The use of bed-side ultrasound is growing — but are ERs ready?
Wednesday, March 11, 2015
Ultrasonographic investigation — in its traditional approach — involves many steps and multiple professionals, including radiologists and certified sonographers. This approach might not be necessarily helpful for critically-ill patients and immediate patient management.
However, recent technological advances in ultrasonography, inherent safety, relative ease of use and portable machines capable of producing high-quality imaging have made it an invaluable point-of-care tool. Acute-care physicians can effectively use ultrasonography to provide important clinical information with a large impact on rapid assessment of critically-ill patients, as well as for patient care and relatively safe invasive procedures.
The range of its utility can be quite wide in the acute-care setting and intensive-care practice, ranging from intracranial pressure (ICP) estimation and transcranial Doppler studies in neurocritical care, airway management in percutaneous tracheostomy, and abdomen imaging, to using it as a screening tool for deep vein thrombosis (DVT) of the lower extremity.
The traditional landmark technique for central venous catheterization has been successful in general. However, in the presence of abnormalities or vein thrombosis, it might encounter some difficulties. To address these scenarios, ultrasound guidance can be effectively used with a high-frequency microconvex or linear probe (8-15 MHz) to maximize the success of ultrasound-guided line insertion.
Likewise, it has been strongly suggested that ultrasound guidance has improved the success rate of internal jugular vein cannulation by reducing the access time and the number of attempts before a successful one, as well as the incidence of potential complications.
As for subclavian vein cannulation, the role of real-time ultrasound guidance is less specified. However, in a randomized controlled trial, researchers achieved a 100 percent success rate upon the use of real-time ultrasound versus 87.5 percent with the use of landmark technique, with significantly more complications in the latter use.
Due to inherent safety of blind techniques for femoral vein cannulation, the use of real-time ultrasound has been less studied in this utility. Lower-limb DVTs can also be effectively diagnosed with compression ultrasound (linear probe of 5-12 MHz frequency) with a high level of specificity and sensitivity.
Furthermore, focused assessment with sonography in trauma (FAST) can assess the presence of free fluid in the peritoneal and pericardial cavities. This can be done with a curvilinear phased array probe (3.5-5 MHz frequency). This could be a quick, useful noninvasive tool as an alternative to CT scans in a critically-ill patient without a need to transfer the patient out of the emergency room.
Also, ocular ultrasound measurement of the optic nerve diameter (ONSD) has been shown to be helpful in a bedside manner in traumatic brain injury patients to measure ICP, which was traditionally measured by invasive intraparenchymal or intraventricular catheterization. This bedside method has been shown to have sensitivity of 83 percent and specificity of 100 percent at a cutoff of 5.2 mm in order to predict an ICP rise of more than 20 Hg.
Furthermore, brain death can be diagnosed with the help of transcranial ultrasonography (TCD), where it can assess the delayed cerebral vasospasm due to subarachnoid hemorrhage by simply measuring the blood flow in the middle cerebral artery. However, one of the drawbacks of TCD is its inability to suggest a range specifically in the elderly as well as female patients.
In the case of extensive orbital edema, it is easily possible to use ultrasound to assess the pupillary size as well as the ultrasound-induced reaction. Finally, bedside ultrasound allows for airway ultrasonography and direct bilateral viewing of lung expansion following endotracheal intubation.
With all this said, it is of crucial importance to practice caution when utilizing point-of-care ultrasound not to rush into inappropriate therapeutic decisions due to inadequate training of the emergency physician with this bedside diagnostic tool.
One way to address this issue could be to include appropriate standardized training modules — both theoretical and practical — for this diagnostic tool in the medical university curriculum to make sure that all the newly graduated doctors in general medicine are capable of effective handling this bed-side diagnostic tool.
Furthermore, we need to think and standardize the scope of practice as well as the quality assurance aspect of it.
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