So we've gone back and forth quite a bit on IVC ultrasound these past couple of days:

So it would probably be helpful to have some physiologic basis for all of this. Enter Jon-Emile S. Kenny MD, intensivist and practical physiologist. Here are some words and a video from him:

Guest Post

It is hard to believe that it was 3 years ago when I entered the vibrant and ever-expanding FOAMed community. The ethos of my contribution – heart-lung.org – was, and remains, the provision of lectures and learning modules in detailed physiology germane to the practice of critical care without cost – world-wide. To initially promote heart-lung.org, I wrote a brief piece on the physiology of IVC collapse at pulmccm.org

[http://pulmccm.org/main/2014/critical-care-review/inspiratory-collapse-inferior-vena-cava-telling-us/]

With that post, I had hoped to raise caution on the use of IVC collapse because of its complex physiology; I followed with another entry in early 2016 describing the mechanisms of false positives and false negatives for IVC collapse and detecting fluid responsiveness

[http://pulmccm.org/main/2016/cardiovascular-disease-review/that-fallible-ivc/]

Given the aforementioned, it is with tremendous interest that I read Dr. Marik’s commentary on IVC collapse and subsequent squabbles. Just 2 weeks ago, I was exceptionally honoured to have been invited to speak at the Department of Emergency Medicine Grand Rounds at Mount Sinai Hospital. For that talk, I started animating a slide on the physiology of IVC collapse & dilation, but did not finish it in time for my presentation. I have since finished the animation and would like to share it with you now. What I hope to illustrate clearly is that the relative simplicity of obtaining IVC data in vivo should not belie its complex physiological underpinnings and, therefore, its nuanced interpretation.

The following are pertinent references [1-8] for the animation:

Corl, K., A.M. Napoli, and F. Gardiner, Bedside sonographic measurement of the inferior vena cava caval index is a poor predictor of fluid responsiveness in emergency department patients. Emerg Med Australas, 2012. 24(5): p. 534-9. Corl, K.A., et al., Inferior vena cava collapsibility detects fluid responsiveness among spontaneously breathing critically-ill patients. Journal of Critical Care, 2017. 41: p. 130-137. Bodson, L. and A. Vieillard-Baron, Respiratory variation in inferior vena cava diameter: surrogate of central venous pressure or parameter of fluid responsiveness? Let the physiology reply. Crit Care, 2012. 16(6): p. 181. Muller, L., et al., Respiratory variations of inferior vena cava diameter to predict fluid responsiveness in spontaneously breathing patients with acute circulatory failure: need for a cautious use. Crit Care, 2012. 16(5): p. R188. Magder, S. and F. Bafaqeeh, The clinical role of central venous pressure measurements. J Intensive Care Med, 2007. 22(1): p. 44-51. Barbier, C., et al., Respiratory changes in inferior vena cava diameter are helpful in predicting fluid responsiveness in ventilated septic patients. Intensive Care Med, 2004. 30(9): p. 1740-6. Feissel, M., et al., Respiratory changes in aortic blood velocity as an indicator of fluid responsiveness in ventilated patients with septic shock. Chest, 2001. 119(3): p. 867-73. Juhl-Olsen, P., C.A. Frederiksen, and E. Sloth, Ultrasound assessment of inferior vena cava collapsibility is not a valid measure of preload changes during triggered positive pressure ventilation: a controlled cross-over study. Ultraschall Med, 2012. 33(2): p. 152-9.