Impact of concomitant injuries on outcomes after traumatic brain injury

Seventeen Austrian centers participated in these projects, all were of tertiary care level and were able to provide guideline-based [5] patient management. The changes made during the revisions of these guidelines in 2000 and 2007, respectively, were taken into account. The number of patients enrolled by these centers (median: 28, IQR 21–65, range 3–150) varied considerably, as four centers participated in both projects, and some centers joined the second project with just few weeks remaining for patient inclusion. Hospital mortality for patients with severe TBI was significantly lower during the 2009–2010 projects (28 vs. 37 %; P = 0.005). However, Glasgow Coma Scale (GCS) score was significantly lower (5.4 vs. 5.9; P = 0.022) and Abbreviated Injury Score (AIS) for the region “head” was significantly higher (4.2 vs. 3.9; P < 0.001) in the patients from the 2002–2005 projects; thus, “period of enrollment” was not significantly associated with outcomes in the logistic regression analysis.

Treatment in the field was provided by emergency physicians. All patients had quick examination with documentation of vital signs. Rapid sequence intubation facilitated by hypnotics and relaxants, ventilation, treatment of hemorrhage, and fluid resuscitation was done as appropriate. After hospital admission each patient was examined by a trauma team (anesthesiologists, trauma surgeons, and/or neurosurgeons, radiologists, nurses), and a computed tomography (CT) scan was done. The patients then underwent surgery as appropriate and/or were admitted to the intensive care unit (ICU). Intensive care was provided by anesthesiologists in cooperation with neuro or trauma surgeons.

Basic demographic data of the patient, cause and location of trauma, prehospital status and treatment, mechanism and severity of trauma [AIS, Injury Severity Score (ISS)], results of CT scans, results of lab testing, and data on surgical procedures and outcomes was recorded prospectively. Prehospital data were documented by paramedics and then transferred into the databases. Summarized CT findings [i.e., data on basal cisterns (open/compressed/absent), midline shift, main findings (edema, hematoma, contusions, etc.), Marshall classification] were entered into a separate CT page in the databases. No central review of CT scans was done in the first project. Central review of the CT scans was done in the second project; a radiologist and a trauma surgeon checked the accuracy of the data entered into the database. Data on duration of various treatments, on complications, and on outcomes were collected at discharge from the ICU, at hospital discharge, and at 6 months after injury. The Glasgow Outcome Scale (GOS) score at 6 months after injury was evaluated by phone calls to the patients or their relatives. Data were collected by local research fellows. Data quality was monitored by INRO project managers. They reported data problems to the local researchers who then submitted the missing or corrected values. Personal data protection was observed and the identifiers were kept separately from the data.

All patients who had an AIS “head” (AIS_H) < 6 and survived at least until admission to the ICU were included. Data on trauma mechanism, trauma severity, CT findings, treatment, and outcomes were retrieved for each patient. The 6-point Rotterdam CT score [6] was used to classify CT findings and to calculate probability of mortality according to this score. The prognostic scores developed by Hukkelhoven et al. [7] were used to estimate probability of hospital death (P _D) and probability of unfavorable long-term outcome (P _U). To describe long-term outcomes the GOS [8] was used. “Favorable outcome” was defined as a GOS score of five or four; “unfavorable outcome” was defined as a GOS score of three or less at 6 months after trauma. Patients were assigned to the group “TBI + injury” if they had one or more extracranial injuries with an AIS > 2. Patients were assigned to the group “TBI isolated” if they had no extracranial injuries with an AIS > 2. The differences between these two groups of patients were analyzed.

Analyses were done using the software provided by P. Wessa (Free Statistics Software version 1.1.23-r6, http://​www.​wessa.​net). Two-tailed t test, Fisher’s exact test, and χ²-test were done as appropriate to identify differences between the groups. To check for associations with outcomes we constructed logistic regression models for hospital death and favorable long-term outcome where outcomes were corrected for confounders, with backward exclusion of non-significant (P > 0.1) parameters. Age, gender, trauma mechanism, number of injured body regions with AIS > 2, ISS, AIS_H, GCS score, pupillary reactivity, presence of hypoxia and hypotension, Rotterdam CT score, and requirement of neurosurgery or extracranial surgery were considered possible confounders. The models were calculated for both groups individually, and for the whole sample as well. Data are presented as means with standard deviations, or as proportions. A P value of <0.05 was considered statistically significant.

Hospital mortality was 2.8 % lower in patients with concomitant injuries (n.s.). In both groups, most patients were male. Mean age was significantly higher in patients with isolated TBI (P < 0.001). It was also higher in females from both groups (n.s.). A significant (P < 0.01) increase in hospital mortality was seen with increasing age, but there was no difference in mortality rates between the groups. With regard to trauma mechanism falls and traffic-related accidents were most common in both groups. There were no significant differences in mortality rates for any of the mechanisms.

The ISS was significantly higher in patients with concomitant injuries (P < 0.001). There was an increase in the severity of concomitant injuries for increasing values of AIS_H: the values for ISS (calculated without AIS_H) were 19.7 ± 8.6 (AIS_H = 2), 22.8 ± 11.0 (AIS_H = 3), 20.0 ± 10.3 (AIS_H = 4), and 27.9 ± 16.6 (AIS_H = 5), respectively (P = 0.1, n.s.). Mean AIS_H and mean GCS scores were not different. Within each group ISS and AIS_H were significantly higher and GCS scores were significantly lower in non-survivors. In both groups, most of the patients had severe TBI: only 17/767 [2.2 %; if (AIS_H > 2) is used as definition] or 95/767 [12.4 %; if (GCS score >8) is used as definition] of the patients had moderate TBI. In patients with AIS_H = 2 mortality was significantly lower in those with isolated TBI. Increasing GCS scores were associated with significant decreases in mortality rates in both groups. In both groups, patients with reactive pupils had significantly lower mortality rates but there were no significant differences in mortality rates between the groups. The same was true for absence of prehospital hypotension and hypoxia, respectively. Incidences of aspiration, use of anticoagulants, and comorbidities were not significantly different between the groups, and these had no significant effects upon mortality. The predicted P _D was 29.2 ± 20.5 % for patients with concomitant injuries, and was 33.4 ± 21.5 % for patients with isolated TBI (P = 0.06), and the P _U values were 50.9 ± 24.0 % and 54.9 ± 24.6 %, respectively (P = 0.02).

Mortality increased significantly with increasing Rotterdam CT scores (P < 0.001), but there were no significant mortality differences between the groups. The mortality rates were lower than those predicted by the Rotterdam score; a significant correlation (y = 15.963x − 2.388; R ² = 0.992; P = 0.03) between observed and predicted values was found for patients with isolated TBI only. With regard to predominant lesions, subdural hematoma was observed most frequently, followed by contusion, EDH and subarachnoid hemorrhage. The overall distribution of predominant lesions was not significantly different between the groups. There were no differences in mortality between the two groups within the different classes of the Marshall CT score (Table 2).

Most patients were admitted directly to the study centers; mortality was lower in the 125 patients (16.3 %) with indirect transfer (P = 0.002). Air and ground transport were associated with comparable mortality rates. Patients who required prehospital airway management had a significantly (P = 0.008) higher mortality. There were no differences regarding the intervals between admission and start of CT scan, and between start of CT scan and start of surgery. The majority of the patients (n = 504; 65.7 %) were managed conservatively and had either no surgical procedure or insertion of an ICP monitoring device only. Mortality was lower in the patients who had primary craniectomy than in those who had craniotomy (P = 0.053). The requirement for extracranial surgery was associated with significantly higher mortality in patients with concomitant injuries. Duration of ventilation (12.8 ± 11.2 vs. 10.1 ± 10.8 days), ICU stay (22.0 ± 18.5 vs. 17.4 ± 16.3 days), and hospital stay (42.0 ± 39.4 vs. 28.2 ± 25.6 days) were significantly shorter in survivors with isolated TBI than in those with concomitant injuries. No significant differences regarding these parameters were found in non-survivors.

Injuries to the thoracic region and to extremities were associated with higher, isolated injuries to the face with lower mortality. None of the observed mortality rates was significantly different from the average mortality for the whole group. The overall incidences of associated injuries were: 191 (24.9 %) patients had thoracic, 166 (21.6 %) had facial, 154 (20.1 %) had extremity, 58 (7.6 %) had spinal, 20 (2.6 %) had abdominal, and 6 (0.8 %) had external injuries. Of the 58 spinal injuries, 20 (34.5 %; 2.6 % of all) were cervical, 28 (48.3 %; 3.7 % of all) were thoracic, and 10 (17.2 %; 1.3 % of all) were lumbar spine injuries.

More than half of the injuries did not require surgical interventions. The number of surgical procedures required was not significantly associated with mortality rates. Orthopedic procedures involving extremities or pelvic region were done most frequently. Abdominal surgery and thoracic surgery were associated with higher mortality rates.

The observed hospital mortality was 27.2 % for patient with concomitant injuries and 30.0 % for patients with isolated TBI, while P _M values were 29.2 ± 20.5 % and 33.4 ± 21.5 %, respectively. The observed vs. expected ratio (O/E ratio) for mortality was 0.93 for patients with concomitant injuries (=25 unexpected survivors), the O/E ratio for mortality was 0.90 for patients with isolated TBI (=40 unexpected survivors). Main causes of death in patients with concomitant injuries were brain death (51.9 %), cardiovascular problems (31.5 %), multiple organ failure (9.8 %), major hemorrhage (4.4 %), and acute respiratory distress syndrome (2.2 %). In patients with isolated TBI brain death was observed significantly more frequently (65.1 %, P = 0.04), and the rates of cardiovascular death (25.7 %) and multiple organ failure (5.5 %) were lower. Long-term outcome was unknown in 28 patients (14 from each group). Favorable outcome was observed in 54.4 % (198/364) of patients with concomitant injuries and in 46.2 % (186/403) of the patients with isolated TBI; this difference was significant (P = 0.02). Unfavorable long-term outcome was observed in 41.8 % (152/364) and 50.4 % (203/403), respectively; this difference was also significant (P = 0.02). The P _U predicted by the Hukkelhoven score was 50.9 ± 24 % for patients with associated injuries, and was 54.1 ± 24.1 % for patients with isolated TBI. The O/E ratio for unfavorable outcome was 0.82 for patients with concomitant injuries (=66 patients with unexpected favorable outcome), the O/E ratio for unfavorable outcome was 0.93 for patients with isolated TBI (=28 patients with unexpected favorable outcome). Factors that significantly influenced outcomes are listed in Table 6. Age, GCS score, pupillary reactivity, AIS_H and CT score were significant in all or almost all analyses. Isolated TBI was significantly associated with unfavorable long-term outcome. Major neurosurgery was associated with higher mortality in patients with isolated TBI, ISS was associated with worse long-term outcomes in patients with concomitant injuries.

The scores used to estimate P _M and P _U have not been validated for our study population. These scores have been created from the international and North American data from the tirilazad trial [21, 22], and have been validated against the core data set of the European Brain Injury Consortium (EBIC) survey [23] and data from the Traumatic Coma Data Bank [24]. It is quite likely that our patients are comparable to those from the EBIC centers and the international arm of the tirilazad trial. There could, however, be subtle differences, and the O/E ratios estimated for our groups of patients may be incorrect.