Introduction
From a public health perspective, injury remains the leading cause of death in individuals up to the age of 44 and the leading cause of morbidity and mortality among children in the USA.1 A 2016 report from the National Academies of Science, Engineering and Medicine, entitled ‘A National Trauma Care System: Integrating Military and Civilian Trauma Systems to Achieve Zero Preventable Deaths After Injury,’ estimated that approximately 30 000 of the 147 790 trauma deaths that occurred in 2014 had potentially survivable injury.2 Based on recommendations for leadership and action to develop and implement a national trauma system, the report set the goal of zero preventable death and disability from injury. Concomitantly, the National Trauma Institute has been developing the infrastructure to support the Multi-Institutional Multidisciplinary Injury Mortality Investigation in the Civilian Pre-Hospital Environment (MIMIC) study to elucidate the epidemiology of prehospital injury mortality. The pragmatic goals of this investigation are to estimate the impact of potentially preventable trauma death on society in terms of years of potential life lost and lost productivity and to develop a blueprint to improve the US civilian and military trauma system.
During the last several decades, advances in care in trauma centers and across trauma systems have substantially reduced death and disability associated with injury.3 However, there remains a substantial opportunity to further reduce the number of deaths in the prehospital setting. From an analysis done by the US military during operations in southwest Asia spanning 2001–2011, it was determined that the majority of battlefield deaths occurred prior to casualties receiving care at a military medical treatment facility. Furthermore, it was determined that approximately 25% of the prehospital casualty mortalities died to potentially survivable injury, largely from hemorrhage. Importantly, this work highlighted clear priorities for research and development of mitigation strategies to improve battlefield casualty outcomes.4 Unlike within the battlefield environment, the magnitude and impact of potentially preventable prehospital death from injury in the civilian environment has not been fully explored. These potential liabilities in civilian prehospital care must be identified and remediated to reduce the number of potentially preventable trauma deaths.
Understanding this deficiency, the purpose of the MIMIC study is to develop a coordinated, multidisciplinary, multi-institutional effort within the civilian clinical sector to identify and characterize the causes of mortality from trauma in the prehospital setting and to identify potential high-yield areas for research and development in prehospital medical care, injury prevention, and trauma systems. Using these data and a network of experts, the analysis aims to define the causes and pathophysiologic mechanisms of a nationally representative sample of 3000 prehospital deaths occurring in six regions of the country and estimate the potential for survivability. Key determinants of this investigation include mechanism of injury, physiologic cause of death, estimated time from injury to definitive care, geographic location of the injury, and access to components of the local trauma system.
A multi-institutional and multidisciplinary group of trauma surgeons, neurosurgeons, orthopedic surgeons, forensic pathologist/medical examiners, and emergency medical service (EMS) personnel was created to review these prehospital deaths. These experts will evaluate the potential for survivability of medical examiner injury cases based on the assumption of immediate access to level I trauma center care and under the actual circumstances of the injury. Injury survivability assessments will be established using a specially developed electronic tool with data abstracted from medical examiner reports, field investigation reports, medical examiner radiographic imaging, injury severity coding, and EMS and trauma center accessibility. One major emphasis of this study is to determine the degree to which access to care in the field and the nearest trauma center impact the potential for survivability among deaths occurring prior to definitive care. Numerous studies have supported the argument that longer prehospital times contribute to higher mortality rates,5–8 and that timely delivery of trauma care to severely injured patients is an effective strategy for reducing mortality.9–11 Current research also indicates designated trauma centers significantly lower the risk of mortality and morbidity, with a 25% reduction in 1 year mortality when compared with non-trauma centers.12 Therefore, the potential to integrate data regarding access to designated trauma centers is critical in the panel’s assessment of potential for survivability, given the circumstances of the injury.
Geographic information system (GIS) analysis has been used in previous trauma studies to measure travel time and distance of medical transportation when EMS was not involved, or when an EMS record with time elements could not be obtained. Widener et al13 and Lerner et al14 used network analysis tools to compare ground emergency medical service (GEMS) and helicopter emergency medical service (HEMS) and determine in which areas each transportation method was faster. The purpose of this article is to describe the GIS methodology developed to estimate the total prehospital time and distance by GEMS and HEMS for 3000 prehospital deaths after injury.