The role of vasopressin V1A receptors in cytotoxic brain edema formation following brain injury.

BACKGROUND: The hormone and neuropeptide arginine-vasopressin is designated to the maintenance of osmotic homoeostasis and blood pressure regulation. While experimental data show vasopressin V(1A) receptors to regulate aquaporin (AQP)4 water channel dependent brain water movement, the specific role in vasogenic and cytotoxic edema formation remains unclear. The present study was designed to quantify the V(1A) receptor mediated regional brain edema formation in two clinically relevant experimental models, brain injury combined with secondary insult and focal ischemia. METHODS: Male Sprague-Dawley rats were randomly assigned to a continuous infusion of vehicle (1 % DMSO) or the selective non-peptide V(1A) antagonist SR49059 (83nM = 1 mg/kg) starting before controlled cortical impact (CCI) injury plus hypoxia and hypotension (HH, 30 min), or middle cerebral artery (MCA) occlusion (2 h + 2 h reperfusion). RESULTS: A global analysis of brain water content by the wet/dry weight method allowed optimizing the SR49059 dosage, and demonstrated the down-regulation of brain AQP4 expression by immunoblotting. Microgravimetrical quantification in 64 one mm(3) samples per animal (n = 6 per group) from bregma +2.7 to -6.3 mm analysis demonstrated brain edema to be reduced at 4 h by SR49059 treatment in the injured and contralateral cortex following CCI + HH (p = 0.007, p < 0.001) and in the infarct area following MCA occlusion (p = 0.013, p = 0.002, p = 0.004). CONCLUSIONS: Our findings demonstrate that an early cytotoxic brain edema component following brain injury plus secondary insult or focal ischemia results from a vasopressin V(1A) receptor mediated response, and occurs most likely through AQP4 up-regulation. The V(1A) antagonist SR49059 offers a new avenue in brain edema treatment and prompts further study into the role of vasopressin following brain injury.

Impact of GOS misclassification on ordinal outcome analysis of traumatic brain injury clinical trials.

This study extends our previous investigation regarding the effect of nondifferential dichotomous Glasgow Outcome Scale (GOS) misclassification in traumatic brain injury (TBI) clinical trials to the effect of GOS misclassification on ordinal analysis in TBI clinical trials. The impact of GOS misclassification and ordinal outcome analysis was explored via probabilistic sensitivity analyses using TBI patient datasets from the IMPACT database (n = 9205). Three patterns of misclassification were explored given the pre-specified misclassification distributions. For the random pattern, we specified a trapezoidal distribution (minimum: 80%, mode: 85%, and 95%, maximum: 100%) for both sensitivity and specificity; for the upward pattern, the same trapezoidal distribution for sensitivity but with a perfect specificity; and for the downward pattern, the same trapezoidal distribution for specificity but with a perfect sensitivity. The conventional 95% confidence intervals and simulation intervals, which accounts for the misclassification and random errors together, were reported. The results showed that given the specified misclassification distributions, the misclassification with a random or upward pattern would have caused a slightly underestimated outcome in the observed data. However, the misclassification with a downward pattern would have resulted in an inflated estimation. Thus the sensitivity analysis suggests that the nondifferential misclassification can cause uncertainties on the primary outcome estimation in TBI trials. However, such an effect is likely to be small when ordinal analysis is applied, compared with the impact of dichotomous GOS misclassifications. The result underlines that the ordinal GOS analysis may gain from both statistical efficiency, as suggested by several recent studies, and a relatively smaller impact from misclassification as compared with conventional binary GOS analysis.

Low-dose recombinant tissue-type plasminogen activator enhances clot resolution in brain hemorrhage: the intraventricular hemorrhage thrombolysis trial.

BACKGROUND AND PURPOSE: Patients with intracerebral hemorrhage and intraventricular hemorrhage have a reported mortality of 50% to 80%. We evaluated a clot lytic treatment strategy for these patients in terms of mortality, ventricular infection, and bleeding safety events, and for its effect on the rate of intraventricular clot lysis. METHODS: Forty-eight patients were enrolled at 14 centers and randomized to treatment with 3 mg recombinant tissue-type plasminogen activator (rtPA) or placebo. Demographic characteristics, severity factors, safety outcomes (mortality, infection, bleeding), and clot resolution rates were compared in the 2 groups. RESULTS: Severity factors, including admission Glasgow Coma Scale, intracerebral hemorrhage volume, intraventricular hemorrhage volume, and blood pressure were evenly distributed, as were adverse events, except for an increased frequency of respiratory system events in the placebo-treated group. Neither intracranial pressure nor cerebral perfusion pressure differed substantially between treatment groups on presentation, with external ventricular device closure, or during the active treatment phase. Frequency of death and ventriculitis was substantially lower than expected and bleeding events remained below the prespecified threshold for mortality (18% rtPA; 23% placebo), ventriculitis (8% rtPA; 9% placebo), symptomatic bleeding (23% rtPA; 5% placebo, which approached statistical significance; P=0.1). The median duration of dosing was 7.5 days for rtPA and 12 days for placebo. There was a significant beneficial effect of rtPA on rate of clot resolution. CONCLUSIONS: Low-dose rtPA for the treatment of intracerebral hemorrhage with intraventricular hemorrhage has an acceptable safety profile compared to placebo and historical controls. Data from a well-designed phase III clinical trial, such as CLEAR III, will be needed to fully evaluate this treatment.

Brain energy depletion in a rodent model of diffuse traumatic brain injury is not prevented with administration of sodium lactate.

Lactate has been identified as an alternative fuel for the brain in situations of increased energy demand, as following a traumatic brain injury (TBI). This study investigates the effect of treatment with sodium lactate (NaLac) on the changes in brain energy state induced by a severe diffuse TBI. Rats were assigned to one of the eight groups (n=10 per group): 1-sham, normal saline; 2-TBI, normal saline; 3-TBI, hypertonic saline; 4-TBI, 100mM NaLac, 5-TBI, 500 mM NaLac; 6-TBI, 1280 mM NaLac; 7-TBI, 2000 mM NaLac and 8-TBI-500 mM NaLac+magnesium sulfate. Cerebrums were removed 6h after trauma. Metabolites representative of the energy state (ATP, ATP-catabolites), N-acetylaspartate (NAA), antioxidant defenses (ascorbic acid, glutathione), markers of oxidative stress (malondialdehyde, ADP-ribose) and nicotinic coenzymes (NAD(+)) were measured by HPLC. TBI induced a marked decrease in the cerebral levels of ATP, NAA, ascorbic acid, glutathione and NAD(+) and a significant rise in the content of ATP-catabolites, malondialdehyde and ADP-ribose. These alterations were not ameliorated with NaLac infusion. We observed a significant reduction in cerebral NAD(+), an essential co-enzyme for mitochondrial lactate-dehydrogenase that converts lactate into pyruvate and thus replenishes the tricarboxylic acid cycle. These results suggest that the metabolic pathway necessary to consume lactate may be compromised following a severe diffuse TBI in rats.

Large between-center differences in outcome after moderate and severe traumatic brain injury in the international mission on prognosis and clinical trial design in traumatic brain injury (IMPACT) study.

BACKGROUND: Differences between centers in patient outcome after traumatic brain injury are of importance for multicenter studies and have seldom been studied. OBJECTIVE: To quantify the differences in centers enrolling patients in randomized clinical trials (RCTs) and surveys. METHODS: We analyzed individual patient data from 9578 patients with moderate and severe traumatic brain injury enrolled in 10 RCTs and 3 observational studies. We used random-effects logistic regression models to estimate the between-center differences in unfavorable outcome (dead, vegetative state, or severe disability measured with the Glasgow Outcome Scale) at 6 months adjusted for differences in patient characteristics. We calculated the difference in odds of unfavorable outcome between the centers at the higher end vs those at the lower end of the outcome distribution. We analyzed the total database, Europe and the United States separately, and 4 larger RCTs. RESULTS: The 9578 patients were enrolled at 265 centers, and 4629 (48%) had an unfavorable outcome. After adjustment for patient characteristics, there was a 3.3-fold difference in the odds of unfavorable outcome between the centers at the lower end of the outcome distribution (2.5th percentile) vs those at the higher end of the outcome distribution (97.5th percentile; P<.001). In the 4 larger RCTs, the differences between centers were similar. However, differences were smaller between centers in the United States (2.4-fold) than between centers in Europe (3.8-fold). CONCLUSION: Outcome after traumatic brain injury differs substantially between centers, particularly in Europe. Further research is needed to study explanations for these differences to suggest where quality of care might be improved.

Comparison between 3 infusion methods to measure cerebrospinal fluid outflow conductance.

OBJECT: There are several infusion methods available to estimate the outflow conductance (Cout) or outflow resistance (Rout=1/Cout) of the CSF system. It has been stated that for unknown reasons, the bolus infusion method estimates a higher C(out) than steady-state infusion methods. The aim of this study was to compare different infusion methods for estimation of Cout. METHODS: The following 3 different infusion methods were used: the bolus infusion method (Cout bol); the constant flow infusion method, both static (Cout stat) and dynamic (Cout dyn) analyses; and the constant pressure infusion method (Cout cpi). Repeated investigations were performed on an experimental model with well-known characteristics, with and without physiological pressure variations (B-waves, breathing, and so on). All 3 methods were also performed in a randomized order during the same investigation in 20 patients with probable or possible idiopathic normal-pressure hydrocephalus; 6 of these patients had a shunt and 14 did not. RESULTS: Without the presence of physiological pressure variations, the concordance in the experimental model was good between all methods. When they were added, the repeatability was better for the steady-state methods and a significantly higher Cout was found with the bolus method in the region of clinically relevant Cout (p<0.05). The visual fit for the bolus infusion was dependent on subjective assessment by the operator. This experimental finding was confirmed by the clinical results, where significant differences were found in the investigations in patients without shunts between Cout of the visual bolus method and Cout stat, Cout dyn, and Cout cpi (4.58, 4.18, and 6.12 µl/[second×kPa], respectively). CONCLUSIONS: This study emphasized the necessity for standardization of Cout measurements. An experienced operator could partly compensate for difficulties in correctly estimating the pressure parameters for the bolus infusion method, but for the general user this study suggests a steady-state method for estimating Cout.

A method for reducing misclassification in the extended Glasgow Outcome Score.

The eight-point extended Glasgow Outcome Scale (GOSE) is commonly used as the primary outcome measure in traumatic brain injury (TBI) clinical trials. The outcome is conventionally collected through a structured interview with the patient alone or together with a caretaker. Despite the fact that using the structured interview questionnaires helps reach agreement in GOSE assessment between raters, significant variation remains among different raters. We introduce an alternate GOSE rating system as an aid in determining GOSE scores, with the objective of reducing inter-rater variation in the primary outcome assessment in TBI trials. Forty-five trauma centers were randomly assigned to three groups to assess GOSE scores on sample cases, using the alternative GOSE rating system coupled with central quality control (Group 1), the alternative system alone (Group 2), or conventional structured interviews (Group 3). The inter-rater variation between an expert and untrained raters was assessed for each group and reported through raw agreement and with weighted kappa (kappa) statistics. Groups 2 and 3 without central review yielded inter-rater agreements of 83% (weighted kappa = 0.81; 95% CI 0.69, 0.92) and 83% (weighted kappa = 0.76, 95% CI 0.63, 0.89), respectively, in GOS scores. In GOSE, the groups had an agreement of 76% (weighted kappa = 0.79; 95% CI 0.69, 0.89), and 63% (weighted kappa = 0.70; 95% CI 0.60, 0.81), respectively. The group using the alternative rating system coupled with central monitoring yielded the highest inter-rater agreement among the three groups in rating GOS (97%; weighted kappa = 0.95; 95% CI 0.89, 1.00), and GOSE (97%; weighted kappa = 0.97; 95% CI 0.91, 1.00). The alternate system is an improved GOSE rating method that reduces inter-rater variations and provides for the first time, source documentation and structured narratives that allow a thorough central review of information. The data suggest that a collective effort can be made to minimize inter-rater variation.

IMPACT recommendations for improving the design and analysis of clinical trials in moderate to severe traumatic brain injury.

Clinical trials in traumatic brain injury (TBI) pose complex methodological challenges, largely related to the heterogeneity of the population. The International Mission on Prognosis and Clinical Trial Design in TBI study group has explored approaches for dealing with this heterogeneity with the aim to optimize clinical trials in TBI. Extensive prognostic analyses and simulation studies were conducted on individual patient data from eight trials and three observational studies. Here, we integrate the results of these studies into the International Mission on Prognosis and Clinical Trial Design in TBI recommendations for design and analysis of trials in TBI: Details of the major baseline prognostic characteristics should be provided in every report on a TBI study; in trials they should be differentiated per treatment group. We also advocate the reporting of the baseline prognostic risk as determined by validated prognostic models. Inclusion criteria should be as broad as is compatible with the current understanding of the mechanisms of action of the intervention being evaluated. This will maximize recruitment rates and enhance the generalizability of the results. The statistical analysis should incorporate prespecified covariate adjustment to mitigate the effects of the heterogeneity. The statistical analysis should use an ordinal approach, based on either sliding dichotomy or proportional odds methodology. Broad inclusion criteria, prespecified covariate adjustment, and an ordinal analysis will promote an efficient trial, yielding gains in statistical efficiency of more than 40%. This corresponds to being able to detect a 7% treatment effect with the same number of patients needed to demonstrate a 10% difference with an unadjusted analysis based on the dichotomized Glasgow outcome scale.

A simulation study evaluating approaches to the analysis of ordinal outcome data in randomized controlled trials in traumatic brain injury: results from the IMPACT Project.

BACKGROUND: Clinical trials in traumatic brain injury have a disappointing track record, with a long history of 'negative' Phase III trials. One contributor to this lack of success is almost certainly the low efficiency of the conventional approach to the analysis, which discards information by dichotomizing an ordinal outcome scale. PURPOSE: Our goal was to evaluate the potential efficiency gains, which can be achieved by using techniques, which extract additional information from ordinal outcome data - the proportional odds model and the sliding dichotomy. In addition, we evaluated the additional efficiency gains, which can be achieved through covariate adjustment. METHODS: The study was based on simulations, which were built around a database of patient-level data extracted from eight Phase III trials and three observational studies in traumatic brain injury. Two different putative treatment effects were explored, one which followed the proportional odds model, and the other which assumed that the effect of the intervention was to reduce the risk of death without changing the distribution of outcomes within survivors. The results are expressed as efficiency gains, reported as the percentage reduction in sample size that can be used with the ordinal analyses without loss of statistical power relative to the conventional binary analysis. RESULTS: The simulation results show substantial efficiency gains. Use of the sliding dichotomy allows sample sizes to be reduced by up to 40% without loss of statistical power. The proportional odds model gives modest additional gains over and above the gains achieved by use of the sliding dichotomy. LIMITATIONS: As with any simulation study, it is difficult to know how far the findings may be extrapolated beyond the actual situations that were modeled. CONCLUSIONS: Both ordinal techniques offer substantial efficiency gains relative to the conventional binary analysis. The choice between the two techniques involves subtle value judgments. In the situations examined, the proportional odds model gave efficiency gains over and above the sliding dichotomy, but arguably, the sliding dichotomy is more intuitive and clinically appealing.

Effect of secondary insults upon aquaporin-4 water channels following experimental cortical contusion in rats.

Although secondary insults of hypoxia and hypotension (HH) are generally considered to cause fulminant brain edema in traumatic brain injury (TBI), the combined effect of TBI with HH on brain edema and specifically the expression of aquaporin-4 (AQP4) have not been fully elucidated. The goal of this study was to document the effect of secondary insults on brain water, AQP4 expression, electrolytes, and blood-brain barrier (BBB) permeability during the acute stage of edema development. We measured brain water content and electrolytes (series 1); BBB permeability based on Evans blue (EB) dye extravasation (series 2); and AQP4 expression using immunoblotting (series 3) at 1 h and 5 h following cortical contusion injury (CCI). Secondary insults significantly worsened BBB function at 5 h post injury. Moreover, a significant reduction of upregulation on AQP4 expression was observed in trauma, coupled with a mild secondary insult of hypoxia hypotension. These findings indicate that a secondary insult following CCI at 5 h post injury worsens brain edema, disrupts ionic homeostasis, and blunts the normal upregulation of AQP4 that occurs after trauma, suggesting that the blunting of AQP4 may contribute to the detrimental effects of secondary insults.

The protein kinase C activator phorbol myristate acetate decreases brain edema by aquaporin 4 downregulation after middle cerebral artery occlusion in the rat.

The protein kinase C activator phorbol 12-myristate 13-acetate (PMA) is known to interact with aquaporin 4 (AQP 4), a water-selective transporting protein that is abundant in astrocytes, and has experimentally been found to decrease osmotically-induced cell swelling. The purpose of this study was to examine whether PMA reduces brain edema following focal ischemia induced by middle cerebral artery (MCA) occlusion by modulation of AQP4 expression. Male Sprague-Dawley rats were randomly assigned to either sham surgery (n = 6), or a continuous intravenous infusion of vehicle (1% dimethylsulfoxide), followed by MCA occlusion (n = 18), and administration of PMA at 50 microg/kg (n = 6) or at 200 microg/kg (n = 6) starting 60 min before or 30 min (200 microg/kg; n = 6) or 60 min (200 microg/kg; n = 6) after MCA occlusion. Cerebral blood flow was monitored with laser Doppler over the MCA territory, and confirmed a 70% reduction during occlusion. After a 2-h period of ischemia and 2 h of reperfusion, the animals were sacrificed for assessment of brain water content and sodium and potassium concentration. AQP4 expression was assessed by immunoblotting and quantified by densitometry (n = 24). Statistical analysis was performed by ANOVA followed by Tukey's post-hoc test. PMA treatment at 200 microg/kg significantly reduced brain water concentration in the infarcted area when started 60 min before or 30 min after occlusion (p < 0.001 and p = 0.022, respectively), and prevented the subsequent sodium shift (p < 0.05). PMA normalized the AQP4 upregulation in ischemia (p = 0.021). A downregulation of AQP4 in the ischemic area paralleling the reduction in brain edema formation following PMA treatment suggests that the effect was mediated by AQP4 modulation.

Baseline characteristics and statistical power in randomized controlled trials: selection, prognostic targeting, or covariate adjustment?

OBJECTIVE: Heterogeneity of patients is a common problem in randomized controlled trials (RCTs) in various fields of clinical research. We aimed to investigate the potential benefits of different approaches for dealing with heterogeneity in a case study on traumatic brain injury (TBI). DESIGN AND SETTING: Statistical modeling studies in three surveys and six randomized controlled trials. PATIENTS: Individual patient data (n = 8033) from the IMPACT database. INTERVENTIONS: We investigated the statistical power and efficiency of randomized controlled trials (RCTs) in relation to (1) selection according to baseline characteristics, (2) prognostic targeting (i.e., excluding those with a relatively extreme prognosis), and (3) covariate-adjusted analysis. Statistical power was expressed as the required sample size for obtaining 80% power and efficiency as the relative change in study duration, reflecting both gains in power and adverse effects on recruitment. Uniform and targeted treatment effects were simulated for 6 month unfavorable outcome. RESULTS: For a uniform treatment effect, selection resulted ina sample size reduction of 33% in the surveys and 5% in the RCTs, but decreased recruitment by 65% and 41%, respectively. Hence, the relative study duration was prolonged (surveys: 95%; RCTs: 60%). Prognostic targeting resulted in sample size reductions of 28% and 17%, and increased relative study duration by 5% in surveys and 11% in the RCTs. Covariate adjustment reduced sample sizes by 30% and 16%, respectively, and did not affect recruitment. For a targeted treatment effect, the sample size reductions by selection (surveys: 47%; RCTs: 20%) and prognostic targeting (surveys: 49%; RCTs: 41%) were larger and adverse effects on recruitment smaller. CONCLUSIONS: The benefits of selection and prognostic targeting in terms of statistical power are reversed by adverse effects on recruitment. Covariate adjusted analysis in a broadly selected group of patients is advisable if a uniform treatment effect is assumed, since there is no decrease in recruitment.

The influence of enrollment criteria on recruitment and outcome distribution in traumatic brain injury studies: results from the impact study.

Substantial heterogeneity exists among patients who suffer from traumatic brain injury (TBI). Strict enrollment criteria may diminish heterogeneity in randomized controlled trials (RCTs), but will also decrease recruitment and may affect the outcome distribution. The aim of this study was to investigate the influences of commonly used enrollment criteria for RCTs in TBI on potential recruitment and on outcome distribution. We used individual patient data from the International Mission on Prognosis and Analysis of Clinical Trials in TBI (IMPACT) database, including six therapeutic phase III RCTs (n = 5816) and three surveys (n = 2217) in TBI. The primary outcome was the Glasgow Outcome Scale (GOS) at 6 months after injury, which we dichotomized as favorable/unfavorable. We investigated the influences of commonly used enrollment criteria on recruitment and outcome distribution: time window between injury and admission to study hospital or= 1 reactive pupil; motor score > 1; Glasgow Coma Scale

Frequency of sustained intracranial pressure elevation during treatment of severe intraventricular hemorrhage.

BACKGROUND: Elevated intracranial pressure (ICP) is an important marker of neurological deterioration. The occurrence and significance of elevated ICP and low cerebral perfusion pressure (CPP) in aggressively treated spontaneous intraventricular hemorrhage (IVH) are not defined. METHODS: We performed a secondary longitudinal exploratory data analysis of a randomized multicenter trial of urokinase (UK) versus placebo (Pcb) as a treatment for IVH. Eleven IVH patients who required an external ventricular drain (EVD) were randomized to receive either intraventricular UK or Pcb every 12 h until clinical response permitted EVD removal. ICP and CPP were recorded every 4 or 6 h, as well as before and 1 h after EVD closure for administration of study agent. ICP, CPP and the proportion of ICP readings above 20, 30, 40 and 50 mm Hg were analyzed. RESULTS: Six UK and 5 Pcb patients aged 39-74 years (mean +/- standard deviation; 53 +/- 11 years) were enrolled. Initial ICP ranged from 0 to 38 mm Hg (10.9 +/- 11.0), initial CPP from 65 to 133 mm Hg (100.5 +/- 17.7). We recorded 472 ICP readings over the entire monitoring period. Of these 65 (14%) were >20 mm Hg, 23 (5%) >30 mm Hg, 9 (2%) >40 mm Hg and 3 (<1%) >50 mm Hg. Only 2 of 141 intraventricular injections of study agent with EVD closure were not tolerated and required reopening of the EVD. CONCLUSIONS: In the intensive care unit, initial ICP measured with an EVD was uncommonly elevated (1/11 patients) in this group of severe IVH patients despite acute obstructive hydrocephalus. Frequent monitoring reveals ICP elevation >20 mm Hg in 14% of observations during use of EVD. ICP elevation, though it can occur, is not routinely associated with EVD closure for thrombolytic treatment with UK.

Outcome in 1,000 head injury hospital admissions: the Athens head trauma registry.

BACKGROUND: The aim of this study was to establish a head trauma registry to (a) examine demographics, etiology, severity, clinical course, and outcome; (b) compare results with previous published series; (c) identify causes of bad outcomes; and (d) propose methods to improve therapy and prognosis. METHODS: The following data were collected on 1,000 consecutive victims with head injury over 14 years of age admitted during a 4-year period: demographic characteristics, cause of injury, clinical variables, neuroimaging, therapy data, and outcome in 6 months. RESULTS: Seventy-four percent were men, and mean age was 43 years. Seventy-one percent suffered injuries due to road crashes, 14% due to alcohol, and 2% due to substances. The secondary transfer rate was 49%. For severe injuries, the time intervals from incident to hospital and subsequently to neurosurgical unit were 35 minutes and 4 hours, respectively. In 65% and 72% of cases, there was no record of preresuscitation hypoxia or hypotension, respectively, whereas suspected or definite episodes of hypoxia and hypotension were 27% and 13%, respectively. Most cases were mild trauma (63%), the remaining were severe (26%) and moderate (11%) injuries. Severe systemic trauma coexisted in 18%. Cranial surgery rate was 19% and it increased to 39% in severe trauma. The 6-month overall good outcome was 71%, with lower rates in moderate (58%) and severe (24%) injuries. CONCLUSIONS: The organization of Greece's first head injury registry offered an important preliminary core data concerning brain trauma etiology, management, and long-term outcome.

Predicting outcome after traumatic brain injury: development and international validation of prognostic scores based on admission characteristics.

BACKGROUND: Traumatic brain injury (TBI) is a leading cause of death and disability. A reliable prediction of outcome on admission is of great clinical relevance. We aimed to develop prognostic models with readily available traditional and novel predictors. METHODS AND FINDINGS: Prospectively collected individual patient data were analyzed from 11 studies. We considered predictors available at admission in logistic regression models to predict mortality and unfavorable outcome according to the Glasgow Outcome Scale at 6 mo after injury. Prognostic models were developed in 8,509 patients with severe or moderate TBI, with cross-validation by omission of each of the 11 studies in turn. External validation was on 6,681 patients from the recent Medical Research Council Corticosteroid Randomisation after Significant Head Injury (MRC CRASH) trial. We found that the strongest predictors of outcome were age, motor score, pupillary reactivity, and CT characteristics, including the presence of traumatic subarachnoid hemorrhage. A prognostic model that combined age, motor score, and pupillary reactivity had an area under the receiver operating characteristic curve (AUC) between 0.66 and 0.84 at cross-validation. This performance could be improved (AUC increased by approximately 0.05) by considering CT characteristics, secondary insults (hypotension and hypoxia), and laboratory parameters (glucose and hemoglobin). External validation confirmed that the discriminative ability of the model was adequate (AUC 0.80). Outcomes were systematically worse than predicted, but less so in 1,588 patients who were from high-income countries in the CRASH trial. CONCLUSIONS: Prognostic models using baseline characteristics provide adequate discrimination between patients with good and poor 6 mo outcomes after TBI, especially if CT and laboratory findings are considered in addition to traditional predictors. The model predictions may support clinical practice and research, including the design and analysis of randomized controlled trials.

Effects of Glasgow Outcome Scale misclassification on traumatic brain injury clinical trials.

The Glasgow Outcome Scale (GOS) is the primary endpoint for efficacy analysis of clinical trials in traumatic brain injury (TBI). Accurate and consistent assessment of outcome after TBI is essential to the evaluation of treatment results, particularly in the context of multicenter studies and trials. The inconsistent measurement or interobserver variation on GOS outcome, or for that matter, on any outcome scales, may adversely affect the sensitivity to detect treatment effects in clinical trial. The objective of this study is to examine effects of nondifferential misclassification of the widely used five-category GOS outcome scale and in particular to assess the impact of this misclassification on detecting a treatment effect and statistical power. We followed two approaches. First, outcome differences were analyzed before and after correction for misclassification using a dataset of 860 patients with severe brain injury randomly sampled from two TBI trials with known differences in outcome. Second, the effects of misclassification on outcome distribution and statistical power were analyzed in simulation studies on a hypothetical 800-patient dataset. Three potential patterns of nondifferential misclassification (random, upward and downward) on the dichotomous GOS outcome were analyzed, and the power of finding treatments differences was investigated in detail. All three patterns of misclassification reduce the power of detecting the true treatment effect and therefore lead to a reduced estimation of the true efficacy. The magnitude of such influence not only depends on the size of the misclassification, but also on the magnitude of the treatment effect. In conclusion, nondifferential misclassification directly reduces the power of finding the true treatment effect. An awareness of this procedural error and methods to reduce misclassification should be incorporated in TBI clinical trials.

Assessment of mitochondrial impairment in traumatic brain injury using high-resolution proton magnetic resonance spectroscopy.

OBJECTIVES: The goal of this study was to demonstrate the posttraumatic neurochemical damage in normal-appearing brain and to assess mitochondrial dysfunction by measuring N-acetylaspartate (NAA) levels in patients with severe head injuries, using proton (1H) magnetic resonance (MR) spectroscopy. METHODS: Semiquantitative analysis of NAA relative to creatine-containing compounds (Cr) and choline (Cho) was carried out from proton spectra obtained by means of chemical shift (CS) imaging and single-voxel (SV) methods in 25 patients with severe traumatic brain injuries (TBIs) (Glasgow Coma Scale scores < or = 8) using a 1.5-tesla MR unit. Proton MR spectroscopy was also performed in 5 healthy volunteers (controls). RESULTS: The SV studies in patients with diffuse TBI showed partial reduction of NAA/Cho and NAA/Cr ratios within the first 10 days after injury (means +/- standard deviations 1.59 +/- 0.46 and 1.44 +/- 0.21, respectively, in the patients compared with 2.08 +/- 0.26 and 2.04 +/- 0.31, respectively, in the controls; nonsignificant difference). The ratios gradually declined in all patients as time from injury increased (mean minimum values NAA/Cho 1.05 +/- 0.44 and NAA/Cr 1.05 +/- 0.30, p < 0.03 and p < 0.02, respectively). This reduction was greater in patients with less favorable outcomes. In patients with focal injuries, the periphery of the lesions revealed identical trends of NAA/Cho and NAA/Cr decrease. These reductions correlated with outcome at 6 months (p < 0.01). Assessment with multivoxel methods (CS imaging) demonstrated that, in diffuse injury, NAA levels declined uniformly throughout the brain. At 40 days postinjury, initially low NAA/Cho levels had recovered to near baseline in patients who had good outcomes, whereas no recovery was evident in patients with poor outcomes (p < 0.01). CONCLUSIONS: Using (1)H-MR spectroscopy, it is possible to detect the posttraumatic neurochemical damage of the injured brain when conventional neuroimaging techniques reveal no abnormality. Reduction of NAA levels is a dynamic process, evolving over time, decreasing and remaining low throughout the involved tissue in patients with poor outcomes. Recovery of NAA levels in patients with favorable outcomes suggests marginal mitochondrial impairment and possible resynthesis from vital neurons.

Assessment of mitochondrial impairment and cerebral blood flow in severe brain injured patients.

BACKGROUND: We believe that in traumatic brain injury (TBI), the reduction of N-acetyl aspartate (NAA) occurs in the presence of adequate cerebral blood flow (CBF) which would lend support to the concept of mitochondrial impairment. The objective of this study was to test this hypothesis in severely injured patients (GCS 8 or less) by obtaining simultaneous measures of CBF and NAA. METHODS: Fourteen patients were studied of which six patients presented as diffuse injury at admission CT, while focal lesions were present in eight patients. CBF using stable xenon method was measured at the same time that NAA was measured by magnetic resonance proton spectroscopy (1HMRS) in the MR suite. Additionally, diffusion weighted imaging (DWI) and maps of the apparent diffusion coefficient (ADC) were assessed. FINDINGS: In diffuse injury, NAA/Cr reduction occurred uniformly throughout the brain where the values of CBF in all patients were well above ischemic threshold. In focal injury, we observed ischemic CBF values in the core of the lesions. However, in areas other than the core, CBF was above ischemic levels and NAA/Cr levels were decreased. CONCLUSIONS: Considering the direct link between energy metabolism and NAA synthesis in the mitochondria, this study showed that in the absence of an ischemic insult, reductions in NAA concentration reflects mitochondrial dysfunction.

Modulation of AQP4 expression by the selective V1a receptor antagonist, SR49059, decreases trauma-induced brain edema.

BACKGROUND: Currently, there are no pharmacological treatments available for traumatically induced brain edema and the subsequent rise of ICP. Evidence indicates that Aquaporin-4 (AQP4) plays a significant role in the pathophysiology of brain edema. Previously we have reported that SR49059 reduced brain edema secondary to ischemia. We, therefore, examined whether the selective V1a receptor antagonist, SR49059, reduces brain edema by modulating AQP4 expression following cortical contusion injury (CCI). METHODS: Traumatic brain injury (TBI) was produced in thirty-two adult male Sprague-Dawley rats by lateral CCI (6.0 m/sec, 3 mm depth). Animals were randomly assigned to vehicle (n=16) or SR49059 treatment (n=16) groups and administered drug (960 microl/hr i.v.) immediately after injury over a 5 hr period. Animals were sacrificed for assessment of brain water content by Wet/Dry method and AQP4 protein expression by immunoblotting expressed as the ratio of AQP4 and Cyclophilin-A densitometries. FINDINGS: Elevated AQP4 expression levels and water content were observed on the right injured side in both the right anterior (RA) and right posterior (RP) section compared to the left non-injured side inclusive of the left anterior (LA) and right anterior (RA) sections. The average AQP4 expression levels in contused areas for animals receiving SR drug treatment (RA: 1.313 +/- 0.172, RP: 1.308 +/- 0.175) were significantly decreased from vehicle-treated animals (RA: 2.181 +/- 0.232, RP: 2.303 +/- 0.370, p = 0.001, p= 0.003). Water content levels on SR treatment (78.89 +/- 0.14) was also significantly decreased from vehicle levels (80.38 +/- 0.38, p < 0.01) in the traumatized hemisphere. CONCLUSIONS: SR49059 significantly reduced trauma-induced AQP4 up-regulation in the contused hemisphere. Moreover, brain water content was also significantly reduced paralleling the AQP4 suppression. These data provide further support that vasopressin (AVP) and V1a receptors can control water flux through astrocytic plasma membranes by regulating AQP4 expression. Taken in concert, these results affirm our laboratories contention that AQP4 can be effectively modulated pharmacologically.