Hypovolemic?

In addition to Stu's post re: hypotension as a late manifestation of shock/the need to think of shock before a patient is hypotensive, one quick bedside tip by one of the army docs: if a patient is hypotensive and you're not sure if it's due to hypovolemia, lift his/her legs up in the air. If the BP improves, you have diagnosed hypovolemia without having to wait for other ancillary studies.