Ultrasound in Medical Practice
June 28, 2011 Leave a comment
Blog Post By Vicki E. Noble MD, RDMS, FACEP is Director, Division of Emergency Ultrasound, Department of Emergency Medicine, Massachusetts General Hospital and Assistant Professor, Harvard Medical School, Boston, MA, USA.
Over the last 15 years, there has been a seismic shift in how and when ultrasound is used by medical professionals. Increasingly, physicians, nurse midwives, nurse practitioners and other medical professional staff have started to incorporate bedside diagnostic ultrasound into their patient evaluation (1). The types of evaluations and the applications specific to different specialty practices vary, but the increasing availability of a bedside diagnostic imaging test has been encouraged by the rapid rate of technology evolution as ultrasound machines have become more portable, cheaper and easier to use.
This explosion of utilization puts point of care ultrasound is in a very interesting position currently. In an era in the United States where there is enormous pressure on curtailing the costs of healthcare and where much focus has been placed on the rapid rate of growth of diagnostic imaging over the last two decades, it might seem that the growth of bedside diagnostic ultrasound is something to be contained. This solution is not as obvious as it may seem at first glance, however, and indeed may be counterproductive. This is because there is more driving the increase in utilization than just technology availability.
The first push has been from highly specialized or tertiary care health care systems where the emphasis on point of care ultrasound has been to try and make more accurate diagnoses in order to streamline consultative testing and disposition to improve efficacy and impact patient outcomes. Evidence of this can be found in the emphasis in emergency medicine residency training; cardiac point of care ultrasound has a mortality benefit when performed on patients with suspected penetrating injury (2); eFAST scans have an impact on length of stay for trauma patients (3); ultrasound in patients suspected of ruptured aortic aneurysm get to the operating room faster when a bedside diagnostic ultrasound is performed (4). In addition, there has been an explosion in the description of point of care hemodynamic evaluations for the patient in shock (cardiac, IVC and lung ultrasound imaging protocols) emphasizing more rapid appreciation of the particular kind of shock (cardiogenic vs distributive) and the patient’s need for resuscitative efforts (fluids vs inotropy)(5-7).
The second push has been from under-resourced areas – whether it be rural health care systems in the United States, systems with long transport times in the prehospital setting (both civilian and military), or hospital systems that have physician and treatment capacity but no diagnostic imaging capacity. This second push is truly an international phenomenon as many hospitals throughout the world have limited access to computed tomography scanning and no access to magnetic resonance imaging. In these systems the only available diagnostic imaging is often xray imaging and image processing time (film development and interpretation) can be significant. The impact a mobile, reusable, battery powered, non-ionizing bedside diagnostic imaging strategy could have in these settings does not take an enormous leap of faith. Indeed, point of care ultrasound has been demonstrated to decrease the length of stay for emergency department patients with biliary colic (8), deep vein thrombosis (9) and first trimester pregnancy complications (10).
The greatest research challenge to point of care ultrasound, however, is to demonstrate its efficacy. While there is some limited evidence that performing lung ultrasound reduces chest radiography in certain settings (18, 19) much work remains to be done. Research into the outcomes of patients who have had diagnostic point of care ultrasound has largely been confined to studies looking at practitioner accuracy. This misses the two main driving forces behind the early adoption of ultrasound in so many settings – the impact on patient outcomes and the impact on the treating physician efficacy. Do patients do better? There is some evidence that they do but not enough. Do clinicians use less diagnostic resources? There is some evidence that they do but not enough. Do patients like ultrasound? There is some evidence that they do but not enough. The challenge remains that in a rapidly evolving health care system performing outcomes studies that isolate the effect of point of care diagnostic ultrasound is difficult but efforts are ongoing.
Vicki Noble is co-editor of Manual of Emergency and Critical Care Ultrasound published by Cambridge University Press