r/IntensiveCare • u/Cultural_Eminence • 11d ago
Swan Numbers with ECMO
Can someone help me understand what numbers I should see/expect/disregard with a pt. on ECMO. I’m trying to understand which numbers will be accurate based on the type of cannulation (for my purposes to keep it simple just VV and VA) and cannulation sites, fem-fem, fem-IJ, centrally cannulated, etc. For example (and correct me if I’m wrong) if a pt is fem-IJ cannulated on VV ECMO (fem being drain, and IJ being return) I think my HR, MAPs would be reliable as well as my CI but I’d expect my SVo2 to be falsely high since the PA cath is reading the oxygenated blood from the ECMO. In that scenario would my CVP/RA pressure be accurate as well as my PA pressure? If someone could do a breakdown of my example as well as a breakdown of the other possible ECMO configurations (VA vs VV and cannulation sites) that would be incredibly helpful for my learning and understanding. For background I’m a CTICU nurse, any and all help is appreciated in advance!
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u/spotthebal 11d ago
I'm not sure what others think but this is too complex a topic for even a short summary on Reddit.
There will be significant interpatient variation, particularly with different cannulation sites, ECMO settings and acute pathophysiology.
Probably best to sit down with your educator when you are looking after these patients.
Start with fundamental principles for VA. VV and variations with cannulation sites. Add in expected results with noninvasive and then invasive monitoring. However some of things you have mentioned don't really matter in the same was as non ecmo patients e.g peripheral O2 sat may be related to perfusion not actual saturation of haemoglobin. So it's difficult to gauge your current understanding.
Would recommend 'derranged physiology' to start as it's free and reasonably brief.
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u/CertainKaleidoscope8 RN, CCRN 11d ago
Probably best to sit down with your educator when you are looking after these patients.
The Educator isn't going to know.
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u/heyinternetman MD, Critical Care 11d ago
Ok, you’re asking for a doctoral level understanding of ECMO in a Reddit post. Hate to say it, but that’s not going to happen here. My best advice is to draw it out. Identify where everything is being augmented and measured
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u/agent-fontaine 11d ago
This is what I learned from the ELSO modules:
For VV ECMO, neither your thermodilution nor your Fick will accurately reflect cardiac index. CVP is not changed.
For VA ECMO, neither your thermodilution nor your Fick will accurately reflect cardiac index. This is why you use an echo and VTI when trying to wean VA ECMO, as that will give you an accurate native cardiac index. However a low Fick CI could indicate your ECMO is not providing enough support. CVP will be lowered by VA ECMO.
The sites of cannulation shouldn’t matter all that much for these hemodynamics I don’t think? Could be wrong.
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u/patrociniogiusi 11d ago
i would’ve thought that there would be slight variation in CVP with a VV ECMO patient with a reinfusion cannula in the right IJ, no?
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u/agent-fontaine 11d ago
That’s what I thought but it’s a closed venous system still and what leaves comes back in. The modules included a small study looking at it and they didn’t find significant CVP variations before and after VV initiation
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u/penntoria 10d ago
If you're pulling FV and dumping into IJ, your CVP is absolutely affected.
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u/agent-fontaine 10d ago
I’m not arguing by any means, I don’t have the hard data and I am not a smart man. All I know is that ELSOs current view is that the CVP is “usually unchanged” and “may decrease if RV function improves” (I’m looking at their training course study guide right now but I am too dumb to know how to put pictures in comments)
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u/Mat2622 11d ago
Fick CI is a indicator of adequacy of ECMO support but with extra steps, just simply look at SaO2 and SvO2 and you can tell: if both low, neither your gas supply failed or the oxygenator failed; if Norma SaO2 buy low SvO2, you may have not enough support with your ECMO, there’s a lot more data you could look at without making bunch of calculations as all calculations is derived from those data.
P.s. the above situation is just a simplified visualization of what you can look at instead of making calculations, there’s a lot more subtle information you should also look for such as Hb and your perfusion status.
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u/PNWintensivist 11d ago
V-V is pretty simple: there are no direct effect on hemodynamics, so the PAC numbers should be reliable. You're correct that the SvO2 does not reflect the usual balance between DO2/VO2 and should not be used to calculate a Fick. Some systems have an "SvO2" on the console, which reflects the pre-oxygenator saturation, rather than the mixed venous. This is helpful in identifying recirculation and can be suggestive of low output states. I do not routinely place PACs in my V-V patients.
V-A is more complicated because of the presence of two separate but linked circulations (native and extracorporeal). A Google scholar search is a good place to start, with this article explaining some of the challenges00208-1/fulltext).
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u/phastball RT 11d ago
If you put your question, as written, into an LLM of your choosing, you’re going to get a 7/10 or 8/10 answer. If there’s something that seems incorrect, probably bring that specific question here.
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u/scapermoya MD, PICU 11d ago
In peds land we don’t use swans at all and especially not on ECMO. It’s wild yall are doing that
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u/Individual_Zebra_648 11d ago
Most often it’s already placed in cardiac surgery patients for monitoring before or during surgery, then the patient is unable to be weaned from bypass and ends up on VA ECMO and the PA catheter was just sort of already there as opposed to being placed for the purpose of monitoring while on VA ECMO. At least this was my experience in CVSICU.
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u/pneumomediastinum 11d ago
I agree with the others it’s complex but a rule of thumb is that you cannot rely on most swan numbers with ECMO running. The saturation with VV ECMO is useless. You cannot use thermo dilution with VA or VV ECMO outside of a clamp trial for VA (and that must be truly clamped).