Differences in Mortality Rates Among Trauma Patients Transported by Helicopter and Ambulance in Maryland

Abstract

AbstractIntroduction:A comprehensive state wide emergency medical services and helicopter transport system has been developed in the State of Maryland on the principle that early definitive care improves patient out comes. The purpose of this study was to determine if empirical data exist to support the theory that air medical transportation services provided by the Maryland State Police (Maryland State Police) Aviation Division contribute to an improved trauma patient survival rate in Maryland.Methods:A retrospective study was conducted on the records of all patients transported by helicopter or ground ambulance and admitted to the R Adams Cowley Shock Trauma Center (R Adams Cowley Shock Trauma Center of the University of Maryland Medical System) of the University of Maryland Medical System. Data were obtained from the Maryland Institute of Emergency Medical Services Systems (Maryland Institute for Emergency Medical Services Systems) Shock Trauma Clinical Registry for the period January 1988 through July 1995, covering 23,002 patients. Patients included those transported directly from the scene of injury to the Maryland Institute for Emergency Medical Services Systems as well as those from interfacility transfers. All patients were stratified by injury severity and compared by outcome (mortality) using Mantel-Haenszel statistics.Results:During the study period, 11,379 patients were transported by ground and 11,623 were transported by Maryland State Police helicopter. The mean Injury Severity Score (Maryland State Police) for patients transported by ground was 12.7 (standard deviation = 12.52) and the mean Injury Severity Score for patients transported by air was 14.6 (Injury Severity Score = 13.42), p <0.001. Among patients classified as having a high index of injury severity, the mortality rate was lower among those transported by Maryland State Police helicopter than among those transported by ambulance. The mortality rate was significantly lower for air transported patient with an Injury Severity Score higher than 31.Conclusion:The State of Maryland has demonstrated a commitment to its citizenry and invested heavily in its public safety air medical service. This study suggests the rapid air transport of victims of traumatic events by specialized personnel in Maryland has a positive effect on the outcome of severely injured patients. Further research is necessary to clarify the causal relationships in order to more fully elucidate the value of this resource.