Ultrasound Comes to the Field
Portable ultrasound technology has become small, durable, and affordable enough for use in prehospital care. What once required a hospital radiology department can now be performed at the patient's side by a trained EMS provider using a device that fits in a cargo pocket. While not yet universal in EMS, prehospital ultrasound (PHUS) is growing rapidly and may become a standard tool for advanced providers.
Prehospital Ultrasound Applications
FAST Exam
The Focused Assessment with Sonography in Trauma (FAST) exam evaluates four areas for free fluid (blood): the right upper quadrant (Morrison's pouch), the left upper quadrant (splenorenal recess), the suprapubic region (pelvis), and the subxiphoid region (pericardium). In the prehospital setting, a positive FAST exam can influence transport destination decisions, guiding patients to trauma centers when internal bleeding is identified.
Cardiac Assessment
A subxiphoid or parasternal cardiac view can identify pericardial effusion, assess cardiac contractility, and help differentiate pulseless electrical activity (PEA) causes during cardiac arrest. Identifying a treatable cause like pericardial tamponade or severe hypovolemia can change resuscitation strategy and improve outcomes.
Pulmonary Assessment
Ultrasound can detect pneumothorax (absent lung sliding), pleural effusion, and pulmonary edema (B-lines). In trauma patients, identifying a pneumothorax in the field can prompt earlier needle decompression. In medical patients, differentiating between CHF and COPD exacerbation guides treatment decisions.
Vascular Access
Ultrasound-guided IV access improves success rates for patients with difficult veins, including patients who are obese, dehydrated, IV drug users, or pediatric. This application alone can significantly improve care by reducing delays in medication and fluid administration.
Limitations and Considerations
Prehospital ultrasound requires significant training to perform and interpret accurately. Image quality can be affected by scene conditions, patient body habitus, and provider experience. Ultrasound findings must always be correlated with the clinical picture. A negative FAST exam does not rule out internal bleeding, and prehospital ultrasound should not delay transport for critical patients. The role of ultrasound in EMS continues to evolve as training programs expand and evidence accumulates.