Inflammatory Biomarkers of Traumatic Brain Injury.

Traumatic brain injury (TBI) has a complex pathology in which the initial injury releases damage associated proteins that exacerbate the neuroinflammatory response during the chronic secondary injury period. One of the major pathological players in the inflammatory response after TBI is the inflammasome. Increased levels of inflammasome proteins during the acute phase after TBI are associated with worse functional outcomes. Previous studies reveal that the level of inflammasome proteins in biological fluids may be used as promising new biomarkers for the determination of TBI functional outcomes. In this study, we provide further evidence that inflammatory cytokines and inflammasome proteins in serum may be used to determine injury severity and predict pathological outcomes. In this study, we analyzed blood serum from TBI patients and respective controls utilizing Simple Plex inflammasome and V-PLEX inflammatory cytokine assays. We performed statistical analyses to determine which proteins were significantly elevated in TBI individuals. The receiver operating characteristics (ROC) were determined to obtain the area under the curve (AUC) to establish the potential fit as a biomarker. Potential biomarkers were then compared to documented patient Glasgow coma scale scores via a correlation matrix and a multivariate linear regression to determine how respective biomarkers are related to the injury severity and pathological outcome. Inflammasome proteins and inflammatory cytokines were elevated after TBI, and the apoptosis-associated speck like protein containing a caspase recruitment domain (ASC), interleukin (IL)-18, tumor necrosis factor (TNF)-α, IL-4 and IL-6 were the most reliable biomarkers. Additionally, levels of these proteins were correlated with known clinical indicators of pathological outcome, such as the Glasgow coma scale (GCS). Our results show that inflammatory cytokines and inflammasome proteins are promising biomarkers for determining pathological outcomes after TBI. Additionally, levels of biomarkers could potentially be utilized to determine a patient's injury severity and subsequent pathological outcome. These findings show that inflammation-associated proteins in the blood are reliable biomarkers of injury severity that can also be used to assess the functional outcomes of TBI patients.

Optimized detection of lung IL-6 via enzymatic liquefaction of low respiratory tract samples: application for managing ventilated patients.

Lung IL-6 is a promising biomarker for predicting respiratory failure during pulmonary infections. This biomarker is found in respiratory samples which need to be liquefied prior to analysis. Traditional liquefying methods use reducing agents such as dithiothreitol (DTT). However, DTT impairs immunodetection and does not liquefy highly viscous samples. We propose an enzymatic method that liquefies samples by means of generating O2 bubbles with endogenous catalase. Low respiratory tract specimens from 48 mechanically ventilated patients (38 with SARS-CoV-2 infection) were treated with DTT or with the enzymatic method. We used turbidimetry to compare the liquefaction degree and IL-6 was quantified with ELISA. Finally, we used AUC-ROC, time-to-event and principal component analysis to evaluate the association between respiratory compromise or local inflammation and IL-6 determined with both methods. Enzymatically treated samples were better liquefied than those reduced by DTT, which resulted in higher ELISA signals. Lung IL-6 levels obtained with the enzymatic procedure were negatively correlated with the oxygenation index (PaO2/FiO2) and the time of mechanical ventilation. The proposed enzymatic liquefaction method improves the sensitivity for lung IL-6 detection in respiratory samples, which increases its predictive power as a biomarker for evaluating respiratory compliance.

Use of diffusion tensor imaging to assess the vasogenic edema in traumatic pericontusional tissue.

BACKGROUND AND OBJECTIVE: Cerebral edema is a frequent and serious complication of traumatic brain injury (TBI). Diffusion tensor imaging (DTI) is considered a useful technique to assess white matter integrity after TBI. The objective of this prospective, observational study was to assess the characteristics of the vasogenic edema in the traumatic pericontusional tissue and compare it to the vasogenic edema found in brain tumors. We also included a control group. METHODS: Using DTI, the Apparent diffusion coefficient (ADC) and Fractional anisotropy (FA) were measured in the area of vasogenic edema in both TBI and tumor patients. The measurements in the control group were done in the gray and white matter. We included 15 TBI patients, 18 tumor patients and 15 controls. RESULTS: ADC and FA showed no differences between TBI and tumor patients (p=0.27 for AF; p=0.79 for ADC). Compared to healthy controls, TBI and tumor patients presented higher ADC values and lower FA values. The differences between TBI and controls were statistically significant (p<0.05). CONCLUSIONS: In this prospective observational study using DTI-MRI in a selected group of mild and moderate TBI patients with vasogenic pericontusional edema we have shown that there were no significant differences of the ADC and FA values compared to brain tumor patients. Furthermore, healthy controls showed significant lower ADC values and higher FA values compared to TBI and tumor patients. Future studies, using DTI-MRI, should address whether any therapy has a favorable impact on the vasogenic edema of TBI patients with brain contusions.

Dexamethasone for the treatment of traumatic brain injured patients with brain contusions and pericontusional edema: Study protocol for a prospective, randomized and double blind trial.

BACKGROUND: Traumatic brain injury (TBI) constitutes a leading cause of death and disability. Patients with TBI and cerebral contusions developing pericontusional edema are occasionally given dexamethasone on the belief that this edema is similar to that of tumors, in which the beneficial effect of dexamethasone has been demonstrated. METHODS: The DEXCON TBI trial is a multicenter, pragmatic, randomized, triple-blind, placebo controlled trial to quantify the effects of dexamethasone on the prognosis of TBI patients with brain contusions and pericontusional edema. Adult patients who fulfill the elegibility criteria will be randomized to dexamethasone/placebo in a short and descending course: 4 mg/6 h (2 days); 4 mg/8 hours (2 days); 2 mg/6 hours (2 days); 2 mg/8 hours (2 days); 1 mg/8 hours (2 days); 1 mg/12 hours (2 days). The primary outcome is the Glasgow Scale Outcome Extended (GOSE) performed 1 month and 6 months after TBI. Secondary outcomes are: number of episodes of neurological deterioration; symptoms associated with TBI; adverse events; volume of pericontusional edema before and after 12 days of treatment; results of the neuropsychological tests one month and 6 months after TBI. The main analysis will be on an "intention-to-treat" basis. Logistic regression will estimate the effect of dexamethasone/placebo on GOSE at one month and at 6 months, dichotomized in unfavorable outcome (GOSE 1-6) and favorable outcome (GOSE 7-8). Efficacy will also be analyzed using the 'sliding dichotomy'. An interim and safety analysis will be performed including patients recruited during the first year to calculate the conditional power. A study with 600 patients would have 80% power (2 sided alpha = 5%) to detect a 12% absolute increase (from 50% to 62%) in good recovery. DISCUSSION: This is a confirmative trial to elucidate the therapeutic efficacy of dexamethasone in a very specific group of TBI patients: patients with brain contusions and pericontusional edema. This trial could become an important milestone for TBI patients as nowadays there is no effective treatment in this type of patients. TRIAL REGISTRATION: eudraCT: 2019-004038-41; Clinical Trials.gov: NCT04303065.

Use of diffusion tensor imaging to assess the vasogenic edema in traumatic pericontusional tissue.

BACKGROUND AND OBJECTIVE: Cerebral edema is a frequent and serious complication of traumatic brain injury (TBI). Diffusion tensor imaging (DTI) is considered a useful technique to assess white matter integrity after TBI. The objective of this prospective, observational study was to assess the characteristics of the vasogenic edema in the traumatic pericontusional tissue and compare it to the vasogenic edema found in brain tumors. We also included a control group. METHODS: Using DTI, the Apparent diffusion coefficient (ADC) and Fractional anisotropy (FA) were measured in the area of vasogenic edema in both TBI and tumor patients. The measurements in the control group were done in the gray and white matter. We included 15 TBI patients, 18 tumor patients and 15 controls. RESULTS: ADC and FA showed no differences between TBI and tumor patients (p=0.27 for AF; p=0.79 for ADC). Compared to healthy controls, TBI and tumor patients presented higher ADC values and lower FA values. The differences between TBI and controls were statistically significant (p<0.05). CONCLUSIONS: In this prospective observational study using DTI-MRI in a selected group of mild and moderate TBI patients with vasogenic pericontusional edema we have shown that there were no significant differences of the ADC and FA values compared to brain tumor patients. Furthermore, healthy controls showed significant lower ADC values and higher FA values compared to TBI and tumor patients. Future studies, using DTI-MRI, should address whether any therapy has a favorable impact on the vasogenic edema of TBI patients with brain contusions.

Predictors of clinical failure of decompressive hemicraniectomy for malignant hemispheric infarction.

OBJECT: The aim of this study is to identify pre-operative clinical and/or radiological predictors of clinical failure of decompressive hemicraniectomy (DH) in the setting of malignant hemispheric infarction. These predictors could guide the decision for adjunctive internal brain decompression (e.g. strokectomy) at the time of the initial DH. METHODS: Retrospective chart review of all patients with malignant hemispheric infarction who underwent DH at our institution, from November 2008 to January 2013. Demographics, pre- and post-operative clinical characteristics and neuroimaging data were reviewed. The surgical outcome after DH was evaluated and clinical failure was defined as follows: lack of post-operative resolution of basal cistern effacement, and/or failure to achieve a post-operative decrease in midline shift by at least 50%, and/or post-operative neurological deterioration felt to be due to persistent mass effect, with or without a second, salvage operation (strokectomy). RESULTS: Out of 26 patients included in the study, 7 were considered to have clinical failure of their DH. Preoperative clinical and imaging variables were similar in the two groups, except that the presence of a nonreactive pupil immediately before surgery was associated clinical failure of the DH (p=0.0015). Patients in the clinical failure group had a lower postoperative GCS motor score and a strong but not statistically significant trend towards less favorable functional outcome (GOS 1-3). CONCLUSIONS: The presence of a nonreactive pupil before surgery is associated with clinical failure of DH, and should be taken into account when deciding whether to perform strokectomy at the time of DH.

Direct observation during surgery shows preservation of cerebral microcirculation in patients with traumatic brain injury.

OBJECTIVE: To describe the alterations of the cortical microcirculation of the brain (blood flow and vessel density) in TBI patients who and compare them with a control group. METHODS: Prospective and observational study in a third-level university hospital. Cortical microcirculation in the brain was directly observed using sidestream dark-field (SDF) imaging in 14 patients who underwent surgery: 5 subdural hematomas (SDH) and 9 parenchymal lesions (contusions/hematomas). In this last set of patients, images were recorded in the "pericontusional" areas and in the "surrounding" brain (areas that were as far from the lesion as the craniotomy allowed). These patients were compared to five patients who underwent craniotomy for a disease that did not affect the cortex. RESULTS: There were fewer "pericontusional" images that could be analyzed due to the presence of subarachnoid hemorrhage. The proportion or perfused vessels was similar in all groups: control 99.5% ± 1.3%; SDH 98.6% ± 2.4%; "pericontusional" area 98.2% ± 2.4%; "surrounding" area 98.4% ± 2.5% (p = 0.145). The perfused vessel density index was smaller in the "pericontusional" area: control 6.5 ± 1.6 l/mm; SDH 6.5 ± 2.5 l/mm; "pericontusional" area 5.4 ± 2.6 l/mm; "surrounding" 6.6 ± 2.1 l/mm (p = 0.07). CONCLUSIONS: Although the analysis of pericontusional zone was difficult, there were fewer vessels than in the controls and there was no change in the flow. In the surrounding zone and in patients with SDH, we did not document alterations in the microcirculation. Direct imaging of cerebral microcirculation in TBI patients showed that despite serious brain injury the cerebral microcirculation was remarkably well preserved.

Direct observation of human microcirculation during decompressive craniectomy after stroke.

OBJECTIVES: Most knowledge related to the pathophysiology of microcirculation in ischemic stroke comes from experimental research. Unfortunately, data on microcirculation in the human brain are limited, partially as a result of the lack of appropriate investigational techniques. The objective of our study was to test the hypothesis that cortical microcirculatory alterations in the brain, in terms of blood flow and vessel density, occur in patients with stroke who require surgical decompression compared with a control group. DESIGN: Prospective and observational study. SETTING: Third-level university hospital. PATIENTS: Six patients who had undergone decompressive surgery as a result of a space-occupying hemispheric infarction. These patients were compared with five patients who had undergone craniotomy for a disease not affecting the cortex. INTERVENTIONS: Cortical microcirculation in the brain was directly observed using sidestream dark-field imaging. All images were analyzed offline. MEASUREMENTS AND MAIN RESULTS: In patients with stroke with a space-occupying hemispheric infarction, 18 good-quality movie images were compared with 25 control group images. In the control group, cortical vessels showed a continuous flow in small, medium, and large vessels compared with patients with stroke who presented intermittent or no flow in all vessels. The proportion of perfused vessels was near 100% in control subjects and 63.44% in patients with stroke. The perfused vessel density index was also higher in control subjects (6.16 1/mm; interquartile range, 5.65-7.56) than in patients with stroke (2.77 1/mm; interquartile range, 1.75-3.86). CONCLUSION: Sidestream dark-field imaging allowed direct visualization of cerebral microcirculatory alterations in the operating room. This technique allowed the documentation of a significant blood flow reduction in the cortical microvascular and a decreased vascular density in patients with stroke compared with control subjects.

Lack of correlation among intracerebral cytokines, intracranial pressure, and brain tissue oxygenation in patients with traumatic brain injury and diffuse lesions.

OBJECTIVES: To determine the evolution of cytokine patterns using microdialysis in patients with traumatic brain injury with diffuse lesions and to study the relationship between cytokines and intracranial pressure, brain tissue oxygenation and lesion type on the computed cranial tomography scan (patients with and without brain swelling). DESIGN: Prospective and observational study. SETTING: Third-level university hospital. PATIENTS: Patients between 15 and 65 yrs with severe traumatic brain injury and a diffuse lesion requiring intracranial pressure and brain tissue oxygenation monitoring were eligible. INTERVENTIONS: Microdialysis catheters with a high-cutoff membrane of 100 kDa were inserted. RESULTS: Sixteen patients were included in the analysis. There was a substantial interindividual variability between cytokine values. The highest concentrations for the interleukin-1ß, interleukin-6, and interleukin-8 were measured during the first 24 hrs followed by a gradual decline. The average concentration for interleukin-10 did not vary over time. This pattern is the most frequent in patients with traumatic brain injury with diffuse lesions. The intracranial pressure-cytokines correlation coefficients for the 16 patients varied substantially: interleukin-1ß-intracranial pressure (-0.76 to 0.63); interleukin-6-intracranial pressure (-0.83 to 0.78); interleukin-8-intracranial pressure (-0.86 to 0.84); and interleukin-10-intracranial pressure (-0.36 to 0.65). The brain tissue oxygenation-cytokine correlation coefficients, like with intracranial pressure, also varied between patients: interleukin-1ß-brain tissue oxygenation (-0.49 to 0.68), interleukin-6-brain tissue oxygenation (-0.99 to 0.84); interleukin-8-brain tissue oxygenation (-0.65 to 0.74); and interleukin-10-brain tissue oxygenation (-0.34 to 0.52). Similarly, we found no difference in the cytokine values inpatient microdialysis with and without swelling in the computed tomographic scan. CONCLUSIONS: No clear relationship was found between the temporal pattern of cytokines and the behavior of the intracranial pressure, brain tissue oxygenation, and the presence or absence of swelling in the computed tomography scan. This study demonstrates the feasibility of microdialysis in recovering cytokines for a prolonged time, although there may be some nonresolved methodologic problems with this technique when we try to study the inflammation during traumatic brain injury that could affect the results and make interpretation of microdialysis data prone to difficulties.

Expression of toll-like receptors 2 and 4 is upregulated during hospital admission in traumatic patients: lack of correlation with blunted innate immune responses.

BACKGROUND: There are reports with conflicting results on the expression of toll-like receptors (TLRs) in trauma patients. In addition, these studies analyzed TLR expression only at patients' hospital admission but not later when complications usually arise. OBJECTIVES: To analyze the surface expression of TLR2 and TLR4 on circulating monocytes from trauma patients during the hospitalization period and to correlate this with cytokine production after stimulation with TLR2 and TLR4 agonists. The phagocytic capacity of monocytes was analyzed at the same time points of TLR expression analysis; to correlate these molecular findings with the presence or absence of infections. METHODS: Prospective and observational study from June 2005 to June 2007. In all analysis, a control group composed of healthy subjects was included. RESULTS: We studied 70 trauma patients admitted to the intensive care unit (ICU) of a tertiary hospital, and 30 healthy volunteers. Blood samples were collected at hospital admission, on day 7 and 14. Forty-four patients (63%) developed at least one episode of infection. Monocytes from trauma patients expressed higher levels of TLR2 and TLR4 than monocytes from control subjects at all time points. Expression of TLR2 and TLR4 in monocytes from those patients who developed any infection was significantly lower than in those patients without infection but still significantly higher than in control subjects. Cellular responses to TLR4 agonist were impaired. Monocytes from traumatic patients phagocytosized less efficiently than monocytes from control subjects. CONCLUSIONS: These results indicate that trauma patients present a dysregulation of the innate immune system that persists during the first 14 days after hospital admission.