International Journal of Clinical Medicine, 2013, 4, 511-524 Published Online December 2013 (http://www.scirp.org/journal/ijcm) http://dx.doi.org/10.4236/ijcm.2013.412090 Open Access IJCM 511 Helicopter EMS beyond Trauma: Utilization of Air Transport for Non-Trauma Conditions Stephen H. Thomas, Lori J. Whelan, Emily Williams, Loren Brown Department of Emergency Medicine, University of Oklahoma College of Medicine, Tulsa, USA. Email: Stephen-Thomas@OUHSC.edu Received October 7th, 2013; revised November 1st, 2013; accepted November 20th, 2013 Copyright © 2013 Stephen H. Thomas et al. This is an open access article distributed under the Creative Commons Attribution Li- cense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. ABSTRACT Helicopter Emergency Medical Services (HEMS) use in civilian medical transport has its roots in th e use of rotor-wing trauma transport in the military setting. Much of the literature and ev idence based on the use of HEMS is therefore re- lated to scene and interfacility transport of injured patients. Regionalization of care and increased understanding of time- criticality of various non-trauma co nditions has contributed to growing utilization of HEMS for non -trauma conditions over recent decades. It is common for HEMS to be utilized for a variety of non-trauma situations ranging from neonatal and obstetrics transports to cardiac and stroke transports. The purpose of this review is to overview the use of HEMS for non-trauma, focusing on situation s in which there is evidence addressing possible HEMS utility. Keywords: Helicopter Emergency Medical Services; Air Medical Transport; Prehospital Care 1. Introduction This discussion strives to overview evidence addressing benefits accrued by utilization of helicopter EMS (HEMS) for non-trauma patients. The primary goal will be to analyze HEMS literature to describe, qualitatively and quantitatively, potential benefits of air medical transport for medical and non-trauma populations. The discussion commences with background informa- tion that is provided to facilitate interpretation of HEMS studies. Next, the non-trauma HEMS outcomes in litera- ture are introduced with division s by diagnostic catego ry. The review concludes with the summary and suggested directions for future investigation. The HEMS outcome deb ate’s long evity and vigo r con- stitute sufficient impetus for evidence-based exploration of whether there is benefit to air medical transport. For- tunately, some detailed exploration of existing data has been executed. One excellent example is a report in 2007 from the independent Institute of Health Economics, prepared for the Canadian health ministry in Alberta. These authors, after reviewing all available studies from the year 2000, concluded: “Overall, patients transported by helicopter showed a benefit in terms of survival, time interval to reach the healthcare facility, time interval to definite treatment, better results, or a benefit in general” [1]. The Alberta publication addressed a variety of patient types, but most direct HEMS outcomes’ information (in- cluding the only Cochrane review of HEMS outcomes) addresses HEMS use for injured patients [2]. Thus, there appears to be a relative paucity of information overview- ing HEMS use fo r n o n -t rau ma. Why a review article on HEMS non-trauma uses? Per- haps the most important reason is that, as to the maturity of the applicable evidence, air medical transport is broadly employed for non-trauma cases. The National Association of EMS Physicians (NAEMSP) Guidelines for HEMS use includes a variety of recommendations (although acknowledging lack of solid evidence base) for HEMS dispatch for non-trauma [3]. Furthermore, as long ago as 2003 a Chest editorial [4] observed that “In many communities, emergency air medical systems have be- come an integral part of the practice of cardiology and critical care medicine.” The Chest authors aver that “We firmly believe that air medical transport is a safe means for transport of cardiac patients and should be considered for patients who require transfer to more specialized centers for additional diagnostic and therapeutic inter- ventions.” There is also a long history of HEMS use for non-trauma surgical cases. An article from a quar- ter-century ago described the use of air transport for pa-
Helicopter EMS beyond Trauma: Utilization of Air Transport for Non-Trauma Conditions 512 tients with ruptured aortic an eurysm [5]. If HEMS are going to be used for non-trauma, then it is important to assess and optimize resource use by iden- tifying cases in which benefit is most likely to occur. This is important because of the highly visible concentra- tion of costs that are present with helicopters. Some in- vestigators have assessed regional costs of HEMS to be no higher than those associated with response-time- equivalent (multivehicle) ground critical care coverage [6]. However, the perception is (and likely will long be) that air medical transport is expensive. Use of an expen- sive resource should be accompanied by an assessment of justification for such use. Since few argue that HEMS benefit is always predi- cated on time and logistics, consideration of HEMS out- comes’ evidence touches upon the broader subject of lev- els of care beyond advanced life support (ALS) in the prehospital setting. Thus, this arena will also be dis- cussed herein. For purposes of consistency within this review, “pre- hospital” is interchangeable with “out-of-hospital” in order to encompass both scene and interfacility transports. HEMS crews’ extended practice scope, even in the US where crews often do not include physicians, facilitates consideration of benefits to advanced care [7]. While most non-trauma HEMS use falls within the realm of secondary (interfacility) transport, the items in this review are not limited in scope to interhospital transfers. Suggestion of potentially growing indications for HEMS “scene” transports of non-injured patients is provided by an evolving literature describing significant utility to direct HEMS response to patients such as those with acute coronary syndrome (ACS) or ischemic stroke [8-11]. Many questions remain unanswered about HEMS. However, there is a body of evidence addressing HEMS’ potential outcome impacts, which is often paid insuffi- cient attention. This discussion’s goal is to provide in- formation on non-trauma HEMS use, in order to aid in- terested parties to understand the evidence pertinent to the outcomes dialogue. It is hoped that the review will assist those physicians and systems planners who are pursuing appropriate and judicious employment of po- tentially life-saving HEMS resources. 2. Outcomes Assessment in HEMS This section covers the approach to considering HEMS’ impact for non-trauma indications. It’s necessary for planners to incorporate HEMS “outcomes” on patients, EMS systems, and regionalized care networks. The sub- ject of mechanics of outcomes assessment in HEMS has been addressed in detail in a 2012 review [12]. High- lights and recent advancements will be covered in this section. One important recent development is a joint position statement promulgated by the Air Medical Physicians Association (AMPA), the National Association of EMS Physicians (NAEMSP), the American College of Emer- gency Physicians (ACEP), and the American Academy of Emergency Medicine (AAEM) [13]. The position statement, published at the end of 2013, includes some important consensus ideas about the state of the art with HEMS; the document also gives directions for forward movement of HEMS development. Among the important points made in the consensus statement are some with relevance to this review. For instance, the consensus statement avers that for many time-critical situations, particularly those for which there is time-windowed therapy, the measurement of HEMS’ impact on outcome is best focused on delineating the amount of time saved by air transport [13]. Before moving to other outcomes, a note on HEMS safety is appropriate. Th e recent jo int organization al con- sensus statement includes the need to emphasize safety and also the importance of separating aviation deci- sion-making from the clinical arena [13]. The subject of aviation safety and HEMS’ flight-related risks is so im- portant that a even a cursory overview does not serve. Interested readers are directed to the work of experts such as Blumen from the University of Chicago [14]. Direct patient outcomes benefits are most important. If there are none, then there is low likelihood that HEMS use is appropriate or cost-beneficial when considered on a system basis. For patient-centered considerations, mor- tality is the most important and most commonly studied endpoint in HEMS trauma studies [12]. For non-injured patients, however, there are few easily applied scales to adjust for the inh erent acuity differences between gro und and air transported patients. Thus, direct assessment of mortality is quite difficult since analysis cannot control for the unadjusted (higher) mortality risk of the air trans- port cohort. Therefore, for non-trauma cases HEMS’ pa- tient benefits tend to be measured indirectly, via end- points that are either secondary (e.g. myocardial muscle salvage) [15] or surrogate (e.g. time-to-cath lab) [16]. Fortunately, for at least two commonly transported diag- nostic populations (cardiac and stroke), there are objec- tive data that allow direct correlation of time savings to improved mortality and morbidity [17,18]. While patient-centered outcomes are of course most important, other “outcomes benefits” (e.g. systems bene- fits) may also contribute to potential justification for in- cluding HEMS in a system. These benefits are comple- mentary to direct patient benefit. HEMS can allow for improved regional performance in getting non-trauma patients to definitive care such as pro vided by stroke cen - ters, cardiac catheterization labs, or operating rooms [19,20]. Open Access IJCM
Helicopter EMS beyond Trauma: Utilization of Air Transport for Non-Trauma Conditions 513 In the absence of randomized controlled trials-gener- ally viewed as nonfeasible for HEMS research [13,21] one approach for non-trauma is to demonstrate that use of HEMS allows for “far-away” patients to achieve the same good outcomes as are achieved for those who live near hospitals. This approach has been executed for car- diac [22], obstetric [23], and neonatal [24] patient popu- lations, with findings that HEMS allows for outcomes that are as good as those seen in patients presenting pri- marily to tertiary care centers. The remainder of this review addresses HEMS use for various non-trauma diagnoses. There are varying depths of evidence for various utilizations, but the goal of the discussion is to include all non-trauma situations for which there are at least some relevant studies. The most data are available for cardiac patients, with stroke fol- lowing. Sparser but still directly relevant evidence is available for non-trauma surgical cases, pediatrics, and obstetrics; these populations are addressed in order in the following sections of this review. 3. HEMS for Cardiac Patients The primary utilization of HEMS for cardiac cases is in the setting of ACS, most notably ST-elevation myocar- dial infarction (STEMI) needing percutaneous coronary intervention (PCI). Other diagnoses are certainly impor- tant, as outlined in the NAEMSP guidelines for helicop- ter use [3], but air transport’s logistics advantages have obvious potential for frequent use in time-critical STEMI. 3.1. Patient Safety In addition to the obvious and overriding importance of aviation safety (outside the scope of this review), lie questions about patients’ medical safety during air transport. Early data [25] indicating catecholamine rise during air medical transport suffered from lack of appro- priate ground EMS controls, and sympathetic “surge” never became an area of concern for HEMS. However, the early questions did prompt consideration of other potential dangers asso ciated with air transpo rt. The majo r issues to be considered were electrical and vibrational. Electrical considerations were focused on the ability of pacemakers to function properly in the aviation setting. In considering theoretical and practical concerns (e.g. pacemaker separation of patients’ intrinsic electrical sig- nals from transient environmental signals), specialists in cardiac transport were able to definitively demonstrate HEMS safety for paced patients [26]. When questions about the electrical environment were settled, focus turned to the movements and vibrations attendant to helicopter transport. In an era in which thrombolytic therapy was the primary treatment for STEMI, there were understandable concerns that high- frequency constant vibrations (such as from jet engines) could mediate increased risk of post-lysis bleeding. For- tunately, these risks turned out not to be encountered or manifest in increase in complication rates. Seminal work by Fromm et al. [27] in Texas (US), whose HEMS unit provided large numbers of post-lysis STEMI transports, demonstrated there was no increased bleeding or other risks in the post-lysis population. With patient safety being demonstrated, HEMS clini- cal researchers’ next task was to ascertain what outcomes benefits may be accrued with use of cardiac air transport. The benefits focused upon were primarily related to STEMI and time savings; these are covered next. 3.2. Moving STEMI Patients to the Cath Lab In terms of cardiac patient transports and time savings, there is increasing emphasis on getting patients with myocardial infarction to primary PCI as the treatment of choice if a 90-minute first-door-to-balloon time can be met; expedited prehospital care—including HEMS—will play an important role in cardiac care systems [28,29]. One of the major dichotomous benefits of HEMS is therefore simply getting patients to primary PCI within the window of benefit. Unlike the case for some diagnoses, for which crew expertise is a major (and perhaps the most important) factor mediating HEMS’ outcome improvement, for PCI transports the key appears to be time savings [16]. Well over a decade ago, cardiologists were positing that the time savings and associated earlier intervention was re- sulting in myocardial salvage and improved HEMS-re- lated morbidity outcomes such as a 2-day decrease in hospital length-of-stay [15]. In fact, early HEMS studies helped establish the over- all desirability of primary PCI as an alternative to throm- bolytic therapy. A major study (Air PAMI) randomized patients to community hospital lysis or transport (by ei- ther ground or air) for primary PCI. Air PAMI results were fascinating: the transported patients took much longer to get to definitive therapy (155 vs. 51 minutes) but had a 6-fold improvement in outcome as compared to those who were lysed. The study results were sufficiently compelling even on interim analysis, that the investiga- tion was halted before full enrollment targets were reached [30]. Ongoing study next demonstrated that despite the im- portance of meeting the dichotomous endpoint of “ar- rived at the cath lab in time for PCI,” there were still benefits to be gained by time savings ev en within th e PCI window. Time really is myocardium. Experts have writ- ten that the maximal benefit of primary PCI is accrued in the initial 60 minutes [31]. It is also known that each 15-minute decrement in time to PCI, from 150 minutes Open Access IJCM
Helicopter EMS beyond Trauma: Utilization of Air Transport for Non-Trauma Conditions 514 down to <90 minutes, is associated with 6.3 fewer deaths per 1000 patients treated [17]. Data from 2009 suggest that the inflection points of the time savings and mortal- ity benefit curve, are somewhere around 45 and 225 minutes; this means that time savings is associated with mortality benefit when patients get to PCI within 45 to 225 minutes of initial “door” time [32]. Considered from another perspective, each 30 minutes’ additional ische- mia time increases mortality by 8% - 10% [33]. Time savings on this level are distinctly possible with appro- priate use of HEM S [16]. 3.3. HEMS as Part of Cardiac Care Systems Improvements in times for individual patients inevitably lead to consideration as to how HEMS can be best inte- grated into systems of cardiac care. Work from both the US and Europe demonstrated the overarch ing cap ab ilities of HEMS as a tool for extending the reach of STEMI care networks for rapid provision of PCI [22]. There is growing system-based recognition of importance of transporting STEMI patients for PCI. A consortium panel of US EMS medical directors has identified as an evi- dence-based benchmark for quality prehospital care, the transport of STEMI patients to primary PCI within 90 minutes of EKG diagnosis [34]. Recent meta-analysis confirms the substantial outcomes benefits, in terms of both systems-level mortality and morbidity, of timely transfer of STEMI patients for mechanical reperfusion [35]. For some regions and patients, HEMS provides a vital capability to meet this benchmark. Just as focus on the entire process from symptom onset to opening of infarct-related artery is important for plan- ners of acute cardiac care, focus on pre-HEMS and post- HEMS activities is necessary to maximize transport-re- lated time savings benefits. In one of the most successful demonstrations of HEMS incorporation into a regional cardiac care system, Blankenship et al. [36] used a “be- fore-and-after” approach to examine endpoints of time savings and health outcomes associated with institution of a new triage and HEMS transfer system. The system’s goal was to expedite community hospital evaluation and referral of STEMI patients to a PCI center. Protocol changes effected midway through the study included: 1) community hospital STEMI care changes emphasizing time savings (e.g. elimination of heparin and nitroglyc- erin infusions), 2) simultaneous PCI lab and HEMS acti- vation from a single call to the receiving center, and 3) bypass of the receiving center’s Emergency Department (ED) after HEMS transport. In the Blankenship study [36] from Pennsylvania, for the main endpoint (community hospital presentation to wire-crossing time), the “after” period was associated with significantly shorter ti mes (105 vs. 205 minutes, p = 0.0001). Time savings were achieved by faster HEMS dispatch (from 35 to 16 minutes) and streamlining time intervals between HEMS dispatch and PCI center arrival (from 56 to 45 minutes). The proportion of patients with door to wire-crossing times under 90 minutes increased from 0% to 24%, and the percentage with door to wire- crossing times under 120 minutes also increased (from 2% to 67%). The study successfully made the point that with use of time as a surrogate endpoint, and one that was well-founded on current physiologic understanding, HEMS could be an important component of a system of care. The promising system-based results of the Blanken- ship group were replicated in a 2013 study that found that combination of HEMS with other streamlined refer- ral processes resulted in a trebling of likelihood of pa- tients getting door-to-balloon time within the desired 90-minute window [37]. The Pennsylvania results have been reproduced else- where. A study from Ohio (US), found that patients were nearly 3x more likely to have door-to-balloon times un- der the 90-minute target when they were transported us- ing a streamlined referral process (that included HEMS “autolaunch”) [37]. A Japanese report finds that, com- pared to ground ambulance transport, HEMS use in their particular system is associated with a half-hour’s decre- ment in times to angiographic evaluation and interven- tion [9]. A preliminary report on simultaneous HEMS dispatch and tertiary care hospital cardiac cath lab activa- tion by ground EMS providers making STEMI diagnosis during transport to a referring (non-PCI) hospital, found the referring hospital time was reduced from 79 to 31 minutes [20]. Others have also demonstrated the signifi- cant time savings able to be accrued from prehospital activation of HEMS for transport directly to the cath lab [38]. For systems-based use of HEMS, the entire system from prehospital through cath lab needs to be considered, and the role of helicopter transport carefully considered for potential integration as part of the overall care net- work. 3.4. Cost-Effectiveness Recently, a group from the large rural US state of Okla- homa has generated preliminary data intended for ulti- mate use in cost-effectiveness calculations. In this paper, the authors were the first to specifically tie time savings to estimated HEMS-mediated mortality improvement [16]. Time savings accrued with HEMS as compared to ground transport were calcu lated estimated using what is becoming a standard geographical information software (GIS) approach [21]. The authors found substantial time savings. Since the novel study methodology was imper- fect, the limited overall conclusions were that the data should serve as the basis for a larger analysis (now on- going) to assess whether the number-needed-to-treat (NNT) of 59 is consistently estimated in different areas. Open Access IJCM
Helicopter EMS beyond Trauma: Utilization of Air Transport for Non-Trauma Conditions 515 If the results of the initial study are replicated in the lar- ger analysis, the NNT of 59 has utility as a variable in the cost-effectiveness analyses important for HEMS and policy-makers. Systems planners designing cardiac care networks are well-advised to incorporate air (as well as ground) trans- port into planning. The importance of judicious planning has been demonstrated by work from Ohio (US). McMullan et al. [39] found that use of HEMS transport for cardiac patients is no guarantee of arrival to cath labs within recommended time frames. HEMS is potentially important as a part of a cardiac care system, but the air medical resource must be used wisely. A 2010 study revealed that centralization of cardiac catheterization resources, with appropriate build-up of EMS transfer systems, is significantly more cost-effec- tive than construction of multiple cardiac catheterization centers; the authors note that 20% of Americans live more than an hour away (by ground) from a cardiac catheterization center [40]. Complementary information is provided by a report by Peterson et al. [41] that HEMS integration into a cardiac care system allows for diagnos- tic catheterization to be performed at community hospi- tals, with rapid air transport for interv entional procedur es when needed. All of these data contribute to a co nclusion that air medical transport does have a role in optimizing cardiac care regionalization. 3.5. HEMS for Other Cardiac Cases The time advantage is also accrued for patients other than those being transported for primary PCI. For patients failing PCI at referring hospitals, HEMS has demon- strated utility as a backup system for rapid transfer for urgent surgical revascularization [42]. Work from the TRANSFER-AMI group suggests that expedited transfer for mechanical intervention after community hospital lysis is associated with a 50% reduction in a 30-day composite endpoint (death, reinfarction, recurrent ische- mia/reinfarction, CHF, or shock) [43]. Another category of “cardiac” patients that has re- ceived attention in the HEMS literature comprises those who have had cardiac arrest. In this broad category, ini- tial work proved true, the common-sense notion that HEMS was not indicated for patients in persistent non- traumatic cardiac arrest [44]. The authors of that study noted some potential logistics advantages (e.g., improved availability of ALS in rural settings) entailed in rural HEMS utilization, but they make a strong argument against HEMS benefit for patients in arrest at time of HEMS activation. For those patients who are resuscitated from cardiac arrest, though, the outcome is different; work by Werman et al. [45] demonstrates that appropri- ately dispatched HEMS can be beneficial in post-arrest patients. 4. HEMS for Neurological Patients The mantra “time is brain” evolved more recently than “time is myocardium,” but it is no less important. From early information that described benefits of time savings (such as with stroke patients) in terms of hours [46], the state of the evidence now supports time savings on smaller scales [18]. When considering how to streamline care on the level of these smaller scales—15 minutes’ increment can make a difference—HEMS becomes an asset to consider. 4.1. Patient Safety As was the case for cardiac cases, one of the first items to address was safety. For stroke patients in whom post- thrombolysis hemorrhagic conversion is a major concern, there were safety questions about helicopters and move- ment (including vibration). Two 1999 studies by Chalela [47] and Conroy [48] established that even in post-lysis patients, there were no increases in rates of stroke com- plications such as bleeds. In demonstrating the safety of HEMS use for even the sickest stroke patients, Conroy further posited that the relatively minimal “packaging” required for neuro patients translated into ideal setup for HEMS to save time [48]. 4.2. Time Savings It has for over a decade been postulated (with support from pooled analysis data) that there is stepwise out- comes improvement associated with each 90-minute im- provement in stroke lysis time (to 270 minutes) [49]. As previously noted, the time frame for which incremental improvement is achieved with more streamlined therapy has continually narrowed. In 2013, Saver et al. [18] drew a direct line between improved functional and vital out- come and incremental time s avings of as little as 15 min- utes. Given clear data from other facets of the HEMS literature that air medical transport very often results in time savings of this magnitude [16,50], it seems quite likely that stroke care networks will continue to benefit from appropriate use of HEMS. Time savings due to HEMS is relatively easy to char- acterize for stroke patients, but streamlining pre-neu- rologic center times can potentially aid a breadth of pa- tients. There are few data describing HEMS crews’ sav- ings of time for other neurological conditions, but it is nevertheless the case that (at least occasionally) such time savings are likely to occur and are a critical con- tributor to improved outcome. 4.3. HEMS as Part of Stroke Systems Stroke patients were among those emerging time-critical populations for whom regionalization of care translated Open Access IJCM
Helicopter EMS beyond Trauma: Utilization of Air Transport for Non-Trauma Conditions 516 into advanced therapies’ being available primarily at re- gional centers, and even in the late 1990s air medical transport seemed well-positioned to be a part of stroke systems. A Resource Document for a position statement of the National Association of EMS Physicians recommends air transport of stroke patients if the closest fibrinolytic- capable facility is more than an hour away by ground [51]. The American Stroke Association Task Force on Development of Stroke Systems [52] identified HEMS as an important part of stroke systems. The report states “Air transport should be cons idered to shorten th e time to treatment, if appropriate.” Authors writing about the utility of HEMS in stroke care systems generally refer to the ability of HEMS to “extend the reach” of tertiary care centers providing time-critical care [19]. The emphasis on time is not unlike the situation with STEMIs: highly trained crew with critical care experience is of course important, but the main contribution of air transport is expedited movement of patients to time-windowed therapy. The case for HEMS use to optimize stroke lysis rates has been convincingly made in a national registry-based study from Austria. Reiner-Deitmeyer et al. [53] used “administration of thrombolytic therapy” as their end- point, focusing on the capability of air transport to get patients to lysis-capable centers. The authors found that both scene and interfacility HEMS transport allowed for higher thrombolysis rates, and that scene HEMS re- sponse was associated with the highest chances of stroke patients’ receiving thrombolytics within 90 minutes of sy mptom onset. The Austrian study’s findings regarding scene trans- ports for stroke confirmed earlier findings from a rural US region (north Florida and southern Georgia). Over a decade ago, Silliman et al. [54] explored the contribution of HEMS to facilitation of patient transport from rural “scenes” to a stroke center. HEMS was called to the scene for patients with suspected stroke, and the diagno- sis was usually correct (stroke was ultimately diagnosed at the receiving center in 76% of cases). During the study period, stroke transports comprised 4% of the HEMS service volume, but HEMS-transported stroke patients accounted for nearly a fourth (23%) of all patients re- ceiving stroke lysis at the receiving center. In short, HEMS was not overused, stroke was not overdiagnosed by prehospital personnel, and many patients were lysed, who would otherwise have not had a chance to receive time-windowed therapy. The lessons on “scene” calls for stroke have been dem- onstrated by others as well. For example, the French have reported HEMS response to cruise ships at sea, enabling time-critical and successful lytic therapy for stroke [55]. The authors from the Florida study and also those from Austria join others in demonstrating that a strictly ap- plied stroke triage protocol (roughly based on the trauma triage model) can widen a stroke center’s coverage area. Even in highly developed urban systems, there is some role for judicious employment of air medical resources to operationalize the regional adherence to the adage “time is brain [8,56].” _ENREF_38. From the systems perspective, HEMS is an important part of stroke care networks in which outcomes are im- proved with stroke care in specialized centers [57]. Addi- tion of air medical resources into logistics calculations halves the numbers of Americans who lack timely (within one hour) access to a primary stroke center (from 136 million to 63 million) [58]. 4.4. Cost-Effectiveness The fact that there is advantage in administering stroke thrombolytic therapy in a more timely fashion is only true to a certain time point. Even for stroke lysis proto- cols that allow for “late” thrombolysis (up to 4.5 hours post-symptom onset) there remains a “wall” that is not safely crossed. If the patient doesn’t get to a lysis-capa- ble center within a certain time frame, the opportunity at morbidity- and mortality-improving lysis care is lost. This strict time-windowing of stroke therapy has gener- ated an important endpoint for HEMS use in stroke care. If HEMS can get patients to stroke lysis-capable centers within a certain time frame, thus allowing them to re- ceiving this salutary therapy, then that is an important benefit of air transport. However, as is the case with any resource, judgment must be exercised. For cases in which time-windowed therapy has already been administered, the costs and be- nefits calculations for HEMS employment are quite dif- ferent as compared to, for example, movement of lysis- eligible patients [59]. Just as employment of HEMS for stroke patients who’ve already received time-windowed therapy may be questionable, there are data suggesting room for im- provement in HEMS triage of non-stroke neurological patients. In a study from Boston (US), authors examined a variety of neurology/neurosurgery patients (largely non-trauma) and concluded there were many cases of HEMS use for neurological conditions that did not in fact warrant air transport [60]. While data are being developed to address questions in more detail, there is cost-effectiveness evidence that strongly supports appropriate use of HEMS for stroke care. Silbergleit et al. [61] have clearly shown that air medical transport is quite cost-effective when it enables stroke patients to receive thrombolytic therapy at receiv- ing centers. 4.5. HEMS for Other Neurological Diagnoses A previously cited study from Boston included mention Open Access IJCM
Helicopter EMS beyond Trauma: Utilization of Air Transport for Non-Trauma Conditions 517 of various diagnostic categories (e.g. tumor with mass effect) for which HEMS transport was potentially useful [60]. There are few data in the HEMS literature that sys- tematically address air medical transport use for non- trauma neurological conditions other than stroke. For stroke and other neurological conditions, it has been suggested that the time-critical nature of these dis- eases lends itself to early intervention by HEMS crews. Neurologists considering how to get their patients lead- ing-edge therapy have theorized about potential benefits of saving an hour or more by having specially trained HEMS crews intervene upon arrival at referring hospital [62]. 5. HEMS for Non-Trauma Surgical Patients It is somewhat ironic, given the trauma surgery roots of air medical transport in general, that there is relatively sparse literature addressing HEMS for non-trauma sur- gical patients. Most likely this is not because of lack of occasional HEMS utility in these patients, but rather due to the heterogeneity of (and difficulty to study HEMS use in) non-trauma surgical patients. 5.1. Flight Crews and Stabilization of Patients What HEMS can bring to the table—in part due to ex- perience with trauma—is the rapid stabilization of surgi- cal patients and the direct transport of those patients to the operating room (OR), bypassing the receiving center ED [5]. Whether the patient has perforated viscus or splenic rupture from infection, there are theoretical (yet hard to demonstrate) benefits from expedited air trans- port. For the most part, these applications of HEMS must be considered on a case-by-case basis. Other components of HEMS care that are doubtless helpful to some general surgical patients are mentioned in the final section of this review. These “supportive care” benefits from expert flight crews are as applicable in critically ill surgical patients, as they are in other di- agnoses. 5.2. Air Transport of Aortic Aneurysm There is one group of surgical patients that has time- criticality, benefits from direct-to-OR transport, and ap- pears well-situated to gain from rapid HEMS transport: patients with leaking AAA. Perhaps because this patient population is so similar to the trauma population with whom HEMS crews have familiarity, there have been reports of HEMS use to improve outcome in AAA pa- tients. In fact, one of the earliest mentions of the concept of “direct-to-OR” transports came in 1989, when Kent et al. [5]described their rural state (Alabama, US) experience with HEMS’ transferring patients directly into the OR. Subsequent assessment of patients in an urban setting (Boston, US) by Shewakramani et al. [63] confirmed the utility of air transport for these most unstable patients. They made the case that while overall numbers and dif- ficulty with control groups serves as a barrier to concrete statistical comparison between air versus ground trans- port, it seems highly likely that expedited movement of leaking-AAA patients into the OR is usually desirable. 6. HEMS for Non-Trauma Pediatrics Asis the case for many other categories of non-tra uma, the group constituting “pediatrics” is characterized by breadth that precludes straightforwa rd outc omes studies. What are present in the pediatric literatu re, are data describing one major subgroup (neonates) and one major procedural intervention (airway management). These are considered in this section. Although the specific-diagnosis informa- tion for pediatric patients is lacking, the fact remains that regionalization of care is quite common in pediatric sys- tems and so it is particularly likely th at HEMS (including specialized teams) will have a role in pediatric care sys- tems. 6.1. HEMS and Neonatal Systems of Care Two decades ago, Pieper et al. [64] performed a descrip- tive analysis of HEMS (and ground) neonatal transfers, and concluded that HEMS was a critical part of a region- alized neonatal critical care network. The study was one of the earliest to establish that air medical transport can be an important part of neonatal care systems. Subsequent studies provided an increasing body of evidence sup- porting a contention that even patients of high acuity and tenuous stability, such as ventilated neonates, suffer no adverse effect from air as compared to ground transport modality [65]. The literature includes population-b ased analyses such as that of Berge et al. [24] from Norway; the Scandina- vians described a 14-y ear series of 256 neonatal transports . They found that the mortality of those transported from long distances was no worse than those who came by ground from nearby the receiving centers. Just as Straumann’s Swiss group [22] had concluded that HEMS allowed far-away patients to benefit from timely access t o specialized care and have outcomes just as good as “close-in” patients, Berge’s study made the case that HEMS was an “equalizer” of outcomes for neonates who were located distant from receiving centers. The Norwegian results included findings of HEMS crews’ occasional performance of life-saving interven- tions in transported neonates [24]. The authors also found that, as compared to the pre-transport time frame at re- ferring hospitals, air medical transport crews were actu- ally able to effect improvements in oxygenation, ventila- Open Access IJCM
Helicopter EMS beyond Trauma: Utilization of Air Transport for Non-Trauma Conditions 518 tion, and circulation during the transport phase. These results dovetailed with data fro m Miami reported by Hon et al. [65], who assessed air transport versus ground transport (by the same university-based transport team) and found that helicopter flight was not associated with any worsening in physiology in critical intubated neo- nates. 6.2. Flight Crew Airway Management For pediatric non-trauma, there are few data on HEMS transport of non-neonat a l pat i e nt s. There is, howe ve r , one other source of information relevant to consideration of air medical transport of pediatrics: the airway manage- ment literature. Even as ped iatric endotracheal intubation (ETI) is being increasingly revealed as difficult and fre- quently unsuccessful in the ground EMS setting [66], HEMS crews are reporting favorable results. Air medical transport crews are intervening to provide highly suc- cessful pediatri c ETI, o ften wi th rates ri valing t hose of t he in-hospital setting [67,68]. Furthermore, air medical transport crews are able to intervene after ETI and provide important adjustments in cuff pressures, insertion depths, and tube size [69,70]. 7. HEMS for Obstetrics The most cases, the optimal neonatal transport system is the maternal intrauterine environment. With the principle that safe and effective obstetrics transports improve both material and fetal outcome, HEMS use for pregnant pa- tients has been long d escribed. Initial reports outlined the safety (in terms of being able to predict which patients would not deliver while in-flight [71], and subsequent data outlined time and systems benefits to air medical obstetrics transports. 7.1. Obstetrics Systems of Care Traditional “extending the reach of the system” advan- tages as previously mentioned for other diagnostic groups, are also applicable to obstetrics patients—HEMS increases coverage area for centralized maternal-fetal hospitals. Particularly in areas characterized by a paucity of maternal-fetal medical specialists, HEMS has been noted to be a vital contributor to system-wide success in optimizing outcomes [72]. In addition to the ad vantage of simply providing access to centralized care, obstetrics HEMS transports also bring another salient endpoint to the discussion: minimized out-of-hospital time. 7.2. Minimized Out-of-Hospital Time Minimization of out-of-hospital time applies to HEMS use for obstetrics as much as for any transport population. Over three decades ago, Elliott et al. [23] extoled the virtues of air medical obstetrics transport not because of crew capabilities, but rather because of the reduction in intratransport (out-of-hospital) time as compared to ground ambulance use. Elliott’s Los Angeles group em- phasized that achievement of the major goal of having high-risk patients deliver at receiving centers (thus using the mother as the “best transport incubator”) was often only enabled by use of fast-moving helicopters. Aircraft speed allowed obstetricians to be sufficiently comfort- able with the low risk of intratransport delivery (unde- sirable, regardless of transport vehicle) that laboring pa- tients could be moved to centers with needed expertise in maternal-fetal medicine. The advantage reported by the California group was not simply theoretical: referring facility obstetricians reported that in the absence of HEMS availability, a quarter of the cases in their series who were transported by HEMS would have been deliv- ered at referring hospitals. In keeping with the sense that maternal and fetal out- comes are both optimized by having deliveries occur at specialized centers (rather than rural referring hospitals), van Hook et al. [71] reported their rural Texas experi- ence as being similar to that from the Californians. Whereas the Los Angeles-area group noted traffic con- gestion was the primary basis for concerns about long transport times, in Texas the problem was more one of geography. Over long distances, helicopter transport al- lowed for safe and effective setup of obstetrics regional centers to which patients were transported for delivery. van Hook’s group concluded that their case series sup- porte d the view “held b y most”, that “maternal/fetal risks associated with HEMS transport are at most, minimal [71].” As previously mentioned, one of the most important HEMS benefits for obstetrics is reduction of the chances of intratransport delivery. This minimization of “out-of- hospital” time is at least as important as any actual time benefits of getting patients to tertiary maternal/fetal me- dical centers of excellence. A Japanese group has pub- lished their experience that und erlies the priority of mini- mizing out-of-hospital time. Ohara et al. [72] point out that their country has limited tertiary care facilities for maternal/fetal medicine, and that maternal (prenatal) transport by air is an important part of providing region- alized care. In assessing a series of 26 HEMS transfers of pregnan t women to their institution , Ohara’s group found that HEMS use was associated with savings of 101 min- utes’ out-of-hospital time (median flight time, 24 minutes; median estimated ground transport time, 125 minutes). Certainly, to those who provide care for high-risk obstet- rics patients, decreasing the out-of-hospital time (and thus the time frame of risk for intratransport delivery), savings of 101 minutes is a substantial benefit. Open Access IJCM
Helicopter EMS beyond Trauma: Utilization of Air Transport for Non-Trauma Conditions 519 8. Other Non-Trauma HEMS Issues The preceding diagnostic situations represent those for which there are at least some available data directly ad- dressing HEMS and outcomes benefit. There are many other situations that are encountered, for which air medi- cal transport’s crew capabilities and/or logistics advan- tages may be of benefit to patients or prehospital care systems. The list of potential types of individual cases for which air m edical transpo rt could possibl y be useful i s too far too lengthy to enumerate in this review. Instead, this final section of the review will address some HEMS benefits that have potential outcomes utility for myriad non-trauma patient types. 8.1. Time Savings There are some areas in which there is growing under- standing of time-criticality of disease management. One example of such, is the population of patients with seps is. with the advent of studies demonstrating improved out- come from early goal-directed therapy. Recent reviews of sepsis care emphasize the importance of the six-hour goal for institution of high-level sepsis care [73]. While this time frame seems lengthy for air transport in some urban areas, it is quite conceivable that HEMS crews’ capabilities could help bring therapeutic approaches and experience to isolated-region patients who would other- wise miss the 6-hour window. On the logistics front, those considering potential benefits of HEMS should not always assume that air transport doesn’ t save time if ground transport is “kno wn to be available” at referring hospitals. The authors of a logistics study from the University of Wisconsin [50] assessed transport times from their 20-hospital network and found the average HEMS total transport time over the study period was at least as good as the best ground transport time. This finding was despite the fact that for many hospitals ground EMS was on-site at the time of transport. Furthermore, the authors found there was clinically significant time savings for all institutions. For close-by hospitals, patients accrued an average of 10 minutes’ time savings. From further-away hospitals, benefits were more marked: HEMS transport times were up to 45 minutes shorter than achievable by ground transport. 8.2. Critical Medicine Delivery Perhaps the easiest cases to consider first, are those in which there is clear logistics and speed capability pro- vided by HEMS that is simply not available by surface transport. Examples from the literature include such situations as use of an aircraft to get a young adult life- saving prostacyclin for adult respiratory distress syn- drome (ARDS) [74]. In a similar case, a Canadian group described use of air transport to get critically needed an- tidotes (fomepizole in one patient, digoxin antibodies in another) to patients up to 6 hours faster than would have been the case had therapy been delayed to ultimate arri- val at receiving centers [75]. Certainly, case reports do not constitute sole or suffi- cient basis to justify HEMS existen ce. On the other hand, these “sporadic” case reports probably reflect a low—but nonzero—frequency with which air assets’ logistical ad- vantages mediate significant outcomes improvement. Just as is the case with trauma, for non-trauma cases there will occasionally be times wh en physicians making transport decision s should remember the time and related benefits accrued only with HE M S. 8.3. Airway and Ventilatory Management There are data from the broader HEMS literature (in- cluding from trauma cases) that can inform judgments about potential benefit from crew expertise. Perhaps the most obvious of these areas of crew contribution are in the airway and ventilatory management arena. The high ETI success rates of HEMS crews have been addressed elsewhere in this review and in the broader literature [76]. _ENREF_59 The ability to manage air- ways with high success rates can accrue advantages to a variety of non-trauma cases. Airway expertise from HEMS crews is not limited to performance of ETI itself. HEMS benefits to patients are seen even after ETI. This is probably due to ventilator management, avoidance of hyperventilation, and better recognition and management of hypoxemia [77,78]. It is illustrative that HEMS has been shown to improve out- come for head-injured patients even when HEMS arrives after ETI has been performed. While focused on head injury, the work of Davis et al. [79] from San Diego is telling: even when ETI is performed by ground EMS, HEMS transport improves outcome as compared with ground transport because of post-ETI ventilation prac- tices. Close attention to parameters such as end-tidal CO2, as well as intensive training and frequent experience with ventilator management, are likely responsible for the more stable peri-ETI physiology seen with HEMS as compared to ground transport [79-82]. While difficult to measure on a broad basis, it is quite likely that such at- tention to oxygenation and ventilation is helpful in a va- riety of non-trauma conditions. 8.4. Critical Care Expertise In addition to airway management expertise, HEMS crews bring to bear critical care experience that can (like ventilator management) be difficult to statistically sum- marize but which is nonetheless occasionally important. Open Access IJCM
Helicopter EMS beyond Trauma: Utilization of Air Transport for Non-Trauma Conditions 520 For some patients, there is simply no substitute for the technical capabilities and critical care expertise brought to bear by many air medical crews [83]. A 2009 study from France demonstrates some of the mechanisms for HEMS’ improvement in outcome. Berlot et al. [84] found—in trauma patients, but with likely ex- trapolation to non-trauma—that as compared to ground EMS, HEMS transport was associated with improved outcomes due to better hemodynamic management. After being neglected for too long as a priority for acute-care (and prehospital) medicine, the subject of pain care is receiving its due. Experts in prehospital care have written that pain care is a valid endpoint in and of itself [85,86]. Whether due to protocol restrictions on ground EMS or other factors, HEMS providers tend to be far more diligent than ground ambulance providers in as- sessing and treating pain [86-88]. As is the case for air- way and ventilator management, this component of care has potential benefit for a breadth of non-trauma patient types. 9. Conclusion In summary, HEMS have the potential to bring both crew expertise and streamlined times to non-trauma patients. The importance of considering logistics benefits is un- derlined by even brief consideration of the enormous breadth of non-trauma situations in which savings of time can contribute to optimal outcome. As outlined in the NAEMSP guidelines for HEMS use [3], these indica- tions include dozens of situations ranging from tumor- mediated cord compression needing radiation therapy, to the need for emergency delivery of an eclamptic, and to the need for emergency valvuloplasty. The spectrum of individual non-trau ma patient types that could potentially benefit from HEMS is daunting in its breadth, but the task of considering benefits of HEMS in these cases is worthy of attention for both clinicians and researchers. It is hoped that the information in this review can inform and assist those efforts. REFERENCES [1] C. Moga and C. Harstall, “Air Ambulance Transportation with Capabilities to Provide Advanced Life Support: IHE Report to the Ministry of Health,” Institute of Health Eco- nomics, Calgary, 2007. [2] S. M. Galvagno Jr., S. Thomas, C. Stephens, E. R. Haut, J. M. Hirshon, D. Floccare and P. Pronovost, “Helicopter Emergency Medical Services for Adults with Major Trauma,” Cochrane Database of Systematic Reviews, Vol. 3, 2013, Article ID: CD009228. [3] D.P. Thomson, S.H. Thomas, “Guidelines for air medical dispatch,” Prehospital Emergency Care, Vol. 7, No. 2, 2003, pp. 265-271. http://dx.doi.org/10.1080/10903120390936923 [4] J. Varon, R. Fromm and P. Marik, “Hearts in the Air,” Chest, Vol. 124, No. 5, 2003, pp. 1636-1637. http://dx.doi.org/10.1378/chest.124.5.1636 [5] R. Kent, L. Newman, R. Johnson and R. Carraway, “Heli- copter Transport of Ruptured Abdominal Aortic Aneu- rysms,” Ala Med, Vol. 58, 1989, pp. 13-14. [6] J. Bruhn, K. Williams and R. Aghababian, “True Costs of Air Medical vs. Ground Ambulance Systems,” Air Medi- cal Journal, Vol. 12, No. 8, 1993, pp. 262-268. http://dx.doi.org/10.1016/S1067-991X(05)80311-6 [7] D. P. Davis, J. Peay, B. Good, M. J. Sise, F. Kennedy, A. B. Eastman, T. Velky and D. B. Hoyt, “Air Medical Re- sponse to Traumatic Brain Injury: A Computer Learning Algorithm Analysis,” Journal of Trauma, Vol. 64, No. 4, 2008, pp. 889-897. http://dx.doi.org/10.1097/TA.0b013e318148569a [8] S. H. Thomas, L. H. Schwamm and M. H. Lev, “Case Records of the Massachusetts General Hospital. Case 16-2006. A 72-Year-Old Woman Admitted to the Emer- gency Department Because of a Sudden Change in Men- tal Status,” New England Journal of Medicine, Vol. 354, No. 21, 2006, pp. 2263-2271. http://dx.doi.org/10.1056/NEJMcpc069007 [9] N. Hata, N. Kobayashi, T. Imaizumi, S. Yokoyama, T. Shinada, J. Tanabe, K. Shiiba, Y. Suzuki, H. Matsumoto and K. Mashiko, “Use of an Air Ambulance System Im- proves Time to Treatment of Patients with Acute Myo- cardial Infarction,” Internal Medicine, Vol. 45, No. 2, 2006, pp. 45-50. http://dx.doi.org/10.2169/internalmedicine.45.1399 [10] T. Imaizumi, N. Hata, N. Kobayashi, S. Yokoyama, T. Shinada, K. Tokuyama, M. Ishikawa, K. Shiiba, H. Ma- tsumoto, K. Takuhiro and K. Mashiko, “Early Access to Patients with Life-Threatening Cardiovascular Disease by an Air Ambulance Service,” Journal of Nippon Medical School, Vol. 71, No. 5, 2004, pp. 352-356. http://dx.doi.org/10.1272/jnms.71.352 [11] C. Palmer, J. McMullan, W. Knight, M. Gunderman and W. Hinckley, “Helicopter Scene Response for a STEMI Patient Transported Directly to the Cardiac Catheteriza- tion Laboratory,” Air Medical Journal, Vol. 30, No. 6, 2011, pp. 289-292. http://dx.doi.org/10.1016/j.amj.2011.08.005 [12] S. H. Thomas and A. Arthur, “Helicopter EMS: Research Endpoints and Potential Benefits,” EM International, 2012. [13] D. J. Floccare, D. F. Stuhlmiller, S. A. Braithwaite, S. H. Thomas, J. F. Madden, D. G. Hankins, H. Dhindsa and M. G. Millin, “Appropriate and Safe Utilization of Helicopter Emergency Medical Services: A Joint Position Statement with Resource Document,” Prehospital Emergency Care, Vol. 17, No. 4, 2013, pp. 521-525. http://dx.doi.org/10.3109/10903127.2013.804139 [14] I. Blumen, “A Safety Review and Risk Assessment in Air Medical Transport,” Air Medical Physician Association, Salt Lake City, 2002. [15] K. S. Berns, D. G. Hankins and S. P. Zietlow, “Compari- son of Air and Ground Transport of Cardiac Patients,” Air Medical Journal, Vol. 20, No. 6, 2001, pp. 33-36. Open Access IJCM
Helicopter EMS beyond Trauma: Utilization of Air Transport for Non-Trauma Conditions 521 http://dx.doi.org/10.1016/S1067-991X(01)70008-9 [16] M. Phillips, A. O. Arthur, R. Chandwaney, J. Hatfield, B. Brown, K. Pogue, M. Thomas, M. Lawrence, M. McCar- roll, M. McDavid and S. H. Thomas, “Helicopter Trans- port Effectiveness of Patients for Primary Percutaneous Coronary Intervention,” Air Medical Journal, Vol. 32, No. 3, 2013, pp. 144-152. http://dx.doi.org/10.1016/j.amj.2012.08.007 [17] B. K. Nallamothu, E. H. Bradley and H. M. Krumholz, “Time to Treatment in Primary Percutaneous Coronary Intervention,” New England Journal of Medicine, Vol. 357, 2007, pp. 1631-1638. http://dx.doi.org/10.1056/NEJMra065985 [18] J. L. Saver, G. C. Fonarow, E. E. Smith, M. J. Reeves, M. V. Grau-Sepulveda, W. Pan, D. M. Olson, A. F. Hernan- dez, E. D. Peterson and L. H. Schwamm, “Time to Treat- ment with Intravenous Tissue Plasminogen Activator and Outcome from Acute Ischemic Stroke,” JAMA, Vol. 309, No. 23, 2013, pp. 2480-2488. http://dx.doi.org/10.1001/jama.2013.6959 [19] W. M. Konstantopoulos, J. Pliakas, C. Hong, K. Chan, G. Kim, L. Nentwich and S. H. Thomas, “Helicopter Emer- gency Medical Services and Stroke Care Regionalization: Measuring Performance in a Maturing System,” Ameri- can Journal of Emergency Medicine, Vol. 25, No. 2, 2007, pp. 158-163. http://dx.doi.org/10.1016/j.ajem.2006.06.016 [20] S. H. Thomas, C. Kociszewski, R. J. Hyde, P. J. Brennan and S. K. Wedel, “Prehospital Electrocardiogram and Early Helicopter Dispatch to Expedite Interfacility Trans- fer for Percutaneous Coronary Intervention,” Critical Pathways in Cardiology, Vol. 5, No. 3, 2006, pp. 155- 159. http://dx.doi.org/10.1097/01.hpc.0000234809.93495.e3 [21] Z. J. Rhinehart, F. X. Guyette, J. L. Sperry, R. M. For- sythe, A. Murdock, L. H. Alarcon, A. B. Peitzman and M. R. Rosengart, “The Association between Air Ambulance Distribution and Trauma Mortality,” Annals of Surgery, Vol. 257, No. 6, 2013, pp. 1147-1153. http://dx.doi.org/10.1097/SLA.0b013e31827ee6b0 [22] E. Straumann, S. Yoon and B. Naegeli, “Hospital Trans- fer for Primary Coronary Angioplasty in High Risk Pa- tients with Acute Myocardial Infarction,” Heart, Vol. 82, 1999, pp. 415-419. [23] J. Elliott, D. O’Keeffe and R. Freeman, “Helicopter Transportation of Patients with Obstetric Emergencies in an Urban Area,” American Journal of Obstetrics & Gy- necology, Vol. 143, 1982, pp. 157-162. [24] S. Berge, C. Berg-Utby and E. Skogvoll, “Helicopter Transport of Sick Neonates: A 14-Year Population-Based Study,” Acta Anaesthesiologica Scandinavica, Vol. 49, No. 7, 2005, pp. 999-1003. http://dx.doi.org/10.1111/j.1399-6576.2005.00712.x [25] A. Tyson, D. Sundberg, D. Sayers, K. Ober and R. Snow, “Plasma Catecholamine Levels in Patients Transported by Helicopter for Acute Myocardial Infarction and Unstable Angina Pectoris,” American Journal of Emergency Medi- cine, Vol. 6, No. 5, 1988, pp. 435-438. http://dx.doi.org/10.1016/0735-6757(88)90240-9 [26] R. Fromm, D. Taylor, L. Cronin, W. McCallum and R. Levine, “The Incidence of Pacemaker Dysfunction during Helicopter Air Medical Transport,” American Journal of Emergency Medicine, Vol. 10, No. 4, 1992, pp. 333-335. http://dx.doi.org/10.1016/0735-6757(92)90014-O [27] R. Fromm, E. Hoskins and L. Cronin, “Bleeding Compli- cations Following Initiation of Thrombolytic Therapy for Acute Myocardial Infarction: A Comparison of Helicop- ter-Transported and Nontransported Patients,” Annals of Emergency Medicine, Vol. 20, No. 8, 1991, pp. 892-895. http://dx.doi.org/10.1016/S0196-0644(05)81433-7 [28] M. R. Le May, D. Y. So, R. Dionne, C. A. Glover, M. P. Froeschl, G. A. Wells, R. F. Davies, H. L. Sherrard, J. Maloney, J. F. Marquis, E. R. O’Brien, J. Trickett, P. Poirier, S. C. Ryan, A. Ha, P. G. Joseph and M. Labinaz, “A Citywide Protocol for Primary PCI in ST-Segment Elevation Myocardial Infarction,” New England Journal of Medici ne, Vol. 358, No. 3, 2008, pp. 231-240. http://dx.doi.org/10.1056/NEJMoa073102 [29] E. Keeley and L. Hills, “Clinical Therapeutics: Primary PCI for Myocardial Infarction with ST-Segment Eleva- tion,” New England Journal of Medicine, Vol. 356, No. 1, 2007, pp. 47-52. http://dx.doi.org/10.1056/NEJMct063503 [30] C. Grines, D. Westerhausen and L. Grines, “A Random- ized Trial of Transfer for Primary Angioplasty versus On-Site Thrombolysis in Patients with High-Risk Myo- cardial Infarction (Air PAMI Trial),” Journal of the American College of Cardiology, Vol. 39, No. 11, 2002, pp. 1713-1719. http://dx.doi.org/10.1016/S0735-1097(02)01870-3 [31] D. B. Diercks, M. C. Kontos, J. E. Weber and E. A. Am- sterdam, “Management of ST-Segment Elevation Myo- cardial Infarction in EDs,” American Journal of Emer- gency Medicine, Vol. 26, No. 1, 2008, pp. 91-100. http://dx.doi.org/10.1016/j.ajem.2007.06.014 [32] S. S. Rathore, J. P. Curtis, J. Chen, Y. Wang, B. K. Nal- lamothu, A. J. Epstein and H. M. Krumholz, “Association of Door-to-Balloon Time and Mortality in Patients Ad- mitted to Hospital with ST Elevation Myocardial Infarc- tion: National Cohort Study,” BMJ, Vol. 338, 2009, p. b1807. [33] D. S. Pinto, A. J. Kirtane, B. K. Nallamothu, S. A. Mur- phy, D. J. Cohen, R. J. Laham, D. E. Cutlip, E. R. Bates, P. D. Frederick, D. P. Miller, J. P. Carrozza Jr., E. M. Antman, C. P. Cannon and C. M. Gibson, “Hospital De- lays in Reperfusion for ST-Elevation Myocardial Infarc- tion: Implications When Selecting a Reperfusion Strat- egy,” Circulation, Vol. 114, No. 19, 2006, pp. 2019-2025. http://dx.doi.org/10.1161/CIRCULATIONAHA.106.6383 53 [34] J. B. Myers, C. M. Slovis, M. Eckstein, J. M. Goodloe, S. M. Isaacs, J. R. Loflin, C. C. Mechem, N. J. Richmond and P. E. Pepe, “Evidence-Based Performance Measures for Emergency Medical Services Systems: A Model for Expanded EMS Benchmarking,” Prehospital Emergency Care, Vol. 12, No. 2, 2008, pp. 141-151. http://dx.doi.org/10.1080/10903120801903793 [35] G. De Luca, G. Biondi-Zoccai and P. Marino, “Transfer- ring Patients with ST-Segment Elevation Myocardial In- Open Access IJCM
Helicopter EMS beyond Trauma: Utilization of Air Transport for Non-Trauma Conditions 522 farction for Mechanical Reperfusion: A Meta-Regression Analysis of Randomized Trials,” Annals of Emergency Medicine, Vol. 52, No. 6, 2008, pp. 665-676. http://dx.doi.org/10.1016/j.annemergmed.2008.08.033 [36] J. C. Blankenship, T. A. Haldis, G. C. Wo od, K. A. Skeld- ing, T. Scott and F. J. Menapace, “Rapid Triage and T r ans- port of Patients with ST-Elevation Myocardial Infarction for Percutaneous Coronary Intervention in a Rural Health System,” American Journal of Cardiology, Vol. 100, No. 6, 2007, pp. 944-948. http://dx.doi.org/10.1016/j.amjcard.2007.04.031 [37] A. P. Reimer, F. M. Hustey and D. Kralovic, “Decreasing Door-to-Balloon Times via a Streamlined Referral Proto- col for Patients Requiring Transport,” American Journal of Emergency Medicine, Vol. 31, No. 3, 2013, pp. 499- 503. http://dx.doi.org/10.1016/j.ajem.2012.09.031 [38] S. Cheskes, L. Turner, R. Foggett, M. Huiskamp, D. Popov, S. Thomson, G. Sage, R. Watson and R. Verbeek, “Paramedic Contact to Balloon in Less than 90 Minutes: A Successful Strategy for ST-Segment Elevation Myocar- dial Infarction Bypass to Primary Percutaneous Coronary Intervention in a Canadian Emergency Medical System,” Prehospital Emergency Care, Vol. 15, No. 4, 2011, pp. 490-498. [39] J. T. McMullan, W. Hinckley, J. Bentley, T. Davis, G. J. Fermann, M. Gunderman, K. W. Hart, W. A. Knight, C. J. Lindsell, C. Miller, A. Shackleford and W. Brian Gibler, “Ground Emergency Medical Services Requests for Helicopter Transfer of ST-Segment Elevation Myocardial Infarction Patients Decrease Medical Contact to Balloon Times in Rural and Suburban Settings,” Academic Emer- gency Medicine, Vol. 19, No. 2, 2012, pp. 153-160. http://dx.doi.org/10.1111/j.1553-2712.2011.01273.x [40] T. W. Concannon, D. M. Kent, S. L. Normand, J. P. Newhouse, J. L. Griffith, J. Cohen, J. R. Beshansky, J. B. Wong, T. Aversano and H. P. Selker, “Comparative Ef- fectiveness of ST-Segment-Elevation Myocardial Infarc- tion Regionalization Strategies,” Circulation: Cardiovascu- lar Quality and Outcomes, Vol. 3, 2010, pp. 506-513. http://dx.doi.org/10.1161/CIRCOUTCOMES.109.908541 [41] L. F. Peterson and L. R. Peterson, “The Safety of Perfor- ming Diagnostic Cardiac Catheterizations in a Mobile Ca- theterization Laboratory at Primary Care Hospitals,” An- giology, Vol. 55, No. 5, 2004, pp. 499-506. http://dx.doi.org/10.1177/000331970405500505 [42] A. D. Frutkin, S. K. Mehta, T. Patel, P. Menon, D. M. Safley, J. House, C. W. Barth Ⅲ, J. A. Grantha m and S. P. Marso, “Outcomes of 1,090 Consecutive, Elective, Non- selected Percutaneous Coronary Interventions at a Com- munity Hospital without Onsite Cardiac Surgery,” Ameri- can Journal of Cardiology, Vol. 101, No. 1, 2008, pp. 53- 57. http://dx.doi.org/10.1016/j.amjcard.2007.07.047 [43] W. J. Cantor, D. Fitchett, B. Borgundvaag, J. Ducas, M. Heffernan, E. A. Cohen, L. J. Morrison, A. Langer, V. Dzavik, S. R. Mehta, C. Lazzam, B. Schwartz, A. Casa- nova, S. G. Goodman and T.-A.T. Investigators, “Routine Early Angioplasty after Fibrinolysis for Acute Myocardial Infarction,” The New England Journal of Medicine, Vol. 360, No. 26, 2009, pp. 2705-2718. http://dx.doi.org/10.1056/NEJMoa0808276 [44] G. Lindbeck, D. Groopman and R. Powers, “Aeromedical Evacuation of Rural Victims of Nontraumatic Cardiac Arrest,” Annals of Emergency Medicine, Vol. 22, No. 8, 1993, pp. 1258-1262. http://dx.doi.org/10.1016/S0196-0644(05)80103-9 [45] H. Werman, R. Falcone, S. Shaner, H. Herron, R. John- son, P. Lacey, S. Childress and G. Kampman “Helicopter Transport of Patients to Tertiary Care Centers after Car- diac Arrest,” The American Journal of Emergency Medi- cine, Vol. 17, No. 2, 1999, pp. 130-134. http://dx.doi.org/10.1016/S0735-6757(99)90043-8 [46] J. L. Saver, “Time Is Brain--Quantified,” Stroke, Vol. 37, No. 1, 2006, pp. 263-266. http://dx.doi.org/10.1161/01.STR.0000196957.55928.ab [47] J. A. Chalela, S. E. Kasner, E. C. Jauch and A. M. Pancioli, “Safety of Air Medical Transportation after Tissue Plasmi- nogen Activat or Ad minist ration in Acute Ischemic S tr ok e ,” Stroke, Vol. 30, No. 11, 1999, pp. 2366-2368. [48] M. B. Conroy, S. U. Rodriguez, S. E. Kimmel and S. E. Kasner, “Helicopter Transfer Offers Benefit to Patients with Acute Stroke,” Stroke, Vol. 30, 1999, pp. 2580-2584. http://dx.doi.org/10.1161/01.STR.30.12.2580 [49] K. R. Lees, E. Bluhmki, R. von Kummer, T. G. Brott, D. Toni, J. C. Grotta, G. W. Albers, M. Kaste, J. R. Marler, S. A. Hamilton, B. C. Tilley, S. M. Davis, G. A. Donnan, W. Hacke, A. N. Ecass, E.r.-P.S. Group, K. Allen, J. Mau, D. Meier, G. del Zoppo, D. A. De Silva, K. S. Butcher, M. W. Parsons, P. A. Barber, C. Levi, C. Bladin and G. Byrnes, “Time to Treatment with Intravenous Alteplase and Outcome in Stroke: An Updated Pooled Analysis of ECASS, ATLANTIS, NINDS, and EPITHET Trials,” Lancet, Vol. 375, No. 9727, 2010, pp. 1695-1703. http://dx.doi.org/10.1016/S0140-6736(10)60491-6 [50] J. Svenson, J. O’Connor and M. Lindsay, “Is Air Trans- port Faster? A Comparison of Air Versus Ground Trans- port Times for Interfacility Transfers in a Regional Re- ferral System,” Air Medical Journal, Vol. 25, No. 4, 2006, pp. 170-172. http://dx.doi.org/10.1016/j.amj.2006.04.003 [51] T. J. Crocco, J. C. Grotta, E. C. Jauch, S. E. Kasner, R. U. Kothari, B. R. Larmon, J. L. Saver, M. R. Sayre and S. M. Davis, “EMS Management of Acute Stroke—Prehospital Triage (Resource Document to NAEMSP Position State- ment),” Prehospital Emergency Care, Vol. 11, No. 3, 2007, pp. 313-317. http://dx.doi.org/10.1080/10903120701347844 [52] L. H. Schwamm, A. Pancioli, J. E. Acker, L. B. Gold- stein, R. D. Zorowitz, T. J. Shephard, P. Moyer, M. Gor- man, S. C. Johnston, P. W. Duncan, P. Gorelick, J. Frank, S. K. Stranne, R. Smith, W. Federspiel, K. B. Horton, E. Magnis and R. J. Adams, “Recommendations for Estab- lishment of Stroke Systems of Care: Recommendations from the American Stroke Association’s Ta sk F o rc e o n t h e Development of Stroke Systems,” Stroke, Vol. 36, No. 3, 2005, pp. 690-703. [53] V. Reiner-Deitemyer, Y. Teuschl, K. Matz, M. Reiter, R. Eckhardt, L. Seyfang, C. Tatschl and M. Brainin, “Heli- copter transport of Stroke Patients and Its Influence on Thrombolysis Rates: Data from the Austrian Stroke Unit Registry,” Stroke, Vol. 42, No. 5, 2011, pp. 1295-1300. http://dx.doi.org/10.1161/STROKEAHA.110.604710 Open Access IJCM
Helicopter EMS beyond Trauma: Utilization of Air Transport for Non-Trauma Conditions 523 [54] S. L. Silliman, B. Quinn, V. Huggett and J. G. Merino, “Use of a Field-to-Stroke Center Helicopter Transport Program to Extend Thrombolytic Therapy to Rural Resi- dents,” Stroke, Vol. 34, No. 3, 2003, pp. 729-733. http://dx.doi.org/10.1161/01.STR.0000056529.29515.B2 [55] R. Lambert, S. Cabardis, J. Valance, E. Borge, J. L. Du- casse and J. J. Arza lier, “ Fibrinolysis and Acute Stroke in Maritime Search and Rescue Medical Evacuation,” An- nales Françaises d’Anesthésie et de Réanimation, Vol. 27, No. 3, 2008, pp. 249-251. http://dx.doi.org/10.1016/j.annfar.2007.11.023 [56] Y. Nakagawa, S. Morita, K. Akieda, M. Nagayama, I. Yamamoto, S. Inokuchi, S. Oda and M. Matsumae, “Cri- tical role of the Doctor-Heli System on Cerebral Infarc- tion in the Superacute Stage—Report of an Outstanding Pilot Case,” Tokai Journal of Experimental and Clinical Medicine, Vol. 30, No. 2, 2005, pp. 123-126. [57] L. Candelise, M. Gattinoni, A. Bersano, G. Micieli, R. Sterzi and A. Morabito, “Stroke-Unit Care for Acute Stroke Patients: An Observational Follow-Up Study ,” Lancet, Vol. 369, No. 9558, 2007, pp. 299-305. http://dx.doi.org/10.1016/S0140-6736(07)60152-4 [58] K. C. Albright, C. C. Branas, B. C. Meyer, D. E. Matherne- Meyer, J. A. Zivin, P. D. Lyden and B. G. Carr, “ACCESS: Acute Cerebrovascular Care In Emergency Stroke Sys- tems,” JAMA Neurology, Vol. 67, No. 10, 2010, pp. 1210- 1218. http://dx.doi.org/10.1001/archneurol.2010.250 [59] M. D. Olso n and A. A. Rabin st ein, “D oe s Hel ico pte r Emer- gency Medical Service Transfer Offer Benefit to Patients with Stroke?” Stroke, Vol. 43, No. 3, 2012, pp. 878-880. http://dx.doi.org/10.1161/STROKEAHA.111.640987 [60] B. P. Walcott, J. V. Coumans, M. K. Mian, B. V. Nahed and K. T. Kahle, “Interfacility Helicopter Ambulance Transport of Neurosurgical Patients: Observations, Utilization, and Outcomes from a Quaternary Care Hospital,” PLoS ONE, Vol. 6, No. 10, 2011, Article ID: e26216. http://dx.doi.org/10.1371/journal.pone.0026216 [61] R. Silbergleit, P. Scott, M. Lowell and R. Silbergleit, “Cost-Effectiveness of Helicopter Transport of Stroke Pa- tients for Thrombolysis,” Academic Emergency Medicine, Vol. 10, No. 9, 2003, pp. 966-972. [62] E. C. Leira, A. Ahmed, D. L. Lamb, H. M. Olalde, R. C. Callison, J. C. Torner and H. P. Adams Jr., “Extending Acu- te Trials to Remote Populations: A Pilot Study During In- terhospital Helicopter Transfer,” Stroke, Vol. 40, No. 3, 2009, pp. 895-901. http://dx.doi.org/10.1161/STROKEAHA.108.530204 [63] S. Shewakramani, S. H. Thomas, T. H. Harrison and J. D. Gates, “Air Transport of Patients with Unstable Aortic Aneurysms Directly into Operating Rooms,” Prehospital Emergency Care, Vol. 11, No. 3, 2007, pp. 337-342. http://dx.doi.org/10.1080/10903120701348024 [64] C. H. Pieper, J. Smith, G. F. Kirsten and P. Malan, “The Transport of Neonates to an Intensive Care Unit,” South African Medical Journal, Vol. 84, Suppl. 11, 1994, pp. 801-803. [65] K. Hon, H. Olsen, B. Totapally and T. Leung, “Air Verus Ground Transportation of Artificially Ventilated Neona- tes: Comparative Differences in Selected Cardiopulmon- ary Parameters,” Pediatric Emergency Care, Vol. 22, No. 2, 2006, pp. 107-112. http://dx.doi.org/10.1097/01.pec.0000199557.11605.c6 [66] M. Gausche-Hill, R. J. Lewis, S. J. Stratton, B. E. Haynes, C. S. Gunter, S. M. Goodrich, P. D. Poore, M. D. McCollough, D. P. Henderson, F. D. Pratt and J. S. Seidel, “Effect of out-of-Hospital Pediatric Endotracheal Intuba- tion on Survival and Neurological Outcome: A Controlled Clinical Trial,” JAMA, Vol. 283, No. 6, 2000, pp. 783- 790. http://dx.doi.org/10.1001/jama.283.6.783 [67] W. W. Tollefsen, C. A. Brown Ⅲ, K. L. Cox and R. M. Walls, “Two Hundred Sixty Pediatric Emergency Airway Encounters by Air Transport Personnel: A Report of the Air Transport Emergency Airway Management (NEAR VI: ‘A-TEAM’) Project,” Pediatric Emergency Care, Vol. 29, No. 9, 2013, pp. 963-968. http://dx.doi.org/10.1097/PEC.0b013e3182a219ea [68] T. H. Harrison, S. H. Thomas and S. K. Wedel, “Success rates of Pediatric Intubation by a Non-Physician-Staffed Critical Care Transport Service,” Pediatric Emergency Care, Vol. 20, No. 2, 2004, pp. 101-107. http://dx.doi.org/10.1097/01.pec.0000113879.10140.7f [69] W. W. Tollefsen, J. Chapman, M. Frakes, M. Gallagher, M. Shear and S. H. Thomas, “Endotracheal Tube Cuff Pressures in Pediatric Patients Intubated before Aerome- dical Transport,” Pediatric Emergency Care, Vol. 26, No. 5, 2010, pp. 361-363. http://dx.doi.org/10.1097/PEC.0b013e3181db224d [70] J. Orf, S. H. Thomas, W. Ahmed, L. Wiebe, P. Chamber- lin, S. K. Wedel and C. Houck, “Appropriateness of En- dotracheal Tube Size and Insertion Depth in Children Un- dergoing Air Medical Transport,” Pediatric Emergency Care, Vol. 16, No. 5, 2000, pp. 321-327. http://dx.doi.org/10.1097/00006565-200010000-00004 [71] J. W. van Hook, T. G. Leicht, C. L. van Hook, P. L. Dick, G. D. Hankins and C. J. Harvey, “Aeromedical Transfer of Preterm Labor Patients,” Texas Medicine, Vol. 94, No. 11, 1998, pp. 88-90. [72] M. Ohara, Y. Shimizu, H. Satoh, T. Kasai, S. Takano, R. Fujiwara, Y. Furusawa, S. Kameda, T. Matsumura, H. Narimatsu, E. Kusumi, Y. Kodama, M. Kami, N. Mura- shige and M. Suzuki, “Safety and Usefulness of Emer- -gency Maternal Transport Using Helicopter,” Journal of Obstetrics and Gynaecology Research, Vol. 34, No. 2, 2008, pp. 189-194. [73] J. A. Russell, “Management of Sepsis,” The New England Journal of Medicine, Vol. 355, No. 16, 2006, pp. 1699- 1713. http://dx.doi.org/10.1056/NEJMra043632 [74] D. Reily, E. Tollok, K. Mallitz, C. W. Hanson III and B. D. Fuchs, “Successful Aeromedical Transport Using In- haled Prostacyclin for a Patient with life-Threatening Hy- poxemia,” Chest, Vol. 125, No. 4, 2004, pp. 1579-1581. http://dx.doi.org/10.1378/chest.125.4.1579 [75] E. Vu, R. Wand and R. Schlamp, “Facilitated Delivery of Antidotes by the British Columbia Air Ambulance Ser- vice during Secondary Aeromedical Transport in Poisoned or Toxic Patients,” Prehospital Emergency Care, Vol. 11, 2007, p. 135. [76] S. Thomas, T. Judge, M. J. Lowell, R. D. MacDonald, J. Open Access IJCM
Helicopter EMS beyond Trauma: Utilization of Air Transport for Non-Trauma Conditions Open Access IJCM 524 Madden, K. Pickett, H. A. Werman, M. L. Shear, P. Patel, G. Starr, M. Chesney, R. Domeier, P. Frantz, D. Funk and R. D. Greenberg, “Airway Management Success and Hy- poxemia Rates in Air and Ground Critical Care Transport: A Prospective Multicenter Study,” Prehospital Emergency Care, Vol. 14 , No. 3, 2010 , pp. 283- 291. http://dx.doi.org/10.3109/10903127.2010.481758 [77] S. H. Thomas, J. Orf, S. K. Wedel and A. K. Conn, “Hy- perventilation in Traumatic Brain Injury Patients: Incon- sistency between Consensus Guidelines and Clinical Practice,” Journal of Trauma-Injury Infection & Critical Care, Vol. 52, No. 1, 2002, pp. 47-52. http://dx.doi.org/10.1097/00005373-200201000-00010 [78] S. Thomas, “Hyperventilation in Patients with Traumatic Brain Injury: Lessons for the Acute Care Provider,” Salud Ciencia—Journal of the Sociedad Iberoamericana de In- formación Científica, Vol. 12, 2004, pp. 22-26. [79] D. Davis, J. Ster n, M. Ochs and D. B. Hoy t, “A Follow-U p Anal ys is of Factors Associated with Head-Injury Mortality after Paramedic Rapid Sequence Intubation,” Journal of Trauma-Injury Infection & Critical Care, Vol. 59, No. 2, 2005, pp. 486-490. http://dx.doi.org/10.1097/00005373-200508000-00037 [80] D. Davis, J. Dunford, M. Ochs, R. Heister, D. Hoyt, M. Ochs and J. V. Dunford, “Ventilation Patterns Following Paramedic Rapid Sequence Intubation of Patients with Se- vere Traumatic Brain I njury,” Neurocritical Care, Vol. 2, No. 2, 2005, pp. 165-171. http://dx.doi.org/10.1385/NCC:2:2:165 [81] D. P. Davis, J. V. Dunford, J. C. Poste, M. Ochs, T. Hol- brook and D. Fortlage, M. J. Size, F. Kennedy and D. B. Hoyt, “The Impact of Hypoxia and Hyperventilation on Outcome Following Paramedic Rapid Sequence Intuba- tion of Patients with Severe Traumatic Brain Injury,” Journal of Trauma-Injury Infection & Critical Care, Vol. 57, No. 1, 2004, pp. 1-10. http://dx.doi.org/10.1097/01.TA.0000135503.71684.C8 [82] M. Helm, R. Schuster, J. Hauke and L. Lampl, “Tight Control of Prehospital Ventilation by Capnography in Major Trauma Victims,” British Journal of Anesthesia, Vol. 90, No. 3, 2003, pp. 327-332. http://dx.doi.org/10.1093/bja/aeg069 [83] B. J. Zink and R. F. Maio, “Out-of-Hospital Endotracheal Intubation in Traumatic Brain Injury: Outcomes Research Provides us with an Unexpected Outcome,” Annals of Emergency Medicine, Vol. 44, No. 5, 2004, pp. 451-453. http://dx.doi.org/10.1016/j.annemergmed.2004.05.001 [84] G. Berlot, C. La Fata, B. Bacer, B. Biancardi, M. Viviani, U. Lucangelo, P. Gobbato, L. Torelli, E. Carchietti, G. Trillo, M. Daniele and A. Rinaldi, “Influence of Prehos- pital Treatment on the Outcome of Patients with Severe Blunt Traumatic Brain Injury: A Single-Centre Study,” European Journal of Emergency Medicine, Vol. 16, No. 6, 2009, pp. 312-317. http://dx.doi.org/10.1097/MEJ.0b013e32832d3aa1 [85] M. A. Turturro, “Pain, Priorities, and Prehospital Care,” Prehospital Emergency Care, Vol. 6, No. 4, 2002, pp. 486-488. http://dx.doi.org/10.1080/10903120290938238 [86] C. McEachin, J. McDermott and R. Swor, “Few EMS Pa- tients with Lower-Extremity Fractures Receive Prehospi- tal Analgesia,” Prehospital Emergency Care, Vol. 6, No. 4, 2002, pp. 406-410. http://dx.doi.org/10.1080/10903120290938030 [87] R. Swor, C. M. McEachin, D. Seguin and K. H. Grall, “Prehospital Pain Management in Children Suffering Traumatic Injury,” Prehospital Emergency Care, Vol. 9, No. 1, 2005, pp. 40-43. http://dx.doi.org/10.1080/10903120590891930 [88] S. H. Thomas and S. Shewakramani, “Prehospital Trauma Analgesia,” The Journal of Emergency Medicine, Vol. 35, No. 1, 2008, pp. 47-57. http://dx.doi.org/10.1016/j.jemermed.2007.05.041
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