Characteristics and outcomes of injured patients presenting by private vehicle in a state trauma system

Unlabelled imageAmerican Journal of Emergency Medicine (2013) 31, 275-281

Original Contribution

Characteristics and outcomes of injured patients presenting by private vehicle in a state Trauma system?,??

Nicholas J. Johnson MD a,?, Brendan G. Carr MD, MS a,b, Rama Salhi MHS b,

Daniel N. Holena MD c, Catherine Wolff BA b, Roger A. Band MD a

aDepartment of Emergency Medicine, University of Pennsylvania, Philadelphia, PA 19104 bDepartment of Epidemiology and Biostatistics, University of Pennsylvania, Philadelphia, PA cDepartment of Surgery, Division of Traumatology, Surgical Critical Care, and Emergency Surgery, University of Pennsylvania, Philadelphia, PA

Received 7 June 2012; revised 18 July 2012; accepted 27 July 2012


Background: Previous studies have demonstrated lower mortality among patients transported to single urban trauma centers by private vehicle (PV) compared with Emergency Medical Services (EMS). We sought to describe the characteristics and outcomes of injured patients transported by PV in a state trauma system compared to patients transported by EMS.

Methods: We performed a retrospective cohort study of state trauma registry data for patients admitted to all Pennsylvania trauma centers over 5 years (1/2003 to 12/2007). Our primary exposure of interest was prehospital Mode of transport and our primary outcome of interest was in-hospital mortality. Unadjusted analyses were performed as were adjusted analyses controlling for injury severity. Data are presented as percents, odds ratios (ORs), and 95% confidence intervals.

Results: Of the 91 132 patients analyzed, 9.6% were transported to the emergency department by PV and 90.4% by EMS. Overall Injury Severity Score (ISS) was 13.3 +- 11.0 (ISS for EMS 13.7 +- 11.3, PV 9.2 +- 7.1, P b .001), and 6.6% of patients died (EMS 7.1%, PV 1.5%, P b .001). After adjusting for injury severity, patients transported by EMS were more likely to die than PV patients (OR 1.9 [95% CI 1.5-2.4]). This effect persisted in blunt, penetrating, advanced life support, and basic life support subgroups, but not in the severely injured (ISS N 15, ISS N 25) subgroups.

Conclusions: Nearly 10% of injured patients arrive at trauma centers by private vehicle. Transport of injured patients by EMS was associated with higher mortality than PV transport. This may reflect the effects of prehospital time, Prehospital interventions, or other confounders.

(C) 2013

? Funding: Dr Carr is supported by career development award K08HS017960 from the Agency for Healthcare Research and Quality.

?? Disclaimer: These data were provided by the Pennsylvania Trauma

Systems Foundation, Mechanicsburg. The Foundation specifically disclaims responsibility for any analyses, interpretations, or conclusions.

* Corresponding author. Tel.: +1 415 793 1716.

E-mail address: [email protected] (N.J. Johnson).


Injury accounts for nearly 40 million emergency depart- ment (ED) visits in the United States annually [1]. Although the optimal modes of prehospital care and transport for injured patients have been extensively debated, the discus- sion has focused on whether injured patients should receive

0735-6757/$ – see front matter (C) 2013

interventions by Emergency Medical Services (EMS) pro- viders in the prehospital setting or simply be rapidly transported to definitive care [2-5]. Rapid stabilization and transport to definitive care by EMS within the “golden hour” has been the paradigm for decades [6] but its validity has been questioned [7,8]. Several studies have suggested that certain interventions by EMS providers might delay transport to definitive care, might be associated with worsened outcomes, or both [9-14]. While a multitude of studies have attempted to define the Optimal care for injured patients transported by EMS providers, a paucity of data exist on the approximately 82% of injured patients brought to EDs and trauma centers by means other than ambulance [1,15].

Existing data have suggested, however, that private vehicle (PV) transport of injured patients may be associated with improved survival compared with those transported by EMS. In a single center study, patients arriving by PV were less severely injured overall, but a Survival benefit persisted among PV patients in the most severely injured subgroup [16]. Single-center studies in urban trauma centers have shown that transport of injured patients by non-EMS vehicles might be safe, even in severely injured patients [17,18]. We sought to examine the characteristics and outcomes of injured patients presenting by PV to trauma centers in a statewide trauma system.

Patients and methods

We performed a retrospective cohort study of prospec- tively collected trauma registry data. The Pennsylvania Trauma Systems Foundation’s (PTSF) State Registry, known as the Pennsylvania Trauma Outcome Study (PTOS), contains over 460,000 trauma contacts collected from Pennsylvania’s accredited trauma centers since October of 1986 [19]. It includes de-identified Demographic and clinical data from all admissions to the 32 accredited trauma centers in Pennsylvania. Data are collected in real time by dedicated trauma registrars within each hospital who have been trained in the PTOS data collection process and are transmitted centrally to the PTSF on a weekly basis [20]. Entries are subject to extensive computer and manual verification, 10% of charts are randomly selected for re- abstraction, and selected data entries from each site are reviewed on a monthly basis. Only data passing quality reviews are merged into the master data set. To ensure quality of abstraction, the PTSF conducts regular site visits and semiannual continuing Education sessions for trauma registrars statewide.

All patients presenting to Pennsylvania trauma centers

are eligible for inclusion in the standardized hospital registry if they have a diagnosis of injury (International Classification of Diseases, Ninth Revision, Clinical Mod- ification codes 800-959) and are admitted to the intensive care unit or step-down unit, are pronounced dead on arrival (patients with a pulse equal to zero upon ED admission

were classified as being dead on arrival [DOA]), die of injuries in the hospital, are transferred, or remain in the ED or hospital longer than 48 hours from the time of ED arrival [20]. Available demographic data include race, age, and sex. Collected clinical data include Trauma-Related Injury Severity Score (TRISS), which is computed by hospital based trauma coders using Abbreviated Injury Scale Version 90 and fed centrally to the register [21], and level of prehospital care.

Level of prehospital care is defined by PTOS by the highest level of actual care provided at scene of injury and en route to the hospital, not solely by the capabilities of the EMS team [20]. Advanced life support is defined by PTOS as prehospital Emergency medical care of serious illness or injury by appropriately trained health professionals and/or certified paramedics who administered any one or combination of the following: drugs, cardiac monitor, defibrillation, intravenous ftuids, intubation, MAST infta- tion, or any other invasive procedures as noted in Pennsylvania Emergency Medical Services Act 45. All other prehospital care provided by certified providers is deemed Basic Life Support (BLS).

The Commonwealth of Pennsylvania spans over 45,000 square miles and has a population of nearly 12.5 million. The state is both geographically and ethnically diverse. Two large urban centers, Philadelphia and Pittsburgh, at its east and west ends respectively, are separated by mostly rural and semi-Rural communities with interspersed urban centers and towns. Approximately 50,000 EMS personnel and over 1,000 licensed ground and Air ambulance services respond to over one million patients each year in Pennsylvania’s EMS delivery system [22]. There are 32 accredited trauma centers in Pennsylvania that collectively care for approximately 30,000 injured patients annually.

Population and protocol

All subjects meeting PTOS registry criteria described above during a 5 year study period (January 1, 2003 to December 31, 2007) were included in our study. Subjects who were transported by police were excluded from the analysis as these were thought to represent a distinct subset of patients dissimilar to the PV or EMS cohorts due to a policy in Philadelphia allowing for police transport of selected trauma patients, which has been described previ- ously by our group [17]. This study was approved by the institutional review board of the University of Pennsylvania with waiver of informed consent.

Outcome measures

Our aim was to assess the effect of mode of transport (EMS versus PV) on the outcomes of injured patients. We compared baseline demographics, prehospital time, injury type, injury severity, rural versus urban location, and our primary outcomes measure of in-hospital mortality for

patients transported by PV to patients transported by EMS. Subgroup analyses were also performed.

Data analysis

We examined population characteristics between the two groups using chi square test for categorical variables, and Wilcoxon rank sum test for independent samples for non- normally distributed, and normally distributed data, respec- tively. We next performed unadjusted analyses examining mortality differences between the two groups using chi- square and logistic regression. Finally, we performed adjusted analyses examining mortality differences between the two groups while controlling for injury severity and patient characteristics. We adjusted for injury severity using TRISS). Subgroup analyses were performed for patients with severe injury, with blunt trauma, with penetrating trauma, for those who transported by ALS, and for those transported by BLS. Data are presented as percents, odds ratios (ORs), and 95% confidence intervals.

We stratified county of injury via the modified Rural Urban

Continuum (mRUC) classification using previously described methodology [23]. “major cities” were defined as being in counties in metro areas of 1 million population or more (mRUC 0 or 1). “Other cities” were defined as being in counties in metro areas of 250,000 to 1 million population (mRUC 2). “Suburbs” were defined as being in counties in metro areas of fewer than 250,000 population or urban

Table 1 Comparison of patients transported by EMS vs. PV, unadjusted

populations of 20,000 or more adjacent to a metro area (mRUC 3 or 4). Rural/Small towns were defined as either as urban counties with a population of less than 20,000 or completely rural counties of less than 2500 urban population (mRUC >= 6). There are no mRUC 5 counties in Pennsylvania.


Description of study population

A total of 148,212 injured patients were transported to Pennsylvania trauma centers during the study period. As our interest was in patients delivered primarily to a trauma center, we excluded 57,080 patients who were transferred into or out of the trauma center or who were transported by means other than EMS or PV. All abstracted variables had less than 5% missing data except for TRISS and prehospital level of care, which were 13% and 10% missing, respectively.

Of the 91,132 patients analyzed, 9.6% were transported to the ED by PV and 90.4% by EMS (Table 1). Overall, 91.6% sustained blunt trauma and 8.5% sustained penetrating trauma. Patients transported by EMS were slightly older (48.2 vs. 47.3, P b .001) and were more likely to be male (62.2% vs. 59.3%, P b .001). ISS was higher for EMS patients compared with patients transported by PV (13.7 +- 11.3 vs. 9.2 +- 7.1, P b .001).

EMS (n = 82,368)

PV (n = 8,764)

Overall (n = 91,132)


Mean (SD)


48.2 (24.1)

47.3 (27.0)

48.1 (24.3)

b .001


13.7 (11.3)

9.2 (7.1)

13.3 (11.0)

b .001

n (%)


51171 (62.2)

5187 (59.3)

56358 (61.9)

b .001

Pre-hospital care



56374 (76.3)




17476 (23.7)






62012 (79.2)

6678 (79.8)

68690 (79.2)


13451 (17.2)

1430 (17.1)

14881 (17.2)


782 (1.0)

76 (0.9)

858 (1.0)


2066 (2.6)

186 (2.2)

2252 (2.6)

Insurance status (primary)

b .001


18081 (22.3)

2957 (34.1)

21038 (23.4)


18356 (22.6)

2610 (30.1)

20966 (23.3)


13416 (16.5)

1723 (19.9)

15139 (16.9)


6412 (7.9)

588 (6.8)

7000 (7.8)


24897 (30.7)

790 (9.1)

25687 (28.6)

Injury type



75354 (91.6)

8014 (91.5)

83368 (91.6)


6945 (8.4)

747 (8.5)

7692 (8.5)

ISS N 15

28831 (35.0)

1784 (20.4)

30615 (33.6)

b .001


5844 (7.1)

128 (1.5)

5972 (6.6)

b .001

prehospital times were missing from our data set for the majority of patients transported by PV (63.6%). However, using available data, patients transported by PV appear to have longer transport times than those transported by EMS (EMS 66.2 +- 106.1 vs. PV 245.5 +- 326.0 minutes).

In-hospital mortality

In unadjusted analyses, patients transported by EMS were more likely to die than patients transported by PV (7.1% vs. 1.5%, OR 5.2 [95% CI 4.3 – 6.2]). Of EMS patients, 76.3%

received ALS care and 23.7% received BLS (Table 1).

We used logistic regression to compare the effect of mode of transport on injury adjusted mortality following trauma. In the injury adjusted model, patients transported by EMS remained more likely to die than PV patients (OR 1.9 [95% CI 1.5-2.4]) (Table 2).

Subgroup analyses

Given the potential differences in injury physiology, we examined patients with blunt and Penetrating injuries separately. We found that in both the blunt and penetrating trauma subgroups, patients transported by EMS were more likely to die (OR 2.2 [95% CI 1.7-2.9] and OR 1.7 [95% CI

1.0-3.0], respectively) (Table 2).

We also stratified patients based on injury severity. There was no mortality difference between EMS transport

Table 2 Comparison of patients transported by EMS vs PV, adjusted


OR (95%CI)


(N = 56,374)


(N = 17,476)


Mean (SD)


45.5 (22.9)



P b .001


15.0 (12.0)



P b .001

n (%)


37577 (66.7)



P b .001

urban/rural location

P b .001

Major cities

29525 (52.4)



Other cities

15510 (27.5)




7124 (12.6)



Rural/small towns

4215 (7.5)



Injury type

P b .001


5798 (10.3)




50527 (89.7)



Prehospital time ?

59.1 (83.1)



P b .001


4966 (8.8)



P b .001

* Defined as time of injury to time of arrival at trauma center.

and PV in severely injured (ISSN15, ISSN25) subgroups (Table 2). Patients with ISS b 15 transported by EMS were more likely to die than those transported by PV (OR 3.4 [95% CI 2.0-5.9]).

Given the potential variability in the interventions performed by different levels of EMS providers, we separately compared the patients receiving BLS and ALS prehospital care to each other and to those transported by PV. Of patients being transported by EMS, 76.3% received ALS care and 23.7% received BLS care (Table 1). Baseline patient demographics and characteristics of the ALS and BLS groups are displayed in Table 3. It should be noted that patients transported by EMS-ALS had higher ISS as well as a greater incidence of PEnetrating trauma. After adjusting for injury severity, both patients receiving ALS and BLS prehospital care were more likely to die than those who were transported by PV (ALS OR 2.0 [95% CI 1.6-2.5] vs. BLS OR 1.6 [95% CI 1.2-2.0]).

Table 3 Comparison of patients receiving ALS and BLS prehospital care, unadjusted

Adjusted ?

All patients



(1.5-2.4) ?

Adjusted subgroups ?









Non-severe (ISS <= 15)




Severe (ISS N 15)




Severe (ISS N 25)




BLS, All patients



(1.2-2.0) ?

ALS, All patients



(1.6-2.5) ?

BLS, non-severe (ISS <= 15)



(2.0-6.0) ?

BLS, severe (ISS N 15)




ALS, non-severe (ISS <= 15)



(2.0-5.9) ?

ALS, severe (ISS N 15)




BLS, non-severe (ISS <= 25)



(1.4-2.6) ?

BLS, severe (ISS N 25)




ALS, non-severe (ISS <= 25)



(1.6-3.0) ?

ALS, severe (ISS N 25)




Adjusted Model 2 ??

All patients




* Adjusted for TRISS.

?? Adjusted for TRISS and pre-hospital care level (ALS/BLS).

There exists potential for marked variability in access to EMS and transport times in rural compared with urban communities. In major cities and suburbs, more patients were transported by EMS (Table 4). The odds of transport

Table 4 Comparison of rural versus urban location by mode of transport (EMS vs. PV)


(n = 82,368) (n = 8,764) (95% CI)

n (%)

* Odds ratio represents odds of being transported by EMS.

Major cities

42487 (51.6)

3542 (40.4)


Other cities

24008 (29.2)

2616 (29.9)

0.8 (0.7-0.8)


8961 (10.8)

818 (9.3)

0.9 (0.8-1.0)

Rural/small towns

6912 (8.4)

1788 (20.4)

0.3 (0.3-0.3)

by EMS were significantly lower in both “Other cities” and “Rural/Small town” locations when compared with “Major cities”. When rural versus urban location was added to our multivariate model also controlling for injury severity by TRISS, it did not significantly modify the effect of mode of transport (EMS vs. PV) on mortality (OR 1.9 [95% CI 1.5-2.3]).


In this Ecological study examining a statewide trauma system over 5 years, we analyzed a large population of injured patients in an effort to better understand the injuries and demographics of the large group of patients transported to the ED by PV. Our aim was to describe the characteristics and outcomes of injured patients transported by PV in a statewide trauma system compared to patients transported by EMS. We found that there were a large number of severely injured patients transported by PV, and consistent with previous single center studies, we found that patients transported by EMS had higher mortality than those transported by PV [16,24]. We also found that in more rural counties, patients were more likely to be transported by PV.

A previous study by Demitriades et al. produced similar findings [16]. This study, conducted at a single urban trauma center, demonstrated that injured patients arriving by EMS had higher mortality compared with those arriving by other modes of transport (friends, relatives, bystanders, or police) even after controlling for injury severity. In their study, mortality was two times higher for severely injured patients in the EMS transport group, whereas in our study the effect was substantially attenuated and not statistically significant in the more severely injured subgroups. Demetriades t al. subsequently sought to elucidate factors contributing to this survival difference in a prospective study comparing patients transported by EMS and non-EMS vehicles [24]. This study demonstrated that injured patients in the non-EMS group arrived at the trauma center more rapidly after their injuries, but was not statistically powered to detect a mortality difference. These studies differ from ours in that they were limited to a single urban trauma center with a much higher incidence of penetrating trauma. In addition, unlike the current study, these studies did not exclude transport by police vehicles.

Our findings, in conjunction with other similar prehospital

studies [2-4,7,9,12,25-30], add to the debate about the preferred prehospital approach to trauma. The uncertainty associated with the decision to perform aggressive pre- hospital care, (stay and stabilize) or to rapidly transport, (scoop and run) patients with injury is well debated in the EMS literature [2-4,7,9,12,25-30]. Several studies have suggested an inverse relationship between on scene time, out of hospital time, and outcomes [11,12,27,28,31-33]. There is also evidence that prehospital ALS interventions do not improve survival in some subsets of critically injured patients [11,12,14,31,34].

In addition, we found that the mean prehospital time in the EMS-ALS group fell just outside of the “golden hour,” and the EMS-BLS group was over twenty minutes longer. In subset analysis, this difference in prehospital time does not appear to reftect the increased proportion of BLS units in rural areas, as most patients in our study who received BLS care were in urban locations. Previous studies have demonstrated associations between paramedic impression of severe injury and more rapid transport to definitive care [35-37]. It is possible that more highly trained providers, who, in this study, are caring for more injured patients, more readily identify acute illness and transport them faster.

To our knowledge, this is largest analysis to date examining outcomes for injured patients presenting by PV to trauma centers. Our analysis however, has limitations. First, our data are collected prospectively as part of the required trauma registry process, but our questions and our analysis are performed retrospectively and thus are subject to the limitations of all retrospective studies.

In addition, we are only able to speculate on the reasons for our finding of decreased mortality with PV transport. Other studies on this topic have postulated that lack of prehospital interventions and resultant decreased transport times may be responsible for reductions in mortality seen with PV. However, we do not have data on what interventions were performed in the EMS group, which limits our ability to support or refute previous findings. A number of important time variables, such as extrication time (entrapped patients may receive more prehospital interven- tions) and scene time were also not captured in our data set. Beyond this, prehospital time was missing for most PV patients in our data set. We thus cannot describe the way in which this important, unmeasured potential confounder contributes to our findings. Where prehospital time was available for PV patients, it appears that it approached 4 hours. As such, a distinction must be made between our PV patient population and other PV populations limited to urban environments. Private vehicle transports in this study are not likely to reftect the “scoop and run” phenomenon reported in other studies, thus limiting application of this study to that specific debate.

Furthermore, while we used established means to adjust for case mix and injury severity, we recognize that these adjustments may not have captured the true severity of injury or illness of our patients. This could bias our results if the unmeasured injury severity were different in the various transport groups. There might have been higher prehospital death in the PV group that was not accounted for in our analysis as these patients may have been less likely to be transported to a trauma center. Civilians typically do not obey prehospital trauma triage guidelines. They may in fact preferentially travel to their closest hospital, which is likely not a trauma center, with the sickest patients. While it may be unlikely that a patient would be transported by PV expire and not continue to reach a receiving facility, we only capture trauma center patients. It is conceivable that non-EMS

personnel transport injured patients to non-trauma centers and that death outside of our study sample is more prominent among PV transports resulting in a survival bias. Finally, since this is a large statewide sample, there may be significant heterogeneity in the care provided both in the field and at receiving trauma centers.

Despite these limitations, our findings may have several important policy implications. Given the substantial number of injured patients who are transported by PV, there exists significant opportunity to impact the prehospital care and outcomes of these patients. Our study highlights the potential importance of educating the public in the care of the injured patient. Significant resources have been dedicated to training laypeople to identify and assist patients suffering from other Prehospital emergencies such as cardiac arrest, stroke, and myocardial infarction. In the case of injury, the lay public could be educated in basic trauma first aid (eg, the use of direct pressure to control bleeding) and the importance of rapid and safe transport to an appropriate trauma receiving facility in areas where access to prehospital care is limited, or in parts of the world, nonexistent.

Clearly, there remains much to be understood about the relationship between prehospital care, time, and outcomes for injured patients, but this study again demonstrates that ALS prehospital care may not improve outcomes for injured patients despite faster transport times.

It should be noted that we chose to explore this unique population of patients because of our desire to improve prehospital care. We hold in the highest regard and maintain the utmost respect for the highly trained and dedicated EMS professionals of Pennsylvania. These men and woman are our colleagues and this study is in no way intended as a critique of their practice.


In conclusion, nearly ten percent of injured patients in the state of Pennsylvania arrive at trauma centers by PV. Transport of injured patients by EMS was associated with higher mortality than PV transport even after controlling for severity of injury. It is possible that these findings reftect the effect of prehospital interventions, inadequate case mix, or unmeasured confounders including prehospital time, which was not available for the majority of PV patients. However, this study suggests that PV transport of selected injured patients may be safe and in turn, there are implications for the design of preHospital systems of care for injured patients.


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