This ultrasound by Dr. EH nicely demonstrates the near complete collapse of a patient’s IVC (inferior vena cava) during inspiration who presented with shortness of breath.

 

During inspiration, the intrathoracic pressure in the chest decreases, causing more blood to rush into the heart and in a normal patient the IVC is expected to collapse around 50%. If a patient is dehydrated, or in hypovolemic or distributive (septic or anaphylactic) shock, the patient with be intravascularly depleted and the IVC will likely collapse more than 50% on inspiration.  If a patient is in cardiogenic or obstructive (PE or tension pneumothorax), when the patient’s breaths in and intrathoracic pressure decreases blood will try to rush to the heart, but will back up, therefore not allowing the IVC to collapse.  A patient in cardiogenic or obstructive shock will therefore likely have a minimally collapsing IVC or one that does not collapse at all.

 

Using a patient’s IVC to determine a patient’s “volume status” has been a highly debated topic in Emergency Medicine literature in the last 10 years.  If you google “IVC” and “emergency medicine” you will find many arguments as to the exact accuracy of IVC measurements and the final “correct” answer has yet to be determined.

 

However, I think most will agree that a patient with an almost fully collapsable IVC (like this one) will likely have lower right atrial pressures and tolerate fluids easily and probably never be in cardiogenic shock while one that is almost not collapsable likely has higher atrial pressures and fluids, if given, should be given very cautiously.

 

So, try to get good at finding the IVC because, like auscultation of the lungs, it can be used as another important piece of information to help you do the right thing for your patient.