Abstract
Background: Helicopter emergency medical services (HEMS) have become an engrained component of trauma systems. In Ontario, transportation for trauma patients is through one of three ways: scene call, modified scene call, or interfacility transfer. We hypothesize that differences exist between these types of transports in both patient demographics and patient outcomes. This study compares the characteristics of patients transported by each of these methods to two level 1 trauma centers and assesses for any impact on morbidity or mortality. As a secondary outcome reasons for delay were identified. Methods: A local trauma registry was used to identify and abstract data for all patients transported to two trauma centers by HEMS over a 36-month period. Further chart abstraction using the HEMS patient care reports was done to identify causes of delay during HEMS transport. Results: During the study period HEMS transferred a total of 911 patients of which 139 were scene calls, 333 were modified scene calls and 439 were interfacility transfers. Scene calls had more patients with an ISS of less than 15 and had more patients discharged home from the ED. Modified scene calls had more patients with an ISS greater than 25. The most common delays that were considered modifiable included the sending physician doing a procedure, waiting to meet a land EMS crew, delays for diagnostic imaging and confirming disposition or destination. Conclusions: Differences exist between the types of transports done by HEMS for trauma patients. Many identified reasons for delay to HEMS transport are modifiable and have practical solutions. Future research should focus on solutions to identified delays to HEMS transport. Key words: helicopter emergency medical services; trauma; prehospital care; delays
Background
Timely access to definitive care is a critical component of modern trauma systems and has been shown to improve patient outcomes after injury.Citation1–3 Access to a trauma center is not consistent throughout the world and patients without immediate access have been shown to have worse outcomes.Citation2 Helicopter emergency medical services (HEMS) have become an engrained component of these systems to expedite transportation to a trauma center. Despite HEMS increasing accessibility to a trauma center there has been mixed results on its benefits.Citation4–13 Helicopter transport is a costly, labor intensive, and limited resource that is not without risk.Citation4,14–17
Immediate access to a trauma center is not always available and patients often undergo initial assessment and resuscitation at a nontrauma facility before transferring to a trauma center. Interfacility transfers can be done by conventional ground emergency medical services (EMS) or HEMS. Multiple factors including injury severity, geographic variation, resource availability, weather, regional practice patterns, and provider preference impact which modality is used.Citation13
Ornge is a provincially run, paramedic-staffed service that is responsible for all HEMS within Ontario, Canada. They provide transportation for trauma patients through one of three ways: scene call, modified scene call, or interfacility transfer. One of the unique challenges in our provincial trauma system is a relative sparsity of trauma centers and large distances that much be travelled in order to transport our injured patients. Longer HEMS transport times to cover these distances mean fewer patients are directly picked up at the scene of their injury and are more likely to be transported to a nontrauma center as part of a modified scene response. Better understanding the patient characteristics for these types of responses can allow for preparation and guidance for transport medicine physicians and sending physicians on how to best prepare for HEMS transport. Additionally by understanding common causes of delay to HEMS transport we can target interventions to improve timely access to definitive care.
In this study we explored differences in the characteristics of patients transported by each of these methods to the two largest volume adult Level I trauma centers in the province and assessed for any impact on morbidity or mortality. As a secondary outcome, we also analyzed times for each method of transport and identified reasons for delays.
Methods
Study Design
This was a retrospective, cross-sectional analysis of trauma registry data from two hospitals. The Sunnybrook Health Sciences Center and St. Michael's Hospital trauma registries were used to identify all patients transported to the two Level I trauma centers during a 36-month period (January 1, 2012 to December 31, 2014). Patients were excluded if they were not transported by HEMS. Patients transported by HEMS were then categorized as being a scene transport, modified scene transport, or interfacility transfer.
A scene call was defined when a patient is transported directly from the scene of injury to a trauma center. In these cases they will bypass the closest hospital to expedite transport to a trauma center. A scene call can be activated based on initial 9-1-1 information obtained by the central ambulance communications center (CACC) or requested by the treating land EMS crew as per field trauma triage guidelines (FTT). A modified scene call was defined as when a local ground EMS crew meets the HEMS crew at a site other than the initial place of injury and then transport the patient to a trauma center. A modified scene response would be activated under the same criteria as a scene call. This may occur at an airport that is convenient for the HEMS crew to meet them, a nearby landing site that is accessible for the aircraft or at a local hospital that is not a trauma center. If a patient is brought to a non-trauma center as part of a modified scene response, the physician at this hospital may help stabilize the patient while awaiting HEMS arrival. This may include intubating, placing chest tubes, plain film x-rays, bedside ultrasound, and any other procedures they deem necessary. The intent of a modified scene response is always to expedite transfer to a trauma center and patients are only brought into a local hospital to rendezvous with the HEMS crew if there is a delay in HEMS arrival. An interfacility transfer was defined when a patient is initially brought to a non-trauma center where they are assessed, worked up, stabilized, and then later transferred to a trauma center. Interfacility transfers are not activated through the CACC or land EMS crews but rather the treating physician decides they may benefit from transfer to a trauma center for definitive management and requests an interfacility transfer.
The data obtained from the trauma registry is entered prospectively during the patient's hospitalization. Abstracted from this database were demographic and arrival characteristics including age, sex, mechanism of injury, admission vital signs, Glasgow Coma Scale (GCS), Injury Severity Score (ISS), airway intubation status, intensive care unit (ICU) admission, mortality, hospital length of stay (LOS), ICU LOS, and ventilator days. Further chart abstraction was done using the HEMS electronic patient care reports (ePCR) to collect times of HEMS dispatch, arrival to patient, time on scene or in referring facility, time of arrival to trauma center and any reasons for delay identified.
Setting
Ornge operates the largest HEMS fleet in Canada, serving over 13 million people over one million square kilometers of land. They have nine bases that operate rotor or fixed-wing aircraft with a fleet of ten AgustaWestland AW-139 helicopters, two Sikorsky S76 helicopters, and ten Pilatus Next Generation PC-12 airplanes. They are staffed by advanced care and critical care paramedics who are trained in a number of advanced procedures including facilitated intubation and airway management, rapid sequence intubation, needle thoracostomy and cricothyrotomy. A transport medicine physician provides online medical oversight. Ornge transports patients to nine different Level 1 trauma centers across the province. Toronto is home to two adult Level I trauma centers (Sunnybrook Health Sciences Center and St. Michael's Hospital) and one pediatric Level 1 trauma center (The Hospital for Sick Children). Sunnybrook Health Sciences Centre is a 1200-bed tertiary care hospital with an annual emergency department (ED) volume of 61,000 of which over 1240 are trauma-related with an ISS of 15 or more. The helipad at Sunnybrook Health Sciences Center is approximately 600 meters away from the entrance to the emergency department, necessitating a land EMS escort from the helipad to the hospital. St. Michael's Hospital is a 500-bed tertiary care hospital with an annual ED volume of 75,000 or which 990 are trauma-related with an ISS of 15 or more. The helipad at St. Michael's Hospital is on the roof of the hospital and an elevator provides direct access to the emergency department. This study was approved by both the Sunnybrook Research Institute and St. Michael's Hospital Research Ethics Board.
Statistical Analysis
Descriptive statistics were used to describe the demographics and characteristics for all patients transported during the 36 month study period along with the various transport times for each transport method. Data from the trauma registry and ePCR were analyzed using SAS Statistical Analysis System (version 9.4; SAS Institute, Cary NC). Normally or near-normally distributed variables are reported as means and non-normally distributed variables are reported as medians with interquartile rangers (IQR). Means were compared using one-way ANOVA and Welch's ANOVA. Categorical variables were compared using Chi-square tests.
Identified delays were categorized as either delays to arriving at patient, delays on scene or in hospital or delays arriving at trauma center or handing over to the receiving team. Two authors (BN and AA) then further identified delays as potentially modifiable delays or non-modifiable delays. Any disagreement between categorization of delays was determined a priori to be settled by a third investigator.
Results
From January 1, 2012 to December 31, 2014 there were a total of 5677 trauma patients brought to Sunnybrook Health Sciences Center and St. Michael's Hospital (). HEMS transported 9-1-1 of these patients. Of these patients 139 were direct scene calls, 333 were modified scene calls and 439 were interfacility transfers. Most of those patients were young males suffering blunt trauma, with 67% being under the age of 55, 74.4% being male and blunt injuries accounting for 94.8% (). Injuries with an ISS of greater than 15 accounted for 72.6% of all transports. For all patients transported 4.3% were discharged home from the ED, 50.9% required admission to the ICU and 49.2% were placed on a ventilator. Overall mortality was 10.9%.
Figure 1. Study flow diagram detailing selection and categorization by transport method for all trauma patients between January 1st, 2012–December 31st, 2014.
Table 1. Baseline characteristics of patients transported by helicopter emergency medical services
The patients requiring interfacility transfers were older than scene and modified scene patients (26.4% being over 65 years of age compared to 14.4% and 10.5%) (). Scene calls had significantly more transports for patients with an ISS of less than 15 (36.7% compared to 23.7% for modified scene and 27.1% for interfacility transfers) and had more patients discharged home from the ED (8.6% compared to 3.9% for modified scene and 3.2% for interfacility transfers). Modified scene calls had more patients with an ISS greater than 25 (46.5% compared to 36.7% for scene calls and 33.0% for interfacility transfers). Modified scene calls also had significantly lower GCS (44.1% with GCS less than 13 compared to 24.1% of scene calls and 33.6% of interfacility transfers) and higher prevalence of being placed on a ventilator (60.1% vs. 41.0% of scene calls and 43.5% of interfacility transfers). There was no significant difference in mortality between the three groups.
Table 2. Comparison of patient characteristics of helicopter emergency medical services by method of transport
Mean overall transport times were 80 minutes for scene calls (IQR 61–100 minutes), 118 minutes for modified scene calls (IQR 91–153 minutes) and 145 minutes for interfacility transfers (IQR 116–175 minutes) (). Identified delays to HEMS transport are listed in . Modifiable delays to arriving at the patient included refueling (34.0% of time), crew change (14.0% of time), and being cancelled and then called back for the same transport (10.0% of the time). Delays on scene or in hospital represented the largest number of delays identified. The most common of these delays that were considered modifiable included the sending physician doing a procedure (24.7% of the time), waiting to meet a land EMS crew (16.5% of the time), delays for diagnostic imaging (14.1% of the time), and confirming disposition or destination (12.9% of the time). Modifiable delays to arriving at trauma center or handing over to the receiving team included waiting for a land EMS escort (37.1% of the time), trauma team was not assembled (14.8% of the time), and unclear directions as to whom the receiving team was (7.4% of the time).
Table 3. Transport times for different methods of transport for helicopter emergency medical services
Table 4. Identified delays to helicopter emergency medical services transport of trauma patients
Discussion
A recent Canadian study comparing HEMS scene calls to land EMS scene calls for injured patients showed that HEMS scene calls outperformed their predicted mortality compared to their land EMS cohort despite higher ISS and longer transport times.Citation18 The proposed reason for this improved mortality was the extended scope of practice of the HEMS paramedics compared to the land EMS paramedics in life prolonging and stabilizing therapies. This adds to the literature of HEMS conferring a survival benefit within the Canadian trauma system.Citation19,20 All previous Canadian studies have either compared only HEMS scene calls to land EMS scene calls or compared all scene and interfacility transfers between HEMS and land EMS. Comparing our outcomes to some US studies, our study population has a higher overall ISS and ICU admissions, as well as a higher percentage of blunt injuries.Citation6,7 In comparison to an Australian HEMS study, our population had a higher ISS, higher mortality and much lower on-scene times (10–20 minutes in our study compared to 50 minutes in the Australian HEMS study).Citation21
We found it interesting that our modified scene calls were more severely injured than our scene calls, particularly as they share the same HEMS launch criteria. They are either dispatched from the CACC based on initial 9-1-1 caller information or are requested by a land EMS crew upon their arrival and assessment of the patient. This discrepancy between scene and modified scene calls may be explained by a few factors. To begin with the CACCs are the primary stakeholders in making the request for a scene call, however once land EMS contact occurs a more definitive medical assessment can be made and if the patient does not meet FTT guidelines HEMS response will be called off by the land EMS crew. As some modified scene calls are longer distances to travel they have a longer period of time where the land EMS crew may call them off. Alternatively if HEMS was not dispatched by the CACC but is requested by a land EMS crew they have a higher likelihood of being more severely injured as they must meet FTT guidelines. Additionally, if Ornge arrives at a non-trauma hospital as part of a modified scene response, they may make a joint decision along with the treating physician to cancel the transport if the patient does not meet FTT guidelines. Lastly, there are also instances where during a modified scene call, the patient is brought to a non-trauma hospital and the treating physician cancels the HEMS response. All of these factors introduce a sampling bias making our modified scene calls a more refined population in comparison to our scene calls. The modified scene patients have been sorted such that less injured modified scene patients are likely to have been cancelled; therefore, the sample is going to contain a higher proportion of sicker patients.
Our results suggest that more information needs to be collected about our scene and modified scene calls. As previously mentioned, are these patients “artificially” more injured as a consequence of more accurate identification of patients requiring transport to a trauma center? Or are they indeed a sicker patient population due to longer transport times to a trauma center and potential under resuscitation at nontrauma centers?
Examining modifiable delays to HEMS transport identified some areas for future study. To begin with 10% of the delays to arriving to the patient were from having been cancelled off from a scene call and then called back to respond. There are not only significant financial costs associated with having multiple HEMS launches for a single patient transport but also potential patient harm from prolonged times to definitive care. Although the struggle for all trauma systems is balancing over-triage and under-triage of patients, additional studies should examine what patients we are being called back to transport. A second area of interest that was identified was minimizing the number of interventions and imaging studies performed at sending facilities. Only procedures and imaging that are necessary for patient stabilization prior to transfer should be performed at non-trauma centers. There were many instances where HEMS paramedics were in a transferring hospital ready to transport the patient but had to wait for them to come back from unnecessary diagnostic imaging. Injured patients often undergo repeat imaging at receiving trauma centers leading to higher costs and increased radiation exposure.Citation22 Better communication with and the creation of guidelines for sending facilities about what must be done prior to sending and what can wait to be done at the receiving trauma center might improve our transport times. This problem is not unique to our trauma system. A study from Oklahoma found that the average time from injury to arrival at a trauma center was three times longer for interfacility transfers than for those taken directly from the scene of injury.Citation23 Finally, there were many instances that communication could have been improved. Currently, in our system most of our paramedic communications go through the CACC. Therefore, there is usually minimal or no direct discussion between the land EMS paramedics and HEMS paramedics. A direct line of communication between land EMS and HEMS without having to go through the CACC could reduce both our delays and communication errors. Furthermore, improvements can be made to ensure a land EMS escort is ready and available at the helipad for all HEMS transports that require an escort from the landing site to the emergency department. Likewise, ensuring that the trauma team is paged and ready to receive the patient upon arrival of the HEMS crew could significantly reduce delays. Decreasing delays can be beneficial not only on an individual patient level by expediting arrival to definitive care but also on a systems level by allowing the aircraft to be ready and available for the next transport.
Our study has many limitations that merit discussion. First, as with all retrospective studies, using a database cohort introduces the risk of missing or incorrect data. Times in the ePCR are manually recorded by the paramedics when it is convenient, which may occur throughout the call in real time if time allows or may occur entirely after a call in the case of sick patients that require intensive resuscitation. In addition, we relied on paramedic documentation to specifically identify a reason of delay if there was a prolonged time. This, however, is not a required part of documentation and as such many ePCRs that had longer than expected transport times did not mention any reason for delay. Second, our HEMS system of a highly skilled dual paramedic crew may not be generalizable to other HEMS systems that utilize flight physicians, flight nurses or flight paramedics with a lower scope of practice. We also saw a relatively low rate of penetrating traumas (5.2%) compared to other trauma systems, which although seems to be consistent across CanadaCitation18–20 may not be applicable to other trauma systems. Finally, while our study showed that our modified scene calls tend to be the most critically ill patients transported, it cannot provide any causation for this finding.
In conclusion, differences exist between the types of transports done by HEMS for trauma patients. Based on our study population, modified scene calls were more severely injured. Many identified reasons for delay to HEMS transport are modifiable and have practical solutions. Future research should focus on solutions to identified delays to HEMS transport, so that the most critically ill trauma patients arrive to definitive care in a safe and timely manner.
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