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.

Subgroup analysis and covariate adjustment in randomized clinical trials of traumatic brain injury: a systematic review

OBJECTIVE

Few randomized clinical trials (RCTs) in the field of traumatic brain injury (TBI) have shown a significant treatment benefit. We critically reviewed the use of two types of secondary analyses, covariate adjustment and subgroup analysis, which are common in TBI trials.

METHODS

We performed a systematic review of therapeutic phase III RCTs, including adult patients with acute, moderate-to-severe TBI. Glasgow Outcome Scale (GOS) at > or =3 months as outcome, and > or =50 patients per arm were required. We compared the actual reporting of covariate adjustment and subgroup analyses with the Consolidated Standards of Reporting Trials (CONSORT) recommendations. Likewise, we reviewed six protocols of large multicenter RCTs and compared planned and reported subgroups.

RESULTS

We identified 18 RCTs (n = 6439). Sixteen trials used GOS at 6 months as outcome. Five RCTs reported covariate adjustment. The number of covariates was limited (< or =5), most frequently including age. Many covariates were outcome predictors. Four RCTs reported only adjusted treatment effects as the main efficacy parameter. Eleven RCTs reported subgroup analyses. Several subgroup factors (< or =7, mainly outcome predictors) and outcomes (< or =4) were included. The highest total number of subgroups was 15, and only three RCTs completely pre-specified subgroups. Notably, 10 of 11 RCTs performed inappropriate separate subgroup analyses. Of 11 RCTs, 5 gave subgroups the same emphasis as the overall effect. Reported subgroup analyses were insufficiently described and clearly differed from those planned in the protocol.

CONCLUSION

The reported covariate adjustment and subgroup analyses from TBI trials had several methodological shortcomings. Appropriate performance and reporting of covariate adjustment and subgroup analysis should be considerably improved in future TBI trials because interpretation of treatment benefits may be misleading otherwise.

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.

Organ donations and unused potential donations in traumatic brain injury, subarachnoid haemorrhage and intracerebral haemorrhage

OBJECTIVE

To obtain insight into the occurrence of brain death and the potential for brain dead and controlled non-heart-beating organ donors (CNHB) in patients with traumatic brain injury (TBI), subarachnoid haemorrhage (SAH) and intracerebral haemorrhage (ICH) in a large neurosurgical serving area (2.1 million inhabitants).

DESIGN

Retrospective analysis of data concerning patients with TBI, SAH and ICH who died during the course of ICU treatment during 1999-2003.

SETTING

A 16-bed neuro-intensive care unit.

PATIENTS

Patients with TBI, SAH or ICH who died during the course of ICU treatment.

MEASUREMENTS AND RESULTS

The number of ICU deaths in patients with TBI, SAH and ICH declined from 111 in 1999 to 64 in 2003. In total, 476 deaths occurred. Of these, 177 patients were not included in the analysis. Two hundred ninety-nine (299) ventilated patients had two or more absent brainstem reflexes (ABSR) and a Glasgow Coma Score of 3-4 at the moment of treatment withdrawal and formed the potential for organ donation; 61 of these patients were treated until full brain death. Organs of 57 patients could be harvested. We analysed the reasons that organs were not procured in the 242 remaining patients. The most important reasons were family refusal (32%), medical contraindications (14%), and the treating physician not considering potential organ donation (20%). The missed potential is 162/299 (54%).

CONCLUSIONS

The number of actual and potential organ donors is declining, but a considerable number of potential CNHB donors exists. Refusal by relatives is the most important reason for failure to procure organs.

Prediction of Outcome in Traumatic Brain Injury with Computed Tomographic Characteristics: A Comparison between the Computed Tomographic Classification and Combinations of Computed Tomographic Predictors

BACKGROUND AND OBJECTIVE

The Marshall computed tomographic (CT) classification identifies six groups of patients with traumatic brain injury (TBI), based on morphological abnormalities on the CT scan. This classification is increasingly used as a predictor of outcome. We aimed to examine the predictive value of the Marshall CT classification in comparison with alternative CT models.

METHODS

The predictive value was investigated in the Tirilazad trials (n = 2269). Alternative models were developed with logistic regression analysis and recursive partitioning. Six month mortality was used as outcome measure. Internal validity was assessed with bootstrapping techniques and expressed as the area under the receiver operating curve (AUC).

RESULTS

The Marshall CT classification indicated reasonable discrimination (AUC = 0.67), which could be improved by rearranging the underlying individual CT characteristics (AUC = 0.71). Performance could be further increased by adding intraventricular and traumatic subarachnoid hemorrhage and by a more detailed differentiation of mass lesions and basal cisterns (AUC = 0.77). Models developed with logistic regression analysis and recursive partitioning showed similar performance. For clinical application we propose a simple CT score, which permits a more clear differentiation of prognostic risk, particularly in patients with mass lesions.

CONCLUSION

It is preferable to use combinations of individual CT predictors rather than the Marshall CT classification for prognostic purposes in TBI. Such models should include at least the following parameters: status of basal cisterns, shift, traumatic subarachnoid or intraventricular hemorrhage, and presence of different types of mass lesions.

The Management of Patients with Intradural Post-Traumatic Mass Lesions: A Multicenter Survey of Current Approaches to Surgical Management in 729 Patients Coordinated by the European Brain Injury Consortium

OBJECTIVE:

Controversy exists about the indications and timing for surgery in head injured patients with an intradural mass lesion. The aim of this study was to survey contemporary approaches to the treatment of head injured patients with an intradural lesion, placing a particular focus on the utilization of decompressive craniectomy.

METHODS:

A prospective international survey was conducted over a 3-month period in 67 centers from 24 countries on the neurosurgical management of head injured patients with an intradural mass lesion and/or radiological signs of raised intracranial pressure. Information was obtained about demographic, clinical, and radiological features; surgical management, and mortality at discharge.

RESULTS:

Over the period of the study, data were collected about 729 patients consecutively admitted to one of the participating centers. The survey included 397 patients with a severe head injury (Glasgow Coma Scale [GCS] 3–8), 155 with a moderate head injury (GCS 9–12) and 143 patients with a mild head injury (GCS 13–15). An operation was performed on 502 patients (69%). Emergency surgery (&lt;24 h) was most frequently performed for patients with an extracerebral mass lesions (subdural hematomas) whereas delayed surgery was most frequently performed for an intracerebral hematoma or contusion. Decompressive craniectomy was performed in a substantial number of patients, either during an emergency procedure (n = 134, 33%) or a delayed procedure (n = 47, 31%). The decompressive procedure was nearly always combined with evacuation of a mass lesion. The size of the decompression was however considered too small in 25% of cases.

CONCLUSION:

The results provide a contemporary picture of neurosurgical surgical approaches to the management of head injured patients with an intradural mass lesion and/or signs of raised intracranial pressure in some Neurosurgical Units across the world. The relative benefits of early versus delayed surgery in patients with intraparenchymal lesions and on the indications, technique and benefits of decompressive craniectomy could be topics for future head injury research.

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

The early prediction of outcome after traumatic brain injury (TBI) is important for several purposes, but no prognostic models have yet been developed with proven generalizability across different settings. The objective of this study was to develop and validate prognostic models that use information available at admission to estimate 6-month outcome after severe or moderate TBI. To this end, this study evaluated mortality and unfavorable outcome, that is, death, and vegetative or severe disability on the Glasgow Outcome Scale (GOS), at 6 months post-injury. Prospectively collected data on 2269 patients from two multi-center clinical trials were used to develop prognostic models for each outcome with logistic regression analysis. We included seven predictive characteristics-age, motor score, pupillary reactivity, hypoxia, hypotension, computed tomography classification, and traumatic subarachnoid hemorrhage. The models were validated internally with bootstrapping techniques. External validity was determined in prospectively collected data from two relatively unselected surveys in Europe (n = 796) and in North America (n = 746). We evaluated the discriminative ability, that is, the ability to distinguish patients with different outcomes, with the area under the receiver operating characteristic curve (AUC). Further, we determined calibration, that is, agreement between predicted and observed outcome, with the Hosmer-Lemeshow goodness-of-fit test. The models discriminated well in the development population (AUC 0.78-0.80). External validity was even better (AUC 0.83-0.89). Calibration was less satisfactory, with poor external validity in the North American survey (p < 0.001). Especially, observed risks were higher than predicted for poor prognosis patients. A score chart was derived from the regression models to facilitate clinical application. Relatively simple prognostic models using baseline characteristics can accurately predict 6-month outcome in patients with severe or moderate TBI. The high discriminative ability indicates the potential of this model for classifying patients according to prognostic risk.

Combined effects of mechanical and ischemic injury to cortical cells: secondary ischemia increases damage and decreases effects of neuroprotective agents

Traumatic brain injury (TBI) involves direct mechanical damage, which may be aggravated by secondary insults such as ischemia. We utilized an in vitro model of stretch-induced injury to investigate the effects of mechanical and combined mechanical/ischemic insults to cultured mouse cortical cells. Stretch injury alone caused significant neuronal loss and increased uptake of the dye, propidium iodide, suggesting cellular membrane damage to both glia and neurons. Exposure of cultures to ischemic conditions for 24h, or a combination of stretch and 24h of ischemia, caused greater neuronal loss compared to stretch injury alone. Next, we tested the neuroprotective effects of superoxide dismutase (SOD), and the nitric oxide (NO) synthase inhibitors 7-nitroindazole (7-NINA) and lubeluzole. In general, these agents decreased neuronal loss following stretch injury alone, but were relatively ineffective against the combined injury paradigm. A combination of SOD with 7-NINA or lubeluzole offered no additional protection than single drug treatment against stretch alone or combined injury. These results suggest that the effects of primary mechanical damage and secondary ischemia to cortical neurons are cumulative, and drugs that scavenge superoxide or reduce NO production may not be effective for treating the secondary ischemia that often accompanies TBI.

Ethical considerations on consent procedures for emergency research in severe and moderate traumatic brain injury

Therapeutic trials in TBI are subject to principles of Good Clinical Practice (GCP), to national legislation, and to international and European ethical concepts and regulations [e.g. 13]. The guiding principles underlying these investigations of treatment are respect for autonomy of research subjects, protection against discomfort, risk, harm and exploitation and the prospect of some benefit. Patients with significant TBI are mentally incapacitated, thus prohibiting obtaining consent directly from the subject. Various approaches to consent procedures are used as surrogate to subject consent: proxy consent, consent by an independent physician and waiver of consent. These approaches are reviewed. A questionnaire soliciting opinions was mailed to 148 EBIC (European Brain Injury Consortium) associated neuro-trauma centers in 19 European countries. 48% respondents believe that relatives were not able to make a balanced decision, 72% believed that consent procedures are a significant factor causing decrease in enrollment rate and 83% stated that consent procedures delay initiation of study treatment, resulting in possible harm if the agent has shown to be effective. 64% of the respondents considered TBI an emergency situation in which clinical research could be initiated under the emergency exception for consent. In new European legislation, emergency research under waiver of consent is not permitted. Nevertheless, we consider that randomising patients with TBI into carefully evaluated trial protocols without prior consent may be considered ethically justified.

Design and Analysis of Phase III Trials with Ordered Outcome Scales: The Concept of the Sliding Dichotomy

The conventional approach to the analysis of a Phase III trial in head injury or stroke takes an ordered scale measuring functional outcome and collapses the scale to a binary outcome of favorable versus unfavorable. This discards potentially relevant information which limits statistical power and moreover is not in accord with clinical practice. We propose an alternative approach where a favorable outcome is defined as better than would be expected, taking account of each individual patient's baseline prognosis. This is illustrated through a worked example based on data from a Phase III trial in head injury. The approach is also compared with the proportional odds model, which is another statistical approach that can exploit an ordered outcome scale. The approach raises issues of clinical, statistical, and regulatory importance, and we initiate what we believe needs to become a widespread debate amongst the community involved in clinical research in head injury and stroke.

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.

A Review and Rationale for the Use of Cellular Transplantation as a Therapeutic Strategy for Traumatic Brain Injury

Experimental research during the past decade has greatly increased our understanding of the pathophysiology of traumatic brain injury (TBI) and allowed us to develop neuroprotective pharmacological therapies. Encouraging results of experimental pharmacological interventions, however, have not been translated into successful clinical trials, to date. Traumatic brain injury is now believed to be a progressive degenerative disease characterized by cell loss. The limited capacity for self-repair of the brain suggests that functional recovery following TBI is likely to require cellular transplantation of exogenous cells to replace those lost to trauma. Recent advances in central nervous system transplantation techniques involve technical and experimental refinements and the analysis of the feasibility and efficacy of transplantation of a range of stem cells, progenitor cells and postmitotic cells. Cellular transplantation has begun to be evaluated in several models of experimental TBI, with promising results. The following is a compendium of these new and exciting studies, including a critical discussion of the rationale and caveats associated with cellular transplantation techniques in experimental TBI research. Further refinements in future research are likely to improve results from transplantation-based treatments for TBI.

Clinical trials in traumatic brain injury: current problems and future solutions

Over the past decade many neuroprotective agents have been developed with the hope of being able to improve outcome in patients with traumatic brain injury. Unfortunately, none of the phase III trials performed have convincingly demonstrated efficacy in the overall population. A common misconception is that consequently these agents are ineffective. Such has not been proven and some trials show evidence of efficacy in subgroups of the population studied. The negative results, as reported in the overall population, may in part be caused by specific aspects of the TBI population, as well as by aspects of clinical trial design and analysis. Clinical trials in TBI pose several complicated design issues. Methodological challenges relate particularly to heterogeneity of the population and to outcome assessment. Heterogeneity pertains both to the range of pathologies included in TBI, and to prognostic factors, each causing specific problems. Mechanistic and/or prognostic targeting, as well as possibilities for covariate adjustment, are suggested as possible solutions to deal with the problems of heterogeneity. The aim in most trials was to demonstrate a 10% absolute improvement in favorable outcome in patients with head injury. This may be considered overoptimistic and unrealistic in relation to the heterogeneous patient population. Specific problems are further incurred by the use of the dichotomized Glasgow Outcome Scale as primary outcome measure. Optimal statistical power may expected to be present when the point of dichotomization results in a 50:50 distribution of outcome categories. It is proposed to differentiate the point of dichotomization according to prognostic risk profile, in order to maintain statistical power. Solutions described may be expected to enhance chances of demonstrating benefit of potentially effective neuroprotective agents in future studies. The complexity of problems occurring in clinical trial design and analysis in TBI is such that a strong and sustained multidisciplinary input and effort is required from all experts involved in the field of neurotrauma.

Patient age and outcome following severe traumatic brain injury: an analysis of 5600 patients

OBJECT

Increasing age is associated with poorer outcome in patients with closed traumatic brain injury (TBI). It is uncertain whether critical age thresholds exist, however, and the strength of the association has yet to be investigated across large series. The authors studied the shape and strength of the relationship between age and outcome, that is, the 6-month mortality rate and unfavorable outcome based on the Glasgow Outcome Scale.

METHODS

The shape of the association was examined in four prospective series with individual patient data (2664 cases). All patients had a closed TBI and were of adult age (96% < 65 years of age). The strength of the association was investigated in a metaanalysis of the aforementioned individual patient data (2664 cases) and aggregate data (2948 cases) from TBI studies published between 1980 and 2001 (total 5612 cases). Analyses were performed with univariable and multivariable logistic regression. Proportions of mortality and unfavorable outcome increased with age: 21 and 39%, respectively, for patients younger than 35 years and 52 and 74%, respectively, for patients older than 55 years. The association between age and both mortality and unfavorable outcome was continuous and could be adequately described by a linear term and expressed even better statistically by a linear and a quadratic term. The use of age thresholds (best fitting threshold 39 years) in the analysis resulted in a considerable loss of information. The strength of the association, expressed as an odds ratio per 10 years of age, was 1.47 (95% confidence interval [CI] 1.34-1.63) for death and 1.49 (95% CI 1.43-1.56) for unfavorable outcome in univariable analyses, and 1.39 (95% CI 1.3-1.5) and 1.46 (95% CI 1.36-1.56), respectively, in multivariable analyses. Thus, the odds for a poor outcome increased by 40 to 50% per 10 years of age.

CONCLUSIONS

An older age is continuously associated with a worsening outcome after TBI; hence, it is disadvantageous to define the effect of age on outcome in a discrete manner when we aim to estimate prognosis or adjust for confounding variables.

Brain tissue oxygen response in severe traumatic brain injury

OBJECTIVE

To investigate clinical relevance and prognostic value of brain tissue oxygen response (TOR: response of brain tissue pO(2) to changes in arterial pO(2)) in traumatic brain injury (TBI).

PATIENTS AND METHODS

In a prospective cohort study TOR was investigated in 41 patients with severe TBI (Glasgow Coma Score < or =8) in whom continuous monitoring of brain tissue oxygen pressure (PbrO(2)) was performed.TOR was investigated each day over a five day period for 15 minutes by increasing FiO(2) on the ventilator setting. FiO(2) was increased directly from baseline to 1.0 for a period of 15 minutes under stable conditions (145 tests). In 34 patients the effect of decreasing PaCO(2) was evaluated on TOR by performing the same test after increasing inspiratory minute volume on the ventilator setting to 20% above baseline. Arterial blood gas analysis was performed before and after changing ventilator settings. Multimodality monitoring, including PbrO(2) was performed in all patients. Outcome at six months was evaluated according to the Glasgow Outcome Scale. For statistical analysis the Mann-whitney U-test was used for ordinally distributed variables, and the Chi-square test for categorical variables. Predictive value of TOR was analyzed in a multivariable model.

RESULTS

145 tests were available for analysis. Baseline PbrO(2) varied from 4.0 to 50 mmHg at PaO(2) values of 73-237 mmHg. At FiO(2) settings of 1.0, PbrO(2) varied from 9.1-200 mmHg and PaO(2) from 196-499 mmHg. Three distinct patterns of response were noted: response type A is characterized by a sharp increase in PbrO(2), reaching a plateau within several minutes; type B by the absence of a plateau, and type C by a short plateau phase followed by a subsequent further increase in PbrO(2). Patterns characterized by a stable plateau (type A), considered indicative of intact regulatory mechanisms, were seen more frequently from 48 hours after injury on. If present within the first 24 hours after injury such a response was related to more favorable outcome (p = 0.06). Mean TOR of all tests was 0.73 +/- 0.59 with an median TOR of 0.58. Patients with an unfavourable outcome had a higher TOR (1.03 +/- 0.60) during the first 24 hours, compared to patients with a favorable outcome (0.61 +/- 0.51; p = 0.02). Multiple logistic regression analysis supported the independent predictive value of tissue oxygen response for unfavorable outcome (odds ratio 4.8). During increased hyperventilation, mean TOR decreased substantially from 0.75 +/- 0.54 to 0.65 +/- 0.45 (p = 0.06; Wilcoxon test). Within the first 24 hours after injury a decrease in TOR following hyperventilation was significantly related to poorer outcome (p = 0.01).

CONCLUSIONS

Evaluation of TOR affords insight in (disturbances in) oxygen regulation after traumatic brain injury, is of prognostic value and may aid in identifying patients at (increased) risk for ischemia.

Traumatic brain injury: classification of initial severity and determination of functional outcome

PURPOSE

The aim of the present manuscript is to review current methods for classifying initial severity and final outcome in traumatic brain injury (TBI) and to suggest a direction and form of further research.

METHOD

The literature on valid and reliable measurements used in TBI-research for classifying initial severity and final outcome was reviewed.

RESULTS

Classifying initial severity in patients with head injury according to clinical condition or CT-parameters is valid. Classifying outcome according to measurement tools of disability showed adequate validity and reliability.

CONCLUSIONS

Future research in TBI outcome, particularly in rehabilitation medicine, should focus on determinants of outcome, identifying those patients who will have the greatest chance of benefiting from intensive rehabilitation programmes. More research is needed to determine the long-term functional outcome in TBI, the long-term socio-economic costs, and the influence of behavioural problems on family cohesion. Finally, validation of outcome measures is required in the TBI-population; the relative value of various outcome measures needs to be determined, and the usefulness and applicability of measures for health related quality of life in TBI should be established.

Serial transcranial Doppler measurements in traumatic brain injury with special focus on the early posttraumatic period

BACKGROUND

Cerebral ischemia is considered a key factor in the development of secondary damage after Traumatic Brain Injury (TBI). Studies on Cerebral Blood Flow (CBF) have documented decreased flow in over 50% of patients with TBI, studied in the acute phase. Transcranial Doppler (TCD) sonography is a non-invasive technique, permitting frequent or continuous measurements of blood flow velocity in the basal cerebral arteries.

OBJECTIVES

To investigate the potential of TCD to detect decreased blood flow velocity in the early phase after TBI;To investigate whether flow velocity differs between hemispheres in patients with focal lesions versus those with more diffuse injuries;To investigate if decreased blood flow velocity is indicative of cerebral ischemia, as evidenced by measurements of brain tissue pO(2).

METHODS

TCD examinations were performed in 57 patients with severe TBI (GCS<or=8) daily over a period of 10 days, with particular attention focused on the first 72 hours, during which period examinations were performed more frequently. A low flow velocity state (LFVS) was defined as a flow velocity<or=35 cm/sec in one or both MCA's within 72 hours after trauma. PbrO(2) was measured in 33 patients with an intraparenchymal Clark type electrode (Licox).Patients were differentiated into those with primarily unilateral pathology on the admission CT scan versus those with primarily more diffuse or bilateral pathology. Outcome was evaluated at six months after injury, according to the Glasgow Outcome Scale (GOS).

RESULTS

A low flow velocity state was observed in 63% of patients studied. Decreased flow was most pronounced during the first eight hours after injury and was accompanied by high pulsatility indices, especially at the side of the lesion. Flow velocity increased significantly after this time period. Initial Vmca values had a strong correlation with ipsilateral measured PbrO(2) values (R=0.73). The occurrence of a LFVS was associated with poorer outcome (odds ratio 3.9).

CONCLUSIONS

TCD studies show reduction of cerebral blood flow velocity in the acute phase after traumatic brain injury. Decreased flow velocity is most pronounced ipsilateral to focal pathology. A low flow velocity state is probably due to high peripheral resistance, and is indicative of ischemia, as demonstrated by the association with decreased PbrO(2). A low flow velocity state is of prognostic value and identifies patients at increased risk for ischemia. Early TCD studies are recommended in TBI.

Regional differences in patient characteristics, case management, and outcomes in traumatic brain injury: experience from the tirilazad trials

Object. Regional differences have been shown in patient characteristics and case management within multiple unselected series of patients suffering from traumatic brain injury (TBI). One might expect that such regional heterogeneity would be small in a more selected population of a randomized clinical trial. The goal of this study was to examine what regional differences in patient characteristics, case management, and outcomes exist between continents and among countries within a patient population included in a randomized clinical trial.

Methods. Data were extracted from two concurrently conducted randomized clinical trials of the drug tirilazad; the designs of these studies were similar. The studies included 1701 patients with severe and 476 patients with moderate TBI. Differences were primarily investigated between studies performed in Europe and North America, but also among European regions and between Canada and the United States. Associations among regions and outcomes (6-month mortality rate and Glasgow Outcome Scale scores) were studied using multivariable logistic regression analysis.

Comparisons between continents and among regions within Europe showed differences in the distribution of patient ages, causes of injury, and several clinical characteristics (motor score, pupillary reactivity, hypoxia, hypotension, intracranial pressure [ICP]), and findings on computerized tomography scans. Secondary referrals occurred 2.5 times more frequently in Europe. Within Europe secondary referral was mainly associated with an increased proportion of patients with mass lesions (46% in the European Study compared with 40% in the North American Study). Therapy for lowering ICP was more frequently applied in North America. After adjustments for case mix and management, mortality and unfavorable outcomes were significantly higher in Europe (odds ratios = 1.58 and 1.46, respectively). Significant differences in outcome between regions within Europe or within North America were not observed.

Conclusions. Despite the use of a strict study protocol, considerable differences in patient characteristics and case management exist between continents and among countries, reflecting variations in social, cultural, and organizational aspects. Outcomes of TBI may be worse in Europe compared with North America, but this finding requires further study.

Advanced monitoring in the intensive care unit: brain tissue oxygen tension

Cerebral monitoring of patients with acute intracranial disorders generally focuses on intracranial pressure and cerebral perfusion pressure monitoring. Over the past few years, several new techniques have become available for more detailed routine monitoring of cerebral oxygenation and metabolism. Brain tissue oxygen pressure measurement is increasingly being used for evaluation of cerebral oxygenation. This article discusses brain tissue oxygen pressure measurement in regards to its technical aspects, safety, reliability, and value relative to other techniques for evaluation of cerebral oxygenation. Published experimental and clinical data are considered, and the current status of the clinical use and indications of the technique are summarized. Monitoring may be performed in relatively undamaged parts of the brain or, preferably, in the penumbra region of an intracerebral lesion. Pathophysiologic evidence warrants targeting therapy for patients with traumatic brain injury and subarachnoid hemorrhage toward improvement of cerebral oxygenation guided by continuous monitoring of brain tissue oxygen tension.

Guidelines for head injury: their use and limitations

Within medicine in general, and particularly in the field of head injury, a revolution is currently occurring wherein the traditional expert opinion-based approach to therapy is quickly changing towards a standardized approach, based on scientific analysis of available evidence. The guideline movement may be considered a child of this revolution. Correct understanding, interpretation and application of guidelines requires an understanding of the reasons for formulating the guidelines and of the methodology on which they are based. From this perspective the North American guidelines and the EBIC guidelines, as main international exponents towards guidelines in head injury, are discussed. Specific attention is focussed on the interpretation of the practice recommendations from the North American guidelines at the level of a standard. The evidence underlying these standards is critically discussed and the conclusions put in to further perspective. The EBIC guidelines were formulated from a desire to obtain a 'common core approach' to basic therapy in centers participating in clinical trials. The recommendations are more pragmatic, based on an understanding of the pathophysiology, and address various issues not analyzed in the North American guidelines. The recommendations of both initiatives however are very similar, illustrating the consensus that already exists to general approach of management in head injury. Guidelines should be considered a very important topic in clinical practice, but on the other hand recommendations should not always be accepted uncritically. The lack of evidence underlying many aspects of management in head injury, as illustrated by the North American approach, should form an incentive for further scientific studies, especially towards targeted therapy. Clinical experience and an understanding of the pathophysiology are the basic ingredients for developing alternative and more targeted approaches which can then be subjected to scientific analysis. Guidelines should be considered a tool which we need to learn how to use; they form part of a process which, following implementation and dissemination should lead to standardized registration, an important element in facilitating improved quality control and assurance.