Physiologic and functional outcome correlates of brain tissue hypoxia in traumatic brain injury.

OBJECTIVE: Assess the prevalence of brain tissue hypoxia in patients with severe traumatic brain injuries (TBI), and to characterize the relationship between brain tissue hypoxia and functional outcome. DESIGN: Retrospective review of severe TBI patients. SETTING: Intensive care unit of a level I trauma center. PATIENTS: Twenty-seven patients with severe TBI requiring intracranial pressure (ICP) monitoring. Median age was 22 yrs, and a majority (63%) had traumatic subarachnoid hemorrhage. INTERVENTIONS: Hourly assessments of ICP, brain tissue oxygen, mean arterial pressure, fraction of inspired oxygen (FiO2), partial pressure of arterial carbon dioxide (PaCO2), and hemoglobin concentration (hemoglobin) were recorded. Outcome was assessed 6-9 months postinjury. MEASUREMENTS AND MAIN RESULTS: Mean (SD) ICP and BTpO2 were 13.7 (6.6) cm H2O and 30.8 (13.6) mm Hg. A total of 13.5% (379) of the BTpO2 values recorded were < 20 mm Hg, only 86 of which were associated with ICP > or = 20 cm H2O. This prevalence was comparable with episodes of ICP elevations above 20 cm H2O (14.1%, 397). Hypoxic episodes were more common when cerebral perfusion pressure was below 60 mm Hg (relative risk = 3.0, p < 0.0001). We did not find an association in hypoxic risk and hemoglobin in the range of 7-12 g/dL or PaCO2 in the range of 25-40 mm Hg. Subjects with hourly episodes (epochs) of hypoxia > 20% of the time had poorer scores on outcome measures compared with those with fewer hypoxic epochs. CONCLUSIONS: Hypoxic episodes are common after severe TBI, and most are independent of ICP elevations. Most episodes of hypoxia occur while cerebral perfusion pressure and mean arterial pressure are within the accepted target range. There is no clear association between PaCO2 and hemoglobin with BTpO2. The young age and high prevalence of traumatic subarachnoid hemorrhage in this cohort may limit its generalizability. Increased frequency of hypoxic episodes is associated with poor functional outcome.

Development and evaluation of a study design typology for human research.

A systematic classification of study designs would be useful for researchers, systematic reviewers, readers, and research administrators, among others. As part of the Human Studies Database Project, we developed the Study Design Typology to standardize the classification of study designs in human research. We then performed a multiple observer masked evaluation of active research protocols in four institutions according to a standardized protocol. Thirty-five protocols were classified by three reviewers each into one of nine high-level study designs for interventional and observational research (e.g., N-of-1, Parallel Group, Case Crossover). Rater classification agreement was moderately high for the 35 protocols (Fleiss' kappa = 0.442) and higher still for the 23 quantitative studies (Fleiss' kappa = 0.463). We conclude that our typology shows initial promise for reliably distinguishing study design types for quantitative human research.

Impact of age on long-term recovery from traumatic brain injury.

OBJECTIVE: To determine whether older persons are at increased risk for progressive functional decline after traumatic brain injury (TBI). DESIGN: Longitudinal cohort study. SETTING: Traumatic Brain Injury Model Systems (TBIMS) rehabilitation centers. PARTICIPANTS: Subjects enrolled in the TBIMS national dataset. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Disability Rating Scale (DRS), FIM instrument cognitive items, and the Glasgow Outcome Scale-Extended. RESULTS: Participants were separated into 3 age tertiles: youngest (16-26y), intermediate (27-39y), and oldest (> or =40y). DRS scores were comparable across age groups at admission to a rehabilitation center. The oldest group was slightly more disabled at discharge from rehabilitation despite having less severe acute injury severity than the younger groups. Although DRS scores for the 2 younger groups improved significantly from year 1 to year 5, the greatest magnitude of improvement in disability was seen among the youngest group. In addition, after dividing patients into groups according to whether their DRS scores improved (13%), declined (10%), or remained stable (77%) over time, the likelihood of decline was found to be greater for the 2 older groups than for the youngest group. A multiple regression model showed that age has a significant negative influence on DRS score 5 years post-TBI after accounting for the effects of covariates. CONCLUSIONS: This study supported our primary hypothesis that older patients show greater decline over the first 5 years after TBI than younger patients. In addition, the greatest amount of improvement in disability was observed among the youngest group of survivors. These results suggest that TBI survivors, especially older patients, may be candidates for neuroprotective therapies after TBI.

Usefulness of the abbreviated injury score and the injury severity score in comparison to the Glasgow Coma Scale in predicting outcome after traumatic brain injury.

BACKGROUND: Assessment of injury severity is important in the management of patients with brain trauma. We aimed to analyze the usefulness of the head abbreviated injury score (AIS), the injury severity score (ISS), and the Glasgow Coma Scale (GCS) as measures of injury severity and predictors of outcome after traumatic brain injury (TBI). METHODS: Data were prospectively collected from 410 patients with TBI. AIS, ISS, and GCS were recorded at admission. Subjects' outcomes after TBI were measured using the Glasgow Outcome Scale (GOS-E) at 12 months postinjury. Uni- and multivariate analyses were performed. RESULTS: Outcome information was obtained from 270 patients (66%). ISS was the best predictor of GOS-E (rs = -0.341, p < 0.001), followed by GCS score (rs = 0.227, p < 0.001), and head AIS (rs = -0.222, p < 0.001). When considered in combination, GCS score and ISS modestly improved the correlation with GOS-E (R = 0.335, p < 0.001). The combination of GCS score and head AIS had a similar effect (R = 0.275, p < 0.001). Correlations were stronger from patients 8). CONCLUSIONS: GCS score, AIS, and ISS are weakly correlated with 12-month outcome. However, anatomic measures modestly outperform GCS as predictors of GOS-E. The combination of GCS and AIS/ISS correlate with outcome better than do any of the three measures alone. Results support the addition of anatomic measures such as AIS and ISS in clinical studies of TBI. Additionally, most of the variance in outcome is not accounted for by currently available measures of injury severity.

Functional outcome scales in traumatic brain injury: a comparison of the Glasgow Outcome Scale (Extended) and the Functional Status Examination.

Clinical trials aimed at developing therapies for traumatic brain injury (TBI) require outcome measures that are reliable, validated, and easily administered. The most widely used of these measures, the Glasgow Outcome Scale (GOS) and the GOS-Extended (GOS-E), have been criticized as suffering from ceiling effects. In an attempt to develop a more useful and dynamic outcome measure, the Functional Status Examination (FSE) was developed, which grades outcome across 10 functional domains. The FSE has been demonstrated to be reliable and sensitive in monitoring recovery after TBI. This manuscript compares FSE with GOS-E in a cohort of patients with a wide range of injury severities. 177 individuals who survived at least 6 months after TBI were studied. The FSE and GOS-E were administered 6-12 months after injury. FSE and GOS-E scores correlated well with each other. FSE scores were distributed throughout the range, indicating that ceiling and floor effects were not present. Physiologic measures of injury severity (Glasgow Coma Score [GCS]) did not correlate with anatomic measures (Abbreviated Injury Scale [AIS] and Injury Severity Score [ISS]). GCS correlated weakly with both outcome measures, but AIS/ISS did not. We conclude that FSE and GOS-E are reliable outcome measures for TBI survivors, and FSE may offer some advantages over GOS-E due its ability to provide a more detailed description of deficits. The majority of the variance in outcome is not accounted for by currently available measures of injury severity.

Evaluation of seizure-like episodes in survivors of moderate and severe traumatic brain injury.

BACKGROUND: Transient paroxysmal alterations of consciousness or behavior are common sequelae of moderate and severe traumatic brain injury (TBI). Clinicians caring for patients with such episodes often diagnose them as epileptic seizures, a frequent and well-studied complication of TBI. As it is difficult to confirm this diagnosis, antiepileptic drugs are often used empirically. However, as such therapy is frequently ineffective, we studied the usefulness of prolonged video electroencephalogram (VEEG) monitoring in the clinical management of paroxysmal behaviors in TBI survivors. METHODS: Records of patients referred evaluation in an epilepsy monitoring unit for management of medically intractable epilepsy were retrospectively reviewed. Patients with a documented history of moderate-to-severe brain injury preceding the onset of epilepsy were identified. These patients were studied by simultaneous videotape and scalp electroencephalographic recordings, and the majority also underwent magnetic resonance imaging and neuropsychologic studies. RESULTS: Of the 1858 consecutive admissions over a 66-month period, 127 (7%) fulfilled enrollment criteria. VEEG monitoring was conducted for an average of 4.6 days. Monitoring was successful in establishing a diagnosis in 82% of the cases referred: 62% had focal seizures, 6% had generalized seizures, and 33% had psychogenic nonepileptic seizures. Of those with temporal lobe epilepsy, 53% had mesial temporal sclerosis, as shown by magnetic resonance imaging. CONCLUSIONS: VEEG is a useful procedure in the evaluation of TBI survivors with spells. The yield of diagnoses that may alter treatment is substantial. Additionally, mesial temporal sclerosis is associated with TBI. Given the variety of seizure types found in survivors of moderate-to-severe TBI, obtaining specific diagnosis of seizure type by VEEG monitoring impacts treatment options.