post-cardiac surgery diuresis

[medicine33123]

Question from a CC fellow:

I've yet to understand the diuresis approach in post-open heart patients in the CVICU that is used at my hospital by all of my cvicu attendings.
I notice the we generally start lasix bid 20-40 mg after 24hrs post-op, sometime 48hrs after if the patient is still unstable. Then there is usually a net negative goal of 500-1L daily with additional lasix doses as needed and this is continued for multiple days thereafter. The patients admission weight and current weight, I/Os, leg edema, CVP are all taken into consideration but it seems to me there is an overriding pattern of giving our patients lasix almost in a protocol manner based on a timeline postop with a goal net negative daily postop. I'm confused about this, can anyone explain having such a goal directed diuresis, has anyone seen something similar before. I cannot find any evidence on this, and I notice attendings making such quick and confident decisions about starting lasix and increasing the lasix dose based on UOP that I wonder if they actually did a volume status assessment and gave it some thought, it seems to me that there is a strong favor of just diuresing in sort of a pre-planned/protocolized way. I finished my cvicu rotation now and I just never asked them about this directly, it took me a long time to even figure out what we were doing, and this is the pattern I have noticed. Can anyone shed some light on this.

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[Radetzky]

Most of these patients will be several liters positive after the first 24 hours. Once their vasoplegia has settled, positive fluid balance is known to have several deleterious effects including on RV function, oxygenation, AKI.

There is some weak evidence that active protocolised “deresuscitation” may reduce duration of icu/MV.

 

[psychbender]

You're right, there's not a lot of data driving the exact regimen employed for a given patient. Most cardiac surgery patients will be several liters up from preop, given all of the resuscitation fluid given in the OR and the first 24hrs post-op. To avoid worsening respiratory status from pulmonary edema or organ dysfunction from venous congestion, some amount of diuresis will be performed to an arbitrary net negative fluid balance. I tend to see surgeons wanting to be super aggressive, often to the detriment of patients, and I take the tact of, "the kidneys are smarter than we are, let's not try to make them ******ed with a whole bunch of lasix and metolazone." If we're not in early organ injury from congestion or having significant respiratory issues, a goal of -500mL to -1L in a day is probably just fine, and the patient can GTFO of my unit. To achieve this, I'll often pick a dose (maybe 20mg IV if diuretic naive), see the response, and decide on an interval to reach that goal. It's not rocket surgery.

 

[chessknt]

In real life the CT surgeons are going to manage this because they are all insane. Just do whatever the attendings say and spend your brain power on something more useful.

 

[lymphocyte]

In real life the CT surgeons are going to manage this because they are all insane. Just do whatever the attendings say and spend your brain power on something more useful.

This is the way.

 

[medicine33123]

appreciate the responses

 

[Katheudontas parateroumen]

It sounds like you really should ask your attendings why they do what they do. And I totally respect someone when they say “This is just my opinion” or “I’m just trying something out” or “this is arbitrary”. At least they are intellectually honest that whatever they are doing isn’t based off some type of evidence. All attendings should explain their thought process in decision making and say “I don’t know” when they really don’t know. So often in medical training at all levels from Med student to fellow, we often think the attending has all the answers some how but in reality we definitely don’t. Sadly, that means a lot of what we do in medicine is just dogma or “it’s just how it’s done here” type medicine. I liked attendings who explained why they did what they did, acknowledged gaps/dogma , asked the right questions, got help. In fellowship, it is all about taking the good you see and improving upon the vast amounts of bad and hopefully not repeating it. Ask about thought process and emulate the people you look up to. You seem to want to base your decisions off of some evidence etc. I believe that is great. From your description, it appears this is just a deresusctiaiton effort based on net fluid balances with an end goal that is largely arbitrary.

 

[aafisahar]

Far more patients are harmed by underdiuresis after seeing a small bump in Cr than overdiuresis.

 

[ShockIndex]

I can only speak to how the surgeons at my shop in fellowship and my current hospital behave when it comes to post-op diuresis. @psychbender hit the nail on the head in that the overwhelming majority of patients will need some diuresis due to both physiologic and iatrogenic volume overload. This is particularly true for the MVR patients who had regurg prior to their procedure (less so for stenosis).

The notable exception is probably the AVR patients with severe AS prior to surgery. They tend to have a very thick LV and relatively small chamber dimensions. These patients can actually get into trouble with aggressive diuresis, and often need significant volume in their first day or two to keep that LV from forming intra-cavitary gradients. They tend to auto-diurese around POD 3 ("On day three, they shall pee") and I rarely push for lasix in the first 72 hours unless there is some competing physiology. The same goes for long, open aortic cases that typically come out of the OR rather volume down and needing resuscitation for the first 24 hours. We had an aortic surgeon who did these massive, open thoracic aortic cases on patients who for whatever reason were not TEVAR candidates that came out needing 4-5 liters of volume in the first 24 hours.

One nice thing about post cardiac surgery patients is that they often have PA caths coming out of the OR - especially if they had decreased function going into the case. So, you can use filling pressures and CI to help guide your resuscitation. The PA cath can also be very helpful in quickly identifying tamponade and RV failure patients who might otherwise look hypovolemic without that invasive data.

Finally, I went into fellowship after many years of practicing EM where albumin was pretty much never on my radar. It was saline until around 2018 and then LR after SALT/SMART were published. In fellowship, all of the surgeons and cardiac surgery PAs favored albumin for post-op and ECMO volume replacement. They still gave a good bit of LR, but we quickly added 250-500 of 5% albumin to patients needing a lot of volume and virtually all of our ECMO chatter got albumin assuming that decreases in RPMs didn't solve the problem. While the evidence is not of great quality, I've certainly had my fair share of post-op cases that were not turning around with crystalloid but loved a hit or two of albumin.

Finally, I know the nuances of who to diuese and when is painful in the CVICU - everyone has stopping opinions and the ABCs are too often Accuse, Blame, Criticize. However, with experience you will get good and this is often a very rewarding patient population to treat. Assuming your surgeons are good at choosing patients, they often come to the ICU sick as piss needing a lot of post-op resuscitation, turn the corner fairly quickly, and are back on the golf course in a month.