EMS Pre-Hospital Ultrasound

Mark Robidoux MD; Kolby Kolbet MSN; John L. Hick MD, FACEP; William G. Heegaard, MD, MPH, FACEP; Barrett Wagner, MD; Rob Reardon, MD

Background 

• EMS is increasingly using sophisticated technologies for patient assessment, particularly during ground and aeromedical (rotor and fixed wing) critical care transport.
• Goal-directed, limited window ultrasounds can provide critical information to guide pre-hospital interventions, guide procedures, and support destination/triage decision-making.
• New tablet-based and other portable ultrasound machines provide a platform useful in the transport environment.
• Ultrasound can be particularly useful in the rotor-wing environment where ambient noise makes auscultation impossible.
• According to a survey published in 2014 about 4% of responding EMS agencies in North America were using ultrasound and 21.7% were considering using it – a majority of those services already using US involved physician operators.¹
• Prehospital ultrasound is more prevalent in EMS systems that routinely utilize physician providers. (e.g., Australia, Europe, Canada)
• Prehospital physicians and paramedics have been shown to accurately perform components of the FAST exam with good accuracy.^2,3
• Flight paramedics and flight nurses have also correctly identified lung sliding with comparable accuracy to in-hospital emergency physicians.⁴
• EMT/Paramedics can accurately perform FAST both in-hospital and out of hospital patients.^5,6
• Paramedics have been trained to correct identify standstill in cardiac arrest patients.⁷

Applications 

Primary

• FAST exam to detect free intra-abdominal fluid in trauma and medical conditions
• Cardiac ultrasound exam in hypotensive or cardiac arrest patients to place them in one of five states: Cardiac standstill, severe hypovolemia, cardiogenic shock, pericardial tamponade or right ventricular obstruction.
• Fetal monitoring and evaluation in obstetric patients
• Sliding lung signs for detection of pneumothorax

Secondary

• Inferior vena cava assessment to guide resuscitation
• Thoracic exam for hemothorax or B-lines (pulmonary edema)
• Vascular access – potentially including central lines and arterial catheters
• Optic nerve sheath assessment for increased intracranial pressure
• Left ventricular function global assessment (good/poor ejection fraction)
• Abdominal Aortic Aneurysm - In patients with suspect rupture/hypotension
• Mass Casualty Triage - provides rapid diagnostic information, can better identify patient at risk for decompensation.8 US can also be utilized during a hospital mass casualty incident when other imaging sources (X-ray, CT) become overwhelmed.⁹

Impact on Care Provided

• Improved, actionable information provided to receiving facility
• Potential change in destination hospital
• Distinguish between cardiac standstill and severe volume deficit or severely impaired LV function (pseudo-PEA)
• Prompt interventions and confirm efficacy – eg, chest decompression, pericardiocentesis, vascular access, blood administration/fluid resuscitation¹⁰
• Accomplish procedures safely – pericardiocentesis, vascular access
• Rule out conditions and avoid ‘blind’ or unnecessary interventions¹¹
• Dutch study (Ketelaars) – of 1495 abdominal studies, 12.6% impacted care, lower than intervention rate found in smaller Walcher (30%) and O’Dochartaigh (26% for EMT-P/RN, 45% for MDs) studies that looked at both abdominal and chest pre-hospital ultrasound^12-14
• Review demonstrates pre-hospital ultrasound likely influences destination and interventions but unclear effect in current studies on outcomes¹⁵
• Brun demonstrated prehospital physicians performing eFAST exams with sensitivity/specificity in the 90th percentile on seen, but improved to near 100% when repeated during transport.³ This supports the value of serial exams on critically ill patients.

Training

• Studies have demonstrated successful acquisition and interpretation of images after a few hours of training.
  • 20 firefighter-paramedics exhibited competence with image acquisition and interpretation for pneumothorax, cardiac activity, and pericardial effusion after 2 hours of training¹⁵
  • Paramedics completing 6 hours of training completed 84 abdominal FAST exams with 100% concordance with physician image over-read⁶
• Ongoing assessments and competencies are necessary to assure skill maintenance
• Personnel tend to group into high, middle, and lower utilizers – additional training is often required for low utilizers to assure comfort and competence
• On-line interpretation testing using multiple clips of normal and abnormal can be a key component of training
• Training should be simple – single or few windows (eg, Morison’s pouch, anterior chest, subxiphoid and parasternal long cardiac views, and suprapubic fetal windows) and binary interpretations (present/absent)
• Training curricula – as an example, LifeLink III (Minnesota/Wisconsin) provides the following – for most clinicians this results in about 6 hours of training:
  • 1 hour orientation to ultrasound imaging
  • 2 hours of image acquisition training (hands-on)
  • On-line imaging interpretation tests
  • Competencies checked by base leads
  • Incorporation of imaging into simulation cases
  • Additional lectures by ultrasound fellows – live and online - optional

Quality Improvement

• Audits of ultrasound should include:
  • Number of studies and indications by employee to determine use patterns
  • Interpretation review – accurate interpretation? (inaccurate interpretation should lead to feedback with coaching and re-education as required)
  • Number of cases in which US findings prompted an intervention or clinical decision
  • Number of cases in which US finding prompted a change in destination
• Competency checks of personnel should occur on a regular basis
• Images and interpretation should be available for review/over-read by expert staff (LifeLink III uploads images and provider interpretations to a cloud-based system for review by ultrasound fellows and faculty at Hennepin County Medical Center) – real-time review should not be necessary for simple, goal directed ultrasound windows.

Experience and Limitations

Ground

• Current relatively high cost of units and need for training is problematic for larger services – benefits may be greater for smaller services with longer transport times – this is an area for future study.

Aeromedical

• Many rotor-wing services are providing or considering ultrasound
• Few services provide image storage and review, limiting quality improvement opportunities. Cloud-based and other systems are beginning to offer options for auditing.
• Patient access may limit windows obtainable during transport

Summary

• Ultrasound technology allows for high quality ultrasound imaging to occur in the pre-hospital settings. Studies can be rapidly performed.
• The use of ultrasound in the pre-hospital setting has the potential to improve trauma, cardiac and obstetric care.
• Several research projects on rotor-wing ultrasound and ground EMS ultrasound are ongoing in the USA and Europe.
• Larger well-designed multicenter pre-hospital ultrasound studies are needed to reduce bias and assess impact on care.
  
  
  Video 1. Positive Morison’s pouch – prompted early blood and tranexamic acid administration
  
  
  Video 2. Absent sliding signs – not resolved after needle thoracostomy
  
  
  Video 3. Sliding lung signs after finger thoracostomy performed

References

1. Taylor J, McLaughlin K, McRae A, et al. Use of prehospital ultrasound in North America: a survey of emergency medical services medical directors. BMC Emerg Med. 2014;14:6.
2. Walcher F, Weinlich M, Conrad G, et al. Prehospital ultrasound imaging improves management of abdominal trauma. Br J Surg. 2006;93:238-42.
3. Brun PM, Bessereau J, Chenaitia H, et al. Stay and play eFAST or scoop and run eFAST? That is the question! Am J Emerg Med. 2014;32:166-70.
4. Quick JA, Uhlich RM, Ahmad S, et al. In-flight Ultrasound Identification of Pneumothorax. Emerg Radiol. 2016;23:3-7.
5. Kim CH, Shin SD, Jun Song K, et al. Diagnostic Accuracy of Focused Assessment with Sonography for Trauma (FAST) Examinations Performed by Emergency Medical Technicians. Prehosp Emerg Care. 2012;16(3):400-6.
6. Heegaard W, Hildebrandt D, Spear D, et al. Prehospital ultrasound by paramedics: results of field trial. Acad Emerg Med. 2010;17(6):624-30.
7. Rooney KP, Lahham S, Lahha S, et al. Pre-hospital assessment with ultrasound in emergencies: implementation in the field. World J Emerg Med. 2016;7(2):117-23.
8. Wydo SM, Seamon MJ, Melanson SW, et al. Portable ultrasound in disaster triage: a focused review. Eur J Trauma Emerg Surg. 2016;42:151-9.
9. Eyre AJ, Stone MB, Kimberly HH. Point-of-care ultrasonography in a domestic mass casualty incident: The Boston marathon experience. Emerg Med Open J. 2016;2(2):32-5.
10. Ketelaars R, Beekers C, Van Geffen GJ, et al. Prehospital Echocardiography During Resuscitation Impacts Treatment in a Physician-Staffed Helicopter Emergency Medical Service: an Observational Study, Prehospital Emergency Care, 2018 DOI: 10.1080/10903127.2017.1416208 (accessed April 12, 2018)
11. Ketelaars R, Holtslag JM, Hoogerwerf N. Abdominal prehospital ultrasound impacts treatment decisions in a Dutch Helicopter Emergency Medical Service. European J Emerg Med. 2018.
12. Ketelaars R, Hoogerwerf N, Scheffer Prehospital chest ultrasound by a Dutch helicopter emergency medical service. J. Emerg. Med. 2013;44(4):811-7.
13. O’Dochartaigh D, Douma M, MacKenzie M. Five-year retrospective review of physician and non-physician performed ultrasound in a Canadian Critical Care Helicopter Emergency Medical Service. Prehosp Emerg Care. 2017;21:24-31.
14. O’Dochartaigh D, Douma M. Prehospital ultrasound of the abdomen and thorax changes trauma patient management: a systematic review. Injury. 2015;46:2093-102.
15. Chin EJ, Chan CH, Mortazavi R, et al. A pilot study examining the viability of a prehospital assessment with ultrasound for emergencies (PAUSE) protocol. J Emerg Med. 2013;44(1):142-9.