introduced by cowley in the 1970s , the  golden hour  concept has since governed planning and preparedness in trauma systems development as a major source of morbidity and mortality to the population that contributes to the economy , i.e. , people less than 45 years of age , trauma is a significant problem that needs continuous systems improvement .
an integrated trauma system improves outcomes for patients of trauma , but the exact parameters that determine effectiveness have yet to be conclusively defined .
the relationship between shortened pre - hospital time and improved survival exists , but is most consistently demonstrated when comparing urban and rural locals .
no data exists that specifically quantifies the relationship between pre - hospital time and outcomes within purely urban areas , and especially in patients sustaining penetrating trauma .
these patients are most likely to benefit from expedited transport if definitive surgical management is required .
current literature has failed to study the association between pre - hospital transport time and survival for penetrating trauma patients .
the studies that have examined the urban setting have yielded contradictory conclusions ; sloan and petri in chicago evaluated blunt and penetrating trauma patients and did not find a relationship between transport time and outcome .
pepe in houston assessed hypotensive patients with penetrating trauma and was unable to demonstrate any relationship .
gervin and feero , on the other hand , demonstrated that shorter pre - hospital time improved survival .
the contradictory results may be secondary to the heterogeneity of the trauma patient population at different locations .
trauma centers in many high - volume locations do not have significant number of penetrating trauma patients .
this begs further investigation to define the influence of pre - hospital time factors on trauma outcomes in urban environments and in particular , in patients with penetrating trauma .
our study explores the impact of pre - hospital times on penetrating trauma outcomes within urban centers of illinois .
we hypothesized that there would be a relationship between total pre - hospital time and outcomes in patients with penetrating thoracic trauma , an injury that is potentially lethal without emergent intervention .
since injury severity is strongly associated with mortality , we specifically studied the patients at highest risk , hypotensive patients who would be most likely to have hemorrhage that would benefit from rapid surgical control .
this registry contains data from all traumatically injured patients brought to the 67 level i and level ii trauma centers in illinois .
the data are entered by a registrar at each trauma center and uploaded to the illinois department of public health , who maintains the data set and website .
not included in this registry are patients who are declared dead - on - scene and not transported to a trauma center and patients not treated at or transferred to a level i or level ii trauma center .
the emergency medical system ( ems ) in illinois is a tiered system with paramedics trained in both basic life support and advanced life support techniques .
the chicago committee on trauma works with the state of illinois and pre - hospital providers to ensure safe , standardized care and undergoes rigorous quality improvement scrutiny .
the illinois state trauma registry ( istr ) includes approximately 45,000 records per year . to limit our study to urban trauma patients
, we selected patients of all ages injured in the major urban areas of chicago , east st .
louis , and springfield ( more than 2/3 of cases annually ) . because our question of interest was the effect of transport time on mortality , we excluded all transfer patients , as well as walk - in and self - transport patients ( 10% of cases annually ) .
we identified patients with penetrating injuries using information regarding the primary mechanism of injury recorded in the database ( approximately 2,500 cases per year ) and then classified those patients with thoracic trauma using icd-9 cm codes .
the final list of icd-9 codes was limited to penetrating thoracic injuries ( codes 860 - 862 , approximately 150 cases per year ) , consistent with the center for medicaid and medicare services ( cms ) designations .
the pre - hospital vital sign data were poorly conserved with fifty percent missing ; for that reason , 
hypotension  was defined as a systolic blood pressure ( sbp ) less than 90 mmhg on the first reading in the emergency department .
total pre - hospital time consisted of response time , scene time , and transport time .
each of these variables was evaluated separately and in aggregate as total pre - hospital time .
student 's t - test was used as the test statistic for the comparisons of mean pre - hospital time between cohorts .
the injury severity score ( iss ) was used as an anatomic marker of injury severity and was highly conserved in the data set ( < 3% missing data ) .
a two - sample test of proportions and pearson 's chi - squared test were used to compare survival among patients with iss < 16 and 16 and total pre - hospital time .
logistic regression statistics were performed to determine the independent effect of transport time on mortality when controlling for age , race , and severity of injury for both hypotensive patients with penetrating thoracic injuries ( hpti ) and non - hypotensive patients with penetrating thoracic injuries ( npti ) . for the models ,
transport times were categorized into 15 min intervals to determine the independent effect of successively longer transport times .
a total of 908 patients with penetrating thoracic injuries ( pti)were evaluated during the study period .
one - hundred forty - three patients ( 16% ) were hypotensive on presentation , with a systolic blood pressure less than 90mmhg ( hypotensive pti group = hpti ) , while 765 patients ( 84% ) had systolic blood pressures greater than 90 mmhg ( normotensive pti group = npti ) .
the mean age was approximately 27 years ( age range 11 - 78 , 99% between ages 15 and 55 ) and the majority of patients were african american , male and uninsured [ table 1 ] . thirty percent ( 230 ) of npti patients had an iss greater than 16 , while 55% ( 79 ) of hpti patients had an iss greater than 16 ( p < 0.001 ) .
the time for paramedics to get to the scene ( mean response time , 4.5 min vs. 5.4 , p = 0.05 ) , mean transport time ( 8.9 min vs. 11.2 , p = 0.02 ) and total pre - hospital time ( 25.67 vs. 29.47 , p = 0.02 ) were significantly shorter for hpti patients with an iss  16 compared to hpti patients with iss < 16 . however , mean scene times did not differ ( p = 0.64 ) [ table 2 ] .
injury severity and transport times , bivariate statistics crude mortality was higher for hpti patients compared with npti patients ( 73% vs. 12% , p < 0.001 ) .
hypotensive patients with penetrating thoracic injuries ( hpti ) patients showed increased mortality with increased total pre - hospital time [ figure 1 ] . the odds ratio ( or ) of death for hpti patients , similarly , increased with increasing total pre - hospital time [ table 3 , figure 2 ] .
for instance , if pre - hospital time was greater than 40 min , then the or was increased to 13 ( p < 0.001 ) . table 3 reports the regression results for hpti patients .
non - hypotensive patients with penetrating thoracic injuries ( npti ) regression results are not included , but the covariates for age , race , gender , and iss were of similar direction and magnitude .
conversely , npti patients with longer total pre - hospital times exhibited decreased mortality ( or 0.93 , 95% ci 0.83 - 0.99 , p < 0.001 ) .
death ratefor non - hypotensive patients with penetrating thoracic injuries and hypotensive patients with penetrating thoracic injuries patients grouped by pre - hospital time adjusted risk of death for hpti patients by pre - hospital time rr of death for hypotensive patients with penetrating thoracic injuries vs. non - hypotensive patients with penetrating thoracic injuries patients grouped by pre - hospital time of the survivors , the majority of patients , in both npti and hpti groups , were discharged directly to home .
there were no significant differences in the discharge destination for ntpi and hpti patients [ table 4 ] .
the study investigates association between transport time and outcome for urbanvictims of penetrating thoracic trauma .
the analysis indicates that more severely injured patients may survive devastating injuries with rapid transit : the sicker the patient , the quicker they should be in the trauma bay .
a significantly positive finding of this study was that patients with higher injury severity experienced shorter pre - hospital transport time .
this finding in our study is not unique ; newgard demonstrated this in a multi - institutional study mixed population of blunt and penetrating trauma .
given the significant correlation between pre - hospital time and mortality for hpti patients , this is clearly a success of the urban trauma system .
the association of transport time with mortality has been well described in rural trauma systems , but never clearly described in the urban setting , with a homogeneous population of patients .
this study is one of the first to show a consistent association between pre - hospital time and survival in an urban trauma system with uniform professional pre - hospital ems care .
variations in transport times might be due to travel distances to the nearest trauma center from incident scenes , traffic congestion or road conditions , or weather conditions .
it is possible with new global positioning systems ( gps ) data that incorporates traffic congestion and travel distances , pre - hospital times may be shortened .
some rural trauma systems have augmented their pre - hospital services with aeromedical transporter provided increased trauma training for first responders to decrease the impact of longer transport times on injury mortality .
these options might be employed to a greater degree in urban trauma systems as well .
however , comprehensive changes in a system that is working well for most patients may not be indicated or cost - effective .
it is important to note that our findings are limited to a small portion of all trauma patients : in our database , pti patients comprised approximately 2% of all trauma patients and hpti patients comprised only 0.4% of all trauma patients .
it is likely that many , less severely injured will not experience a survival benefit associated with decreased pre - hospital time ; as notably seen in the npti group , in whom survival was not adversely affected by increased transport time , and was actually improved .
it is important to recognize that the majority of the overall trauma patient population with penetrating thoracic injuries did not benefit from shorter transport times .
in addition , pre - hospital data were missing up to 50% of the time , including sbp .
though no systematic changes have occurred in urban pre - hospital transport during that time , additional years of data should be accessed when available to validate these results . despite these limitations
, these results suggest that careful planning to optimize transport time - encompassing hospital capacity and existing resources , traffic patterns , and trauma incident densities - may be beneficial in areas with a high burden of penetrating trauma .
in conclusion , we have shown that minimizing pre - hospital times does in fact impact survival in patients that are hypotensive victims of penetrating thoracic trauma .
hpti patients in an optimally designed trauma system should be delivered to definitive care expeditiously .
 background : achieving definitive care within the  golden hour  by minimizing response times is a consistent goal of regional trauma systems . 
 this study hypothesizes that in urban level i trauma centers , shorter pre - hospital times would predict outcomes in penetrating thoracic injuries.materials and methods : a retrospective cohort study was performed using a statewide trauma registry for the years 1999 - 2003 . 
 total pre - hospital times were measured for urban victims of penetrating thoracic trauma . 
 crude and adjusted mortality rates were compared by pre - hospital time using stata statistical software.results:during the study period , 908 patients presented to the hospital after penetrating thoracic trauma , with 79% surviving . 
 patients with higher injury severity scores ( iss ) were transported more quickly . 
 injury severity scores ( iss ) 16 and emergency department ( ed ) hypotension ( systolic blood pressure , sbp < 90 ) strongly predicted mortality ( p < 0.05 for each ) . in a logistic regression model including age , race , and iss , longer transport times for hypotensive patients were associated with higher mortality rates ( all p values < 0.05 ) . 
 this was seen most significantly when comparing patient transport times 0 - 15 min and 46 - 60 min ( p < 0.001).conclusion : in victims of penetrating thoracic trauma , more severely injured patients arrive at urban trauma centers sooner . 
 mortality is strongly predicted by injury severity , although shorter pre - hospital times are associated with improved survival . 
 these results suggest that careful planning to optimize transport time - encompassing hospital capacity and existing resources , traffic patterns , and trauma incident densities may be beneficial in areas with a high burden of penetrating trauma . 
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
CONCLUSION