The widely recognized concept of the “golden hour” proposes that trauma victims should receive definitive care within 60 minutes of their injuries to achieve the lowest possible mortality.1 While little consensus exists regarding the validity of the golden hour, timely prehospital care remains a critical component of a trauma system.2–4 The Commonwealth of Kentucky is mostly rural, and 1 hour or more may be required to travel to any hospital.5 When compared with the national average, a much higher percentage of Kentucky residents inhabit rural areas, and only 60.5% to 74.2% of Kentucky residents live within 1 hour of level I/II trauma centers (national average, 84.1%).5 Kentucky also experiences injury-related mortality rates that are higher than the national average. Prolonged emergency medical system (EMS) transport time has been reported to increase trauma mortality and could therefore be a causative factor.6
Availability of high-level trauma centers where emergency surgery can be provided may also contribute to prolonged transport times. In Kentucky, there are only two adult level I trauma centers, both near one another in metro areas; one level II center in the far eastern region; and four level III centers roughly clustered in the central region of the state. For ambulances in rural regions to reach high-level centers, not only will long transport times be necessary, but EMS services may also find it necessary to bypass low-level and nonverified trauma centers to reach definitive care. Because patient outcomes are known to worsen with longer transport times,5,7–9 it is imperative that EMS carefully and quickly determine the appropriate level of care required for each patient and transport them accordingly while also considering transport time and the risks of bypass.
To aid EMS personnel in making destination decisions, the American College of Surgeons Committee on Trauma created the Field Triage Decision Scheme (FTDS) in 1986. The latest revision, made in 2011 in partnership with the Centers for Disease Control and Prevention (CDC), uses four decision steps: physiology (systolic blood pressure [SBP], respiratory rate [RR], and Glasgow Coma Scale [GCS] score, step 1), anatomy of injury (step 2), mechanism of injury and evidence of a high-level impact (step 3), and special patient or system considerations such as patient age (step 4).10 The FTDS states that patients meeting step 1 physiologic criteria should “preferentially be taken to the highest level of care within the trauma system.”10 As stated previously, in Kentucky rural counties, the highest level of care available within an hour of the injury scene is most often a level III trauma center. However, little is known regarding EMS adherence to the protocol, especially in a rural trauma system, or about which patients will decline during transport. This investigation seeks to (1) determine compliance with the FTDS relative to appropriate patient destination and (2) determine the degree of patient clinical decline associated with increasing transport times in a rural state. We hypothesized that (1) EMS compliance with FTDS was less than 100% and that (2) clinical decline is rare in transport times under 60 minutes (the golden hour).
PATIENTS AND METHODS
This study was a retrospective review of deidentified National EMS Information System (NEMSIS) data for EMS patient transports occurring in Kentucky from January 1, 2017, to December 31, 2017. The study was reviewed and approved by the University of Kentucky Institutional Review Board.
The NEMSIS incident records were triaged for the study following the diagram shown as Figure 1. Of 83,757 recorded incidents, 8,946 were canceled in route or at the scene and 31,614 did not result in the EMS treating and transporting the patient for the reasons listed; thus, almost half of EMS calls did not result in transports. After excluding incidents for patients dead at the scene (n = 624), rare transport methods (boat, fixed wing, etc.), nonhospital destinations, and records missing times or vital signs, 34,822 EMS incident records were available for analysis. These data were divided into subgroups for further analysis by mode of transportation (helicopter emergency medical system [HEMS] vs. ground emergency medical system [GEMS]) and by vital sign status using the EMS FTDS step 1 criteria.
The FTDS step 1 criteria include the following: systolic blood pressure, less than 90 mm Hg (low SBP); Glasgow Coma Score, less than 14 points (low GCS); or respiratory rate, less than 10 breaths per minute (bpm, low RR) or greater than 29 bpm (high RR).10 The first vital sign recorded at the scene and the last vital sign recorded before EMS arrival at the final destination were used to determine whether the criteria were met at EMS arrival, as well as in route clinical decline.
We defined GCS decline as a decrease of 2 or more points.11 There are little extant data regarding validated measures of prehospital SBP and RR clinical decline. We therefore calculated the SD of SBP (22 mm Hg) and RR (3 breaths per minute, BPM) in step 1 patients and classified vitals decline as a decrease in SBP of 1 SD, a change of 1 SD in RR from high to higher or from low to lower, or a decrease in GCS of 2 or more points. In non–step 1 patients, a change of at least 1 SD into the high RR range or into the low SBP or RR ranges, as well as a decrease in GCS of 2 or more points, was considered decline regardless of step 1 status. Thus, the same definition of clinical decline was applied to both groups. In a cross-sectional study of National Trauma Databank patients without severe head injury and with SBP below 110 in the emergency department, mortality increased 4.8% per 10 mm Hg decrement.12 This suggests that a decrease of 22 mm Hg to below 90 mm Hg is likely to have a mortality effect.
Step 1 patients reaching a certified level I, II or III trauma center were classified as reaching the “appropriate” hospital. Levels to III provide surgical care, while level IV does not, and in Kentucky rural counties, level III centers are often the highest level of trauma care available within 1 hour of the injury scene.
Time of dispatch, arrival at scene, departure from scene, and arrival at destination were used to calculate dispatch-to-scene time, time at scene, and transport to destination time. These were aggregated to a total dispatch-to-destination time.
We analyzed adherence to the FTDS protocol for destination facility and the effect of mode and duration of transportation on clinical decline. Bivariate relationships were analyzed using analysis of variance and t tests for continuous variables and χ2 or Fisher exact tests for categorical variables. For significant χ2 tests of proportions of ordinal variables, the test for linear trend was also calculated. All statistical calculations were performed using the Statistical Package for Social Sciences version 25 (SPSS; IBM Corp, Armonk, NY). Significance was set at p < 0.05.
The most common incident complaints reported for the 34,822 included patients were traffic incidents (n = 19,194), traumatic injury (n = 7,005), hemorrhage/laceration (n = 3,193), assault (n = 2,810), and request for airmedical transport (n = 1,785). Almost 93% of patients were transported by GEMS (32,354; 92.9%) rather than by HEMS (2,468; 7.1%). The median dispatch-to-destination duration of Kentucky EMS incidents was 34 minutes for GEMS transports (interquartile range [IQR], 25–48) and 72 for HEMS transports (IQR, 59–85; p < 0.001). Helicopter EMS transports took longer to arrive at the scene and were of longer transport duration (both p < 0.001) but took similar time at the scene (Fig. 2). Upon EMS arrival at the scene, 7.5% (2,617 of 34,822 patients) of the patients met step 1 FTDS criteria for transport to a level I, II, or III trauma center; this rate increased with dispatch-to-scene time (Fig. 3, linear association, p < 0.001). Overall, 1.7% (588 of 34,822 patients) of patients experienced decline. Step 1 patients experienced much more decline (12.2%) than non–step 1 patients (0.8%, p < 0.001).
Step 1 Patients
Of the 2,617 step 1 patients, the most common step 1 criterion met was GCS of less than 14, followed by SBP of less than 90 mm Hg, RR of greater than 29 bpm, and RR of less than 10 bpm (Fig. 4). Helicopter EMS transports were more likely to meet step 1 criteria than GEMS (29.9% vs. 5.8%, p < 0.001), and HEMS patients disproportionately met step 1 criteria because of GCS of less than 14.
In step 1 patients, decline occurred in 6.1% of GEMS patients and 27.8% of HEMS patients (p < 0.001 for difference). Glasgow Coma Scale decline was the most common reason for decline, with 8.0% of step 1 patients experiencing GCS decline, followed by RR decline (3.2%) then SBP decline (2.0%). The percent of step 1 patients who declined in route increased with the duration of dispatch-to-destination for both ground and helicopter transport patients (p < 0.001, Fig. 5).
Just over half (53.7%) of the 2,617 patients who met step 1 criteria were transported to an appropriate facility (level I, II, or III trauma center). The most common reason for transport to an incorrect facility type was “closest facility” (57.8%), followed by “patient's/family choice” (18.4%). Seventy-two percent (1,879 of 2,617 patients) of step 1 transports were GEMS, and only 39.2% of those arrived at levels I to III trauma center. Of the 738 HEMS step 1 patients, 90.7% arrived at an appropriate destination (p for difference, <0.001).
Non–Step 1 Patients
The percentage of initially non–step 1 patients who declined in route increased with duration of dispatch-to-destination for both ground and helicopter transport (p < 0.001, Fig. 6). Non–step 1 patients transported by helicopter declined more often than ground transported patients (3.7% vs. 0.8%, p < 0.001).
Rather than a certain prehospital duration at which patients begin to decline, our data indicate that patients are more likely to experience clinical decline with increasing prehospital time, including longer dispatch-to-scene and dispatch-to-destination times. This relationship was found in both HEMS and GEMS transports. Clinical decline among non–step 1 patients was rare, but the risk increased with longer dispatch-to-destination time and occurred more often in HEMS patients. The ground transports were of shorter duration than expected; however, nearly half of step 1 patients were transported to the closest facility rather than the appropriate facility, which made for shorter transports on average.
While patients are far more likely to be transported by GEMS (92.9%), HEMS patients were sicker on arrival at scene and more likely to decline in both step 1 and non–step 1 groups. Patients for whom a helicopter is called are often suspected of having more significant injuries than those transported by GEMS. The average duration of HEMS transports was nearly double that of GEMS despite a similar scene time. The difference in rate of decline between HEMS and GEMS may be attributed to significantly longer dispatch-to-scene and dispatch-to-destination times in HEMS transports. Almost all step 1 patients transported by helicopter arrived at an appropriate destination, but this may have contributed to longer prehospital transport times because levels I to III trauma centers in Kentucky are few.
In both the HEMS and GEMS groups, the most common criterion met among step 1 patients was GCS of less than 14. Among step 1 patients who experienced further decline, this was most often in the form of a decrease in mental status. Prehospital GCS decline (≥2) has been shown to predict increased hospital mortality and resource utilization in traumatic brain injury patients transported to trauma centers.11 Thus, coma score may be a more sensitive predictor of clinical decline and eventual death than the other FTDS criteria, and its importance regarding EMS transport destination recommendations should be investigated further.
Others have attempted to assess the validity or accuracy of existing prehospital triage decision schemes, including the FTDS. A recent systematic review by Van Rein et al.13 of existing literature on this subject found studies to have extremely heterogeneous methods. Only 7 of the 21 articles analyzed used prehospital data recorded by EMS, and 15 of the 21 articles limited their analysis to a specific group of trauma patients rather than analyzing all trauma patients regardless of hospital destination or injury severity. The reviewers concluded that the heterogeneity of existing studies precludes a recommendation for the “best” prehospital triage protocol, and there were none that met the American College of Surgeons Committee on Trauma and CDC goals of 95% sensitivity and 50% specificity when using reasonable methods. Our analysis attempts to limit selection bias by including all trauma victims who meet FTDS step 1 criteria regardless of destination. We show that, in a rural system, excluding patients transported to lower level facilities omits nearly half of the patients who meet step 1 criteria for transport to higher levels of care and can underestimate the validity of the protocol.
Step 1 patients who were undertriaged to lower level centers were most commonly transported to the “closest hospital” or a hospital of the “patient's choice.” In this study, we only examined the three objective step 1 criteria of the FTDS. Using this data set, we cannot fully analyze all of the factors considered in destination decision-making by the EMT in each case. In a rural state with long transport times between hospitals, transport to a trauma center is often dictated by proximity more than physiology. Although the FTDS indicates that patients who meet any one of the step 1 criteria should go to the highest level center in the trauma system, noncompliance with this guideline is likely to be high if transport times are long and EMTs fear clinical decline. We have previously reported that medics who work in rural communities without a nearby trauma center were more likely to transport trauma victims to a geographically closer hospital than those who work near a trauma center.14 Adzemovic et al.15 have reported that patients with derangements in vital signs such as GCS of less than 13, respiratory distress, tachycardia, and certain types of injury initially transported to a level III/IV trauma center benefit from transfer to a level I/II trauma center. Others have shown similar benefit to timely interfacility transfer of patients who were undertriaged to lower levels of care.16,17 While others report that there is little utility in trending prehospital vital signs as injured patients often experience episodes of physiologic instability,18,19 our data indicate that the concern for clinical decline in route for select patients is valid. This has significant implications for trauma transport, bypass, trauma systems, and trauma center geography. Concern for clinical decline in route must be considered in the context of evidence showing that critically injured patients have better outcomes when taken to a facility that can provide definitive care.
Among step 1 patients, HEMS patients experienced decline more often compared with GEMS patients at a rate that increased with transport duration. Brown et al.20 showed that HEMS transport confers a survival advantage regardless of the prehospital time when compared with GEMS. Others have demonstrated a survival benefit for patients transported by HEMS,21 and while we show that HEMS patients are more likely to experience clinical decline than GEMS patients, these data should be linked with outcomes data in future studies for appropriate interpretation of significance. Not all patients are appropriate for HEMS transport, and the monetary cost of overtriage can be enormous. As others have shown,22,23 the FTDS may not be the most accurate or cost-effective triage algorithm to implement when deciding if a patient is HEMS appropriate.
Potential confounding factors that are not possible to control for in a retrospective analysis of third-party data such as this are differences in quality of care provided by more experienced EMS or flight crews, difference in monitoring equipment between vehicles or modes of transport, differing mechanisms of injury, or bias in the HEMS population because of suspected increased injury severity. The limitations of the data set prevented us from analyzing these potential confounders for their effect on the data.
As we have addressed previously, we do not have outcomes data to determine morbidity and mortality in patients who experienced a clinical decline. Future studies linking prehospital data with outcomes will yield a robust analysis of the markers of clinical decline and hopefully allow us to create validated measures of clinical decline, which could be used by EMS personnel during prehospital transport. The deidentified data contained no patient demographics, precluding us from stratifying our analysis by age. Traumatic injury in both young and elderly patients pose unique challenges,24 and our analysis included patients of all ages. The universal inclusion in this data set allows us to test the non–age-specific step 1 criteria in a broad trauma cohort. The limitations of the data set itself prevented subgroup analysis by mechanism of injury because this data point was a free-text entry and often left blank.
Finally, there are no reported validated measures of clinical decline using raw vital sign changes, aside from data showing increased mortality with a decrease in GCS of 2 or more points.11 For this preliminary study using changes in vital signs to assess clinical decline in the field, we chose to use a change of at least 1 SD into or within the FTDS step 1 criteria. In a cross-sectional study of emergency department SBP levels, hospital mortality increased linearly as SBP below 110 decreased, suggesting that prehospital decreases in SBP will likely be found to increase mortality.12 Further analysis in the National Trauma Data Bank, similar to the GCS study cited, could provide more specific change parameters for SBP and RR associated with mortality and resource utilization. Here we show that patients who meet FTDS step 1 criteria are a vulnerable population prone to worsening of their already abnormal vital signs, while those who do not meet these criteria are less likely to experience clinical decline in route. Future EMS research should create and validate decision tools to predict optimal destination, transport method, and risk of decline during transport.
This study demonstrates that, in a rural state, injured patients meeting FTDS step 1 criteria reach levels I to III trauma centers only about half the time. The FTDS step 1 criteria identified patients at higher risk of further prehospital clinical decline. Rather than decline after 1 hour, these data show that incremental decline occurs throughout prehospital transport.
T.R.K. was responsible for literature search, data interpretation, writing, and critical revision. M.J.B. was responsible for literature search, data collection, and data analysis. D.L.D. was responsible for data analysis, data interpretation, and critical revision. A.C.B. was responsible for study design, data interpretation, and critical revision.
We thank the assistance with data procurement by the National EMS Information System and the Kentucky Injury Prevention and Research Center.
The authors declare no conflict of interest.
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JAN O. JANSEN, M.B.B.S. (Birmingham, Alabama): Thank you for giving me the opportunity to discuss this paper. I would like to congratulate the authors on an important and nicely conducted study and a very nice presentation.
I think we all recognize that the performance and the functioning of emergency care systems remains an important issue. A trauma system – and we all know this – attempts to match patients’ needs with centers’ capabilities, but only when geography allows. And as the investigators have correctly pointed out, when an incident occurs in a remote area, then there is a problem and either the patient has to be taken to a more local facility, which may not have the clinical capabilities, or there will be a longer transfer time with an attendant risk of on-ride clinical deterioration, which is what the authors have investigated. Your analysis shows that there is an association between prehospital time and the worsening of clinical conditions, measured in terms of the Step 1 physiological criteria of the field-triage decision scheme. I have a few comments and a few questions about this.
First of all, I think your study is interesting and novel but I’m a little bit perplexed why you decided to make the comparison between ground and helicopter transfer such a big focus of your paper. I think the results would have been clearer and easier to interpret if you had only just done one of those.
I also think the appropriateness of the destination healthcare facility is a tricky one which maybe also would have been better covered separately. Nevertheless, I don’t really have any questions about the analysis in terms of the Step 1 criteria. I think it’s neat. I think it’s appropriate and I think it’s well done. And the criteria for Step 1 have been used in this way a number of times so I think that’s great.
I do have issues with the comparison between ground and helicopter transport. And as you alluded to in your discussion, there may be inherent differences, both clinical and geographical, between the patients that were taken to a hospital by ground or by helicopter. This might explain why HEMS patients experienced more physiological decline. I think it would have been helpful to have a more detailed examination of the baseline characteristics of these two groups of patients. Have you considered including such a table to describe these two groups?
In addition, I wanted to ask if you have considered an analysis of the geographical distribution of these incidents because it seems very probable that the HEMS patients, in addition to probably being sicker, may also have come from more remote areas of the state. Even if you are just focusing on the GEMS patients that were taken by ground ambulance, is it possible that the incidents which required longer transport times differed in terms of the clinical characteristics from the ones that had short transport times? I think this is something that will be interesting to look at.
Secondly, although your paper is primarily about physiology and physiological deterioration, it also makes reference to the appropriateness of the destination healthcare facilities. This is always really complicated. I realize that most prehospital data sets don’t record this data well or in a way that’s helpful or easy to analyze. But I think it is important to recognize that the field triage decision scheme recommendation of transfer to highest level of care is or can result both from Step 1 and the Step 2. And so, the question is – do you have data on how many of these patients actually met the Step 2 criteria as well? And how many of these inappropriate transfers were the result of provider judgment? You gave us some data on patient or family preferences. But, often, this actually comes out of provider judgment, as well.
Lastly, and I’m sure you will have seen this one coming, what is the impact of all of this on outcomes? I realize that the data set will probably not give you that data, but the question is – have you thought about how you might be able to look at this in the future?
Thank you very much. Really interesting paper.
ERRINGTON C. THOMPSON, M.D. (Huntington, West Virginia): I truly enjoyed your paper. As you know, we are neighbors. In West Virginia we have approximately 20 percent of our patients actually come from Kentucky. I was wondering if you could comment on the helicopter transport.
In our experience there are really 2 separate types of patients who come in via helicopter. We have one group of patients who at the scene EMS thinks are severely injured and, therefore, they come by helicopter.
And then there are those that they think it’s going to take a long time to be transported to the hospital and therefore they come by helicopter. So, we see, two different groups of patients.
Again, I enjoyed your paper. Thank you.
MICHEL B. ABOUTANOS, M.D. (Richmond, Virginia): I really enjoyed your paper and presentation. In Virginia we have a similar demographic and similar aspect of what is happening in Kentucky. Most than 50 percent of our patients are going to non-trauma center that meet Step 1 criteria so it’s pretty common.
The question I have is that did you look at after they went to a non-trauma center and how many of them actually did get transferred? And was there a difference for those that did not get transferred? Did you stratify by age? Did age make a difference with regard to those?
And, finally, any speculation if you cannot change this what is our obligation for non-, for those non-trauma centers such as considering the RTDC course and other courses for us to look at a system-wide approach? Thank you.
MARK L. GESTRING, M.D. (Rochester, New York): I had two quick questions. First off, the destination hospitals you had mentioned when you compare helicopters to ambulances, helicopters fly to trauma centers, ambulances go to hospitals that might not be trauma centers so your comparison looked like it was kind of one to the other.
But I would ask you to look at the population of ground transports that went to trauma centers compared to helicopter transports that went to trauma centers. I think it’s potentially a little bit more complicated otherwise.
And then the other point is looking at the concept of time as a surrogate for distance. You know an hour in a helicopter you are covering a huge amount of ground compared to an hour in an ambulance.
And I noticed from your graphs that the scene times looked to be about the same. So, it looks like the differences are truly in transport time. And so, using that as a surrogate more for distance to your point earlier about the rural nature of some of these cases.
TAYLOR R. KAI, B.S. (Lexington, Kentucky): Thank you very much to the audience and to Dr. Jansen for your thoughtful comments and questions.
First to touch on some of the audience questions, Dr. Thompson, you bring up a very good point. We agree with you that in the helicopter transport population there is a dichotomous group there between the severe patients and the ones that we think are just very far away and would benefit going to a high level center.
We did not specifically look at that and break that down. But I think that would be a really interesting topic of our future study that we plan to do.
And then Dr. Aboutanos, for your question about non-trauma center transfers to a higher level of care, we actually did not look at that. It was hard for us with the data set we were working with to actually link to any sort of outcomes like that.
But to touch on – to jump ahead a little bit to one of Dr. Jansen’s comments about outcomes, we do plan to do a future study where we link to outcomes using probabilistic linking and demographics data from the NEMSIS data set so I think that’s a really good point, as well.
As for what we tell non-trauma centers with regards to, you know, do we transport them or not, I think that will largely depend on what we see when we look at outcomes data. As of right now I don’t think we can reliably answer that with the data that we have.
And then to Dr. Gestring, time does not always equal distance, you are exactly right. In our initial analysis we did not analyze things based on geography. But that is something we would really like to do in our future study and we plan to do so.
And I think it would also be very interesting to split up these helicopter and ground transports that are going to trauma centers by demographics, like you suggested. I think that’s a really good suggestion that we can look into.
For Dr. Jansen’s comments and questions, you have touched on some of our limitations of our study. As I said, we did not have outcomes data in this initial analysis. But we do definitely plan on doing some probabilistic linking to determine outcomes in a future study.
As far as comparing between the ground and helicopter groups, that was not initially one of our objectives. When we analyzed the data with respect to mode of transportation we realized that these are likely two very different groups.
And we thought it would make sense to go ahead and split them up because we thought it might alter our data in terms of who actually experiences clinical decline since a lot of times it seems that, you know, when you get to the scene the EMS providers will call a helicopter for who they think is most severely injured. So we went ahead and split those two groups.
Regarding the Step 2 criteria or the anatomic criteria, there are physical exam fields in the NEMSIS data set and a few specific injury data points. But we didn’t analyze it. It was, there were a lot of holes in that data so we chose to just stick with the Step 1 criteria at this time.
Regarding geography, county of origin is available in the NEMSIS data set. And we can analyze for the effects of geography. But as our primary objective was to examine how often patients who need to go to a trauma center were transported there we decided not to do that in this initial study.
And then, finally, regarding how many inappropriate transfers occur based on EMS provider judgment, there is not a lot in the data set that can give us insight into that. But just based on their responses, you know, almost 60 percent of people say, well, it was the closest facility.
We can infer that they were worried that these patients were declining at a pretty rapid rate and that’s why they went ahead and stopped but we can’t say that for sure.
Thank you very much.