Ultrasound has long been accepted as a safe and accurate imaging modality. Over the last several decades, advances in the equipment, training, and applications of ultrasound have expanded its use as a point-of-care tool. Increasing evidence supports the use of bedside ultrasound as advantageous to both the clinician and the patient, particularly in the critical care and emergency setting.
Ultrasound first became available for clinical care in the 1960s and began to be used widely by various specialties by the 1970s. Early ultrasound machines were bulky, expensive, complex, and time consuming to use. In the late 1980s, advances in ultrasound equipment made point-of-care ultrasound (POC US) more feasible. Machines became more compact and portable, allowing them to be taken to the bedside easily. This equipment has continued to develop with improved imaging, better displays, easier image transmission and storage, and less expensive equipment.
Initial reports of POC US use emerged in the 1970s from Europe. These studies described the use of ultrasound in detecting free fluid by surgeons in acute trauma. In 1988, David Plummer, an emergency physician from the United States, described how bedside echocardiography could save lives in patients with penetrating trauma. In 1993, the FAST acronym was coined at an international consensus conference, initially standing for “focused abdominal sonography in trauma” and later expanded to “focused assessment with sonography in trauma.” The FAST exam allowed expeditious diagnosis of hemoperitoneum, hemothorax, and hemopericardium in trauma patients. The FAST exam is widely used and has been incorporated into the ATLS (Advanced Trauma Life Support) protocol.
Emergency medicine as a specialty was a relatively early adopter of POC US. In 1994, the Society for Academic Emergency Medicine (SAEM) published a “model curriculum” for bedside ultrasound training in residency. In 2001, the American College of Emergency Physicians (ACEP) published their “Emergency Ultrasound Guidelines,” including recommendations on the scope of practice, indications to perform bedside exams, the credentialing process, quality assurance measures, documentation procedures, and the appropriate practices and standards that emergency physicians should adhere to. These guidelines were updated in 2008 to reflect the advancing technology and new applications that have since emerged.
POC US has been used in the critical care setting for decades, particularly to guide procedures such as central venous access. Ultrasound-guided central venous access was listed by the Agency for Healthcare Research and Quality (AHRQ) as one of the top ways to reduce medical errors, based largely on data from the critical care setting. More recently, interest in the use of POC US for focused diagnostic and additional procedural applications in critical care has increased. Organizations such as the Society of Critical Care Medicine (SCCM) have endorsed the benefits and have developed recommended training guidelines for the use of ultrasound in the intensive care unit. Recently, the Accreditation Council for Graduate Medical Education (ACGME) has required ultrasound training as part of critical care fellowships.
The core philosophy of bedside POC US is that it is a focused goal-directed examination (or set of focused exams) intended to answer specific binary questions or guide a procedure with direct impact on the care of the patient. POC US should be integrated with the history and physical examination of the patient.
The focus of acute POC US is different from exams done by consultative services, such as radiology, gynecology, or cardiology. These other specialties typically perform comprehensive organ-based ultrasound. Bedside POC US exams are focused, limited, and goal-directed. They are typically intended to answer a simple “yes” or “no” question: “Is there an aortic aneurysm present in this elderly patient with abdominal pain?” or “Is there an intrauterine pregnancy in a young woman presenting with pain and hypotension?” These exemplify patients who may have life-threatening conditions and the use of timely ultrasound can accelerate their treatment and improve the prognosis.
While consultant-performed ultrasound may be indicated in certain situations, there are many advantages to bedside POC US. Consultant-performed ultrasound typically involves transport of a patient out of the care area, where an examination is often performed by a sonographer, with images transmitted and interpreted by another individual. Any step of this process may be delayed or not easily available. Removing the patient from the care area consumes time and resources, and may be dangerous in patients with life-threatening conditions. Ultrasound at the bedside can be repeated as many times as needed to monitor a patient’s response to treatment. In many situations, bedside ultrasound may obviate the need for additional studies, particularly those that may be invasive (such as diagnostic peritoneal lavage), or imaging involving ionizing radiation.
Another advantage of POC US is that several goal-directed questions may be answered during a single POC examination. This is particularly helpful when a presenting sign or symptom could have several potentially serious etiologies. The fact that POC US may easily transition between cardiac and general applications also allow examinations that often could not be done without involving two separate consultants. The FAST exam is a good early example of this, combining focused views of the abdomen, pelvis, thorax, and heart as part of an integrated examination. Other such examinations may combine several focused applications in trying to determine the etiology of unexplained hypotension, dyspnea, or chest pain.