Helicopter-based emergency medical services (HEMS) evolved from rudimentary transportation-only services to advanced, critical-care capable units that offer some of the most advanced pre-hospital care available. HEMS offers many benefits including the ability to expeditiously access rural or remote locations, provide multiple advanced crew configurations, and intervene when ground-based units are not available. However, HEMS utilization must be weighed against the disadvantages of rotor-wing flight including the inherent risk of crashes with subsequent injury or death of the crew or patients. Other considerations for HEMS use include changes in physiology associated with flight, cost, and expenditure of a limited resource. Given the risks and benefits of HEMS, certain guidelines should be considered to determine the need for HEMS response. Establishing the indications and contraindications for HEMS can greatly reduce the stress on requesting providers during already stressful patient encounters. As always, guidelines should be used in conjunction with clinical judgment on a case-by-case basis.
Many organizations, including the American College of Emergency Physicians (ACEP), National Association of EMS Physicians (NAEMSP), and Air Medical Physician Association (AMPA), have recommendations for appropriate utilization of HEMS. When considering HEMS activation, evaluation of the following items, as outlined by the NAEMSP, can help determine appropriate HEMS activation:
It must be kept in mind that recommendations for HEMS activation are not intended to replace clinical judgment, nor are they intended to be the sole determinators as to which patients should be transported by HEMS units.
Several principles should be kept in mind when considering HEMS activation. First and foremost, critical care resources should be provided to patients who require them as rapidly as possible. Patients who are critical or unstable require transport as rapidly as possible and will likely require critical intervention during transport. Time to destination for definitive care is a consideration, and any delays should be minimized. The most appropriate crew should be used to transport more stable patients with the most suitable mode of transportation. Ground-based critical care may be more appropriate when a patient requires critical care during transport, and more rapid transport is not required. Furthermore, stable patients who do not require critical care during transport may be best served by local EMS transport or non-critical care transport unless doing so would place an undue burden on the system. Mass casualty or disaster incidents may also necessitate the use of HEMS to provided extended capabilities, extra personnel, or rapid treatment and transport of critically injured or ill patients.
Scene Trauma Considerations
Scene responses by HEMS units typically involve trauma patients. In an age of regionalized trauma care, rapid aeromedical transport of trauma patients helps provide earlier definitive care and delivery of treatment to help stabilize critically injured patients. The NAEMSP recommendations for scene response include the following as possible indications for HEMS activation for trauma patients:
Orthopedic and Extremity Injuries
While the above list is extensive, individual system requirements, destination facility resources, and availability, and geographic location influence HEMS activation. For example, a motor vehicle crash involving several patients in a large metropolitan area with a trauma center 20 minutes from the scene via ground transport would not typically warrant HEMS activation; however, a mass casualty incident in the same location might necessitate HEMS use. Alternatively, a motor vehicle crash with 2 critical patients in a county served by 2 advanced life support (ALS) units 45 minutes from the hospital would almost certainly be appropriate for HEMS activation. In this case, the patients will benefit from rapid transport and critical care capabilities while preventing the depletion of the entirety of that county’s ALS resources if both units were required for transport.
More recently, Thomas et al., attempted to develop an evidence-based guideline for the use of HEMS for trauma patients. While a lack of high-quality research confounded their efforts, they proposed guidelines based on the Center for Disease Control and Prevention (CDC) 2011 Guidelines for the Field Triage of Injured Patients.
Medical and Interfacility Considerations
Regionalization of care is commonplace and likely to continue as hospital systems grow and merge. This allows for the centralization of advanced care and provides previously unavailable specialty care to more patients by transfer agreements and referrals. Timely transport of patients requiring critical interventions can often be accomplished via ground-based units, but certain conditions may benefit from rapid aeromedical transport and the capabilities provided by HEMS units. The NAEMSP identified the following conditions and possible indications for HEMS transport of medical and interfacility patients.
When considering aeromedical transport for obstetric patients, it is extremely important to weigh the risks and benefits of HEMS. Delivery of an infant while in flight in a helicopter is challenging at best and may be impossible due to airframe limitations. Patients at risk of imminent delivery are best served by ground-based critical care units in which delivery of the infant is more manageable. Nevertheless, situations may exist where distance, crew capabilities, or referring hospital limitations may necessitate the use of HEMS to transport an obstetric patient. Such indications may include:
Similar to cardiac and trauma care, neonatal care may be highly regionalized. While many neonates do not require rapid transport to a referral center, they still require the advanced care available in regional centers. In many cases, HEMS can deliver specialized personnel and equipment to a referring hospital allowing stabilization of a neonate. Following stabilization, transport to the regional neonatal center may be best accomplished via a ground unit, allowing the HEMS unit to return to service. Ground transport times greater than 30 minutes may be an indication for HEMS transport of neonates and should be considered on a case-by-case basis. Neonates with the below conditions may benefit from HEMS activation.
Other Medical or Surgical Patients
Patients who require care beyond that available at a referring facility may be candidates for HEMS transport. Many times these patients can be cared for by ground-based critical care units. However, some patients will be too unstable to remain out of a hospital for the duration of a ground-based transport. In these cases, HEMS transport may be a viable alternative.
Cardiac arrest patients who remain in cardiac arrest are rarely appropriate for HEMS transport and activation. Cardiopulmonary resuscitation (CPR) cannot be safely performed in an aircraft, although mechanical CPR devices may allow safe CPR in the future.
Autolaunch or auto dispatch is a concept in which a HEMS unit is activated automatically by a 911 dispatch center upon receipt of a call. Typically, criteria are predetermined on a local basis so that when they are met, a HEMS unit is placed on standby or dispatched simultaneously with the ground-based EMS crew. Crews placed in standby typically complete pre-flight preparations and await final activation before lifting off. In certain regions, an autolaunch can reduce the response time to a scene, quickly provide care, and shorten transport times. Data is sparse concerning autolaunch impacting patient outcomes, but some reviews do show that it reduces response times and lengths of stay in the hospital.
Typical HEMS crews consist of a pilot and 2 or 3 medical providers. In an attempt to prevent flight crews from feeling pressured into accepting missions, many HEMS organizations notify flight crews only of destinations so that they may determine if a mission is acceptable from a weather and safety standpoint. Details of the mission beyond destinations are given only when the mission is determined to be safe for the crew. HEMS programs may participate in a notification service such as www.weatherturndown.com which allows programs to post declined missions. Declined missions are visible to all users to prevent "helicopter shopping" whereby a referring facility requests HEMS activation from nearby programs when the initial HEMS program declines the mission. Direct dispatch, whereby a local 911 dispatcher calls the HEMS base and directly requests a HEMS unit, potentially bypasses multiple safety layers built into the call triage and dispatch process and should be discouraged. All HEMS programs should have a dispatch center that fields all requests for service thereby allowing missions to be triaged, evaluated for safety by the flight crew, and appropriately tracked.
HEMS activation is a constantly evolving field. Regionalization of specialty resources, access to remote locations, advanced in-flight care, and referring hospital capabilities all influence HEMS use. As a critical component of any regional EMS system, HEMS must be appropriately utilized to provide the greatest benefit to the largest number of patients. These guidelines are intended to offer a framework for appropriate HEMS activation and do not serve as a replacement for clinical assessment and decision-making.
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