Increased distance or time from a major trauma centre in South Australia is not associated with worse outcomes after moderate to severe traumatic brain injury

Considerations in traumatic brain injury (TBI) management include time to critical interventions and neurosurgical care, which can be influenced by the geographical location of injury. In Australia, these distances can be vast with varying degrees of first‐responder experience. The present study aimed to evaluate the association that distance and/or time to a major trauma centre (MTC) had on patient outcomes with moderate to severe TBI.


Introduction
Traumatic brain injury (TBI) is one of the leading causes of prehospital mortality, 1 with majority of deaths occurring from road traffic crashes and falls. 2 Rapid transport to neurosurgical care with supportive physiological management to minimise secondary brain injury is crucial in the early management of TBI. 3 Modern advances in prehospital and primary emergency care have led to improvements in airway management, fluid replacement therapy and • Increasing distance or time from a major trauma centre is not associated with increased mortality or impact on discharge destination for patients with moderate to severe TBI in South Australia.• Patients injured in regional areas had a LOS almost a week longer than those from a major city.• Patients who received neurosurgical intervention had almost 18 days longer LOS and were less likely to be discharged home.
supplementary pharmacology with aims to decrease secondary neurological injury.These interventions have decreased mortality in severe TBI, albeit at the cost of prolonging scene times. 4,5While increasing time to a neurosurgical centre can be due to greater levels of intervention, occasionally, extended times are due to the geographical remoteness, or difficult terrain. 6,7ustralia has a land size of 7.68 million km 2 , 31 times the size of the UK, with a high proportion of the 25 million inhabitants living in coastal cities. 8 There are often exceptionally large distances between medical facilities, with varying levels of care, and remote inland communities.These distances have been shown to be associated with double the mortality rate of major trauma in rural settings compared to metropolitan areas. 6outh Australia's trauma system consists of three major trauma centres (MTCs) all based in the Adelaide metropolitan area.The South Australian Ambulance Service (SAAS) is responsible for responding to prehospital trauma, and within SAAS there is a dedicated state-wide prehospital retrieval service (MedSTAR), utilising three different transport platforms: road, rotary-wing and fixed-wing (with aircraft provided by the Royal Flying Doctor Service).SAAS and the trauma system service the entire state, as well as parts of neighbouring states.Depending on distance to hospital and other logistical factors (such as retrieval team availability), the paramedic-based ambulance service also transports patients directly to the hospital.
Although historically emergency neurosurgical procedures have been performed in rural settings by local doctors or neurosurgeons travelling to the patient, 9 currently acute neurosurgical intervention (craniectomy or burr holes) outside of Adelaide is not performed due to the responsiveness of the pre-hospital retrieval service in South Australia in combination with the limited availability of suitable personnel, equipment and/or facilities available to perform the procedures.Therefore, any moderate to severe TBI is retrieved to either the Royal Adelaide Hospital (RAH) in central Adelaide or Flinders Medical Centre (FMC) in southern Adelaide, or for children aged 16 years and under to the Women's and Children's Hospital in central Adelaide.The RAH sees approximately 1800 trauma cases per year, equating to roughly 70% of South Australia's major trauma cases. 10iven the large geographical area of South Australia and consequently the variable distances to the three MTCs, we aimed to investigate any relationship between distance or time from site of injury to an MTC and outcome for patients with moderate to severe TBI.Our hypothesis was that increased time or distance from injury site to arrival at the MTC would be associated with poorer outcomes including increased mortality.

Methods
We undertook a retrospective data analysis to assess the impact of time or distance from injury to neurosurgical care at one of the MTCs (the RAH) on the outcomes for patients with moderate to severe TBI.The protocol for this research project was approved by the Central Adelaide Local Health Network Human Research Ethics Committee and endorsed by SAAS.

Trauma registry
Patients are entered into the RAH Trauma Registry when they meet the State-wide Trauma Team Activation Criteria -Level 1 or Level 2, or injured with an Injury Severity Score (ISS) >12.They are entered by Trauma Service admin staff by utilising electronic medical records, and injuries entered using the Abbreviated Injury Scale (AIS) coding module.Injuries are gathered from a combination of clinical notes, imaging findings and surgical reports.

Patients and data
A retrospective analysis of patients who arrived at the RAH ED in a 3-year period (1 January 2018 to 31 December 2020) was conducted, using data from the RAH's Trauma Registry.Patients were included if they were over 16 years old, with a moderate to severe head injury (Glasgow Coma Scale [GCS] ≤13 and AIS head ≥2 at MTC ED arrival) and transferred to the RAH.The Registry records were reviewed for patient characteristics, time details, postcode of injury, injury type, ISS, prehospital and ED GCS, pre-MTC intubation, length of stay (LOS), injury description and discharge destination.Pre-MTC intubation was classified as intubation occurring before MTC ED arrival, either on-scene or in a peripheral transferring facility.

Exclusion criteria
To limit factors influencing mortality and discharge destination, patients were excluded if they had a cardiorespiratory arrest prior to ED arrival, or documented pre-existing brain injury, neurological or cognitive deficits.

Distance
Distance was calculated from the centre of the postcode of injury to the MTC.Distances were categorised into three groups based on the most likely choice of retrieval transport platform, being a road vehicle (0-50 km), rotary-wing aircraft (50-300 km) and fixed-wing aircraft (300-1500 km). 11Postcodes were classified into areas of remoteness using the Modified Monash Model (MMM), and further classified into 'Major City' (MMM 1) or 'Regional' (MMM 2-7). 12

Time
Prehospital time was taken from time of injury (taken from prehospital notes, '000' call to emergency services or patient/bystander history) to arrival at the MTC ED.Time was dichotomised into <4 h (early) and >4 h (late) groups, highlighted as the standard of care by The Royal College of Surgeons. 13

Outcomes
The primary outcome was in-hospital mortality.Secondary outcomes consisted of LOS and discharge destination (home or any rehabilitation/ peripheral hospital).While functional patient outcomes were considered, these were not captured in the database and hence not financially feasible or realistic given the timeframe to collect.

Statistics
The present study utilised convenience sampling, capturing cases over a specific time frame, and as such a sample size calculation was not performed.Data were summarised as mean and standard deviation (SD), or median values and interquartile range (IQR) for normally and non-normally distributed data, respectively.Age was categorised into ranges (<25, 26-40, 41-60, >60) aligning closely with our cohort IQR, and age predictor outcomes, 14 ISS was dichotomised (<25, ≥25), 15 and ED GCS was categorised into severe (GCS ≤8) or not severe (GCS 9-13). 16Stepwise logistic regression analysis (probability for entry 0.05 and removal 0.10) was undertaken to determine independent variable predictors of outcomes.Variables used for adjusted analysis included age (ranges), dichotomised ISS, ED GCS severity and pre-MTC intubation.Logistic regression assumptions and multicollinearity were assessed.Statistical significance was set at P < 0.05.All statistical analyses were performed using SPSS version 27.

Results
During the 3-year study period, 378 patients were identified from the trauma database with a GCS ≤13 and AIS ≥2 on MTC ED arrival.Of these, 94 were excluded as not having a TBI after reviewing their description of injury as noted in Figure 1.A further 48 patients met exclusion criteria and were removed from analysis; one patient had incorrect information recorded and a further nine patients had a significant delay between time of injury and interacting with a medical service (>24 h), and thus were not assessed as a primary trauma response (e.g.46-year-old male attending ED 2 weeks following an assault).Cases in which delays due to distance, clinical presentation or logistics were included.The final study cohort comprised 226 patients.Ten cases had missing postcode data.
Baseline characteristics are presented in Table 1.Most patients were male, aged in their 30s and presented directly to the MTC (without secondary transfer).The median elapsed time from suspected injury to arrival at MTC ED was 1 h and 50 min, with a median distance of 22 km.Over half the patients were classified as having their injury in a major city (54.8%), with almost a third receiving neurosurgical intervention (31.4%).
Road traffic incidents (motor vehicle accident [MVA], motorcycle, pedestrian hit by car and cyclist) accounted for over half of injuries.Prehospital GCS data were available for 217 patients; about half the patients had a prehospital GCS ≤8, while 13 patients had an initial prehospital GCS of 15.
Characteristics for patient cohorts arriving early or late, and major city or regional areas are shown in Table 2. Patients arriving late had a median distance of over 200 km further than the early cohort and were more likely to live in regional areas.Regional patients took longer to arrive at the MTC, were further away, more likely to be intubated prior to arrival and had an LOS almost a week longer than those from a major city.
Neurosurgical intervention was categorised into ICP monitor insertion, craniotomy for haematoma evacuation or decompressive craniectomy, with patients often requiring a combination of more than one procedure type (such as craniotomy for haematoma evacuation with associated insertion of ICP monitor).As seen in Table 3, patients who received neurosurgical intervention had a higher ISS and AIS (head), were more likely to be intubated prior to arriving at the MTC and had an increased LOS.Intervention patients were also less likely to be discharged back home.

In-hospital mortality
Distance to the MTC was not shown to be associated with mortality when analysed as a continuous variable, by distance grouping or by regional versus major city patients.ISS >25, ED GCS ≤8 and age >60 were significantly associated with increased mortality.Increasing continuous time to the MTC was not associated with a change in mortality; neither was time when dichotomised into <4 and >4 h, as seen in Figure 2.

Discharge destination
Discharge destination data from seven cases were missing, and patients who died in-hospital were removed from analysis.Most patients were discharged to an inpatient rehabilitation facility or to a peripheral hospital.Increasing distance to the MTC was not shown to be significantly associated with discharge destination when analysed as a continuous variable, distance groups or regional versus major city patients.Patients with an ISS >25, age >60 years and ED GCS ≤8 had significantly increased odds for discharge to a rehabilitation/peripheral hospital.Time when adjusted both as a continuous variable and dichotomised into 4 h did not show any association with discharge destination, as seen in Figure 2.

Discussion
The uniqueness of the Australian population geography with the associated vast distances between medical services can prove challenging in the management of patients with a moderate to severe TBI in regional Australia.Our study aimed to capture patients in South Australia who presented to one MTC (the RAH) with a moderate to severe TBI over a 3-year period.
Our findings demonstrate that increasing distance and time, both as continuous variables and when categorised, were unable to find a significant variable-outcome association for any of the outcome measures.This remained unchanged even when adjusting for confounding variables.8][19] South Australia's integrated state trauma system includes a 24/7 state-wide consulting service between the duty senior clinician in the retrieval service and regional EDs, providing real-time support (AEtelemedicine) for regional clinicians.The combination of these, alongside early diagnosis with availability of imaging in rural locations, and advancements in on-scene resuscitation all with the aim of reducing secondary neurological injury, could help explain why we were unable to observe any impacts on distance or time on patient outcomes.While increasing retrieval time is associated with increasing distance in South Australia, 20 we believe this is the first report looking at distance as an independent variable on patient outcomes in an Australian setting for patients with moderate-severe TBI.
Regional patients within our cohort had a median LOS almost a week longer than those from a major city.While a previous study in neighbouring New South Wales found no difference in LOS for patients with a severe TBI, 21 LOS outcomes for regional trauma patients seem to vary state-tostate. 22The increased LOS identified within our cohort could be explained by limited access to rehabilitation or community services in regional areas, as well as discharge planning and transfer delays back to regional hospitals.South Australia has one brain injury rehabilitation programme available to both regional and urban patients, located within Adelaide, with the service offering a combination of community and inpatient rehabilitation.This specialised service is reserved for patients most in need, and therefore patients requiring general rehabilitation following injury are either transferred to an inpatient rehabilitation facility or outpatient day rehabilitation services or rehabilitation-in-the-home.These outpatient rehabilitation services are offered sparsely within regional South Australia, and generally result in regional patients remaining in hospital waiting for an inpatient rehabilitation bed to become available.Compounding this, regional patients occasionally are transferred back to peripheral hospitals to complete rehabilitation and discharge planning.This transfer, depending on distance, logistics and available modes of travel can sometimes prolong their stay for days.Although distance from injury site to the MTC was significantly longer for regional patients compared to those from a major city (125 km vs 8.2 km), a median distance of 22 km highlights most of the cohort was relatively close.Short distances have been seen previously in South Australia, with Flabouris et al. who looked at allcause ICU admitted patients in South Australia, found a median distance of only 7.6 km. 11The small distance found within our data could be attributable to the higher incidence of major trauma seen in major cities, 23,24 the higher population density in Adelaide, 25 as well as not capturing regional patients south of Adelaide who may have presented to FMC.
While it is known that a in time-to-surgery for spaceoccupying haematomas is associated with a decrease in mortality, this benefit was not seen within our cohort. 26This could be explained by the broad inclusion criteria of patients in the present study, with only a third of patients receiving neurosurgical intervention.Myburgh et al., who looked at the epidemiologic profile of TBI in Australia and New Zealand, found that almost a quarter of patients with a severe TBI (GCS ≤8) had no visible intracranial pathology on CT.
The patients who underwent surgical intervention had a higher AIS (head), a median LOS almost 18 days longer and were less likely to discharge home.Lui et al. found that infection and neurosurgical intervention were both independently associated with an increased likelihood of inpatient rehabilitation, 27 providing a possible explanation as to why this subset of our cohort had a longer LOS and was less likely to be discharged home.
The present study provides support for the prehospital management of moderate to severe TBI consisting of early and aggressive measures to limit secondary brain injury.Within the limitations of our study, it is reasonable in the South Australia environment to focus on optimising the patient while aiming to retrieve and transfer at the earliest opportunity.
Improvements in mortality have been seen by correcting hypoxaemia, hypotension, hypercarbia and hypothermia, and therefore should receive paramount focus in the field regardless of distance to or time from an MTC. 28,29ur study has several limitations.Firstly, it is a single-centred retrospective cohort study.Distance was calculated from the available postcode data and not the specific injury site.Time of injury was taken from varying sources, occasionally including estimates based on history, and therefore potentially inaccurate.We were limited to values captured by the database, excluding variables such as CT findings, co-morbidities or functional outcome scores.Discharge destination, captured in the database, provided a rudimentary proxy for functional outcome, and therefore difficult to translate into patient morbidity.Patients with preexisting brain injury or cognitive deficits were excluded to limit these factors influencing discharge destination, and hence producing bias.There is a potential for survivor bias in our cohort for those patients who died prior to MTC arrival.Davis et al. established that 8% of potentially survivable prehospital death were due to neurotrauma. 30herefore, these potential lost cases could prove fundamental in establishing correlation and should not be dismissed.Similarly, patients excluded due to both pre-existing TBI/cognitive deficits or cardiac arrest prior to arrival could influence outcomes within this cohort.The retrospective anatomical nature of the ISS as a marker of severity in the present study fails to capture the full clinical presentation; this could be addressed in future by including many markers of injury severity.Finally, sample size power calculation post hoc indicated that the present study was large enough to detect an unadjusted odds ratio (OR) 1.6 using distance/time as continuous predictors, OR 2.2 using distance/time as categorical predictors and OR 2.08 for major city versus regional predictors, therefore we are unable to exclude effect sizes lower than these.

Conclusion
The present study was unable to demonstrate any effect that increasing distance or time to a MTC had on patient outcomes, including inhospital mortality and discharge destination.ISS ≥25, GCS ≤8 on ED arrival and age >60 were significantly associated with increased mortality and likelihood to discharge to rehabilitation/peripheral hospital.Regional patients had a longer LOS compared to the major city cohort, and patients who received neurosurgical intervention had a longer LOS and were less likely to be discharged home.

Figure 2 .
Figure 2. Adjusted odds ratio logistic regression models adjusted for age groups, Injury Severity Score binary, ED Glasgow Coma Scale groups and pre-major trauma centre intubation.

TABLE 2 .
Patient Figure 1.Case filtering diagram.AIS, Abbreviated Injury Scale; GCS, Glasgow Coma Scale; TBI, traumatic brain injury.*Statistical significance (P < 0.05).†Of patients with distance data.‡Of patients with discharge data.Median values provided.ISS, Injury Severity Score; LOS, length of stay.

TABLE 3 .
Neurosurgical characteristics 2%) †Of patients who survived discharge.‡Of patients who received neurosurgical intervention.Median values provided.ISS, Injury Severity Score; LOS, length of stay; MTC, major trauma centre.