Introduction
Point-of-care ultrasound (POCUS) has seen a sharp increase in usage for emergency patients over the past two decades. Reference Becker, Martin-Gill, Callaway, Guyette and Schott1–Reference Yoo, Kang and Jo3 Any recent studies have demonstrated the ability for POCUS to improve diagnostic accuracy, Reference Shahbazipar, Seyedhosseini, Vahidi, Motahar Vahedi and Jahanshir4,Reference Alcaraz, Vaca, Hawker and Klas5 provide crucial information for management change, and may reduce mortality rates in critically ill and emergency patients. Reference Kanji, McCallum, Bhagirath and Neitzel6 However, providing care to prehospital patients was extremely challenging. Emergency Medical Services (EMS) are the type of operations that necessitates quick decision making to offer emergency treatment to patients in distress.
Research shows POCUS is an effective tool when it comes to performing a quick initial evaluation, detecting aberrant pathology, and making a diagnosis in both cases of medical illness as well as for injured patients. Moreover, prehospital ultrasonography has been proved in numerous studies Reference Scharonow and Weilbach7–Reference Press, Miller and Hassan9 to be feasible for a wide range of operators, including flight attendant nurses, paramedics, and emergency medicine physicians.
In Thailand, over the past decade, ultrasonography education has become more accessible to emergency physicians leading to a dramatic increase in the use of ultrasound in the emergency department. This new technology also includes the handheld ultrasound device that has been introduced to university centers. Due to recent advances, ultrasound technology is now less expensive than other diagnostic imaging equipment, making it available in a wide range of health care economies; they have also become relatively portable, which makes them ideal for the unique environments of various prehospital settings where they are being used. Reference Lapostolle, Petrovic and Lenoir10
The body of current studies regarding portable or handheld ultrasounds is limited in number. Most studies reported include the assessment of EMS personnel to perform ultrasounds, Reference Becker, Martin-Gill, Callaway, Guyette and Schott1,Reference Nadim, Laursen and Pietersen11–Reference Joyce, Tozer, Vitto and Evans13 the feasibility of ultrasounds for triage in the field setting, Reference Yuen, Chan and Ahuja14 and the utility of ultrasounds in disaster settings. Reference Shorter and Macias15 However, ultrasounds used in prehospital settings in Thailand during the initial phase of diagnosis is limited in the university centers. In addition, there have been no studies on the use of POCUS for EMS in Thailand. The primary objective of this study was to describe the characteristic of POCUS used in the care of prehospital patients and to demonstrate the diagnostic accuracy of POCUS used in a prehospital setting.
Methods
Design and Setting
This study was carried out as a cross-sectional, observational analysis of ultrasound images obtained from 169 patients presented to the EMS unit of Srinagarind Hospital in Khon Kaen Province, Thailand for evaluation and treatment over a 12-month period from January 2021 through December 2021. This hospital is the leading medical training hospital of Khon Kaen University and advanced tertiary care institution in Northeastern Thailand, which has an average of roughly two thousand EMS operations per year.
Data Collection
Images were obtained using a Butterfly IQ handheld ultrasound machine (Guilford, Connecticut USA). This ultrasound device permits users to obtain two-dimensional imaging, utilizing the M-mode, B-mode, and Color Doppler mode. The preset of the ultrasound device can be set as: Abdomen, Aorta, Gall Bladder, Bladder, Cardiac, FAST, Lung, Musculoskeletal, Nerve, Obstetric, Ophthalmic, Pediatric Abdomen, Pediatric Cardiac, Pediatric Lung, Small Organ, MSK-Soft Tissue, and Vascular.
Ultrasonography was performed either at the emergency site (on scene) or during patient transport by emergency medicine residents who had completed POCUS training which included didactic lectures and hands-on POCUS practice with actual patients. These sessions were monitored by POCUS experts (emergency ultrasound certified physicians) and guidance was provided when needed. Selection of cases depended on the treating physician. Exclusion criteria included unstable trauma patients, shockable cardiac arrest patients, and patients with incomplete data. Standard treatments were given during POCUS examination including airway protection, oxygen therapy, intravenous fluid, and drug administration. Patients’ provisional diagnoses were given by treating physicians after performing POCUS in an ambulance. The POCUS images and video clips were recorded in the Butterfly IQ web-based platform, which were reviewed by POCUS experts to determine the accuracy of the interpretation. The electronic emergency department medical records and the EMS database were reviewed and extracted data including patient demographic information, type of illness, patients’ provisional diagnoses at the scene, and patients’ final diagnoses by two independent emergency physicians. Following that, the duplicate data entry was completed. In the event that the data did not match, the senior emergency physician was consulted, and the correct data were obtained.
Study Size
The sample size was calculated based on the following formula. Reference Šimundić16 The estimate for P was made using data from a previously published study; Reference Scharonow and Weilbach7 it was determined that a sample size of 169 would be required. Statistical analysis was performed with Khon Kaen University license (SPSS Inc.; Chicago, Illinois USA) by IBM SPSS for Windows version 27.0. Unless otherwise stated, continuous variables are reported as mean and standard deviation (SD), and categorical variables are presented as number (n) or frequency (percent).
Ethical Considerations
Ethical approval was provided by the Khon Kaen University Ethics Committee for Human Research (HE641323). Requirement for informed consent from the patients was waived since patient confidentiality protection had been guaranteed, as patients were not identified by name but by a unique study number.
Results
The study was performed over a period of 12 months which included 2,012 EMS operations. A total of 1,348 patients were assessed by emergency medicine residents, with 180 of them receiving POCUS examinations. In 169 cases, POCUS images and videos were recorded.
Male patients were represented as 45.6% in this study. All patients receiving POCUS examinations were medical cases (100.0%). Most patients assessed with POCUS were triaged as Level 1 and Level 2, categorized as red (42.0%), and Level 3, categorized as yellow (58.0%), according to the Emergency Severity Index (ESI), as shown in Table 1.
Table 1. Demographic Data of Prehospital Patients Receiving POCUS Examination (N = 169)
Abbreviations: EMS, Emergency Medical Services; POCUS, Point-of-Care Ultrasound.
The prehospital emergency ultrasound was most used in patients with dyspnea (45.6%), hypotension/shock (30.1%), and syncope (8.2%). There was no ultrasound protocol used in a prehospital setting. There were 208 POCUS examinations performed in this study, which showed that the most common area where POCUS was performed was the lung (37.0%), followed by the inferior vena cava (30.8%), and finally for cardiac (26.4%). This study demonstrated that 34.9% of findings were abnormal sonographic findings (Table 2).
Table 2. Characteristics of POCUS Performed in EMS Patients
Abbreviations: EMS, Emergency Medical Services; POCUS, Point-of-Care Ultrasound.
In patients who underwent prehospital POCUS examinations, treating physicians confirmed the prehospital diagnosis in 66 cases (39.1%). The accuracy of prehospital diagnosis was 75.8% (50/66). In 28 out of 77 (36.4%) patients who presented with tachypnea/dyspnea, the prehospital diagnosis was confirmed as pneumonia (8/12; 66.7%), heart failure (4/6; 66.7%), and volume overload (9/9; 100.0%). One patient who came with tachypnea and one patient with hypotension were confirmed to be diagnosed as having a pulmonary embolism. In two out of eight cases (25.0%) that presented with chest pain, the diagnosis of acute coronary syndrome was confirmed. Prehospital POCUS examination demonstrated intra-abdominal free fluid in four cases, which confirmed the diagnosis as ruptured ovarian cyst and spontaneous bacterial peritonitis. In six out of 14 cases (42.9%) that presented with syncope, the treating physician arrived at the diagnosis as hypovolemia (5/5; 100.0%) and cardiogenic syncope (1/1; 100.0%). In 12 out of 51 cases (42.9%) that presented with hypotension/shock, small inferior vena cava was detected and confirmed the diagnosis as hypovolemic shock (9/12; 75.0%).
Discussion
This study highlighted the utility of POCUS examination in prehospital care. There are two main objectives: firstly, describe the characteristic of POCUS used in prehospital care, and second, determine the correlation between prehospital diagnosis given by treating physicians who used POCUS examination in patient care and in hospital diagnosis results.
This study demonstrated prehospital patients who received POCUS examinations were all medical cases, which was in contrast to previous studies. Reference Scharonow and Weilbach7,Reference Ay and Canakci17–Reference Lenz, Phelan and Grawey19 This may be due to the nature of EMS operations in trauma patients in Thailand, which are usually performed as “Scoop and Run” in which treating physicians perform Focused Assessment with Sonography for Trauma (FAST) examination in a hospital setting after the primary survey according to Advanced Trauma Life Support (ATLS) protocol. Reference Bloom and Gibbons20 No ultrasound protocol was used in this study, which was in contrast to other studies. Reference Scharonow and Weilbach7,Reference Mercer, Ball, Cash, Rivard, Chrzan and Panchal21,Reference Keikha, Salehi-Marzijarani, Soldoozi Nejat, Sheikh Motahar Vahedi and Mirrezaie22 The main reason was the short transport time in Srinagarind EMS operations due to the area covered by EMS being not too far from the hospital. The most POCUS indication was dyspnea and shock, which was consistent with previous studies. Reference Scharonow and Weilbach7,Reference Bøtker, Jacobsen, Rudolph and Knudsen18 This study did not include patients with cardiac arrest. This may be due to the fact that complicated interventions Reference Yalçınlı, Karbek Akarca, Can, Uz and Konakçı23 are usually performed to take care of these patients during the transport; hence, physicians could not have enough time to perform POCUS. However, previous studies Reference Kreiser, Hill and Karki24–Reference Chang, Jeong and Eun Park26 demonstrated the feasibility and the utility of POCUS in out-of-hospital cardiac arrest patients, which showed the advantage of POCUS used.
This study recorded 34.9% of sonographic findings as abnormal and the accuracy of prehospital diagnosis was 75.8%. In another study, Reference Scharonow and Weilbach7 the prehospital diagnosis was confirmed in almost 90% of cases. This study has shown lower percentages of the diagnostic accuracy. The main reason may be due to the emergency medicine residents who were treating physicians at that time were pioneering the use of handheld ultrasound in prehospital care, which likely affected the sonographic skill. Another reason may be due to the limit of operation area in the ambulance, the limitation of brightness in the ambulance, and the physicians’ pressure from time constraints.
In Thailand, this study was the first prehospital POCUS study which demonstrated the correlation between the diagnostic accuracy of prehospital diagnosis and in hospital diagnosis. There is no formal POCUS training program for EMS providers. Reference Apiratwarakul, Ruamsuk and Suzuki27 Training courses in POCUS were limited in the medical training center, especially for emergency medicine residents. Reference Ienghong, Cheung, Tiamkao, Bhudhisawasdi and Apiratwarakul28 This initial effort to apply POCUS in prehospital care needs to be reproduced in the community to improve the current situation. The trained emergency medicine physicians could be potential trainers in future training programs for the other levels of EMS providers.
Limitations
The study’s limitations were: (1) data collection from a single EMS, single level of EMS personnel, which may have a different perspective on the studied population than other organizations – as a result, data should be gathered from a variety of research organizations; (2) this study did not demonstrate the quality of image acquisition acquired from other handheld ultrasound devices; (3) this study did not determine the effect of POCUS examination to the time of EMS operation; and (4) this study did not identify the association of POCUS examination among the change of patient management and the patient outcome.
Conclusions
Handheld POCUS can potentially be an additional diagnostic tool in the prehospital setting. The POCUS examinations revealed significant pathology that aided treating physicians in giving correct diagnoses. Future studies are needed to determine what role POCUS may play in prehospital care.
Conflicts of interest/funding
This research was funded by the Research and Graduate Studies, Khon Kaen University, Thailand. The authors declare no conflicts of interest.
Acknowledgment
The authors would like to express their sincere gratitude to Josh Macknick for acting as an English consultant. They also would like to thank the EMS unit, Srinagarind Hospital for the collection of valuable operational data.
Open access
