Except when that picture causes the pt to receive an invasive procedure that they didn't need in the first place. There are very few emergency indications for bedside US, even in the ER. I will agree that a FAST exam can change pt care in the field. In the proper setting (ie trauma), fluid in the belly means go to the trauma center. There are not very many services that allow pericardiocentesis. OB, eh. If they are pregnant and have anything that might be OB related you should be going to a properly equipped hospital anyway. Anything else is to reduce length of stay in the ER and not really necessary in the field (gallbladder, DVT, retina, etc).