Predicting Outcome after Traumatic Brain Injury: Development and Validation of a Prognostic Score Based on Admission Characteristics

Apoptosis of neuronal cells induced by serum of patients with acute brain injury: a new in vitro prognostic model

OBJECTIVE

To investigate whether serum draining from the jugular bulb of patients with traumatic or haemorrhagic brain injury induced apoptosis of neuronal PC12 cells in vitro and whether the apoptotic rate correlated with patients' outcome at 6 months.

DESIGN AND SETTING

Prospective clinical investigation in a 21-bed intensive care unit (ICU) in a university hospital.

PATIENTS

Seventy patients who had suffered from acute brain injury requiring intensive care.

INTERVENTIONS

Jugular bulb vein and systemic samples were obtained on admission to the ICU and after 48 h. PC12 cells were incubated in the presence of 10% of heat-inactivated patient's sera and apoptotic rate was determined by flow cytometry using annexin V and 7-aminoactinomycin D.

RESULTS

Regional serum draining from the lesions induced higher early apoptosis of PC12 cells than systemic serum. Early apoptotic rate, Glasgow coma score, APACHE II score and the presence of pupil abnormalities were associated with mortality at 6 months in univariate statistical analyses. In logistic regression analysis only early apoptotic rate was an independent factor associated with mortality at 6 months (odds ratio: 1.502, 95% CI 1.2-1.9; p<0.001). The final model has a sensitivity of 82.4% and a specificity of 84.8% for predicting death within 6 months.

CONCLUSIONS

We developed a simple and reproducible in vitro model for predicting outcome in patients with traumatic or haemorrhagic brain injury that survived in the early phase. Our in vitro model combined with clinical and radiological measurements might improve the value of prognostic models to predict acute brain injury patients' outcome.

Adjustment for Strong Predictors of Outcome in Traumatic Brain Injury Trials: 25% Reduction in Sample Size Requirements in the IMPACT Study

The aim of this study was to quantify the potential reduction in sample size that can be achieved by adjustment for predictors of outcome in traumatic brain injury (TBI) trials. We used individual patient data from seven therapeutic phase III randomized clinical trials (RCTs; n = 6166) in moderate or severe TBI, and three TBI surveys (n = 2238). The primary outcome was the dichotomized Glasgow Outcome Scale at 6 months (favorable/unfavorable). Baseline predictors of outcome considered were age, motor score, pupillary reactivity, computed tomography (CT) classification, traumatic subarachnoid hemorrhage, hypoxia, hypotension, glycemia, and hemoglobin. We calculated the potential sample size reduction obtained by adjustment of a hypothetical treatment effect for one to seven predictors with logistic regression models. The distribution of predictors was more heterogeneous in surveys than in trials. Adjustment of the treatment effect for the strongest predictors (age, motor score, and pupillary reactivity) yielded a reduction in sample size of 16-23% in RCTs and 28-35% in surveys. Adjustment for seven predictors yielded a reduction of about 25% in most studies: 20-28% in RCTs and 32-39% in surveys. A major reduction in sample size can be obtained with covariate adjustment in TBI trials. Covariate adjustment for strong predictors should be incorporated in the analysis of future TBI trials.

Quantitation of ischemic events after severe traumatic brain injury in humans: a simple scoring system

BACKGROUND

Cerebral ischemia is recognized as one of the most important mechanisms responsible for secondary brain damage following severe traumatic brain injury (TBI), contributing to an increased mortality and a worse neurologic outcome.

METHOD

A simple 5-item scoring system, taking into account the occurrence of specific potentially brain-damaging events (hypoxemia, hypotension, low cerebral blood flow, herniation, and low cerebral perfusion pressure) has been tested in a large population of severe TBI patients. Aims of this retrospective study were to validate the ability of the proposed ischemic score to predict neurologic outcome and to correlate the ischemic score with the results of microdialysis-based neurochemical monitoring and brain tissue oxygen monitoring.

FINDINGS

In a population of 172 severe TBI patients, a significant correlation was found between ischemic score and neurologic outcome, both at 3 months (r = -0.32; P < 0.01) and at 6 months (r = -0.31; P < 0.01). Significant correlations were also found with the most important neurochemical analytes.

CONCLUSIONS

The ischemic score proposed here, may be determined during the acute intensive care unit period, and correlates closely with outcome, which can only be determined 3 to 6 months, after injury. It also shows a correlation with neurochemical analytes.

Some prognostic models for traumatic brain injury were not valid

OBJECTIVE

Various prognostic models have been developed to predict outcome after traumatic brain injury (TBI). We aimed to determine the validity of six models that used baseline clinical and computed tomographic characteristics to predict mortality or unfavorable outcome at 6 months or later after severe or moderate TBI.

STUDY DESIGN AND SETTING

The validity was studied in two selected series of TBI patients enrolled in clinical trials (Tirilazad trials; n = 2,269; International Selfotel Trial; n = 409) and in two unselected series of patients consecutively admitted to participating centers (European Brain Injury Consortium [EBIC] survey; n = 796; Traumatic Coma Data Bank; n = 746). Validity was indicated by discriminative ability (AUC) and calibration (Hosmer-Lemeshow goodness-of-fit test).

RESULTS

The models varied in number of predictors (four to seven) and in development technique (two prediction trees and four logistic regression models). Discriminative ability varied widely (AUC: .61-.89), but calibration was poor for most models. Better discrimination was observed for logistic regression models compared with trees, and for models including more predictors. Further, discrimination was better when tested on unselected series that contained more heterogeneous populations.

CONCLUSION

Our findings emphasize the need for external validation of prognostic models. The satisfactory discrimination indicates that logistic regression models, developed on large samples, can be used for classifying TBI patients according to prognostic risk.

Efficacy and safety of dexanabinol in severe traumatic brain injury: results of a phase III randomised, placebo-controlled, clinical trial

BACKGROUND

Traumatic brain injury is a major cause of death and disability. We sought to assess the safety and efficacy of dexanabinol, a synthetic cannabinoid analogue devoid of psychotropic activity, in severe traumatic brain injury.

METHODS

861 patients with severe traumatic brain injury admitted to 86 specialist centres from 15 countries were included in a multi-centre, placebo-controlled, phase III trial. Patients were randomised to receive a single intravenous 150 mg dose of dexanabinol or placebo within 6 h of injury. The primary outcome was the extended Glasgow outcome scale assessed at 6 months, with the point of dichotomisation into unfavourable versus favourable outcome differentiated by baseline prognostic risk. Prespecified subgroup analyses were defined by injury severity, recruitment rate, and time to dosing. Secondary analysis included control of intracranial pressure and quality of life. Analysis were prespecified in the protocol and the statistical analysis plan. This study is registered with ClinicalTrials.gov, number NCT00129857.

FINDINGS

846 patients were included in the efficacy analysis. The extended Glasgow outcome scale at 6 months did not differ between groups; 215 (50%) patients in the dexanabinol group and 214 (51%) patients in the placebo group had an unfavourable outcome (odds ratio for a favourable response 1.04; 95% CI 0.79-1.36). Improvements in the control of intracranial pressure or quality of life were not recorded and subgroup analysis showed no indication of differential treatment effects. Dexanabinol was not associated with hepatic, renal, or cardiac toxic effects.

INTERPRETATION

Dexanabinol is safe, but is not efficacious in the treatment of traumatic brain injury.

Admission of patients with severe and moderate traumatic brain injury to specialized ICU facilities: a search for triage criteria

OBJECTIVE

To investigate whether triage for direct admission of patients with traumatic brain injury to a trauma center is facilitated by predicting the risk of potentially removable lesions or raised intracranial pressure (ICP).

DESIGN AND SETTING

Cohort study in a level I university trauma center.

PATIENTS AND PARTICIPANTS

A prospective cohort of primarily (n=200) and secondarily (n=75) referred patients with moderate or severe traumatic brain injury.

MEASUREMENTS AND RESULTS

Predictive characteristics for the risk of surgically removable lesions and the risk of raised ICP (repeatedly > or = 20 mmHg) were identified and included in prognostic models. These models were validated internally with bootstrapping techniques and externally on a historic sample (n=205) regarding discriminative ability (AUC). Among the cohort patients, 67% had raised ICP and 54% had surgically removable lesions. Both outcomes occurred more frequently in patients secondarily referred, but the incidence in patients primarily referred was also high (62% and 33% respectively). No strong predictors of raised ICP were identified. Age and pupillary reactivity were significant predictors of surgically removable lesions. The models discriminated reasonably for surgically removable lesions (AUC=0.78 at development and AUC=0.67 at external validation) but not for raised ICP (AUC=0.59 at development and AUC=0.50 at external validation).

CONCLUSIONS

It is difficult accurately to identify patients in need of specialized intensive care using baseline characteristics. The high incidence of both outcomes in patients primarily referred support direct admission of more and particularly older patients with severe or moderate brain trauma to level I trauma centers.