It's useful in a ton of situations, here are just a few examples: In a cardiac arrest patient, it's useful to know if the heart is actually moving or not (i.e.

It's useful in a ton of situations, here are just a few examples: In a cardiac arrest patient, it's useful to know if the heart is actually moving or not (i.e. you may be seeing electrical signals on an EKG, but the heart isn't physically responding). It's also useful to look for a buildup of fluid around the heart, called cardiac tamponade (which squeezes the heart and prevents it from working effectively). In trauma patients, a "focused assessment with sonography for trauma" or "FAST scan" is a quick way to check the common sources of major internal bleeding (which can provide useful guidance for treatment decisions in a very time sensitive setting). It's also useful for "routine" stuff like the placement of IVs. Ultrasound can be used to positively identify and locate veins that are otherwise difficult to feel through the skin.