Glasgow Coma Scale score at intensive care unit discharge predicts the 1-year outcome of patients with severe traumatic brain injury

The data for this study were collected in 13 centres located in Austria, Bosnia, Croatia, Macedonia and Slovakia. All centres were of the tertiary-care level; treatment quality, however, was not uniform [1], as the centres from the lower income countries were less able to provide treatment according to the guidelines for TBI management [12]. The centres [possible Therapy Intensity Level (TIL) given in square brackets] included six University Departments of Neurosurgery (Graz [4], Osijek [4], Rijeka [4], Sarajevo [2], Skopje [1] and Zagreb [4]), five Departments of Neurosurgery at large City Hospitals (Banská Bystrica [3], Klagenfurt [4], Martin [2], Michalovce [2] and Salzburg [4]), one free-standing Centre for Neurosurgery and Neurology (Linz [4]) and one free-standing Trauma Centre (Vienna [4]). Treatment quality was significantly associated with long-term outcomes: compared to expected mortality rates, hospital mortality was 6.5 % lower in Austrian centres, 2.4 % lower in the Croatian and Slovak centres, and 13 % higher in Sarajevo and Skopje [1]. There was no “centre effect” for post-ICU mortality, i.e. the main differences between the centres were the possible TIL and/or quality of intensive care.

The data were collected between January 2001 and June 2005, but none of the centres provided data for more than 3 years. This reflects the fact that the data were collected for different projects. All projects were purely observational and prospectively enrolled all patients that were admitted to the study centres during their period of data collection. Patients were included if they had “severe TBI” according to the criteria defined by the US National Traumatic Coma Data Bank [13], such as a GCS score of 8 or less following resuscitation or a GCS score deteriorating to 8 or less within 48 h of injury. Only patients who survived at least until admission to the ICU were enrolled into this study.

Treatment in the field was provided by emergency physicians or paramedics. All patients had a rapid examination which included documentation of vital signs (GCS, pupillary status, blood pressure, heart rate, oxygen saturation). Rapid sequence intubation facilitated by hypnotics and relaxants, ventilation, treatment of haemorrhage and fluid resuscitation were done as appropriate. After admission, each patient was examined by a trauma team (anaesthesiologists, trauma surgeons or neurosurgeons, radiologists, nurses) and a computed tomography (CT) scan was performed as soon as possible. The patients then underwent surgery as appropriate and/or were admitted to the ICU. Surgical care was provided by neurosurgeons alone (Departments of Neurosurgery) or by trauma surgeons (Trauma Departments, Trauma Centre), who had the option of consulting neurosurgeons if deemed necessary. Intensive care was provided by anaesthesiologists in cooperation with neuro- or trauma surgeons. The whole treatment process in each centre was supposed to be based on the guidelines for the management of patients with severe TBI published by the Brain Trauma Foundation [12] and introduced at the start of the projects in each centre.

Data collection was done using the International Traumatic Coma Project (ITCP) database, which allowed for data collection over the Internet. Basic demographic data of the patient, cause and location of trauma, pre-hospital status and treatment, mechanism and severity of trauma, results of CT scans, results of laboratory testing and data on surgical procedures and outcomes were recorded. Pre-hospital data were documented by the local paramedics, and these data were then transferred into the ITCP database. CT scans were interpreted by neurosurgeons, trauma surgeons and radiologists, and the summarised findings were entered into a separate CT page in the ITCP database. This page collected detailed data on basal cisterns (open/closed), midline shift (in mm) and main findings [subdural haematoma (SDH), oedema, contusions etc.]. No central review of CT scans was done, as no actual images were uploaded into the ITCP database. Information on status and treatment was recorded in detail for the first 10 days. In addition, data on the duration of various treatments, on complications and on outcome were collected at discharge from the ICU. Information on status and location was recorded at 3, 6 and 12 months after injury. This was done by phone calls to the patients and/or their relatives; in some cases, the Glasgow Outcome Scale (GOS) score was recorded at patients’ follow-up visits to the centres. In most centres, data were collected by local research fellows; data quality was monitored by the INRO data manager. Missing or implausible data were reported to local research fellows, who then submitted missing or corrected values. In the Austrian centres, data were extracted from the prospectively collected records by a single researcher (I.W.), who visited the centres at regular intervals. Personal data protection was observed and the identifiers were kept separately from the data.

Files from all patients who survived their ICU stay were selected for this analysis. Data on trauma mechanism, trauma severity, CT findings, treatment and outcomes were retrieved for each patient. Files that did not include information about 1-year outcomes were excluded from further analysis. The Trauma and Injury Severity Score (TRISS) method [14] was used to estimate the probability of hospital survival (Ps). To describe 1-year outcomes, the GOS was used [15]. “Favourable outcome” was defined as a GOS score of 5 or 4 and “unfavourable outcome” was defined as a GOS score of 3 or less at 12 months after trauma. According to the GCS score at ICU discharge, the patients were classified into four groups: GCS scores 3–6, 7–9, 10–12 and 13–15. Differences between these four groups were analysed to identify the factors that contributed to the status at ICU discharge. To identify factors contributing to 1-year outcomes, within each of the four groups, patients who reached favourable outcomes were compared to those that had unfavourable outcomes.

Statistical analysis was performed with the open-source statistical package R. Chi-square tests or Fisher’s exact test were used, as appropriate, to test differences between proportions, two-way analysis of variance was used to test differences between means and the Kruskal–Wallis test was used to test differences between medians when comparing the four categories. For pairwise comparisons, the two-sample t-test was used for comparisons of means and the two-sample Wilcox test was used for comparisons of medians. A p-value of <0.05 was considered to be statistically significant. Factors that were significant in the univariate analysis were entered into logistic regression models, with backward elimination of non-significant factors. These factors included age (per year increase), trauma mechanism (“fall” vs. “other”), GCS, Injury Severity Score (ISS), Abbreviated Injury Scale (AIS) “head” score, basal cisterns (“open” vs. “compressed/closed”), midline shift (“<5 mm” vs.“>5 mm”) and pupillary status (“normal” vs. “abnormal”). Two models were constructed in order to elucidate which factors influence hospital survival and favourable outcome one year after trauma, respectively.