Hemodynamics 2: cardiac output, mixed venous O2, shock indices- Elias Hanna, Univ Iowa

-Methods to estimate cardiac output, and detailed explanation of their pitfalls
-Importance of mixed venous O2, and which chambers to sample, and importance of SVC O2 vs IVC O2
-Cardiogenic shock indices
**Note regarding the use of thermodilution in atrial fibrillation (22:20):
CO (heart rate x stroke volume) rises with increased heart rate, up to a certain rate wherein diastolic filling sharply drops (~R-R of 500 ms or rate beyond 120 bpm). CO also sharply drops at R-R over 700 ms (rate less than 85 bpm), as diastolic filling does not rise enough to compensate for the rate drop. For the same heart rate, e.g., 100 bpm, the worst CO is seen when R-R varies between too long (rate less than 85 bpm) and too short (rate over 120 bpm). CO particularly drops with a long-short R-R sequence, causing at times a pulse deficit.
Thermodilution estimates cardiac output from few cardiac beats and assumes steady flow. In irregular rhythms with beat-to-beat variability, the sampled beats may not represent the average cardiac output. Less CO variability is seen when all sampled R-R intervals are within a rate range of 85-120 bpm, or when all R-R intervals correspond to less than 85 bpm, with no long-short sequences. Perform at least 5 measurements, and average the ones that are within 25% range. The same rate ranges are desired when assessing transvalvular gradients.

[@Nikesnipe]

thank you Doc Hanna

[@matheuscsmed]

Thank you, Matheus Silva

[@ahmeddaoud9901]

Thanks so much for amazing Lecture

[@user-wm6hf2nw2j]

Thank you for the helpful video!

[@moustafakamalsaad2293]

thank you very much

[@duhaaljowder4929]

Thank you for the amazing video and clear explanation. Which reading resources do you recommend for hemodynamics?

[@awaisshafi9314]

how can we get slides ?

[@m.s3815]

Hi Dr Hanna and thanks again for this excellent talk. Please what's your suggestion for how to measure cardiac output in the presence of AV fistula (hemodialysis' access)?

[@eliashanna8248]

Thank you. The same methods of cardiac output calculation, particularly thermodilution, remain applicable in AV fistula. Keep in mind that AV fistula may cause a high output state (depending on the size of the AV shunting). One caveat is that SVC saturation may be excessively increased from the stream of AV shunting at the upper limb level, and may excessively exceed IVC sat. PA sat usually still correlates with CO, and Fick using PA sat is usually still applicable, unless the shunt flow is very large (but thermo should remain accurate).

[@m.s3815]

@@eliashanna8248 Excellent. Thank you very much. what's your view of closing the av fistula manually or in cath lab by device and then calculating output with or without av fistula flow? I haven't seen any document evaluating this.

[@eliashanna8248]

Yes, this is appropriate in dialysis patients with fistula and high-output HF. You can assess the hemodynamic response (esp RA/PA/PCWP and CO) to manual compression of the fistula, in order to decide about its revision. Hemodynamics generally improve with this in high-output HF, as preload is significantly reduced, but beware that compression may also abruptly raise afterload and SVR which may counterbalance some of the benefit (esp on LVEDP). There are many case reports in the literature, many from the 1970s (jamanetwork.com/journals/jamainternalmedicine/article-abstract/585402). I had one such case in my hemodynamic book (2012). Here is a recent review: www.annalsofvascularsurgery.com/article/S0890-5096(21)00109-6/pdf

[@m.s3815]

@@eliashanna8248 Thank you very much. As always, excellent. Thanks for your time. Very helpful.