Natural Experiment Outcomes Studies in Rotor Wing Air Medical Transport: Systematic Review and Meta-Analysis of Before-and-After and Helicopter-Unavailable Publications From 1970 to 2022.

OBJECTIVE: Helicopter emergency medical services (HEMS) is widely used for prehospital and interfacility transport, but there is a paucity of HEMS outcomes data from studies using randomized controlled trial designs. In the absence of robust randomized controlled trial evidence, judgments regarding HEMS potential benefit must be informed by observational data. Within the study design set of observational analyses, the natural experiment (NE) is notable for its high potential methodologic quality; NE designs are occasionally denoted "quasi-experimental." The aim of this study is to examine all NE outcomes studies in the HEMS literature and to discern what lessons can be learned from these potentially high-quality observational data. METHODS: HEMS NE studies were identified during the development of a new HEMS Outcomes Assessment Research Database (HOARD). HOARD was constructed using a broad-ranging search of published and gray literature resources (eg, PubMed, Embase, and Google Scholar) that used variations of the terms "helicopter EMS," "air ambulance," and "air medical transport." Among the 221 studies ultimately included in HOARD, 16 NE publications describing 13 sets of observational data comprising myriad diagnostic groups were identified. Of these 16 HEMS NEs, 4 HEMS NE studies assessing trauma outcomes were used in a meta-analysis. A meta-analysis was also performed of 4 HEMS NE studies. RESULTS: Although the disparity of studies (in terms of both case mix and end points) precluded the generation of a pooled effect estimate of an adjusted mortality benefit of HEMs versus ground emergency medical services, HEMS was found to be associated with outcomes improvement in 8 of the 13 cohorts. CONCLUSION: The weight of the NE evidence supports a conclusion of some form of HEMS-mediated outcomes improvement in a variety of patient types. Meta-analysis of 4 HEMS NE studies assessing trauma outcomes generated a model with acceptable heterogeneity (I2 = 43%, Q test: P = .16), which significantly (P < .01) favored HEMS use with a pooled HEMS survival odd ratio estimate of 1.66 (95% confidence interval, 1.23-2.22).

Management Considerations for Air Medical Transport Programs Transfusing RhD-Positive Red Blood Cell-Containing Products to Females of Childbearing Potential.

Recent years have seen increased discussion surrounding the benefits of damage control resuscitation, prehospital transfusion (PHT) of blood products, and the use of whole blood over component therapy. Concurrent shortages of blood products with the desire to provide PHT during air medical transport have prompted reconsideration of the traditional approach of administering RhD-negative red cell-containing blood products first-line to females of childbearing potential (FCPs). Given that only 7% of the US population has blood type O negative and 38% has O positive, some programs may be limited to offering RhD-positive blood products to FCPs. Adopting the practice of giving RhD-positive blood products first-line to FCPs extends the benefits of PHT to such patients, but this practice does incur the risk of future hemolytic disease of the fetus and newborn (HDFN). Although the risk of future fetal mortality after an RhD-incompatible transfusion is estimated to be low in the setting of acute hemorrhage, the number of FCPs who are affected by this disease will increase as more air medical transport programs adopt this practice. The process of monitoring and managing HDFN can also be time intensive and costly regardless of the rates of fetal mortality. Air medical transport programs planning on performing PHT of RhD-positive red cell-containing products to FCPs should have a basic understanding of the pathophysiology, prevention, and management of hemolytic disease of the newborn before introducing this practice. Programs should additionally ensure there is a reliable process to notify receiving centers of potentially RhD-incompatible PHT because alloimmunization prophylaxis is time sensitive. Facilities receiving patients who have had PHT must be prepared to identify, counsel, and offer alloimmunization prophylaxis to these patients. This review aims to provide air medical transport professionals with an understanding of the pathophysiology and management of HDFN and provide a template for the early management of FCPs who have received an RhD-positive red cell-containing PHT. This review also covers the initial workup and long-term anticipatory guidance that receiving trauma centers must provide to FCPs who have received RhD-positive red cell-containing PHT.

A comparison between sudden cardiac arrest on military bases and non-military settings.

INTRODUCTION: Out-of-hospital cardiac arrests contribute to significant morbidity and mortality in both non-military/civilian and military populations. Early CPR and AED use have been linked with improved outcomes. There is public health interest in identifying communities with high rates of both with the hopes of creating generalizable tactics for improving cardiac arrest survival. METHODS: We examined a national registry of EMS activations in the United States (NEMSIS). Inclusion criteria were witnessed cardiac arrests from January 2020 to September 2022 where EMS providers documented the location of the arrest, whether CPR was provided prior to their arrival (yes/no), and whether an AED was applied prior to their arrival (yes/no). Cardiac arrests were then classified as occurring on a military base or in a non-military setting. RESULTS: A total of 60 witnessed cardiac arrests on military bases and 202,605 witnessed cardiac arrests in non-military settings met inclusion criteria. Importantly, the prevalence of CPR and AED use prior to EMS arrival was significantly higher on military bases compared to non-military settings. CONCLUSIONS: Reasons for the trends we observed may be a greater availability of CPR-trained individuals and AEDs on military bases, as well as a widespread willingness to provide aid to victims of cardiac arrest. Further research should examine cardiac arrests on military bases.

Full Moons and Helicopter Emergency Medical Services (HEMS) Activations in The United States.

A long-standing misconception in emergency medicine is that full moons are associated with increased patient volume. Although there has been ample work debunking this belief, virtually no scholarship has tackled this question from the perspective of helicopter emergency medical services (HEMS). We examined a national-level database populated by EMS agencies throughout the United States (NEMSIS) and compared three-day periods containing every full moon in 2019 with control three-day periods one week immediately before and one week immediately after a given full moon. The daily average number of HEMS activations was then compared. A significant increase was defined as full moon periods having at least 20% more HEMS activations than the control periods before and after the full moon. In 2019, full moons had a daily average of 496 HEMS activations, and non-full moon periods had a daily average of 510 HEMS activations. Furthermore, no months saw full moons having a significant increase in HEMS activations. Our data provides important support for the idea that full moons do not translate into increased HEMS activations.

Frequency of Mass Casualty Incidents (MCIs) Responded to by Helicopter Emergency Medical Services (HEMS).

OBJECTIVE: Mass casualty incidents (MCIs) challenge out-of-hospital and in-hospital personnel as well as impose significant pressure on available resources. Helicopter emergency medical services (HEMS) crews may be involved in the response to an MCI. Thus, there is epidemiological interest to understand the frequency of MCIs responded to by HEMS. METHODS: We used a nationally representative database of emergency medical services activations in the United States (National Emergency Medical Services Information System). We queried 911-initiated (scene) activations during the years 2021 and 2022 within the database and paid special attention to activations defined by crews as MCIs. From this, we were able to calculate the frequency at which HEMS crews responded to MCIs relative to the total number of HEMS scene activations. RESULTS: Of a total of 177,509 HEMS scene activations, less than 1% involved MCIs (0.27%, 486/177,509). Nationally, HEMS crews responded to roughly 2.74 MCIs per 1,000 activations. Variation in MCI frequency was noted across the day of the week, the month of the year, and the time of the day. CONCLUSION: HEMS crews do respond to MCIs although infrequently. Certain time periods are associated with a greater frequency of MCIs. These data will hopefully be able to inform preparedness and training.

Helicopter Emergency Medical Services Outcomes Research 1983 to 2022: Evidence Overview and Longitudinal Trends.

OBJECTIVE: Helicopter emergency medical services (HEMS) literature has been assessed in reviews focusing on various diagnoses, but there are few, if any, summaries of the entire body of HEMS outcomes evidence. Our goal was to summarize the existing research addressing patient-centered outcomes potentially accrued with HEMS. METHODS: As part of the Critical Care Transport Collaborative Outcomes Research Effort, we generated the HEMS Outcomes Assessment Research Database and executed descriptive analyses of longitudinal trends from 1983 to 2022. Both indexed and gray literature sources were incorporated in the HEMS Outcomes Assessment Research Database. Studies were reviewed by at least 2 authors to select those that addressed a patient-centered outcome. Studies addressing solely HEMS logistics were excluded. Categoric analyses were executed with the Fisher exact test, and continuous variables were evaluated for normality with normal quantile plotting and a comparison of medians and 95% confidence intervals. RESULTS: We found that HEMS outcomes study sample sizes increased steadily from 1983 to 2012, with the most recent decade demonstrating a marked increase in the rate of publication of HEMS outcomes studies. Most research (70.6%) addressed trauma patient outcomes, but recent decades have seen a significant increase in non-trauma studies. Recent decades have also been characterized by an increase in the production of HEMS outcomes research outside of North America and Europe. CONCLUSION: This study summarizes the current state of the HEMS outcome literature. We highlight increasing contributions from worldwide researchers and increasing focus on HEMS benefits in non-trauma cases, particularly time-critical cases such as cardiac or stroke diagnoses. This provides a basis for further investigations into patient-oriented benefits potentially accrued with HEMS.

Mechanical Cardiopulmonary Resuscitation's Role in Helicopter Air Ambulances: A Narrative Review.

Helicopter emergency medical services (HEMS) frequently respond to out-of-hospital cardiac arrest (OHCA) situations. Some have speculated mechanical cardiopulmonary resuscitation (mCPR) may be able to rectify the inadequacy of human performance of cardiopulmonary resuscitation (CPR) during transport. A number of studies have examined the performance of mCPR devices in the air medical setting specifically. Many aspects of the HEMS environment seem uniquely conducive to mCPR, and a growing body of research seems to suggest mCPR holds promise for the treatment of cardiac arrest by HEMS clinicians. Simulation studies show that mCPR leads to improved CPR performance compared with manual CPR in HEMS. Case reports and the experience of several HEMS programs suggest that mCPR can be effectively integrated into HEMS care. However, further research regarding the effectiveness of mCPR in the HEMS environment and in general cardiac arrest care is needed.

Helicopter emergency medical services (HEMS) response to out-of-hospital cardiac arrest (OHCA) in the United States.

Introduction: Helicopter emergency medical services (HEMS) are used in the United States and globally to respond to patients with critical illness and victims of traumatic injury. Relatively limited research has examined their role in responding to out-of-hospital cardiac arrests (OHCA) in the United States. In this study, we compared OHCA treated by HEMS units with cardiac arrests treated by ground ambulances. Methods: We queried a large national-level database of emergency medical services (EMS) activations in the United States (NEMSIS). Inclusion criteria were OHCA activations between January 1, 2022 and December 31, 2022 treated by either HEMS or ground ambulance. Key arrest data from both groups were then compared. Interfacility transfers and cardiac arrests after EMS arrival were excluded. Results: A total of 1,233 cardiac arrests treated by HEMS and 341,096 cardiac arrests treated by ground ambulances met inclusion criteria. Comparing the two groups, cardiac arrests with HEMS response were more likely to be male (66.7% vs. 62.8%, p < 0.01), White (50.2% vs. 45.7%, p < 0.01), under 18 years old (10.9% vs. 2.7%, p < 0.001), associated with traumatic injury (19.1% vs. 5.7%, p < 0.001), witnessed (72.7% vs. 37.3%, p < 0.001), and initially-shockable (24.7% vs. 11.1%, p < 0.001). Conclusion: Our comparison of cardiac arrests treated by HEMS with cardiac arrests treated by ground ambulance reveals significant differences between the two groups. Further research is needed to better characterize HEMS' ideal role in the response to OHCA as new prehospital resuscitative techniques for non-traumatic and traumatic cardiac arrest are developed.

Fatal Air Medical Accidents in the United States (2000-2020).

INTRODUCTION: Currently, many airplanes and helicopters are used as air ambulances to transport high-acuity patients. Unfortunately, civilian air medical transport in the United States has experienced a significant number of serious and fatal accidents. At the moment, additional research is needed to identify what factors affect air medical safety. METHODS: Accident reports from the National Transportation Safety Board (NTSB) were queried. Accident reports were analyzed if the accident occurred from 2000 through 2020, involved a helicopter or airplane on an air medical flight (as identified by the NTSB), and had at least one fatality. The date of the accident, the model of aircraft involved, and NTSB-determined probable causes of the accident were examined. RESULTS: Eighty-seven (87) accidents and 239 fatalities took place from January 2000 through December 2020. Nearly three-fourths (72.4%) of fatalities occurred on helicopters, while just 27.6% occurred on airplanes. Interpreting the NTSB findings, various human factors probably contributed to 87.4% of fatalities. These include pilot disorientation, pilot errors, maintenance errors, impairment, fatigue, or weather misestimation. Nighttime-related factors probably contributed to 38.9% of fatalities, followed by weather-related factors (35.6%), and various mechanical failures (17.2%). CONCLUSION: These data show that the probable causes of fatal air medical accidents are primarily human factors and are, therefore, likely preventable. Developing a safety-first culture with a focus on human factors training has been shown to improve outcomes across a wide range of medical specialties (eg, anesthesia, surgery, and resuscitation). While there have been fewer fatal accidents in recent years, a continued emphasis on various training modalities seems warranted.