An emergency physician uses ultrasound to provide a reliable and quick assessment on an incoming patient. One of the primary things that the physician needs to determine is does the patient have enough fluid in their system. Not enough fluid presents a number of risks. As too much fluid can also be problematic, a patient should not be put on fluid until their current state can be determined. This is an excellent article on determining the intravascular volume status using point-of-care bedside ultrasound to measure the diameter of the IVC at the end of expiration. A diameter of 2 cm is normal. 1. 5 to 2 cm is in the gray zone. A diameter of less than 1 cm is consistent with low intravascular volume. Additionally if the inspiration diameter depletes more than 50% from the expiration diameter then you are definitely dealing with a patient in need of crystalloid.
Another one of my favorites is Steve Socransky’s chapter on IVC in the “Point-of-Care Ultrasound for Emergency Physicians” ISBN 978-0-09880123-0-1