AST and ALT levels after open heart surgery

Specialties NP

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Hello, I have a question regarding what AST and ALT levels can indicate regarding heart function after open heart surgery. I understand that these levels are found in the liver, skeletal muscle and the heart, but I am used to evaluating liver function. I was told that elevated AST levels with normal ALT levels is indicative of "low flow". Can someone explain this to me? I can't find anything! Sorry for any errors or abruptness, I'm on my iPad.

I think they are relating it along with the concept of 'shock liver'-where you have low blood pressure (or low flow) for a period of time and the liver takes a hit. We don't measure these enzymes post surg in the ICU anyway so I can't really tell ya. Of course we do if there are issues esp with other pts not open heart. Relating to low flow in general it shouldn't be an issue when on pump in the OR since they regulate 'cardiac' output, etc with their perfusion machines...but I know in the post op period there is often issues with keeping a minimum blood pressure or MAP...often using both volume and vasopressors to increase it.

Hope this isn't all info you already know, it's just what sparked in my brain at the minute!

me

Specializes in CT ICU, OR, Orthopedic.

Thanks for your reply, but I asked if he was referring to shock liver, and he said no. He was referring to post op AVR patients. The clinical I just finished, they monitor all LFTs daily. He was speaking to POD 2 and on, and specifically its indications of heart issues. I couldn't understand him, but planned on going home and looking it up. Of course now I can't find it!

TX RN

255 Posts

Specializes in ICU, CV-Thoracic Sx, Internal Medicine.

All just comes down to perfusion. Valvuloar disorders like any other cardiac related disorder places pt's at risk for "low flow," i.e., decreased perfusion.

You can read up on De Ritis raito. This is a ratio of ALT/AST that is used to better predict the cause of liver disorder, cirrhosis, hep C, etc.

ALT is more specific for acute conditions, such as MI, which is why there is more emphasis postoperatively. AST is used more to trend "chronic" liver disease.

I worked for a CV surgery group and to be perfectly honest with you, outside of academia it really doesn't matter which liver enzyme is elevated. Clinical discretion takes laboratory results as only a small part of the overall picture in decision making.

core0

1,830 Posts

Thanks for your reply, but I asked if he was referring to shock liver, and he said no. He was referring to post op AVR patients. The clinical I just finished, they monitor all LFTs daily. He was speaking to POD 2 and on, and specifically its indications of heart issues. I couldn't understand him, but planned on going home and looking it up. Of course now I can't find it!

This actually sounds a little suspect. If they are talking about shock liver then AST usually rises first but ALT isn't normal. If they are talking about low flow state in the setting of AVR then there are two scenarios that I can think of. First of all is precipitating some kind of right heart failure. This leads to increased SVR which leads to hepatic congestion which leads to poor portal flow. This is why portal hypertension is so dangerous in liver disease. The other possibility is failed AVR. This would resemble acute aortic insufficiency and give you both elevated preload and afterload. Either way you would have both enzymes go up, but I would think that this would be an ALT predominant picture. What they may mean is that the AST will go up first (ie post op day two) since the enzyme rises and falls as a second order derivative not a first like ALT.

The other possibility is that they are thinking that since AST is found in other organs while the ALT is found only in the heart (for the most part) increases in AST without a rise in ALT indicate heart dysfunction. The problem is that its also found in significant amounts in the kidney and given the pressure variations in heart surgery you will almost always see some kidney dysfuction (which is more likely to cause AST rise than heart).

Either way it seems a poor way to monitor AVR function given all the other modalities they have available.

Specializes in CT ICU, OR, Orthopedic.

This actually sounds a little suspect. If they are talking about shock liver then AST usually rises first but ALT isn't normal. If they are talking about low flow state in the setting of AVR then there are two scenarios that I can think of. First of all is precipitating some kind of right heart failure. This leads to increased SVR which leads to hepatic congestion which leads to poor portal flow. This is why portal hypertension is so dangerous in liver disease. The other possibility is failed AVR. This would resemble acute aortic insufficiency and give you both elevated preload and afterload. Either way you would have both enzymes go up, but I would think that this would be an ALT predominant picture. What they may mean is that the AST will go up first (ie post op day two) since the enzyme rises and falls as a second order derivative not a first like ALT.

The other possibility is that they are thinking that since AST is found in other organs while the ALT is found only in the heart (for the most part) increases in AST without a rise in ALT indicate heart dysfunction. The problem is that its also found in significant amounts in the kidney and given the pressure variations in heart surgery you will almost always see some kidney dysfuction (which is more likely to cause AST rise than heart).

Either way it seems a poor way to monitor AVR function given all the other modalities they have available.

Thanks so much.. I could have misunderstood him. He spoke softly (unless he was yelling at me lol) and he had an accent. So I figured I'd look it up... But found very little information on it regarding the heart. Now I have a place to start. We had a clinical picture where both enzymes were elevated and he was trying to explain why the elevation was not associated with his AVR repair...

CRF250Xpert

233 Posts

Specializes in ICU, ER, OR, FNP.

Was this the surgeon who was explaining that elevated enzymes were an incidental finding and completely unrelated to AVR? I used to work ICU with a CT surgeon who claimed everything was an incidental and unrelated finding - most of his folks died; incidentally and unrelated to surgery - of course.

Specializes in CT ICU, OR, Orthopedic.
Was this the surgeon who was explaining that elevated enzymes were an incidental finding and completely unrelated to AVR? I used to work ICU with a CT surgeon who claimed everything was an incidental and unrelated finding - most of his folks died; incidentally and unrelated to surgery - of course.

Lol no, but that's funny! He was trying to educate me on assessment findings... It's my fault I didn't ask for clarification. I tend to go home and look it up, then ask questions the next day if I still don't understand... But it was my final day of clinical...

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