to demonstrate a significantly increased expression of CD69 on CD4+ Tregs after trauma. Subgroup analysis revealed that the absence of severe TBI is associated with a significantly higher expression of CD69 on CD4+ Tregs and on Th17 cells. Platelets expanded and showed signs of dysfunction, while an overall tendency of posttraumatic hypercoagulation was detected. Conclusions: Our results support the concept of injury-specific immune responses and add to a further understanding of the complex pathophysiology of post-traumatic immune dysfunction.

A Four-Probiotic Regime to Reduce Surgical Site Infections in Multi-Trauma Patients

Investigations that focused on the protective role of probiotics against Surgical Site Infections (SSI) in multiple-trauma (MT) patients are generally few, probably due to the complexity of the concept of trauma. We aimed to assess the efficacy of a four-probiotic regime to reduce the incidence of SSI in MT patients, with a brain injury included. MT patients, being intubated and expected to require mechanical ventilation for >10 days, were randomly allocated into placebo (n = 50) or probiotic treatment (n = 53) comprising Lactobacillus acidophilus LA-5 (1.75 × 109 cfu), Lactiplantibacillus plantarum UBLP-40 (0.5 × 109 cfu), Bifidobacterium animalis subsp. lactis BB-12 (1.75 × 109 cfu), and Saccharomycesboulardii Unique-28 (1.5 × 109 cfu) in sachets. All patients received two sachets of placebo or probiotics twice/day for 15 days and were followed-up for 30 days. The operations were classified as neurosurgical, thoracostomies, laparotomies, orthopedics, and others; then, the SSI and the isolated pathogen were registered. A total of 23 (46.0%) and 13 (24.5%) infectious insults in 89 (50 placebo patients) and 88 (53 probiotics-treated) operations (p = 0.022) were recorded, the majority of them relating to osteosynthesis—17 and 8, respectively. The most commonly identified pathogens were Staphylococcus aureus and Acinetobacter baumannii. Our results support published evidence that the prophylactic administration of probiotics in MT patients exerts a positive effect on the incidence of SSI.

Distinct Injury Responsive Regulatory T Cells Identified by Multi-Dimensional Phenotyping

CD4⁺ regulatory T cells (Tregs) activate and expand in response to different types of injuries, suggesting that they play a critical role in controlling the immune response to tissue and cell damage. This project used multi-dimensional profiling techniques to comprehensively characterize injury responsive Tregs in mice. We show that CD44^high Tregs expand in response to injury and were highly suppressive when compared to CD44^low Tregs. T cell receptor (TCR) repertoire analysis revealed that the CD44^high Treg population undergo TCRαβ clonal expansion as well as increased TCR CDR3 diversity. Bulk RNA sequencing and single-cell RNA sequencing with paired TCR clonotype analysis identified unique differences between CD44^high and CD44^low Tregs and specific upregulation of genes in Tregs with expanded TCR clonotypes. Gene ontology analysis for molecular function of RNA sequencing data identified chemokine receptors and cell division as the most enriched functional terms in CD44^high Tregs versus CD44^low Tregs. Mass cytometry (CyTOF) analysis of Tregs from injured and uninjured mice verified protein expression of these genes on CD44^high Tregs, with injury-induced increases in Helios, Galectin-3 and PYCARD expression. Taken together, these data indicate that injury triggers the expansion of a highly suppressive CD44^high Treg population that is transcriptionally and phenotypically distinct from CD44^low Tregs suggesting that they actively participate in controlling immune responses to injury and tissue damage.

The posttraumatic response of CD4+ regulatory T cells is modulated by direct cell-cell contact via CD40L- and P-selectin-dependent pathways

CD4+ FoxP3+ regulatory T cells (CD4+ Tregs) are important for the posttraumatic anti-inflammatory host response. As described previously, platelets are able to modulate CD4+ Treg activity in a reciprocally activating interaction following injury. The underlying mechanisms of the posttraumatic interaction between platelets and CD4+ Tregs remain unclear. We investigated the potential influence of CD40L and P-selectin, molecules known to be involved in direct cell contact of these cell types. In a murine burn injury model, the potential interaction pathways were addressed using CD40L- and P-selectin-deficient mice. Draining lymph nodes were harvested following trauma (1 h) and following a sham procedure. Early rapid activation of CD4+ Tregs was assessed by phospho-flow cytometry (signaling molecules (p)PKC-δ and (p)ZAP-70). Platelet function was analyzed performing rotational thromboelastometry (ROTEM). We hypothesized that disruption of the direct cell-cell contact via CD40L and P-selectin would affect posttraumatic activation of CD4+ Tregs and influence the hemostatic function of platelets. Indeed, while injury induced early activation of CD4+ Tregs in wild-type mice (ZAP-70: p = 0.13, pZAP-70: p < 0.05, PKC-δ: p < 0.05, pPKC-δ: p < 0.05), disruption of CD40L-dependent interaction (ZAP-70: p = 0.57, pZAP-70: p = 0.68, PKC-δ: p = 0.68, pPKC-δ: p = 0.9) or P-selectin-dependent interaction (ZAP-70: p = 0.78, pZAP-70: p = 0.58, PKC-δ: p = 0.81, pPKC-δ: p = 0.73) resulted in reduced posttraumatic activation. Furthermore, hemostatic function was impaired towards hypocoagulability in either deficiency. Our results suggest that the posttraumatic activation of CD4+ Tregs and hemostatic function of platelets are affected by direct cell-cell-signaling via CD40L and P-selectin.

Brain-lung interactions and mechanical ventilation in patients with isolated brain injury

During the last decade, experimental and clinical studies have demonstrated that isolated acute brain injury (ABI) may cause severe dysfunction of peripheral extracranial organs and systems. Of all potential target organs and systems, the lung appears to be the most vulnerable to damage after brain injury (BI). The pathophysiology of these brain–lung interactions are complex and involve neurogenic pulmonary oedema, inflammation, neurodegeneration, neurotransmitters, immune suppression and dysfunction of the autonomic system. The systemic effects of inflammatory mediators in patients with BI create a systemic inflammatory environment that makes extracranial organs vulnerable to secondary procedures that enhance inflammation, such as mechanical ventilation (MV), surgery and infections. Indeed, previous studies have shown that in the presence of a systemic inflammatory environment, specific neurointensive care interventions—such as MV—may significantly contribute to the development of lung injury, regardless of the underlying mechanisms. Although current knowledge supports protective ventilation in patients with BI, it must be born in mind that ABI-related lung injury has distinct mechanisms that involve complex interactions between the brain and lungs. In this context, the role of extracerebral pathophysiology, especially in the lungs, has often been overlooked, as most physicians focus on intracranial injury and cerebral dysfunction. The present review aims to fill this gap by describing the pathophysiology of complications due to lung injuries in patients with a single ABI, and discusses the possible impact of MV in neurocritical care patients with normal lungs.

Extrathoracic multiple trauma dysregulates neutrophil function and exacerbates pneumonia-induced lung injury

BACKGROUND

Forty percent of critically ill trauma patients will develop an infectious complication. Pneumonia is the most common cause of death of trauma patients surviving their initial insult. We previously demonstrated that polytrauma (PT), defined as two or more severe injuries in at least two areas of the body, induces emergency hematopoiesis characterized by accelerated myelopoiesis in the bone marrow and increased myeloid cell frequency in the peripheral tissues. We hypothesized that PT alone induces priming of neutrophils, resulting in hyperactivation upon secondary exposure to bacteria and causing acute lung injury and increased susceptibility to secondary exposure to Pseudomonas aeruginosa pneumonia.

METHODS

C57BL/6 mice were subjected to PT consisting of a lower extremity pseudofracture, liver crush injury, and 15% blood-volume hemorrhage. Pneumonia was induced by intratracheal injection of 5 × 106 CFU live P. aeruginosa or 1 × 107 of heat-killed P. aeruginosa (HKPA). For reactive oxygen species (ROS), studies polymorphonuclear neutrophils (PMNs) were isolated by immunomagnetic bead negative selection and stimulated ex-vivo with HKPA. Reactive oxygen species production was measured by immunofluorescence. For histology, lung sections were stained by hematoxylin-eosin and analyzed by a blinded grader.

RESULTS

Polytrauma induced persistent changes in immune function at baseline and to secondary infection. Pneumonia after injury resulted in increased mortality (60% vs. 5% p < 0.01). Blood neutrophils from PT mice had higher resting (unstimulated) ROS production than in naive animals (p < 0.02) demonstrating priming of the neutrophils following PT. After intratracheal HKPA injection, bronchoalveolar lavage PMNs from injured mice had higher ROS production compared with naive mice (p < 0.01), demonstrating an overexuberant immunopathologic response of neutrophils following PT.

CONCLUSION

Polytrauma primes neutrophils and causes immunopathologic PMN ROS production, increased lung injury and susceptibility to secondary bacterial pneumonia. These results suggest that trauma-induced immune dysfunction can cause immunopathologic response to secondary infection and suggests neutrophil-mediated pulmonary damage as a therapeutic target for posttrauma pneumonia.

Trauma induces expansion and activation of a memory-like Treg population

CD4+ regulatory T cells (Tregs) are acutely activated by traumatic injury, which suggests that they may react to injury with similar kinetics as memory T cells. Here, we used a mouse burn trauma model to screen for memory-like T cell responses to injury by transferring T cells from sham or burn CD45.1 mice into CD45.2 mice and performing secondary injuries in recipient mice. Among all T cell subsets that were measured, only Tregs expanded in response to secondary injury. The expanded Tregs were a CD44high /CD62Llow subpopulation, markers indicative of memory T cells. CyTOF (cytometry by time-of-flight) mass cytometry was used to demonstrate that injury-expanded Tregs expressed higher levels of CD44, CTLA-4, ICOS, GITR, and Helios than Tregs from noninjured mice. Next, we tested whether a similar population of Tregs might react acutely to burn trauma. We observed that Tregs with a phenotype that matched the injury-expanded Tregs were activated by 6 h after injury. To test if Treg activation by trauma requires functional MHC class II, we measured trauma-induced Treg activation in MHC class II gene deficient (MHCII-/- ) mice or in mice that were given Fab fragment of anti-MHC class II antibody to block TCR activation. Injury-induced Treg activation occurred in normal mice but only partial activation was detected in MHCII-/- mice or in mice that were given Fab anti-MHCII antibody. These findings demonstrate that trauma activates a memory-like Treg subpopulation and that Treg activation by injury is partially dependent on TCR signaling by an MHC class II dependent mechanism.

Damage-associated molecular patterns in trauma

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

Crosstalk between brain, lung and heart in critical care

Extracerebral complications, especially pulmonary and cardiovascular, are frequent in brain-injured patients and are major outcome determinants. Two major pathways have been described: brain-lung and brain-heart interactions. Lung injuries after acute brain damages include ventilator-associated pneumonia (VAP), acute respiratory distress syndrome (ARDS) and neurogenic pulmonary œdema (NPE), whereas heart injuries can range from cardiac enzymes release, ECG abnormalities to left ventricle dysfunction or cardiogenic shock. The pathophysiologies of these brain-lung and brain-heart crosstalk are complex and sometimes interconnected. This review aims to describe the epidemiology and pathophysiology of lung and heart injuries in brain-injured patients with the different pathways implicated and the clinical implications for critical care physicians.

Effects of Fibroblast Growth Factor 2 on Burn Injury and Repair Process: Analysis Using a Refined Mouse Model

Background

Burn injury is one of the most debilitating traumas, which induces multiple organ dysfunctions, resulting in high levels of morbidity and mortality. Fibroblast growth factor 2 (FGF2) has been applied to burn injury, whose precise mechanisms underlying facilitating the healing have not been fully understood. Although various animal models have been developed in pigs, rabbits, rats, and mice, no mouse model that creates burns consistent in their extent and depth have not been developed. Here, we developed a mouse burn model, and investigated details of the burn process, and elucidated the mechanisms of FGF2 effects.

Methods

A device with an 8-mm metal probe and a temperature controller was developed, which controls the temperature of the probe. Using the device, 1 or 2 of full-thickness burn injuries were generated on the back under catagen/telogen of 6-month-old C57BL/6 male mice. After 24 hours, FGF2 or phosphate-buffered saline was injected into the injured region, and at days 3, 5, and 7, histological and immunohistochemical analysis was performed to observe the injury and repair process.

Results

The device constantly generated a mouse full-thickness burn injury. The repair was initiated on the bottom of the burn as well as the margin. Local treatment with FGF2 displayed higher levels of immunostaining for both CD31+ and alpha-smooth muscle actin.

Conclusions

The device we developed is useful to generate a mouse burn injury model. FGF2 facilitates tissue repair with an increased number of both CD31+ and αSMA+ cells.

Cortisol total/CRP ratio for the prediction of hospital-acquired pneumonia and initiation of corticosteroid therapy in traumatic brain-injured patients

BACKGROUND

To propose a combination of blood biomarkers for the prediction of hospital-acquired pneumonia (HAP) and for the selection of traumatic brain-injured (TBI) patients eligible for corticosteroid therapy for the prevention of HAP.

METHODS

This was a sub-study of the CORTI-TC trial, a multicenter, randomized, double-blind, controlled trial evaluating the risk of HAP at day 28 in 336 TBI patients treated or not with corticosteroid therapy. Patients were between 15 and 65 years with severe traumatic brain injury (Glasgow coma scale score ≤ 8 and trauma-associated lesion on brain CT scan) and were enrolled within 24 h of trauma. The blood levels of CRP and cortisoltotal&free, as a surrogate marker of the pro/anti-inflammatory response balance, were measured in samples collected before the treatment initiation. Endpoint was HAP on day 28.

RESULTS

Of the 179 patients with available samples, 89 (49.7%) developed an HAP. Cortisoltotal&free and CRP blood levels upon ICU admission were not significantly different between patients with or without HAP. The cortisoltotal/CRP ratio upon admission was 2.30 [1.25-3.91] in patients without HAP and 3.36 [1.74-5.09] in patients with HAP (p = 0.021). In multivariate analysis, a cortisoltotal/CRP ratio > 3, selected upon the best Youden index on the ROC curve, was independently associated with HAP (OR 2.50, CI95% [1.34-4.64] p = 0.004). The HR for HAP with corticosteroid treatment was 0.59 (CI95% [0.34-1.00], p = 0.005) in patients with a cortisoltotal/CRP ratio > 3, and 0.89 (CI95% [0.49-1.64], p = 0.85) in patients with a ratio < 3.

CONCLUSION

A cortisoltotal/CRP ratio > 3 upon admission may predict the development of HAP in severe TBI. Among these patients, corticosteroids reduce the occurrence HAP. We suggest that this ratio may select the patients who may benefit from corticosteroid therapy for the prevention of HAP.

Circulating growth/differentiation factor 15 is associated with human CD56bright natural killer cell dysfunction and nosocomial infection in severe systemic inflammation

Background

Systemic inflammation induced by sterile or infectious insults is associated with an enhanced susceptibility to life-threatening opportunistic, mostly bacterial, infections due to unknown pathogenesis. Natural killer (NK) cells contribute to the defence against bacterial infections through the release of Interferon (IFN) γ in response to Interleukin (IL) 12. Considering the relevance of NK cells in the immune defence we investigated whether the function of NK cells is disturbed in patients suffering from serious systemic inflammation.

Methods

NK cells from severely injured patients were analysed from the first day after the initial inflammatory insult until the day of discharge in terms of IL-12 receptor signalling and IFN-γ synthesis.

Findings

During systemic inflammation, the expression of the IL-12 receptor β2 chain, phosphorylation of signal transducer and activation 4, and IFN-γ production on/in NK cells was impaired upon exposure to Staphylococcus aureus. The profound suppression of NK cells developed within 24 h after the initial insult and persisted for several weeks. NK cells displayed signs of exhaustion. Extrinsic changes were mediated by the early and long-lasting presence of growth/differentiation factor (GDF) 15 in the circulation that signalled through the transforming growth factor β receptor I and activated Smad1/5. Moreover, the concentration of GDF-15 in the serum inversely correlated with the IL-12 receptor β2 expression on NK cells and was enhanced in patients who later acquired septic complications.

Interpretation

GDF-15 is associated with the development of NK cell dysfunction during systemic inflammation and might represent a novel target to prevent nosocomial infections.

Fund

The study was supported by the Department of Orthopaedics and Trauma Surgery, University Hospital Essen.

Anti-PD-1 Antibody Administration following Hip Fracture Surgery Reverses Immune Dysfunction and Decreases Susceptibility to Infection

The aim of this investigation was to assess expression of programmed death-1 (PD-1) and inflammatory status after hip fracture surgery in aged mice and to evaluate the effect of anti-PD-1 antibody intervention. Male C57BL/6 mice aged 22-28 months underwent hip fracture and femoral intramedullary pinning or a sham procedure. Expression of PD-1 was measured on CD4⁺ and CD8⁺ T cells. Additionally, the effects of anti-PD-1 antibody on lymphocyte apoptosis, cytokine production, bacterial clearance, and survival were determined. Expression of PD-1 on T cells was upregulated in mice after hip fracture and surgery compared to sham controls. Administration of anti-PD-1 antibody prevented T lymphocyte apoptosis, increased IFN-γ production in splenocytes, and decreased systemic inflammation. Antibody blockade of PD-1 significantly decreased susceptibility to bacteria and improved survival rates of aged mice after hip fracture and surgery followed by the induction of Pseudomonas aeruginosa pneumonia. This study showed that hip fracture and surgical trauma cause significant increases in PD-1 expression in aged mice. Antibody blockade of PD-1 partially reverses T cell apoptosis, decreases the systemic inflammatory response and susceptibility to bacteria, and reduces mortality.

Increased perioperative C-reactive protein and decreased postoperative albumin is associated with acute posttraumatic osteomyelitis in patients with high-energy tibial fractures

BACKGROUND

Early diagnosis of acute posttraumatic osteomyelitis (POM) is of vital importance for avoiding devastating complications. Diagnosing POM is difficult due to the lack of a highly specific and sensitive test, such as in myocardial infarct, stroke and intracranial bleeding. Serum inflammatory markers, C-reactive protein (CRP), procalcitonin (PCT), white blood cells (WBC) can support clinical findings but they are not able to differentiate between inflammatory response to infection and the host response to non-infection insult with high specificity and sensitivity.

AIM

The objectives of the study were to investigate whether the biochemical and immunoinflammatory patient profile could facilitate postoperative monitoring, guide the antibiotic treatment and timing of revision surgery.

PATIENTS AND METHODS

This prospective nonrandomised cohort study included 86 patients after high-energy injury to the shin requiring primary surgical treatment (open or closed reduction and internal fixation of tibial fracture). Values of the biochemical and immunoinflammatory profile were measured on admission (ADD), first postoperative day (POD1) and fourth-postoperative day (POD4).

RESULTS

We discovered on our sample that the development of POM is associated with increased CRP on ADD, POD1 and decreased albumins on POD4. Further studies are needed to prove that these differences can be useful in diagnosing the risk of infection. The assessment of other important risk factors such as: the extent of soft tissue damage, multiple fractures, transfusion rate, need for conversion primary external fixation to intramedullary (IM) nailing or locking plate fixation can empower our clinical judgment of POM.

CONCLUSIONS

We can improve prediction of posttraumatic osteomyelitis by using the perioperative inflammatory biomarker CRP in combination with postoperative albumins levels and other associated independent risk factors.

An observational study of incidence, risk factors & outcome of systemic inflammatory response & organ dysfunction following major trauma

Background & objectives:

Trauma is known to lead to systemic inflammatory response syndrome (SIRS) and multiple organ dysfunction syndrome (MODS), which is often a cause of late deaths after injury. SIRS and MODS have been objectively measured using scoring systems. This prospective observational study was carried out in a tertiary care hospital in India to evaluate SIRS and MODS following trauma in terms of their incidence, the associated risk factors and the effect on the outcome.

Methods:

All adult patients with major life- and limb-threatening trauma were included. Patients who died within 24 h, those with severe head injury, known comorbidity, immunocompromised state, on immunosuppressants or pregnancy were excluded. SIRS and MODS scores were recorded after initial management (baseline score), on days 3 and 6 of admission. SIRS was defined as SIRS score of ≥2 and MODS was defined as MODS score of ≥1.

Results:

Two hundred patients were enrolled. SIRS was noted in 156 patients (78%). MODS was noted in 145 (72.5%) patients. Overall mortality was 39 (19.5%). Both SIRS and MODS scores were significantly associated with age >60 yr, blunt injury, (lower) revised trauma score hypotension on admission and (higher) injury severity score, but not with gender, pre-hospital time or operative treatment.

Interpretation & conclusions:

Both SIRS and MODS scores were associated with longer Intensive Care Unit (ICU) stay, more ICU interventions and higher mortality. Incidence of MODS was significantly higher in patients with SIRS. Both scores showed rising trend with time in non-survivors and a decreasing trend in survivors. The serial assessment of scores can help prognosticate outcome and also allocate appropriate critical care resources to patients with rising scores.

Trauma-Induced Damage-Associated Molecular Patterns-Mediated Remote Organ Injury and Immunosuppression in the Acutely Ill Patient

Trauma is one of the leading causes of death and disability in the world. Multiple trauma or isolated traumatic brain injury are both indicative of human tissue damage. In the early phase after trauma, damage-associated molecular patterns (DAMPs) are released and give rise to sterile systemic inflammatory response syndrome (SIRS) and organ failure. Later, protracted inflammation following sepsis will favor hospital-acquired infection and will worsen patient’s outcome through immunosuppression. Throughout medical care or surgical procedures, severe trauma patients will be subjected to endogenous or exogenous DAMPs. In this review, we summarize the current knowledge regarding DAMP-mediated SIRS or immunosuppression and the clinical consequences in terms of organ failure and infections.

Guiding Management in Severe Trauma: Reviewing Factors Predicting Outcome in Vastly Injured Patients

Trauma is one of the leading causes of death worldwide, with road traffic collisions, suicides, and homicides accounting for the majority of injury-related deaths. Since trauma mainly affects young age groups, it is recognized as a serious social and economic threat, as annually, almost 16,000 posttrauma individuals are expected to lose their lives and many more to end up disabled. The purpose of this research is to summarize current knowledge on factors predicting outcome - specifically mortality risk - in severely injured patients. Development of this review was mainly based on the systematic search of PubMed medical library, Cochrane database, and advanced trauma life support Guiding Manuals. The research was based on publications between 1994 and 2016. Although hypovolemic, obstructive, cardiogenic, and septic shock can all be seen in multi-trauma patients, hemorrhage-induced shock is by far the most common cause of shock. In this review, we summarize current knowledge on factors predicting outcome - more specifically mortality risk - in severely injured patients. The main mortality-predicting factors in trauma patients are those associated with basic human physiology and tissue perfusion status, coagulation adequacy, and resuscitation requirements. On the contrary, advanced age and the presence of comorbidities predispose patients to a poor outcome because of the loss of physiological reserves. Trauma resuscitation teams considering mortality prediction factors can not only guide resuscitation but also identify patients with high mortality risk who were previously considered less severely injured.

Systemic inflammatory response syndrome, infection, and outcome in intracerebral hemorrhage

Objective:

Systemic inflammatory response syndrome (SIRS) may be related to poor outcomes after intracerebral hemorrhage (ICH).

Methods:

The Ethnic/Racial Variations of Intracerebral Hemorrhage study is an observational study of ICH in whites, blacks, and Hispanics throughout the United Sates. SIRS was defined by standard criteria as 2 or more of the following on admission: (1) body temperature <36°C or >38°C, (2) heart rate >90 beats per minute, (3) respiratory rate >20 breaths per minute, or (4) white blood cell count <4,000/mm³ or >12,000/mm³. The relationship among SIRS, infection, and poor outcome (modified Rankin Scale [mRS] 3–6) at discharge and 3 months was assessed.

Results:

Of 2,441 patients included, 343 (14%) met SIRS criteria at admission. Patients with SIRS were younger (58.2 vs 62.7 years; p < 0.0001) and more likely to have intraventricular hemorrhage (IVH; 53.6% vs 36.7%; p < 0.0001), higher admission hematoma volume (25.4 vs 17.5 mL; p < 0.0001), and lower admission Glasgow Coma Scale (GCS; 10.7 vs 13.1; p < 0.0001). SIRS on admission was significantly related to infections during hospitalization (adjusted odds ratio [OR] 1.36, 95% confidence interval [CI] 1.04–1.78). In unadjusted analyses, SIRS was associated with poor outcomes at discharge (OR 1.96, 95% CI 1.42–2.70) and 3 months (OR 1.75, 95% CI 1.35–2.33) after ICH. In analyses adjusted for infection, age, IVH, hematoma location, admission GCS, and premorbid mRS, SIRS was no longer associated with poor outcomes.

Conclusions:

SIRS on admission is associated with ICH score on admission and infection, but it was not an independent predictor of poor functional outcomes after ICH.

Retrospective evaluation of 140 dogs involved in road traffic accidents

This study has retrospectively reviewed the medical records of 140 dogs sustaining road traffic accident (RTA), and has examined the population characteristics, medical history, injury type, physical examination, emergency laboratory tests and radiography findings, the animal trauma triage (ATT) score, the length of hospitalisation, the complications and the outcome. The survival rate was 83.2 per cent. Younger dogs sustained more frequently lung contusions and limb fractures, while larger dogs more frequently suffered limb fractures, and smaller dogs and older ones sustained more frequently pelvic fractures and sacroiliac luxation (P<0.05 for all). Dogs sustaining orthopaedic injuries required longer hospitalisation (P<0.001). The survival rates of non-ambulatory dogs (P<0.001) and those with neurological abnormalities (P<0.001), abnormal body temperature (P=0.001), hyperglycaemia (P=0.026) or hypoproteinaemia (P=0.04) at presentation were lower compared with those in which these were absent. The number of injured body systems was significantly (P<0.001) and positively associated with death. Dogs surviving RTA to presentation to the hospital have a good prognosis for survival to discharge. Older age, and high ATT score, abnormal body temperature, neurological deficits, hyperglycaemia and hypoproteinaemia at presentation, and occurrence of multiorgan trauma are negative prognostic indicators in such dogs.

Consequences of Transfusing Blood Components in Patients With Trauma: A Conceptual Model

Transfusion of blood components is often required in resuscitation of patients with major trauma. Packed red blood cells and platelets break down and undergo chemical changes during storage (known as the storage lesion) that lead to an inflammatory response once the blood components are transfused to patients. Although some evidence supports a detrimental association between transfusion and a patient's outcome, the mechanisms connecting transfusion of stored components to outcomes remain unclear. The purpose of this review is to provide critical care nurses with a conceptual model to facilitate understanding of the relationship between the storage lesion and patients' outcomes after trauma; outcomes related to trauma, hemorrhage, and blood component transfusion are grouped according to those occurring in the short-term (≤30 days) and the long-term (>30 days). Complete understanding of these clinical implications is critical for practitioners in evaluating and treating patients given transfusions after traumatic injury.

Burn Injury Leads to Increased Long-Term Susceptibility to Respiratory Infection in both Mouse Models and Population Studies

Background

Burn injury initiates an acute inflammatory response that subsequently drives wound repair. However, acute disruption to the immune response is also common, leading to susceptibility to sepsis and increased morbidity and mortality. Despite increased understanding of the impact of burn injury on the immune system in the acute phase, little is known about long-term consequences of burn injury on immune function. This study was established to determine whether burn injury has long-term clinical impacts on patients’ immune responses.

Methods

Using a population-based retrospective longitudinal study and linked hospital morbidity and death data from Western Australia, comparative rates of hospitalisation for respiratory infections in burn patients and a non-injured comparator cohort were assessed. In addition, a mouse model of non-severe burn injury was also used in which viral respiratory infection was induced at 4 weeks post-injury using a mouse modified version of the Influenza A virus (H3NN; A/mem/71-a).

Results and conclusions

The burn injured cohort contained 14893 adult patients from 1980–2012 after removal of those patients with evidence of smoke inhalation or injury to the respiratory tract. During the study follow-up study a total of 2,884 and 2,625 respiratory infection hospital admissions for the burn and uninjured cohorts, respectively, were identified. After adjusting for covariates, the burn cohort experienced significantly elevated admission rates for influenza and viral pneumonia (IRR, 95%CI: 1.73, 1.27–2.36), bacterial pneumonia (IRR, 95%CI: 2.05, 1.85–2.27) and for other types of upper and lower respiratory infections (IRR, 95% CI: 2.38, 2.09–2.71). In the mouse study an increased viral titre was observed after burn injury, accompanied by a reduced CD8 response and increased NK and NKT cells in the draining lymph nodes. This data suggests burn patients are at long-term increased risk of infection due to sustained modulation of the immune response.

Burns and long-term infectious disease morbidity: A population-based study

BACKGROUND

There is a growing volume of data that indicates that serious injury suppresses immune function, predisposing individuals to infectious complications. With recent evidence showing long-term immune dysfunction after less severe burn, this study aimed to investigate post-burn infectious disease morbidity and assess if burn patients have increased long-term hospital use for infectious diseases.

METHODS

A population-based longitudinal study using linked hospital morbidity and death data from Western Australia for all persons hospitalised for a first burn (n=30,997) in 1980-2012. A frequency matched non-injury comparison cohort was randomly selected from Western Australia's birth registrations and electoral roll (n=123,399). Direct standardisation was used to assess temporal trends in infectious disease admissions. Crude annual admission rates and length of stay for infectious diseases were calculated. Multivariate negative binomial and Cox proportional hazards regression modeling were used to generate adjusted incidence rate ratios (IRR) and hazard ratios (HR), respectively.

RESULTS

After adjustment for demographic factors and pre-existing health status, the burn cohort had twice (IRR, 95% confidence interval (CI): 2.04, 1.98-2.22) as many admissions and 3.5 times the number of days in hospital (IRR, 95%CI: 3.46, 3.05-3.92) than the uninjured cohort for infectious diseases. Higher rates of infectious disease admissions were found for severe (IRR, 95%CI: 2.37, 1.89-2.97) and minor burns (IRR, 95%CI: 2.22, 2.11-2.33). Burns were associated with significantly increased incident admissions: 0-30days (HR, 95%CI: 5.18, 4.15-6.48); 30days-1year (HR, 95%CI: 1.69, 1.53-1.87); 1-10 years (HR, 95%CI: 1.40:1.33-1.47); >10years (HR, 95%CI: 1.16, 1.08-1.24). Respiratory, skin and soft tissue and gastrointestinal infections were the most common. The burn cohort had a 1.75 (95%CI: 1.37-2.25) times greater rate of mortality caused by infectious diseases during the 5-year period after discharge than the uninjured cohort.

CONCLUSIONS

These findings suggest that burn has long-lasting effects on the immune system and its function. The increase in infectious disease in three different epithelial tissues in the burn cohort suggests there may be common underlying pathophysiology. Further research to understand the underlying mechanisms are required to inform clinical interventions to mitigate infectious disease after burn and improve patient outcomes.

Exaggerated plasma interleukin 6, interleukin 10, and subsequent development of health care-associated infections in patients with sepsis

BACKGROUND

Health care-associated infections (HAIs) are the target of many well-known preventive measures in the intensive care unit (ICU); however, little is known about post-sepsis-induced immunosuppression.

OBJECTIVES

This study explores the relationship between baseline plasma levels of inflammatory cytokines interleukin 6 (IL-6), IL-10, and IL-6:IL-10 and subsequent development of HAIs in patients with admitted with sepsis.

METHODS

Prospective observational study was conducted among veterans admitted to the ICU with sepsis and monitored daily through ICU discharge (up to 28 days) to investigate HAI development. Baseline plasma IL-6 and IL-10 levels were measured with a multiplex bead based assay. Exaggerated systemic inflammation was defined as the fourth quartile (IL-6 and IL-10) compared with other quartiles.

RESULTS

We recruited 78 patients over 18 months, primarily older (65.5 ± 12.6 years) men (94.9%) with underlying comorbidities (93.9%) and a high severity of illness (Acute Physiologic and Chronic Health Evaluation II score 20.6 ± 6.4). Seventeen patients (21.7%) developed at least 1 HAI, and candidemia was the leading infection. Patients with exaggerated baseline systemic inflammation developed a nonsignificantly higher proportion of HAI as compared with those not developing HAI (IL-6: 31.6% vs 18.6%, P = .55; IL-10: 26.3% vs 20.3%, P = .43).

DISCUSSION

Patients with exaggerated systemic inflammation had a higher severity of illness, but not a statistically significant higher incidence of HAI. A larger, more adequately powered sample with serial cytokine measures is needed. Routine surveillance cultures are needed. Health care-associated infection may occur in the absence of fever, and the emerging incidence of Candida is a concern. Immune suppression after sepsis should be recognized as a risk for HAI development. Antibiotic therapy should be targeted with prompt de-escalation of empiric therapy per established guidelines to preserve normal flora.

Respiratory Morbidity After Childhood Burns: A 10-Year Follow-up Study

BACKGROUND AND OBJECTIVE

The systemic responses triggered by burns and resuscitative measures may cause pulmonary damage and edema in the acute phase. These effects may occur in the absence of inhalation injury. Currently, there is a paucity of data on the recovery of the respiratory system postburn. This study aimed to examine 10-year hospital service use for respiratory morbidity in children with cutaneous burns and no smoke inhalation injury.

METHODS

A population-based longitudinal study with 10-year follow-up using linked hospital and death from Western Australia for children <5 years when hospitalized for a first burn injury (n = 5290) between 1980 and 2012 and a frequency matched noninjury comparison cohort, randomly selected from Western Australia's birth registrations (n = 27 061). Multivariate negative binomial and Cox proportional hazards regression models were used to generate adjusted incidence rate ratios (IRR) and hazard ratios, respectively.

RESULTS

After adjustment for demographic factors and preexisting health status, the burn cohort had higher rates of admissions for influenza and viral pneumonia (IRR, 1.78; 95% confidence interval [CI], 1.10-2.87), bacterial pneumonia (IRR, 1.34; 95% CI, 1.06-1.70), and other respiratory infections (IRR, 1.65; 95% CI, 1.43-1.90. No significant difference was found for other upper respiratory tract conditions (IRR, 1.10; 95% CI, 0.98-1.23) or chronic lower respiratory diseases (IRR, 0.99; 95% CI, 0.80-1.23) compared with the uninjured cohort.

CONCLUSIONS

These findings demonstrated increased respiratory infection admissions after burns. These outcomes suggest that immune changes triggered by a burn injury may persist in some children for at least 10 years after wound healing.

Temporal Patterns of Circulating Inflammation Biomarker Networks Differentiate Susceptibility to Nosocomial Infection Following Blunt Trauma in Humans

BACKGROUND

Severe traumatic injury can lead to immune dysfunction that renders trauma patients susceptible to nosocomial infections (NI) and prolonged intensive care unit (ICU) stays. We hypothesized that early circulating biomarker patterns following trauma would correlate with sustained immune dysregulation associated with NI and remote organ failure.

METHODS

In a cohort of 472 blunt trauma survivors studied over an 8-year period, 127 patients (27%) were diagnosed with NI versus 345 trauma patients without NI. To perform a pairwise, case-control study with 1:1 matching, 44 of the NI patients were compared with 44 no-NI trauma patients selected by matching patient demographics and injury characteristics. Plasma obtained upon admission and over time were assayed for 26 inflammatory mediators and analyzed for the presence of dynamic networks.

RESULTS

Significant differences in ICU length of stay (LOS), hospital LOS, and days on mechanical ventilation were observed in the NI patients versus no-NI patients. Although NI was not detected until day 7, multiple mediators were significantly elevated within the first 24 hours in patients who developed NI. Circulating inflammation biomarkers exhibited 4 distinct dynamic patterns, of which 2 clearly distinguish patients destined to develop NI from those who did not. Mediator network connectivity analysis revealed a higher, coordinated degree of activation of both innate and lymphoid pathways in the NI patients over the initial 24 hours.

CONCLUSIONS

These studies implicate unique dynamic immune responses, reflected in circulating biomarkers that differentiate patients prone to persistent critical illness and infections following injury, independent of mechanism of injury, injury severity, age, or sex.

Brain-lung crosstalk: Implications for neurocritical care patients

Major pulmonary disorders may occur after brain injuries as ventilator-associated pneumonia, acute respiratory distress syndrome or neurogenic pulmonary edema. They are key points for the management of brain-injured patients because respiratory failure and mechanical ventilation seem to be a risk factor for increased mortality, poor neurological outcome and longer intensive care unit or hospital length of stay. Brain and lung strongly interact via complex pathways from the brain to the lung but also from the lung to the brain. Several hypotheses have been proposed with a particular interest for the recently described “double hit” model. Ventilator setting in brain-injured patients with lung injuries has been poorly studied and intensivists are often fearful to use some parts of protective ventilation in patients with brain injury. This review aims to describe the epidemiology and pathophysiology of lung injuries in brain-injured patients, but also the impact of different modalities of mechanical ventilation on the brain in the context of acute brain injury.

Current views on the mechanisms of immune responses to trauma and infection

According to the World Health Organization, post-traumatic mortality rates are still very high and show an increasing tendency. Disorders of innate immune response that may increase the risk of serious complications play a key role in the immunological system response to trauma and infection. The mechanism of these disorders is multifactorial and is still poorly understood. The changing concepts of systemic inflammatory response syndrome (SIRS) and compensatory anti-inflammatory response syndrome (CARS) early inflammatory response, presented in this work, have been extended to genetic studies. Overexpression of genes and increased production of immune response mediators are among the main causes of multiple organ dysfunction syndrome (MODS). Changes in gene expression detected early after injury precede the occurrence of subsequent complications with a typical clinical picture. Rapid depletion of energy resources leads to immunosuppression and persistent inflammation and immune suppression catabolism syndrome (PICS). Early diagnosis of immune disorders and appropriate nutritional therapy can significantly reduce the incidence of complications, length of hospital stay, and mortality. The study presents the development of knowledge and current views explaining the mechanisms of the immune response to trauma and infection.

Where's the difference? Presentation of nosocomial infection in critically ill trauma versus general surgery patients

BACKGROUND

Diagnosing infection efficiently is integral to managing critically ill patients. Knowing if and how trauma and general surgery patients differ in their presentation of new infectious complications could be useful. We hypothesized these populations would differ in presentation in the intensive care unit (ICU).

METHODS

We analyzed data collected prospectively from all 1,657 trauma and general surgery patients admitted to the surgical and trauma ICU (STICU) over a 21-month period. Clinical data from the first day of a newly diagnosed infection were compared for trauma (82% of the series) and general surgery (18%) patients.

RESULTS

A total of 10,424 STICU days were included, and 267 nosocomial infections were diagnosed. Trauma patients were younger (50 vs. 62 years; p<0.001) and more likely to be male (78% vs. 46%; p<0.001) than were general surgery patients. Similar percentages of the two groups were infected (11% and 13%, respectively), and infections occurred after a similar number of days in the STICU. The mean maximum temperature on the day prior to diagnosis was higher in trauma patients (38.4°C vs. 37.7°C; p<0.001), and the mean leukocyte count was lower (13,500 vs. 15,800 10(6)/L; p=0.013). General surgery patients were more likely to be hypotensive (13% vs. 2%; p=0.002) and to have a positive fluid balance >2 L on the first day of infection (27% vs. 13%; p=0.02). Respiratory infections were more common in trauma patients (40% vs. 7%; p<0.001), and urinary tract infections were less common (19% vs. 36%; p=0.011).

CONCLUSION

Differences exist in how new infections manifest in trauma and general surgery patients in the ICU. General surgery patients appeared sicker on their first day of infection, as evidenced by a higher leukocyte count, lower blood pressure, and substantial positive fluid balance. Intensivists may need differing thresholds for triggering infection workups when employed in a mixed unit.

Update on the definition of polytrauma

PURPOSE

The definition and use of the term "polytrauma" is inconsistent and lacks validation. This article describes the historical evolution of the term and geographical differences in its meaning, examines the challenges faced in defining it adequately in the current context, and summarizes where the international consensus process is heading, in order to provide the trauma community with a validated and universally agreed upon definition of polytrauma.

CONCLUSION

A lack of consensus in the definition of "polytrauma" was apparent. According to the international consensus opinion, both anatomical and physiological parameters should be included in the definition of polytrauma. An Abbreviated Injury Scale (AIS) based anatomical definition is the most practical and feasible given the ubiquitous use of the system. Convincing preliminary data show that two body regions with AIS >2 is a good marker of polytrauma-better than other ISS cutoffs, which could also indicate monotrauma. The selection of the most accurate physiological parameters is still underway, but they will most likely be descriptors of tissue hypoxia and coagulopathy.

Immune response to traumatic injury: harmony and discordance of immune system homeostasis

Trauma remains one of the leading causes of death worldwide. Traumatic injury disrupts immune system homeostasis and may predispose patients to opportunistic infections and inflammatory complications. Prevention of multiple organ dysfunction syndrome due to septic complications following severe trauma is a challenging problem. Following severe injury, the immune system usually tends toward a pro-inflammatory phenotype and then changes to a counter-inflammatory phenotype. This immune system homeostasis is believed to be a protective response based on the balance between the innate and adaptive immune systems. We reported that injury activates inflammasomes and primes Toll-like receptors. The primed innate immune system is prepared for a rapid and strong antimicrobial immune defense. However, trauma can also develop the "two-hit" response phenotype. We also reported that injury augments regulatory T cell activity, which can control the "two-hit" response phenotype in trauma. We discuss the current idea that traumatic injury induces a unique type of innate and adaptive immune response that may be triggered by damage-associated molecular pattern molecules, which are a combination of endogenous danger signal molecules that include alarmins and pathogen-associated molecular pattern molecules.

Operative care and surveillance in severe trauma patients. Interference between resuscitation treatments and anaesthesiology, and consequence on immunity

Major trauma remains a worldwide cause of morbi-mortality. Early mortality is the consequence of hemorrhagic shock and traumatic brain injury. During early resuscitation, anaesthesia is often mandatory to perform surgery. It is mandatory to master the hemodynamic effects of hypnotic drugs in order to anticipate their potential deleterious effects in the setting of hemorrhagic shock. After early resuscitation, trauma patients present a high prevalence of nosocomial pneumonia, which sustains major morbidity. Nosocomial pneumonia are the consequence of an overwhelming systemic inflammatory response syndrome (SIRS) as well as a trauma-related immunosuppression. The administration of hemisuccinate of hydrocortisone modulates the SIRS and reduces the risk of nosocomial pneumonia as well as the length of mechanical ventilation. Finally in the operating theatre, fighting against hypothermia and un-anatomical positions, which can aggravate rhabdomyolysis, are both mandatory.

The practicality of including the systemic inflammatory response syndrome in the definition of polytrauma: experience of a level one trauma centre

BACKGROUND

The systemic inflammatory response syndrome (SIRS) has been advocated as a significant predictor of outcome in trauma. Recent trauma literature has proposed SIRS as a surrogate for physiological derangements characteristic of polytrauma with some authors recommending its inclusion into the definition of polytrauma. The practicality of daily SIRS collection outside of specifically designed prospective trials is unknown. The purpose of this study was to assess the availability of SIRS variables and its appropriateness for inclusion into a definition of polytrauma. We hypothesised SIRS variables would be readily available and easy to collect, thus represent an appropriate inclusion into the definition of polytrauma.

METHOD

A prospective observational study of all trauma team activation patients over 7-months (August 2009 to February 2010) at a University affiliated level-1 urban trauma centre. SIRS data (temperature>38°C or <36°C; Pulse >90 bpm; RR>20/min or a PaCO(2)<32 mmHg; WCC>12.0×10(9)L(-1), or <4.0×10(9)L(-1), or the presence of >10 immature bands) collected from presentation, at 24 h intervals until 72 h post injury. Inclusion criteria were all patients generating a trauma team activation response age >16.

RESULTS

336 patients met inclusion criteria. In 46% (155/336) serial SIRS scores could not be calculated due to missing data. Lowest rates of missing data observed on admission [3% (11/336)]. Stratified by ISS>15 (132/336), in 7% (9/132) serial SIRS scores could not be calculated due to missing data. In 123 patients ISS>15 with complete data, 81% (100/123) developed SIRS. For Abbreviated Injury Scale (AIS)>2 in at least 2 body regions (64/336) in 5% (3/64) serial SIRS scores could not be calculated, with 92% (56/61) of patients with complete data developing SIRS. For Direct ICU admissions [25% (85/336)] 5% (4/85) of patients could not have serial SIRS calculated [mean ISS 15(±11)] and 90% (73/81) developed SIRS at least once over 72 h.

CONCLUSION

Based on the experience of our level-1 trauma centre, the practicability of including SIRS into the definition of polytrauma as a surrogate for physiological derangement appears questionable even in prospective fashion.

Burn injury triggered dysfunction in dendritic cell response to TLR9 activation and resulted in skewed T cell functions

Severe trauma such as burn injury is often associated with a systemic inflammatory syndrome characterized by a hyperactive innate immune response and suppressed adaptive immune function. Dendritic cells (DCs), which sense pathogens via their Toll-like receptors (TLRs), play a pivotal role in protecting the host against infections. The effect of burn injury on TLR-mediated DC function is a debated topic and the mechanism controlling the purported immunosuppressive response remains to be elucidated. Here we examined the effects of burn injury on splenic conventional DC (cDC) and plasmacytoid DC (pDC) responses to TLR9 activation. We demonstrate that, following burn trauma, splenic cDCs' cytokine production profile in response to TLR9 activation became anti-inflammatory dominant, with high production of IL-10 (>50% increase) and low production of IL-6, TNF-α and IL-12p70 (∼25-60% reduction). CD4+ T cells activated by these cDCs were defective in producing Th1 and Th17 cytokines. Furthermore, burn injury had a more accentuated effect on pDCs than on cDCs. Following TLR9 activation, pDCs displayed an immature phenotype with an impaired ability to secrete pro-inflammatory cytokines (IFN-α, IL-6 and TNF-α) and to activate T cell proliferation. Moreover, cDCs and pDCs from burn-injured mice had low transcript levels of TLR9 and several key molecules of the TLR signaling pathway. Although hyperactive innate immune response has been associated with severe injury, our data show to the contrary that DCs, as a key player in the innate immune system, had impaired TLR9 reactivity, an anti-inflammatory phenotype, and a dysfunctional T cell-priming ability. We conclude that burn injury induced impairments in DC immunobiology resulting in suppression of adaptive immune response. Targeted DC immunotherapies to promote their ability in triggering T cell immunity may represent a strategy to improve immune defenses against infection following burn injury.

Endogenous glucocorticoids promote the expansion of myeloid-derived suppressor cells in a murine model of trauma

Stress-dose of glucocorticoid has been demonstrated to be beneficial for trauma patients in clinical studies. Recently, a heterogeneous population of myeloid cells with immunosuppressive activity named myeloid-derived suppressor cells (MDSCs) has been found to accumulate in the trauma host and can be induced by glucocorticoids in vitro. In order to explore the effect of endogenous glucocorticoids on MDSCs under trauma conditions, we blocked the glucocorticoid signal in a murine trauma model using the antagonist of the glucocorticoid receptor RU486 (mifepristone). We found for the first time that RU486 not only blunted MDSC expansion induced by trauma in the spleen, peripheral blood and bone marrow especially at 6 h after traumatic stress but also decreased the survival rate from 100 to 20% in traumatic mice within 7 days. Moreover, neither MDSCs producing arginase-1 nor the morphological characterization of trauma-induced MDSCs was affected by the blockage of the glucocorticoid receptor. Our results suggest that endogenous glucocorticoids may promote MDSCs expansion in a murine trauma model and MDSCs may be beneficial for the trauma host.

A protective role for inflammasome activation following injury

The inflammasome is activated in response to pathogen or endogenous danger signals and acts as an initiator and mediator of inflammatory reactions. In this study, we wished to identify whether the inflammasome is activated in vivo by injury. And if so, we wanted to characterize the kinetics, the immune cell distribution, and the functional impact of inflammasome activation on the injury response. Because caspase-1 activation is the final product of the inflammasome pathway, we used cleaved caspase-1 p10 and p20 as a measure for inflammasome activation in cells. We first developed a procedure to stain for caspase-1 p10 and p20 by flow cytometry (FACS) in lipopolysaccharide + adenosine triphosphate-stimulated spleen cells. This method for measuring caspase-1 activation was validated using FLICA (fluorochrome inhibitor of caspase), a fluorescently tagged specific binding reagent for activated caspase-1. Once validated by in vitro studies, we measured caspase-1 activation by FACS in immune cell subsets prepared from the lymph nodes and spleens of sham- or burn-injured mice at different time points. Lastly, the functional significance of inflammasome activation following burn injury was tested in mice treated with the specific caspase-1 inhibitor, AC-YVAD-CMK. The results of in vitro studies indicated that adenosine triphosphate and lipopolysaccharide stimulation induced significant caspase-1 activation in dendritic cells, macrophages, and natural killer (NK) cells. This approach also revealed caspase-1 activation in CD4 and CD8 T cells as well as B cells. We then measured caspase-1 activation in cells prepared from the lymph nodes and spleens of sham- or burn-injured mice. Significant caspase-1 activation was detected in macrophages and dendritic cells by 4 h after injury and peaked by day 1 after injury. FLICA staining confirmed that caspase-1 activation occurred in these cells at 1 day after injury. We also found significant injury-induced caspase-1 activation in NK cells, CD4 T cells, and B cells, but CD8 T cells did not demonstrate caspase-1 activation. Surprisingly, we found that blocking caspase-1 activation with AC-YVAD-CMK in vivo caused significantly higher mortality in burn-injured mice (P < 0.01). Taken together, these findings document that injury induces inflammasome activation in many immune cell subsets, but primarily in macrophages, and that inflammasome activation plays a protective role in the host response to severe injury.