Many may look at the Inferior Vena Cava (IVC) to get a sense of a patient's “fluid responsiveness.” However, there are many pitfalls to using the IVC. An article by Via et al outlines these pitfalls and is an interesting read! 

To summarize, IVC can be affected by:

1. Ventilator Settings such as high PEEP
2. Patient's inspiratory efforts such as significant respiratory efforts
3. Asthma/COPD exacerbations
4. Cardiac Conditions impeding venous return such as tamponade or RV dysfunction
5. Increased abdominal pressure such as intra-abdominal hypertension
6. Other factors such as asking the patient to take a breath in, poor measurements, ivc compression by masses or ECMO cannulae

Bottom Line: Think twice before using IVC to evaluate for fluid responsiveness.

References

Via G, Tavazzi G, Price S. Ten situations where inferior vena cava ultrasound may fail to accurately predict fluid responsiveness: a physiologically based point of view. Intensive Care Med. 2016 Jul;42(7):1164-7. doi: 10.1007/s00134-016-4357-9.