Search by Topic
Join our mailing list!
Thanks! You've been successfully signed up for the BTU newsletter!
Micro-Touch NitraFree Pink Gloves
Micro-Touch® NitraFreeTM pink nitrile examination gloves are manufactured without sulfur-based chemical accelerators.
Curaplex Opioid Overdose Kits
Opioid Overdose Kits are ideal solutions for first responders in any profession, including EMTs, paramedics, social workers, police officers and community outreach workers.
Nexterone Premixed Injection
In situations when every second counts, NEXTERONE (Amiodarone HCl) Premixed Injection is available at your fingertips.
March 18, 2016
Prehospital Ultrasound: Emerging technology for EMS
Prehospital ultrasound is a form of medical imaging that is portable, non-invasive, painless, and does not expose the patient to ionizing radiation. With proper training and education, prehospital providers can use ultrasound to obtain immediate anatomical, diagnostic, and functional information on their patients .
In recent years, ultrasound devices have decreased in size and cost while producing images of enhanced quality. The recent advances in bedside devices have made ultrasound more accessible to prehospital providers with the introduction of field ultrasound devices that are more affordable, smaller in size, durable, lightweight, and with high-resolution imaging quality.
Prehospital ultrasound may be beneficial in the diagnosis and management of critically ill patients [2,3,4,5,6,7]. EMS providers can apply training to interpret ultrasound scans with a high degree of accuracy in a relatively short period of time [5,8].
For example, prehospital focused abdominal sonography for trauma (FAST) exams have the potential to provide valuable information in abdominal trauma with high reliability leading to more appropriate transport destination decisions [9,10,11]. In addition, field ultrasound images can be transmitted enroute to the emergency department to facilitate further evaluation by ED physicians and trauma surgeons to expedite care [12,13,14].
Prehospital ultrasound has been widely adopted in most states and around the world with a continuously growing list of diagnostic applications [5,6]. The enhanced technology enables prehospital professionals to answer focused clinical questions, which translate into faster and more accurate diagnosis and care of patients presenting with time-sensitive emergency conditions [2,3,4]. Better outcomes have been reported with the use of prehospital ultrasound [2,5,6,15,16].
Bedside ultrasound is well accepted by patients and has shown to improve patient satisfaction . However, like any other nontraditional intervention, the addition of field ultrasound raises several questions in terms of potential clinical applications, feasibility, training requirements, cost, and more importantly its impact on the care process and patient outcome.
Clinical applications for field ultrasound
In EMS systems with regionalized trauma care and field triage guidelines, field ultrasound offers earlier detection of time-critical conditions that may require deliberate transport to an accredited trauma center, chest pain center, stroke center, or pediatric specialty care facility. There is an abundance of clinical applications for the use field ultrasound discussed in the literature with varying degrees of benefit:
1. Causes of dyspnea
Field ultrasound increases the accuracy of diagnosing pulmonary edema versus chronic obstructive pulmonary disease as the cause of acute dyspnea [1,18,]. It is effective in patients with unexplained hemodynamic instability to help differentiate between cardiac and non-cardiac causes of shock [18,19]. In some limited cases the potential of field ultrasound to detect massive pulmonary emboli in patients has been demonstrated [15,20].
2. Recognizing OB emergencies
Although advanced training is necessary, some prehospital providers have shown that ectopic pregnancy, placenta previa, and placenta abruption can be identified with about 95 percent reliability [4,21,22].
3. Cardiac evaluation and resuscitation
Specialized prehospital resuscitation protocols using ultrasound have shown that in patients undergoing CPR, ultrasound helped prehospital providers determine cardiac wall motion when the initial ECG diagnosis was identified as asystole . This was associated with an increased survival to hospital admission .
In addition to cardiac motion, ultrasound helped differentiate between true PEA — electromechanical dissociation — and pseudo-PEA — coordinated electrical activity with no palpable pulse [23,24]. Pseudo-PEA was also associated with increased survival to hospital admission when compared with true-PEA [23,24].
In patients in a peri-resuscitation state, ultrasound improved the diagnostic accuracy for potential diagnoses of tamponade, profound hypovolemia, myocardial insufficiency (severe left and/or right ventricular dysfunction), or thromboembolism (pulmonary or cardiac) [25,26]. EMS systems with prehospital protocols that use asystole or PEA as criteria for field resuscitation termination can benefit from adding ultrasound to such protocols [23,25,26].
4. Airway placement confirmation and monitoring
Another diagnostic application of field ultrasound includes confirming endotracheal tube placement through high-resolution detection . Although waveform capnography is considered the gold standard for successful ETT verification, this method has some limitations in specific situations such as cardiac arrest, low cardiac output, acute pulmonary embolism, and hypothermia .
Ultrasound offers prehospital professionals an alternative method for ETT confirmation for recognizing tube displacement or differentiating between main tracheal intubation and right mainstem intubation [27,28,29,30,31]. For example, Adi et al's (2013) study showed an impressive result of 98.1 percent accuracy in initial verification .
5. Gastric tube placement confirmation
Gastric tube placement — nasogastric or orogastic — remains a recommended critical care intervention for all intubated patients as it decreases the risk of aspiration and improves tidal volume. Some EMS systems that place gastric tubes report that placement is easily confirmed using field ultrasound .
6. Fracture determination
Many types of suspected long-bone fractures are managed in the prehospital setting. Growing evidence suggests that use of field ultrasound can successfully identify several types of long bone fractures [33,49,50].
7. Prehospital needle thoracostomy placement
Prehospital ultrasound use in trauma patients with suspected pneumothorax can be effective in preventing unnecessary field needle thoracostomys [34,35]. One study showed that when thoracic ultrasound was used to detect pneumothorax, only 26 percent of the patients were actually found to not have a pneumothorax [34,35,36,37]. Using field ultrasound could help decrease potentially unnecessary needle thoracostomys and other invasive procedures en route to hospital .
8. Peripheral intravenous access
Establishing vascular access is one of the most common procedures performed in the prehospital setting and on occasion is a high priority for the critically ill and unstable patient. The condition of the patient often presents challenges in attaining intravenous access. Conditions associated with difficult vascular access include very young age, obesity, chronic illness, IV drug abuse, and hypovolemia to list a few [39,40,41].
Patients with difficult IV access are often subjected to repeated attempts as in some cases time to IV placement can affect optimal resuscitation of the critically ill patient. Ultrasound guided IV access has shown to increase the success rate and decrease complications [42,43,44,45,46,47,48].
9. Stroke diagnosis
It is well discussed in the literature that improving the outcome of stroke patients requires early and rapid time-sensitive diagnosis and treatment as well as transport to an accredited stroke center. Early diagnosis using telestroke protocols with field transcranial ultrasound for stroke diagnosis has shown to decrease diagnosis-to-fibrinolytic therapy times and expand the use of special interventional radiology procedures [51,52,53].
Practice challenges for field ultrasound
Widespread adoption of field ultrasound in the United States has been limited due to several factors. The most commonly reported barriers to field ultrasound implementation include, but are not limited to, cost, training deficits, short transport times, concerns about delaying time to definitive care, lack of evidence, approval by EMS administration, buy-in by medical directors and ED staff, and acceptance by veteran EMS providers [1,52,54].
In most cases initial ultrasound education and training is possible with relatively short training courses. Like any other clinical skill, ultrasound competency requires practice, ongoing education, and quality management programs with physician oversight [55,56].
Prehospital emergency ultrasound has many clinical applications that can potentially reduce patient morbidity and mortality from life-threatening emergency conditions. The potential for the evolution of field ultrasound is largely dependent upon developing a growing body of prehospital data that demonstrates its safety and effectiveness in clinical procedures and timely diagnosing medical and trauma conditions.
Above all, the value of ultrasound use in the prehospital setting must illustrate how it improves patient outcomes. This could be facilitated by enhancing the technology of telesonography for real-time assistance with interpretation of ultrasound images by physicians [43,57]. Also, developing effective ultrasound training programs for different level providers is important to maximize its use. In addition, a cost-benefit analysis for prehospital ultrasound must be entertained.
One area of future research must include the early ultrasound diagnosis of ischemic stroke in the prehospital setting to improve time to thrombolysis. Hopefully, this research will correlate into better neurologic outcomes of stroke affected patients . Considering the growing areas of mobile integrated healthcare and community paramedic programs, one cannot anticipate the endless possibilities that prehospital ultrasound could offer these diverse community healthcare services .
2. Brun, P., Chenaitia, H., Gonzva, J., Bessereau, J., Bobbia, X., & Peyrol, M. (2013). The value of prehospital echocardiography in shock management. The American Journal of Emergency Medicine, 31(2). doi:10.1016/j.ajem.2012.05.021
3. Byhahn, C., Bingold, T. M., Zwissler, B., Maier, M., & Walcher, F. (2008). Prehospital ultrasound detects pericardial tamponade in a pregnant victim of stabbing assault. Resuscitation, 76(1), 146-148. doi:10.1016/j.resuscitation.2007.07.020
4. Cooney, N. L., & Cooney, D. R. (2016). Chapter 63: Field Diagnostics. In Cooney's EMS medicine. Retrieved February 5, 2016, from http://accessemergencymedicine.mhmedical.com/content.aspx?bookid=1650&Sectionid=107957501
5. Heegaard, W., Hildebrandt, D., Spear, D., Chason, K., Nelson, B., & Ho, J. (2010). Prehospital ultrasound by paramedics: Results of field trial. Academic Emergency Medicine, 17(6), 624-630. doi:10.1111/j.1553-2712.2010.00755.x
6. Jørgensen, H., Jensen, C. H., & Dirks, J. (2010). Does prehospital ultrasound improve treatment of the trauma patient? A systematic review. European Journal of Emergency Medicine, 17(5), 249-253. doi:10.1097/mej.0b013e328336adce
7. Quick, J. A., Uhlich, R. M., Ahmad, S., Barnes, S. L., & Coughenour, J. P. (2015). In-flight ultrasound identification of pneumothorax. Emerg Radiol Emergency Radiology, 23(1), 3-7. doi:10.1007/s10140-015-1348-z
8. Brooke, M., Walton, J., Scutt, D., Connolly, J., & Jarman, B. (2011). Acquisition and interpretation of focused diagnostic ultrasound images by ultrasound-naive advanced paramedics: Trialing a PHUS education programme. Emergency Medicine Journal, 29(4), 322-326. doi:10.1136/emj.2010.106484
9. Chaudery, M., Clark, J., Wilson, M. H., Bew, D., Yang, G., & Darzi, A. (2015). Traumatic intra-abdominal hemorrhage control. Journal of Trauma and Acute Care Surgery, 78(1), 153-163. doi:10.1097/ta.0000000000000472
10. O'Dochartaigh, D., & Douma, M. (2015). Prehospital ultrasound of the abdomen and thorax changes trauma patient management: A systematic review. Injury, 46(11), 2093-2102. doi:10.1016/j.injury.2015.07.007
11. Ruesseler, M., Kirschning, T., Breitkreutz, R., Marzi, I., & Walcher, F. (2009). Prehospital and emergency department ultrasound in blunt abdominal trauma. Eur J Trauma Emerg Surg European Journal of Trauma and Emergency Surgery, 35(4), 341-346. doi:10.1007/s00068-009-9082-4
12. Sibert, K., Ricci, M. A., Caputo, M., Callas, P. W., Rogers, F. B., Charash, W., . . . Kocmoud, C. (2008). The feasibility of using ultrasound and video laryngoscopy in a mobile telemedicine consult. Telemedicine and E-Health, 14(3), 266-272. doi:10.1089/tmj.2007.0050
13. Strode, C. A. (2003). Satellite and mobile wireless transmission of focused assessment with sonography in trauma. Academic Emergency Medicine, 10(12), 1411-1414. doi:10.1197/s1069-6563(03)00547-5
14. Takeuchi, R., Harada, H., Masuda, K., Ota, G., Yokoi, M., Teramura, N., & Saito, T. (2008). Field testing of a remote controlled robotic tele-echo system in an ambulance using broadband mobile communication technology. J Med Syst Journal of Medical Systems, 32(3), 235-242. doi:10.1007/s10916-008-9128-x
15. Sayed, M. J., & Zaghrini, E. (2013). Prehospital emergency ultrasound: A review of current clinical applications, challenges, and future implications. Emergency Medicine International, 2013, 1-6. doi:10.1155/2013/531674
16. Garrone, M. (2011). Prehospital ultrasound as the evolution of the Franco-German model of prehospital EMS. Critical Ultrasound Journal Crit Ultrasound J, 3(3), 141-147. doi:10.1007/s13089-011-0077-0
17. Howard, Z. D., Noble, V. E., Marill, K. A., Sajed, D., Rodrigues, M., Bertuzzi, B., & Liteplo, A. S. (2014). Bedside ultrasound maximizes patient satisfaction. The Journal of Emergency Medicine, 46(1), 46-53. doi:10.1016/j.jemermed.2013.05.044
18. Zechner, P. M., Aichinger, G., Rigaud, M., Wildner, G., & Prause, G. (2010). Prehospital lung ultrasound in the distinction between pulmonary edema and exacerbation of chronic obstructive pulmonary disease. The American Journal of Emergency Medicine, 28(3). doi:10.1016/j.ajem.2009.07.021
19. Rempell, J. S., & Noble, V. E. (2011). Using lung ultrasound to differentiate patients in acute dyspnea in the prehospital emergency setting. Critical Care Crit Care, 15(3), 161. doi:10.1186/cc10226
20. Nelson, B. P., & Chason, K. (2008). Use of ultrasound by emergency medical services: A review. Int J Emerg Med International Journal of Emergency Medicine, 1(4), 253-259. doi:10.1007/s12245-008-0075-6
21. Galinski, M., Petrovic, T., Rodrigues, A., Hermann, M., Catineau, J., Adnet, F., & Lapostolle, F. (2010). Out-of-hospital diagnosis of a ruptured ectopic pregnancy: Myometrial embryo implantation, an exceptional diagnosis. Prehospital Emergency Care Prehosp Emerg Care, 14(4), 496-498. doi:10.3109/10903127.2010.493984
22. Chin, E. J., Chan, C. H., Mortazavi, R., Anderson, C. L., Kahn, C. A., Summers, S., & Fox, J. C. (2013). A pilot study examining the viability of a prehospital assessment with ultrasound for emergencies (PAUSE) protocol. The Journal of Emergency Medicine, 44(1), 142-149. doi:10.1016/j.jemermed.2012.02.032
23. Aichinger, G., Zechner, P. M., Prause, G., Sacherer, F., Wildner, G., Anderson, C. L., . . . Fox, J. C. (2012). Cardiac movement identified on prehospital echocardiography predicts outcome in cardiac arrest patients. Prehospital Emergency Care Prehosp Emerg Care, 16(2), 251-255. doi:10.3109/10903127.2011.640414
24. Breitkreutz, R., Price, S., Steiger, H. V., Seeger, F. H., Ilper, H., Ackermann, H., . . . Walcher, F. (2010). Focused echocardiographic evaluation in life support and peri-resuscitation of emergency patients: A prospective trial. Resuscitation, 81(11), 1527-1533. doi:10.1016/j.resuscitation.2010.07.013
25. Blyth, L., Atkinson, P., Gadd, K., & Lang, E. (2011). 262 Does cardiac standstill mean we can stop CPR? Focused ultrasound as predictor of survival in cardiac arrest patients: A systematic review. Annals of Emergency Medicine, 58(4). doi:10.1016/j.annemergmed.2011.06.292
26. Blyth, L., Atkinson, P., Gadd, K., & Lang, E. (2012). Bedside focused echocardiography as predictor of survival in cardiac arrest patients: A systematic review. Academic Emergency Medicine, 19(10), 1119-1126. doi:10.1111/j.1553-2712.2012.01456.x
27. Bailitz, J., Gottlieb, M., Russell, F., Ehrman, R., Kishfe, B., Christian, E., . . . Ross, C. (2013). Accuracy of airway ultrasound for confirmation of endotracheal intubation by expert and novice emergency physicians. Annals of Emergency Medicine, 62(4). doi:10.1016/j.annemergmed.2013.07.070
28. Brun, P., Bessereau, J., Cazes, N., Querellou, E., & Chenaitia, H. (2012). Lung ultrasound associated to capnography to verify correct endotracheal tube positioning in prehospital. The American Journal of Emergency Medicine, 30(9). doi:10.1016/j.ajem.2011.10.023
29. Chou, H., Tseng, W., Wang, C., Ma, M. H., Wang, H., Huang, P., . . . Chen, S. (2011). Tracheal rapid ultrasound exam (T.R.U.E.) for confirming endotracheal tube placement during emergency intubation. Resuscitation, 82(10), 1279-1284. doi:10.1016/j.resuscitation.2011.05.016
30. Adi, O., Chuan, T., & Rishya, M. (2013). A feasibility study on bedside upper airway ultrasonography compared to waveform capnography for verifying endotracheal tube location after intubation. Critical Ultrasound Journal Crit Ultrasound J, 5(1), 7. doi:10.1186/2036-7902-5-7
31. Li, Y., Wang, J., & Wei, X. (2015). Confirmation of endotracheal tube depth using ultrasound in adults. Can J Anesth/J Can Anesth Canadian Journal of Anesthesia/Journal Canadien D'anesthésie, 62(7), 832-832. doi:10.1007/s12630-015-0359-2
32. Brun, P., Chenaitia, H., Lablanche, C., Pradel, A., Deniel, C., Bessereau, J., & Melaine, R. (2014). 2-Point ultrasonography to confirm correct position of the gastric tube in prehospital setting. Military Medicine, 179(9), 959-963. doi:10.7205/milmed-d-14-00044
33. Waterbrook, A. L., Adhikari, S., Stolz, U., & Adrion, C. (2013). The accuracy of point-of-care ultrasound to diagnose long bone fractures in the ED. The American Journal of Emergency Medicine, 31(9), 1352-1356. doi:10.1016/j.ajem.2013.06.006
34. Blaivas, M. (2008). 342: Inadequate needle thoracostomy rate of the chest in the out-of-hospital setting for presumed pneumothorax, as documented on ultrasound. Annals of Emergency Medicine, 52(4). doi:10.1016/j.annemergmed.2008.06.368
35. Blaivas, M. (2010). Inadequate needle thoracostomy rate in the prehospital setting for presumed pneumothorax: An ultrasound study. Journal of Ultrasound in Medicine, 29(9), 1285-1289. doi:10.1016/j.annemergmed.2008.06.368
36. Irwin, Z., & Cook, J. O. (2016). Advances in point-of-care thoracic ultrasound. Emergency Medicine Clinics of North America, 34(1), 151-157. doi:10.1016/j.emc.2015.09.003
37. Weichenthal, L., Crane, D., & Rond, L. (2016). Needle thoracostomy in the prehospital setting: A retrospective observational study. Prehospital Emergency Care, 1-5. doi:10.3109/10903127.2015.1102992
38. Schaal, J., Pasquier, P., Renner, J., Dubost, C., & Mérat, S. (2014). Ultrasounds for prehospital recognition of tension pneumothorax. Injury, 45(6), 1019. doi:10.1016/j.injury.2013.11.025
39. Nafiu, O. O., Burke, C., Cowan, A., Tutuo, N., Maclean, S., & Tremper, K. K. (2010). Comparing peripheral venous access between obese and normal weight children. Pediatric Anesthesia, 20(2), 172-176. doi:10.1111/j.1460-9592.2009.03198.x
40. Stein, J., George, B., River, G., Hebig, A., & Mcdermott, D. (2009). Ultrasonographically guided peripheral intravenous cannulation in emergency department patients with difficult intravenous access: A randomized trial. Annals of Emergency Medicine, 54(1), 33-40. doi:10.1016/j.annemergmed.2008.07.048
41. Rauch, D., Dowd, D., Eldridge, D., Mace, S., Schears, G., & Yen, K. (2009). Peripheral difficult venous access in children. Clinical Pediatrics, 48(9), 895-901. doi:10.1177/0009922809335737
42. Panebianco, N. L., Fredette, J. M., Szyld, D., Sagalyn, E. B., Pines, J. M., & Dean, A. J. (2009). What you see (Sonographically) is what you get: Vein and patient characteristics associated with successful ultrasound-guided peripheral intravenous placement in patients with difficult access. Academic Emergency Medicine, 16(12), 1298-1303. doi:10.1111/j.1553-2712.2009.00520.x
43. Perera, P., Mailhot, T., Riley, D., & Mandavia, D. (2010). The RUSH exam: Rapid ultrasound in shock in the evaluation of the critically ill. Emergency Medicine Clinics of North America, 28(1), 29-56. doi:10.1016/j.emc.2009.09.010
44. Gregg, S. C., Murthi, S. B., Sisley, A. C., Stein, D. M., & Scalea, T. M. (2010). Ultrasound-guided peripheral intravenous access in the intensive care unit. Journal of Critical Care, 25(3), 514-519. doi:10.1016/j.jcrc.2009.09.003
45. Doniger, S. J., Ishimine, P., Fox, J. C., & Kanegaye, J. T. (2009). Randomized controlled trial of ultrasound-guided peripheral intravenous catheter placement versus traditional techniques in difficult-access pediatric patients. Pediatric Emergency Care, 25(3), 154-159. doi:10.1097/pec.0b013e31819a8946
46. Fields, J., Todman, R., Anderson, K., Panebianco, N., & Dean, A. (2010). 229: Early failure of ultrasonography-guided peripheral intravenous catheters in the emergency department: It's not just about getting the IV - It's about keeping it. Annals of Emergency Medicine, 56(3). doi:10.1016/j.annemergmed.2010.06.277
47. Leung, S. (2015). A review of pediatric ultrasound-guided peripheral intravenous access. Clinical Pediatric Emergency Medicine, 16(4), 240-243. doi:10.1016/j.cpem.2015.10.004
48. Ismailoglu, E. G., Zaybak, A., Akarca, F. K., & K?yan, S. (2015). The effect of the use of ultrasound in the success of peripheral venous catheterisation. International Emergency Nursing, 23(2), 89-93. doi:10.1016/j.ienj.2014.07.010
49. Colon, R. M., & Chilstrom, M. L. (2015). Diagnosis of an occult hip fracture by point-of-care ultrasound. The Journal of Emergency Medicine, 49(6), 916-919. doi:10.1016/j.jemermed.2015.06.077
50. Cross, K. P. (2011). Bedside ultrasound for pediatric long bone fractures. Clinical Pediatric Emergency Medicine, 12(1), 27-36. doi:10.1016/j.cpem.2010.12.002
51. Jauch, E. C., French, D. M., & Mcgeorge, T. (2016). Prehospital stroke treatment (EMS Stabilization Protocols). Ischemic Stroke Therapeutics, 7-12. doi:10.1007/978-3-319-17750-2_2
52. Hölscher, T., Dunford, J. V., Schlachetzki, F., Boy, S., Hemmen, T., Meyer, B. C., . . . Voie, A. (2013). Prehospital stroke diagnosis and treatment in ambulances and helicopters—a concept paper. The American Journal of Emergency Medicine, 31(4), 743-747. doi:10.1016/j.ajem.2012.12.030
53. Schlachetzki, F., Herzberg, M., Hölscher, T., Ertl, M., Zimmermann, M., Ittner, K. P., . . . Boy, S. (2012). Transcranial ultrasound from diagnosis to early stroke treatment – Part 2: Prehospital neurosonography in patients with acute stroke – The Regensburg Stroke Mobile Project. Cerebrovasc Dis Cerebrovascular Diseases, 33(3), 262-271. doi:10.1159/000334667
54. Mccallum, J., Vu, E., Sweet, D., & Kanji, H. D. (2015). Assessment of paramedic ultrasound curricula: A systematic review. Air Medical Journal, 34(6), 360-368. doi:10.1016/j.amj.2015.07.002
55. Press, G. M., Miller, S. K., Hassan, I. A., Blankenship, R., Junco, D. D., Camp, E., & Holcomb, J. B. (2013). Evaluation of a training curriculum for prehospital trauma ultrasound. The Journal of Emergency Medicine, 45(6), 856-864. doi:10.1016/j.jemermed.2013.05.001
56. Roline, C. E., Heegaard, W. G., Moore, J. C., Joing, S. A., Hildebrandt, D. A., Biros, M. H., . . . Reardon, R. F. (2013). Feasibility of bedside thoracic ultrasound in the helicopter emergency medical services setting. Air Medical Journal, 32(3), 153-157. doi:10.1016/j.amj.2012.10.013
57. Tazarourte, K., Dékadjévi, H., Sapir, D., Desmettre, T., Libert, N., Pasquier, P., & Tourtier, J. (2010). Ultrasound and prehospital triage: A tool for limiting the undertriage. The Journal of Trauma: Injury, Infection, and Critical Care, 69(4), 997. doi:10.1097/ta.0b013e3181e96bcc
58. Wang, R., & Frazee, B. W. (2011). Visual stimulus: Splinter localization with ultrasound. The Journal of Emergency Medicine, 41(3), 294-295. doi:10.1016/j.jemermed.2009.02.036