Liver Labs Are Not Just Background Noise

What rising bilirubin can reveal about right-sided congestion, mechanical support, and the value of asking the question

I used to think of liver labs as background noise.

In the NICU, I was well-versed in bilirubin. We watched it closely, trended it, and treated it. Bili lights were routine, and it felt very routine.

Years later, I moved into adult cardiovascular care, and honestly, I stopped thinking about it. The liver function panel was there, but it didn’t feel immediately useful. I was focused on the lungs, the circuit, and the hemodynamics. The liver felt like something that went bad later, not something I could do anything about at the bedside.

That changed recently.

I remember standing there while a physician was adjusting RVAD support with C-Mag and saying something like, “His LFTs are up, so we can try more flow.” I nodded like I understood exactly what he meant.

I didn’t.

And honestly, I probably shouldn’t have nodded. It’s easy to do that at the bedside—to go along with something so you don’t look like you’re missing it. But if you actually want to get better at this, you have to ask the question, even if it makes you feel a little uncomfortable in the moment.

Later, I went and talked to my supervisor. She’s one of those people who just gets it. She’s basically my Red Book at work. I asked her to explain it to me, and she did.

When the right side of the heart isn’t moving blood forward well, pressure backs up. It doesn’t just stay in the heart. It moves into the venous system, and one of the places that feels that pressure the most is the liver. The liver becomes congested.

Over time, that congestion starts to show up in the labs. Bilirubin begins to rise, and AST and ALT can creep up as well. But bilirubin was the one that really made it click for me. It wasn’t that the liver was the primary problem. It was that it was sitting in a system under too much pressure.

That was the connection I had been missing.

The part that really stuck with me was seeing that tied directly to support. In a patient with right-sided failure, the thought process wasn’t just “the labs are abnormal.” It was: if pressure is backing up, can we improve forward flow and relieve that congestion?

One way to do that, in the right situation, is to increase right-sided support flow. Not for oxygenation. Not for CO2. For decongestion.

I remember thinking, “Hmm… we’re changing flow for the liver?”

That doesn’t mean liver labs are something you treat by turning a knob. They’re delayed, not specific, and not every elevation is due to congestion. Sometimes it’s low flow or ischemia. Sometimes it’s something else entirely. But they can be a signal.

If the liver is congested, it’s often because the venous side of the circulation is congested.

Now, when I see rising bilirubin or abnormal LFTs, I don’t just think “the patient is getting worse.” I will now ask the question: Is this telling me something about right-sided pressures or congestion?

When it comes to mechanical support, the answer isn’t always simple. Increasing flow may help if it truly unloads the right side and improves forward flow, but it depends on the whole picture.

But the way I think about it has changed.

The liver function panel is no longer background noise for me. It’s another piece of the hemodynamic picture. Not something I react to in isolation, but something I will start paying attention to.

Because sometimes the liver is just quietly telling you that the right side of the circulation isn’t doing what you think it is.

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