Temporal Profile of Serum Neurofilament Light (NF-L) and Heavy (pNF-H) Level Associations With 6-Month Cognitive Performance in Patients With Moderate-Severe Traumatic Brain Injury.

OBJECTIVE: Identification of biomarkers of cognitive recovery after traumatic brain injury (TBI) will inform care and improve outcomes. This study assessed the utility of neurofilament (NF-L and pNF-H), a marker of neuronal injury, informing cognitive performance following moderate-to-severe TBI (msTBI). SETTING: Level 1 trauma center and outpatient via postdischarge follow-up. PARTICIPANTS: N = 94. Inclusion criteria : Glasgow Coma Scale score less than 13 or 13-15 with clinical evidence of moderate-to-severe injury traumatic brain injury on clinical imaging. Exclusion criteria : neurodegenerative condition, brain death within 3 days after injury. DESIGN: Prospective observational study. Blood samples were collected at several time points post-injury. Cognitive testing was completed at 6 months post-injury. MAIN MEASURES: Serum NF-L (Human Neurology 4-Plex B) pNF-H (SR-X) as measured by SIMOA Quanterix assay. Divided into 3 categorical time points at days post-injury (DPI): 0-15 DPI, 16-90 DPI, and >90 DPI. Cognitive composite comprised executive functioning measures derived from 3 standardized neuropsychological tests (eg, Delis-Kaplan Executive Function System: Verbal Fluency, California Verbal Learning Test, Second Edition, Wechsler Adult Intelligence Scale, Third Edition). RESULTS: pNF-H at 16-90 DPI was associated with cognitive outcomes including a cognitive-executive composite score at 6 months ( ß = -.430, t34 = -3.190, P = .003). CONCLUSIONS: Results suggest that "subacute" elevation of serum pNF-H levels may be associated with protracted/poor cognitive recovery from msTBI and may be a target for intervention. Interpretation is limited by small sample size and including only those who were able to complete cognitive testing.

Sedation Intensity in Patients with Moderate to Severe Traumatic Brain Injury in the Intensive Care Unit: A TRACK-TBI Cohort Study.

BACKGROUND: Interventions to reduce intracranial pressure (ICP) in patients with traumatic brain injury (TBI) are multimodal but variable, including sedation-dosing strategies. This article quantifies the different sedation intensities administered in patients with moderate to severe TBI (msTBI) using the therapy intensity level (TIL) across different intensive care units (ICUs), including the use of additional ICP-lowering therapies. METHODS: Within the prospective Transforming Research and Clinical Knowledge in TBI (TRACK-TBI) study, we performed a retrospective analysis of adult patients with msTBI admitted to an ICU for a least 5 days from seven US level 1 trauma centers who received invasive ICP monitoring and intravenous sedation. Sedation intensity was classified prospectively as one of three ordinal levels as part of the validated TIL score, which were collected at least once a day. RESULTS: A total of 127 patients met inclusion criteria (mean age 41.6 ± 17.7 years; 20% female). The median Injury Severity Score was 27 (interquartile range 17-33), with a median admission Glasgow Coma Score of 3 (interquartile range 3-7); 104 patients had severe TBI (82%), and 23 patients had moderate TBI (18%). The sedation intensity score was highest on the first ICU day (2.69 ± 1.78), independent of patient severity. Time to reaching each sedation intensity level varied by site. Sedation level I was reached within 24 h for all sites, but sedation levels II and III were reached variably between days 1 and 3. Sedation level III was never reached by two of seven sites. The total TIL score was highest on the first ICU day, with a modest decrease for each subsequent ICU day, but there was high site-specific practice-pattern variation. CONCLUSIONS: Intensity of sedation and other therapies for elevated ICP for patients with msTBI demonstrate large practice-pattern variation across level 1 trauma centers within the TRACK-TBI cohort study, independent of patient severity. Optimizing sedation strategies using patient-specific physiologic and pathoanatomic information may optimize patient outcomes.

Transcriptomic Signatures of Neuronally Derived Extracellular Vesicles Reveal the Presence of Olfactory Receptors in Clinical Samples from Traumatic Brain Injury Patients.

Traumatic brain injury (TBI) is defined as an injury to the brain by external forces which can lead to cellular damage and the disruption of normal central nervous system functions. The recently approved blood-based biomarkers GFAP and UCH-L1 can only detect injuries which are detectable on CT, and are not sensitive enough to diagnose milder injuries or concussion. Exosomes are small microvesicles which are released from the cell as a part of extracellular communication in normal as well as diseased states. The objective of this study was to identify the messenger RNA content of the exosomes released by injured neurons to identify new potential blood-based biomarkers for TBI. Human severe traumatic brain injury samples were used for this study. RNA was isolated from neuronal exosomes and total transcriptomic sequencing was performed. RNA sequencing data from neuronal exosomes isolated from serum showed mRNA transcripts of several neuronal genes. In particular, mRNAs of several olfactory receptor genes were present at elevated concentrations in the neuronal exosomes. Some of these genes were OR10A6, OR14A2, OR6F1, OR1B1, and OR1L1. RNA sequencing data from exosomes isolated from CSF showed a similar elevation of these olfactory receptors. We further validated the expression of these samples in serum samples of mild TBI patients, and a similar up-regulation of these olfactory receptors was observed. The data from these experiments suggest that damage to the neurons in the olfactory neuroepithelium as well as in the brain following a TBI may cause the release of mRNA from these receptors in the exosomes. Hence, olfactory receptors can be further explored as biomarkers for the diagnosis of TBI.

Predicting Clinical Outcomes 7-10 Years after Severe Traumatic Brain Injury: Exploring the Prognostic Utility of the IMPACT Lab Model and Cerebrospinal Fluid UCH-L1 and MAP-2.

BACKGROUND: Severe traumatic brain injury (TBI) is a major contributor to disability and mortality in the industrialized world. Outcomes of severe TBI are profoundly heterogeneous, complicating outcome prognostication. Several prognostic models have been validated for acute prediction of 6-month global outcomes following TBI (e.g., morbidity/mortality). In this preliminary observational prognostic study, we assess the utility of the International Mission on Prognosis and Analysis of Clinical Trials in TBI (IMPACT) Lab model in predicting longer term global and cognitive outcomes (7-10 years post injury) and the extent to which cerebrospinal fluid (CSF) biomarkers enhance outcome prediction. METHODS: Very long-term global outcome was assessed in a total of 59 participants (41 of whom did not survive their injuries) using the Glasgow Outcome Scale-Extended and Disability Rating Scale. More detailed outcome information regarding cognitive functioning in daily life was collected from 18 participants surviving to 7-10 years post injury using the Cognitive Subscale of the Functional Independence Measure. A subset (n = 10) of these participants also completed performance-based cognitive testing (Digit Span Test) by telephone. The IMPACT lab model was applied to determine its prognostic value in relation to very long-term outcomes as well as the additive effects of acute CSF ubiquitin C-terminal hydrolase-L1 (UCH-L1) and microtubule associated protein 2 (MAP-2) concentrations. RESULTS: The IMPACT lab model discriminated favorable versus unfavorable 7- to 10-year outcome with an area under the receiver operating characteristic curve of 0.80. Higher IMPACT lab model risk scores predicted greater extent of very long-term morbidity (ß = 0.488 p = 0.000) as well as reduced cognitive independence (ß = - 0.515, p = 0.034). Acute elevations in UCH-L1 levels were also predictive of lesser independence in cognitive activities in daily life at very long-term follow-up (ß = 0.286, p = 0.048). Addition of two CSF biomarkers significantly improved prediction of very long-term neuropsychological performance among survivors, with the overall model (including IMPACT lab score, UCH-L1, and MAP-2) explaining 89.6% of variance in cognitive performance 7-10 years post injury (p = 0.008). Higher acute UCH-L1 concentrations were predictive of poorer cognitive performance (ß = - 0.496, p = 0.029), whereas higher acute MAP-2 concentrations demonstrated a strong cognitive protective effect (ß = 0.679, p = 0.010). CONCLUSIONS: Although preliminary, results suggest that existing prognostic models, including models with incorporation of CSF markers, may be applied to predict outcome of severe TBI years after injury. Continued research is needed examining early predictors of longer-term outcomes following TBI to identify potential targets for clinical trials that could impact long-ranging functional and cognitive outcomes.

Characterization of Calpain and Caspase-6-Generated Glial Fibrillary Acidic Protein Breakdown Products Following Traumatic Brain Injury and Astroglial Cell Injury.

Glial fibrillary acidic protein (GFAP) is the major intermediate filament III protein of astroglia cells which is upregulated in traumatic brain injury (TBI). Here we reported that GFAP is truncated at both the C- and N-terminals by cytosolic protease calpain to GFAP breakdown products (GBDP) of 46-40K then 38K following pro-necrotic (A23187) and pro-apoptotic (staurosporine) challenges to primary cultured astroglia or neuron-glia mixed cells. In addition, with another pro-apoptotic challenge (EDTA) where caspases are activated but not calpain, GFAP was fragmented internally, generating a C-terminal GBDP of 20 kDa. Following controlled cortical impact in mice, GBDP of 46-40K and 38K were formed from day 3 to 28 post-injury. Purified GFAP protein treated with calpain-1 and -2 generates (i) major N-terminal cleavage sites at A-56*A-61 and (ii) major C-terminal cleavage sites at T-383*Q-388, producing a limit fragment of 38K. Caspase-6 treated GFAP was cleaved at D-78/R-79 and D-225/A-226, where GFAP was relatively resistant to caspase-3. We also derived a GBDP-38K N-terminal-specific antibody which only labels injured astroglia cell body in both cultured astroglia and mouse cortex and hippocampus after TBI. As a clinical translation, we observed that CSF samples collected from severe human TBI have elevated levels of GBDP-38K as well as two C-terminally released GFAP peptides (DGEVIKES and DGEVIKE). Thus, in addition to intact GFAP, both the GBDP-38K as well as unique GFAP released C-terminal proteolytic peptides species might have the potential in tracking brain injury progression.

Longitudinal Changes in Disability Rating Scale Scores: A Secondary Analysis Among Patients With Severe TBI Enrolled in the Epo Clinical Trial.

OBJECTIVES: Long-term neurological response to treatment after a severe traumatic brain injury (sTBI) is a dynamic process. Failure to capture individual heterogeneity in recovery may impact findings from single endpoint sTBI randomized controlled trials (RCT). The present study re-examined the efficacy of erythropoietin (Epo) and transfusion thresholds through longitudinal modeling of sTBI recovery as measured by the Disability Rating Scale (DRS). This study complements the report of primary outcomes in the Epo sTBI RCT, which failed to detect significant effects of acute treatment at 6 months post-injury. METHODS: We implemented mixed effects models to characterize the recovery time-course and to examine treatment efficacy as a function of time post-injury and injury severity. RESULTS: The inter-quartile range (25th-75th percentile) of DRS scores was 20-28 at week1; 8-24 at week 4; and 3-17 at 6 months. TBI severity group was found to significantly interact with Epo randomization group on mean DRS recovery curves. No significant differences in DRS recovery were found in transfusion threshold groups. CONCLUSIONS: This study demonstrated the value of taking a comprehensive view of recovery from sTBI in the Epo RCT as a temporally dynamic process that is shaped by both treatment and injury severity, and highlights the importance of the timing of primary outcome measurement. Effects of Epo treatment varied as a function of injury severity and time. Future studies are warranted to understand the possible moderating influence of injury severity on treatment effects pertaining to sTBI recovery. (JINS, 2019, 25, 293-301).

Arginase overexpression in neurons and its effect on traumatic brain injury.

Arginine is a semi-essential amino acid which serves as a substrate for nitric oxide (NO) production by nitric oxide synthase (NOS) and a precursor for various metabolites including ornithine, creatine, polyamines, and agmatine. Arginase competes with nitric oxide synthase for substrate arginine to produce orthinine and urea. There is contradictory evidence in the literature on the role of nitric oxide in the pathophysiology of traumatic brain injury (TBI). These contradictory perspectives are likely due to different NOS isoforms - endothelial (eNOS), inducible (iNOS) and neuronal (nNOS) which are expressed in the central nervous system. Of these, the role of nNOS in acute injury remains less clear. This study aimed to employ a genetic approach by overexpressing arginase isoforms specifically in neurons using a Thy-1 promoter to manipulate cell autonomous NO production in the context of TBI. The hypothesis was that increased arginase would divert arginine from pathological NO production. We generated 2 mouse lines that overexpress arginase I (a cytoplasmic enzyme) or arginase II (a mitochondrial enzyme) in neurons of FVB mice. We found that two-weeks after induction of controlled cortical injury, overexpressing arginase I but not arginase II in neurons significantly reduced contusion size and contusion index compared to wild-type (WT) mice. This study establishes enhanced neuronal arginase levels as a strategy to affect the course of TBI and provides support for the potential role of neuronal NO production in this condition.

Repeated mild traumatic brain injury produces neuroinflammation, anxiety-like behaviour and impaired spatial memory in mice.

PRIMARY OBJECTIVE: Repeated traumatic brain injuries (rmTBI) are frequently associated with debilitating neuropsychiatric conditions such as cognitive impairment, mood disorders, and post-traumatic stress disorder. We tested the hypothesis that repeated mild traumatic brain injury impairs spatial memory and enhances anxiety-like behaviour. RESEARCH DESIGN: We used a between groups design using single (smTBI) or repeated (rmTBI) controlled cranial closed skull impacts to mice, compared to a control group. METHODS AND PROCEDURES: We assessed the effects of smTBI and rmTBI using measures of motor performance (Rotarod Test [RT]), anxiety-like behaviour (Elevated Plus Maze [EPM] and Open Field [OF] tests), and spatial memory (Morris Water Maze [MWM]) within 12 days of the final injury. In separate groups of mice, astrocytosis and microglial activation were assessed 24 hours after the final injury using GFAP and IBA-1 immunohistochemistry. MAIN OUTCOMES AND RESULTS: RmTBI impaired spatial memory in the MWM and increased anxiety-like behaviour in the EPM and OFT. In addition, rmTBI elevated GFAP and IBA-1 immunohistochemistry throughout the mouse brain. RmTBI produced astrocytosis and microglial activation, and elicited impaired spatial memory and anxiety-like behaviour. CONCLUSIONS: rmTBI produces acute cognitive and anxiety-like disturbances associated with inflammatory changes in brain regions involved in spatial memory and anxiety.

A joint logistic regression and covariate-adjusted continuous-time Markov chain model.

The use of longitudinal measurements to predict a categorical outcome is an increasingly common goal in research studies. Joint models are commonly used to describe two or more models simultaneously by considering the correlated nature of their outcomes and the random error present in the longitudinal measurements. However, there is limited research on joint models with longitudinal predictors and categorical cross-sectional outcomes. Perhaps the most challenging task is how to model the longitudinal predictor process such that it represents the true biological mechanism that dictates the association with the categorical response. We propose a joint logistic regression and Markov chain model to describe a binary cross-sectional response, where the unobserved transition rates of a two-state continuous-time Markov chain are included as covariates. We use the method of maximum likelihood to estimate the parameters of our model. In a simulation study, coverage probabilities of about 95%, standard deviations close to standard errors, and low biases for the parameter values show that our estimation method is adequate. We apply the proposed joint model to a dataset of patients with traumatic brain injury to describe and predict a 6-month outcome based on physiological data collected post-injury and admission characteristics. Our analysis indicates that the information provided by physiological changes over time may help improve prediction of long-term functional status of these severely ill subjects. Copyright © 2017 John Wiley & Sons, Ltd.

Evaluation of a Device Combining an Inferior Vena Cava Filter and a Central Venous Catheter for Preventing Pulmonary Embolism Among Critically Ill Trauma Patients.

PURPOSE: To evaluate efficacy and safety of a novel device that combines an inferior vena cava (IVC) filter and central venous catheter (CVC) for prevention of pulmonary embolism (PE) in critically ill patients. MATERIALS AND METHODS: In a multicenter, prospective, single-arm clinical trial, the device was inserted at the bedside without fluoroscopy and subsequently retrieved before transfer from the intensive care unit (ICU). The primary efficacy endpoint was freedom from clinically significant PE or fatal PE 72 hours after device removal or discharge, whichever occurred first. Secondary endpoints were incidence of acute proximal deep venous thrombosis (DVT), catheter-related thrombosis, catheter-related bloodstream infections, major bleeding events, and clinically significant thrombus (occupying > 25% of volume of filter) detected by cavography before retrieval. RESULTS: The device was placed in 163 critically ill patients with contraindications to anticoagulation; 151 (93%) were critically ill trauma patients, 129 (85%) had head or spine trauma, and 102 (79%) had intracranial bleeding. The primary efficacy endpoint was achieved for all 163 (100%) patients (95% confidence interval [CI], 97.8%-100%, P < .01). Diagnosis of new or worsening acute proximal DVT was time dependent with 11 (7%) occurring during the first 7 days. There were no (0%) catheter-related bloodstream infections. There were 5 (3.1%) major bleeding events. Significant thrombus in the IVC filter occurred in 14 (8.6%) patients. Prophylactic anticoagulation was not initiated for a mean of 5.5 days ± 4.3 after ICU admission. CONCLUSIONS: This novel device prevented clinically significant and fatal PE among critically ill trauma patients with low risk of complications.

Morbidity and mortality associated with hypernatremia in patients with severe traumatic brain injury.

OBJECTIVE Hypernatremia is independently associated with increased mortality in critically ill patients. Few studies have evaluated the impact of hypernatremia on early mortality in patients with severe traumatic brain injury (TBI) treated in a neurocritical care unit. METHODS A retrospective review of patients with severe TBI (admission Glasgow Coma Scale score ≤ 8) treated in a single neurocritical care unit between 1986 and 2012 was performed. Patients with at least 3 serum sodium values were selected for the study. Patients with diabetes insipidus and those with hypernatremia on admission were excluded. The highest serum sodium level during the hospital stay was recorded, and hypernatremia was classified as none (≤ 150 mEq/L), mild (151-155 mEq/L), moderate (156-160 mEq/L), and severe (> 160 mEq/L). Multivariate Cox regression analysis was performed to determine independent predictors of early mortality. RESULTS A total of 588 patients with severe TBI were studied. The median number of serum sodium measurements for patients in this study was 17 (range 3-190). No hypernatremia was seen in 371 patients (63.1%), mild hypernatremia in 77 patients (13.1%), moderate hypernatremia in 50 patients (8.5%), and severe hypernatremia in 90 patients (15.3%). Hypernatremia was detected within the 1st week of admission in 79.3% of patients (n = 172), with the majority of patients (46%) being diagnosed within 72 hours after admission. Acute kidney injury, defined as a rise in creatinine of ≥ 0.3 mg/dl, was observed in 162 patients (27.6%) and was significantly associated with the degree of hypernatremia (p < 0.001). At discharge, 148 patients (25.2%) had died. Hypernatremia was a significant independent predictor of mortality (hazard ratios for mild: 3.4, moderate: 4.4, and severe: 8.4; p < 0.001). Survival analysis showed significantly lower survival rates for patients with greater degrees of hypernatremia (log-rank test, p < 0.001). CONCLUSIONS Hypernatremia after admission in patients with severe TBI was independently associated with greater risk of early mortality. In addition to severe hypernatremia, mild and moderate hypernatremia were significantly associated with increased early mortality in patients with severe TBI.

Axon initial segment-associated microglia.

Microglia are the brain's resident immune cells and function as the main defense against pathogens or injury. However, in the absence of disease, microglia have other functions in the normal brain. For example, previous studies showed that microglia contribute to circuit refinement and synaptic plasticity in the developing and adult brain, respectively. Thus, microglia actively participate in regulating neuronal excitability and function. Here, we report that in the cortex, but not other brain regions, a subset of microglia extend a single process that specifically associates and overlaps with the axon initial segment (AIS), the site where action potentials are generated. Similar associations were not observed with dendrites or distal axons. Microglia-AIS interactions appear early in development, persist throughout adulthood, and are conserved across species including mice, rats, and primates. However, these interactions are lost after microglial activation following brain injury, suggesting that such interactions may be part of healthy brain function. Loss of microglial CX3CR1 receptors, or the specialized extracellular matrix surrounding the AIS, did not disrupt the interaction. However, loss of AIS proteins by the neuron-specific deletion of the master AIS scaffold AnkyrinG disrupted microglia-AIS interactions. These results reveal a unique population of microglia that specifically interact with the AIS in the adult cortex.

Predicting Intracranial Pressure and Brain Tissue Oxygen Crises in Patients With Severe Traumatic Brain Injury.

OBJECTIVES: To develop computer algorithms that can recognize physiologic patterns in traumatic brain injury patients that occur in advance of intracranial pressure and partial brain tissue oxygenation crises. The automated early detection of crisis precursors can provide clinicians with time to intervene in order to prevent or mitigate secondary brain injury. DESIGN: A retrospective study was conducted from prospectively collected physiologic data. intracranial pressure, and partial brain tissue oxygenation crisis events were defined as intracranial pressure of greater than or equal to 20 mm Hg lasting at least 15 minutes and partial brain tissue oxygenation value of less than 10 mm Hg for at least 10 minutes, respectively. The physiologic data preceding each crisis event were used to identify precursors associated with crisis onset. Multivariate classification models were applied to recorded data in 30-minute epochs of time to predict crises between 15 and 360 minutes in the future. SETTING: The neurosurgical unit of Ben Taub Hospital (Houston, TX). SUBJECTS: Our cohort consisted of 817 subjects with severe traumatic brain injury. MEASUREMENTS AND MAIN RESULTS: Our algorithm can predict the onset of intracranial pressure crises with 30-minute advance warning with an area under the receiver operating characteristic curve of 0.86 using only intracranial pressure measurements and time since last crisis. An analogous algorithm can predict the start of partial brain tissue oxygenation crises with 30-minute advanced warning with an area under the receiver operating characteristic curve of 0.91. CONCLUSIONS: Our algorithms provide accurate and timely predictions of intracranial hypertension and tissue hypoxia crises in patients with severe traumatic brain injury. Almost all of the information needed to predict the onset of these events is contained within the signal of interest and the time since last crisis.

Critical Care Management of the Patient with Traumatic Brain Injury.

The critical care management of patients with traumatic brain injury is complex. The primary goal is to minimize the effects of secondary injury that would otherwise serve to further worsen neurologic function. This requires an understanding of the abnormal brain physiology that is found in these patients. In this article the authors discuss this physiology and describe suggested treatment strategies for these patients based on evidence-based guidelines.

Hypothermia for Increased Intracranial Pressure: Is It Dead?

Mild to moderate therapeutic hypothermia (HT) has been used to alleviate intracranial hypertension in traumatic brain injury (TBI). Its main contribution is thought to be via reduction in cerebral metabolic requirement leading both to favorable oxygen/metabolic delivery-demand ratios as well as a reduction of cerebral blood volume resulting in decreased ICP. Nevertheless, HT is a clinically complex, labor-intensive procedure with numerous potential adverse effects. Furthermore, randomized controlled trials suggest either no effect or harm. These facts challenge the role of HT in TBI. We address this challenge by posing three questions that relate to the overarching value of controlling ICP, the effectiveness of HT in reducing ICP, and the benefit-risk ratio of the intervention. We conclude that HT should not be used as an "early" intervention unless as a part of a clinical trial, although it may still have a role in patients with refractory intracranial hypertension.

Plasma cytokines IL-6, IL-8, and IL-10 are associated with the development of acute respiratory distress syndrome in patients with severe traumatic brain injury.

BACKGROUND: Patients with severe traumatic brain injury (TBI) are at risk of the development of acute respiratory distress syndrome (ARDS). TBI and ARDS pathophysiologic mechanisms are known to independently involve significant inflammatory responses. The literature on the association between plasma inflammatory cytokines and ARDS in patients with TBI is sparse. METHODS: The study was a secondary analysis of the safety of a randomized trial of erythropoietin and transfusion threshold in patients with severe TBI. Inflammatory markers within the first 24 hours after injury were compared in patients who developed ARDS and patients without ARDS, using Cox proportional hazards models. RESULTS: There were 200 patients enrolled in the study. The majority of plasma and cerebrospinal fluid (CSF) cytokine levels were obtained within 6 hours. Plasma proinflammatory markers IL-6 and IL-8 and anti-inflammatory marker IL-10 were associated with the development of ARDS (adjusted hazard ratio (HR) = 1.55, confidence interval (CI) = 1.14, 2.11, P = 0.005 for IL-6; adjusted HR = 1.32, CI = 1.10, 1.59, P = 0.003 for IL-8). CONCLUSION: Plasma markers of IL-6, IL-8, and IL-10 are associated with ARDS in patients with severe TBI. TRIAL REGISTRATION: NCT00313716 registered 4/2006.

Multi-modality neuro-monitoring: conventional clinical trial design.

Multi-modal monitoring has become an integral part of neurointensive care. However, our approach is at this time neither standardized nor backed by data from randomized controlled trials. The goal of the second Neurocritical Care Research Conference was to discuss research priorities in multi-modal monitoring, what research tools are available, as well as the latest advances in clinical trial design. This section of the meeting was focused on how such a trial should be designed so as to maximize yield and avoid mistakes of the past.

Biomarkers improve clinical outcome predictors of mortality following non-penetrating severe traumatic brain injury.

OBJECTIVE: This study assessed whether early levels of biomarkers measured in CSF within 24-h of severe TBI would improve the clinical prediction of 6-months mortality. METHODS: This prospective study conducted at two Level 1 Trauma Centers enrolled adults with severe TBI (GCS ≤8) requiring a ventriculostomy as well as control subjects. Ventricular CSF was sampled within 24-h of injury and analyzed for seven candidate biomarkers (UCH-L1, MAP-2, SBDP150, SBDP145, SBDP120, MBP, and S100B). The International Mission on Prognosis and Analysis of Clinical Trials in TBI (IMPACT) scores (Core, Extended, and Lab) were calculated for each patient to determine risk of 6-months mortality. The IMPACT models and biomarkers were assessed alone and in combination. RESULTS: There were 152 patients enrolled, 131 TBI patients and 21 control patients. Thirty six (27 %) patients did not survive to 6 months. Biomarkers were all significantly elevated in TBI versus controls (p < 0.001). Peak levels of UCH-L1, SBDP145, MAP-2, and MBP were significantly higher in non-survivors (p < 0.05). Of the seven biomarkers measured at 12-h post-injury MAP-2 (p = 0.004), UCH-L1 (p = 0.024), and MBP (p = 0.037) had significant unadjusted hazard ratios. Of the seven biomarkers measured at the earliest time within 24-h, MAP-2 (p = 0.002), UCH-L1 (p = 0.016), MBP (p = 0.021), and SBDP145 (0.029) had the most significant elevations. When the IMPACT Extended Model was combined with the biomarkers, MAP-2 contributed most significantly to the survival models with sensitivities of 97-100 %. CONCLUSIONS: These data suggest that early levels of MAP-2 in combination with clinical data provide enhanced prognostic capabilities for mortality at 6 months.

Enrollment of racially/ethnically diverse participants in traumatic brain injury trials: effect of availability of exception from informed consent.

BACKGROUND: The Final Rule regulations were developed to allow exception from informed consent (EFIC) to enable clinical trial research in emergency settings where major barriers exist for informed consent. There is little known evidence of the effect of the Final Rule in minority enrollment in clinical trials, particularly in traumatic brain injury (TBI) trials. A clinical trial funded by the National Institute of Neurological Disorders and Stroke was conducted to study the effects of erythropoietin on cerebral vascular dysfunction and anemia in subjects with TBI. There were periods of time when EFIC was and was not available for enrollment into the study. PURPOSE: To explore the effect of EFIC availability on TBI trial enrollment of minority versus non-minority subjects. METHODS: Minority status of screened (n = 289) and enrolled (n = 191) TBI subjects was determined for this study. We tested for the presence of a minority and EFIC availability interaction in a multiple logistic regression model after controlling for EFIC and minority group main effects and other covariates. RESULTS: An interaction between the availability of EFIC minority and non-minority enrollment was not detected (odds ratio = 1.22; 95% confidence interval (CI) = 0.29-5.16). LIMITATIONS: Our study was conducted at a single site, and the CI for the EFIC and minority interaction term was wide. Therefore, a small interaction effect cannot be ruled out. CONCLUSION: EFIC increased the odds of being enrolled regardless of minority status.

Monitoring biomarkers of cellular injury and death in acute brain injury.

BACKGROUND: Molecular biomarkers have revolutionalized diagnosis and treatment of many diseases, such as troponin use in myocardial infarction. Urgent need for high-fidelity biomarkers in neurocritical care has resulted in numerous studies reporting potential candidate biomarkers. METHODS: We performed an electronic literature search and systematic review of English language articles on cellular/molecular biomarkers associated with outcome and with disease-specific secondary complications in adult patients with acute ischemic stroke (AIS), intracerebral hemorrhage (ICH), subarachnoid hemorrhage (SAH), traumatic brain injury (TBI), and post-cardiac arrest hypoxic ischemic encephalopathic injuries (HIE). RESULTS: A total of 135 articles were included. Though a wide variety of potential biomarkers have been identified, only neuron-specific enolase has been validated in large cohorts and shows 100% specificity for poor outcome prediction in HIE patients not treated with therapeutic hypothermia. There are many promising candidate blood and CSF biomarkers in SAH, AIS, ICH, and TBI, but none yet meets criteria for routine clinical use. CONCLUSION: Current studies vary significantly in patient selection, biosample collection/processing, and biomarker measurement protocols, thereby limiting the generalizability of overall results. Future large prospective studies with standardized treatment, biosample collection, and biomarker measurement and validation protocols are necessary to identify high-fidelity biomarkers in neurocritical care.