Journal of the New Zealand Medical Association, 11-September-2009, Vol 122 No 1302
Time to definitive care for patients with moderate and severe traumatic brain injury—does a trauma system matter?
Ritwik Kejriwal, Ian Civil
The presence of a trauma system has been associated with decreased mortality and improved outcomes by potentially speeding up transfer of trauma patients to a major trauma centre.1–3 This is particularly relevant in patients with head injuries where time to neurosurgical intervention from the time of significant traumatic brain injury (TBI) is important in determining the outcome.4 North American guidelines recommend a maximum of four hours from the time of injury to neurosurgical attention for patients requiring evacuation of an intracranial haematoma.4–7
Trauma care in New Zealand is delivered in an ad hoc trauma system as opposed to a regional trauma system.8 Auckland City Hospital (ACH) provides adult brain trauma care for a population of approximately two million people in the upper North Island of New Zealand with the most distant referring hospital 346 km from ACH by air.9 Patients with TBI are transported to the closest regional hospital for airway, breathing and circulation assessment and stabilisation. Once haemodynamically stable, an urgent computed tomography brain scan is performed that is then reviewed electronically by the neurosurgeon and intensivist in ACH. Transfer is recommended on the basis of a need for neurosurgical intervention or brain-oriented intensive care.
The objectives of this study were to determine the timelines associated with the sequence of care for TBI patients and identify any correlations between time to definitive care and outcome. We aimed to do so by comparing patients that were transported directly to ACH with those transferred from another hospital, as well as comparing the data with the current literature.
The study was carried out at ACH, New Zealand. The ACH Trauma Registry was interrogated for all patients admitted in 2004 with an Abbreviated Injury Scale (AIS) of 3 or greater for head injury. The registry used AIS-90 (98 update) version software.10 This extraction method was selected as Glasgow Coma Scale (GCS) on arrival is often confounded by intoxication or other injuries. Therefore we sought to specifically identify that cohort of TBI patients who had a clinically significant TBI.
The ACH Trauma Registry includes all patients presenting to the hospital following injury who are admitted. 1137 patients were recorded in the ACH registry in 2004 calendar year. Patients who presented with an injury due to an underlying chronic subdural haematoma were not included in the Registry.
The following data were extracted from the registry: patient demographics, AIS, Injury Severity Score (ISS), details of injury, entrapment time, GCS, presence of other trauma, mode of transport, time and type of surgery, intracranial pathology, in-hospital survival, length of Intensive Care Unit (ICU) stay, and length of stay in the hospital. Patients transferred to ACH after 24 hours and patients without time of injury or time of arrival were excluded.
The primary outcomes of the study were median time from injury to arrival at ACH, time to neurosurgical intervention, mortality, length of intensive care, and length of hospital stay. The secondary outcome was effect of age, sex, mode of transport, ISS, GCS, presence of multiple trauma and road crashes on time from injury to arrival at ACH.
Statistical analysis—All analysis was performed using SAS version 8.2 (SAS Institute Inc., Cary, NC, USA). Comparison between primary and secondary groups was made using chi-square tests for equal proportion and student t-tests, and validated using Wilcoxon rank sum tests. Time from injury to arrival was found to be well approximated by a lognormal distribution and was consequently log-transformed prior to analysis. The univariate relationships between log (time from injury to arrival) and all other variables were assessed using linear regression, whilst multivariate analysis was performed using multiple linear regressions.
Multivariate models were constructed using a stepwise selection procedure and validated using a backwards elimination procedure. Results are presented as parameter estimates with a standard error. A two-sided p-value of 0.05 was considered to be statistically significant.
198 patients were admitted at ACH in 2004 with moderate and severe TBI (defined as an AIS score of 3 or greater for head injury) in this study. Baseline data is outlined in Table 1; 48% of patients were transferred from another hospital.
Table 1. Baseline data
Fifteen percent of the patients were excluded due to time of injury or arrival time not being available, or due to patients presenting to the trauma hospital more than 24 hours after injury. After excluding these patients, the data was divided in two groups—patients transported to ACH directly from the scene of injury (PRIMARY group) and patients taken to another hospital before they were transferred to ACH (SECONDARY group). There were 97 patients (57%) in the PRIMARY group and 73 (43%) patients in the SECONDARY group. 43 (59%) patients in the SECONDARY group were transferred from two hospitals within Auckland region. Baseline comparison between the two groups at ACH is outlined in Table 2.
Neurosurgical procedures performed within 24 hours of injury were included in the analysis. 24 neurosurgical procedures were performed on 13 patients in the PRIMARY group and 18 procedures were performed on 16 patients in the SECONDARY group. 20 procedures were excluded due to missing data or surgery performed later than 24 hours after injury.
Primary outcome of median time from injury to arrival at ACH was adjusted for entrapment (Table 3). Overall the median time from injury to arrival was 1 hour 43 minutes. The median time from injury to arrival at ACH as well as to neurosurgery for the SECONDARY group was significantly greater than the PRIMARY group (p<0.0001). There were no statistically significant differences between the two groups for in-hospital survival, length of ICU stay, and length of hospital stay.
Table 2. PRIMARY group vs SECONDARY Group
Table 3. Primary outcome
Time to definitive care was analysed for patients transferred to ACH from other hospitals in Auckland region as well (Table 4). Median time from injury to arrival for Auckland region transfers (6 hours 16 minutes) was significantly greater than the PRIMARY group (p<0.0001).
Table 4. Analysis of Auckland region transfers
Transport by road ambulance (p=0.04) and road crashes (p=0.05) were predictors of a reduction in time from injury to arrival in univariate regression analysis as well as the multivariate model.
It is well established that time to neurosurgery from time of injury is critical in determining neurological outcome. In the United States, the Brain Trauma Foundation recommends a time limit of four hours to surgical intervention for acute subdural haematomas based on 1981 study by Seelig et al.4
European guidelines do not set a time frame, but there is a consensus that the speed of referral and transfer to neurosurgical care may critically influence the outcome.3,11 Even as Wilberger et al found no improvement in mortality rate in patients treated within four hours,12 other studies show that time from point of neurological deterioration to surgery is related to improved outcome.13,14
From the time of injury, the PRIMARY group median time to arrival (50 minutes) and median time to surgery (3 hours 50 minutes) at ACH were within four hours. On the other hand, median time from injury to arrival at ACH for the SECONDARY group was well outside the recommended guidelines (7 hours 3 minutes). Therefore patients transported directly to ACH are likely to undergo neurosurgery within international guidelines whereas those transferred are not.
These times are comparable to the ones reported in the literature. Our SECONDARY group times were similar to a Liverpool Hospital study that reported a median time to definitive care of 6 hours 39 minutes for patients transferred from another hospital.15 Another study reported a median delay of 4 hours and 22 minutes in patients who were transferred from another hospital.16
ACH had significantly larger proportion of patients transported from another hospital (48%) compared to the trauma systems in the literature16, which means that the effect of undue delay and its potential effect on outcome even more important than in systems where there are fewer transfers. It is particularly relevant that even from hospitals within the metropolitan region there was a significant delay to from injury to surgery compared with those transported directly to ACH.
While there were no differences between the two groups in hospital stay ICU stay, and mortality in this study, the numbers were very small. A similar study in western Virginia found that patients transferred from another hospital had worse outcomes in the above-mentioned parameters compared to patients directly transferred to a major trauma centre.17
The linear regression analyses of ACH data suggests that transport by road is associated with shorter transport times than when transport is by helicopter. This is due to rotary wing transfers being used sparingly in the region serviced by ACH and being limited to patient transfers from places with difficult road access.
Benefits of a state trauma system have been well documented. Cooper et al assessed management of road traffic fatalities and suggested that having a trauma system in Victoria, Australia is likely to decrease preventable death rates.18 Similarly, Mullins et al attributed improved outcomes among patients with head injuries in Oregon to the institution of a state trauma system.2 It compared the state trauma system of Oregon to an ad-hoc trauma system of Washington and found a significant difference in patient mortality. Another study carried out in Rhode Island concluded that the presence of a major trauma centre that is not part of a state trauma system results in delays in time to definitive care for injured patients.1
State trauma systems have triage criteria that allow patients with major trauma injury to be directly transported to a designated major trauma centre. This is related to improved outcomes according to Poon et al,19 who concluded that direct admission of head injury patients to the primary care of the neurosurgeons is the best policy in the reduction of mortality and morbidity. Patel et al and Cooper et al provided strong evidence as well in his observational study that patients who have neurosurgical trauma are better managed in a neurosurgical centre as part of a Level 1 Trauma Centre.14,20
While the ACH SECONDARY group were not worse off in outcomes measured, based on the literature ACH trauma care may be improved by an introduction of a triage criteria or an ambulance bypass protocol. Lind et al stated that triaging is not an option for patients outside Auckland,9 but triaging for patients within Auckland may be beneficial as 43 out of 73 patients in the secondary group were transferred from hospitals within the Auckland metropolitan area. This will potentially enable these patients to undergo neurosurgical intervention within recommended guidelines.
This retrospective study is only a snapshot of the performance of ACH ad-hoc trauma system in one calendar year. A limitation of the study is incomplete data for some of the patients at ACH. Nonetheless, approximately 85% of the patients with AIS of three or greater were still included for primary outcome analysis making it a fair representation of the baseline population.
Another limitation was the small proportion of patients that underwent neurosurgery within 24 hours, which made it difficult to compare time to surgery between the two groups. This study was also limited by lack of available data from the hospitals of primary presentation. Were NZ to have a national trauma registry, such as the state registry in Victoria, Australia, a much more comprehensive dataset could have been assembled to allow more comprehensive analysis of this topic.
Almost half of the TBI patients treated at ACH in 2004 were transferred from another hospital and they arrived well outside the recommended time guidelines. While this made no difference in patient outcomes as measured by LOS and survival in our study, there may be benefit in having a greater proportion of patients directly transferred from the scene of injury. Development of a prospective national trauma registry would allow ongoing analysis of the process of trauma care and outcome in NZ. Future prospective studies are recommended to look at outcomes including neurological outcome of patients with TBI in New Zealand.
Competing interests: None known.
Author information: Ritwik Kejriwal, House Officer; Ian Civil, Director; Trauma Services, Auckland City Hospital, Auckland
Correspondence: Dr Ritwik Kejriwal, 6U Carlton Gore Road, Grafton, Auckland, New Zealand. Email: firstname.lastname@example.org
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