Alright, Let's Do A Case

[OB1🤙]

Advertisement - Members don't see this ad

Sup folks. I don't come around here much anymore. But popped in and saw that tips and tricks thread from years ago got bumped and figured hey, I'll post a silly little case for the residents for funsies.

The patient is a 60 something year old getting a mitral repair. Otherwise healthy. The pump run is about 3.5 hours since it's a complex valve, and there are issues with bleeding from cannula sites after coming off. Still, the repair looks ok, and the heart looks fine on echo. LV is dynamic. The SVR is low and you're on 6 mcg/min of levophed.

Your tech runs an iSTAT gas about half an hour after coming off. It comes back 7.32/36/124/18/99%, with a base deficit of 8. Hct is 29.

What's going on here, residents?

 

[teacher2md]

Is this just post-pump vasoplegia with expected coagulopathy?

Check coags and iCa, try some more pressors or methylene blue.

 

[teacher2md]

Also confirm that the patient is normothermic.

 

[Hork Bajir]

Not a resident, or an attending anymore, but now a cardiac fellow so I’ll take a stab: Little bit more of a metabolic acidosis than I’d like to see, though not outside the range of reason after a long pump run (washing out ischemic metabolites after x-clamp comes off). Especially given difficulty with bleeding at the cannula sites would want to take a look at the aorta to rule out dissection and visceral malperfusion, though it’s far less likely than low cardiac output and relative hypoperfusion. How are the kidneys? Making urine? What’s the CO by echo and/or thermodilution if you have a PAC? Have you checked a lactate? Agree with needing to interpret all of this in the context of patient temp.

 

[GassYous]

prolenepenia

 

[MirrorTodd]

Stealing off the others...hypothermia, metabolic acidosis. 3.5 hours doesn't seem like a huuuuuge pump run, but vasoplegia could certainly be a problem...blood products during the case? CaCl given? ACT? Appropriate protamine dose?
I think overall, my plan would be to confirm normothermia, give Cacl, give bicarb for the acidosis/base deficit (pretty standard at places I've rotated to treat a base deficit of around 1.5 or 2). Bleeding wise if the cannula sites still look bad, I'd pull an ACT, review heparin/protamine dose, maybe get a TEG since that's been available everywhere I've been.

 

[OB1🤙]

Pt is normothermic. Protamine has been given. There isn’t a generalized coagulopathy, but discrete bleeding related to some tearing at the IVC cannulation site. It’s under control but there has been some blood loss after protamine went in.

The SVR is lowish but 6 mcg/min levo isn’t crazy high. The CI is in the high 2s.

UOP is normal. Have not checked a lactate.

So there’s a weird acidemia. The cardiac output and therefore oxygen delivery seem adequate.

 

[vector2]

Pt is normothermic. Protamine has been given. There isn’t a generalized coagulopathy, but discrete bleeding related to some tearing at the IVC cannulation site. It’s under control but there has been some blood loss after protamine went in.

The SVR is lowish but 6 mcg/min levo isn’t crazy high. The CI is in the high 2s.

UOP is normal. Have not checked a lactate.

So there’s a weird acidemia. The cardiac output and therefore oxygen delivery seem adequate.

Recheck an ABG that includes lytes, glucose, H&H, lactate, coags. And check a mixed venous. Possible that the blood loss from the cannula had not equilibrated before the last H&H check. Given the clinical picture with normothermia, good UOP, minimal pressor requirement, there are a bunch of reasons for hyperlactatemia and mild acidosis post-CPB which are relatively benign, but there are some other reasons which are quite serious. Currently, it seems as if there is no sign of LCOS (what's the HR thats maintaining the CI in the high 2's?) or inadequate oxygen delivery and utilization. How is the rest of the post-TEE exam other than the repair and LV function?

There are some zebras out there like they microperforated a viscus or the liver through the diaphragm when doing IVC cannulation or placing a pacing wire, or there is malperfusion to the gut or to an extremity which is not obvious at this time. Any signs of thrombotic history in this patient? Are we sure the current picture isn't generalized coagulopathy or early DIC? Keep searching.

 

[teacher2md]

What's the glucose level?

 

[MirrorTodd]

Did he get a **** ton of saline? Co2 scrubber is still good and has been good?

 

[OB1🤙]

Did he get a **** ton of saline? Co2 scrubber is still good and has been good?

We’re off pump.

Has not *directly* received a bunch of normal saline...

But what are you thinking?

 

[MirrorTodd]

We’re off pump.

Has not *directly* received a bunch of normal saline...

But what are you thinking?

If it's non gap acidosis, and the pt did get a ton of saline through the bypass machine or something, then a hyperchloremic metabolic acidosis. If it's a gap acidosis, then further down on the classic mudpiles list is CO poisoning which CAN be caused by an expired Baralyme scrubber...more specifically with Desflurane.

 

[OB1🤙]

Heading in the right direction! What happens to the blood lost in the heart room after we come off pump and give protamine?

 

[MirrorTodd]

Heading in the right direction! What happens to the blood lost in the heart room after we come off pump and give protamine?

Cell saver and we usually get a bag of pump blood filled by perfusion....that usually contains a bunch of heparin as well since it's taken before protamine dosing.

 

[OB1🤙]

Cellsaver.

Let’s talk about Cellsaver.

Cellsaver blood is simply red cells in saline. Every institution has its own philosophy on Cellsaver- whether there exists some cutoff volume above which you shouldn't give it, whether or not it represents a heparin bolus, etc. When I was a fellow it was basically forbidden, the surgeons believed it was "bring-back juice." Which is, of course, ridiculous.

The manufacturers of Cellsaver systems recommend the washing fluid be saline, and so most institutions do this. For this reason, if you give any significant volume of Cellsaver, you may develop a hyperchloremic acidosis. And indeed, that's what was going on here- I had given probably a liter and a half of CellSaver because of all the bleeding after we came off. Now, there exist iSTAT cartridges that can tell you the serum chloride, but most do not. So it is very very easy to fall into the trap of looking at this gas, interpreting it as likely malperfusion, and going down that rabbit hole incorrectly.

The same thing happens in trauma, incidentally. You'll have someone come in, and between EMS and the ED they've gotten a ton of saline. You get a gas and they're acidemic. I've seen people say "oh I better give more fluid, the patient has a acidosis so they must be dry" and then they give MORE SALINE. Then they wonder why the acidosis isn't getting better. I've seen people start inotropes to try to "improve oxygen delivery" when all that's going on is an iatrogenic hyperchloremic acidosis.

So back to the case. Long ago, for this reason, I told my perfusionists that I want them to wash the Cellsaver in Normosol (you might have Plasmalyte, same same). They balked because the manufacturers didn't recommend it. But I convinced them, for this exact reason. But the dude pumping that case just forgot, and washed it in saline instead that day.

So when I got that gas, knowing that the Cellsaver volume had been significant, I asked him if he used saline. He fessed up and said yeah, he forgot. No biggie. Sent lytes and indeed, the serum chloride was 115. So this acidosis was completely benign, except to whatever extent a hyperchloremic acidosis is bad for the kidneys (and it may well be).

Last thing about Cellsaver. This whole business of it being "bring-back juice" is absurd. It's red cells in fluid. If they need red cells, give them red cells. BUT- always be cognizant of the volume, because a dilutional coagulopathy is a potential entity with any fluid you give that doesn't contain clotting factors. And while there might be a few molecules of residual heparin floating around, that's generally a clinical non-entity. Give a couple cc's of protamine after if it makes you feel better.

tl;dr the patient was fine, and the acidemia was iatrogenic. No treatment was needed.

 

[drmwvr]

I don't think you mention just how much CS return there was...there can't be more than 100 cc NS per 500 ml cell saver if even that (shooting from the hip here, but probably not really far off). We're talking about 3 or 4 or more L of NS to cause a hyperchloremic acidosis in the time frame of an MVR. How much could your patient possibly have received, assuming your pump prime is albumin and Normosol?

Edit: Just doing the math...if 500 ml cs return has a hct of even 60% which is about average, thats 200 ml NS.

 

[OB1🤙]

It's weird. I don't disagree- you'd think that 1.5 liters wouldn't be enough to cause a hyperchloremic acidosis.

But until I had them switch over to washing in Normosol, I would see it time and time again. And it stopped when we made the change.

No other routes for chloride to get in there. I only use Normosol as a fluid, and my general IVF during a pump case is 1500mL.

Pump is primed with Normosol.

So on the one hand- yeah. It "shouldn't" happen.

But it did. And until I had the perfusionists switch to washing the Cellsaver in Normosol, I would see it frequently.

Go figure.

 

[abolt18]

I don't think you mention just how much CS return there was...there can't be more than 100 cc NS per 500 ml cell saver if even that (shooting from the hip here, but probably not really far off). We're talking about 3 or 4 or more L of NS to cause a hyperchloremic acidosis in the time frame of an MVR. How much could your patient possibly have received, assuming your pump prime is albumin and Normosol?

Edit: Just doing the math...if 500 ml cs return has a hct of even 60% which is about average, thats 200 ml NS.

Maybe the washing leads to significant electrolyte shifts in the red cells that then equilibrates upon re-entering the body? Making the effective volume greater.

 

[Shimmy8]

In your experience what amount of cell saver given leads to this? 99.99% we use normosol, but just to keep in back of mind.

 

[Maverikk]

Good case, for the residents: anyone know the contraindications to cell-saver use? If you're at an academic center someone else probably takes care of this for you, when you get out into private practive and a newer surgeon calls for it after mucho mucking they'll be looking to you to manage it (had this happen for a lap chole with someone with RCC on chemo)

 

[deleted697127]

Good case, for the residents: anyone know the contraindications to cell-saver use? If you're at an academic center someone else probably takes care of this for you, when you get out into private practive and a newer surgeon calls for it after mucho mucking they'll be looking to you to manage it (had this happen for a lap chole with someone with RCC on chemo)

Cell saver, eh? Lucky if you have more than a couple of units of blood at most community hospitals.

 

[MirrorTodd]

Good case, for the residents: anyone know the contraindications to cell-saver use? If you're at an academic center someone else probably takes care of this for you, when you get out into private practive and a newer surgeon calls for it after mucho mucking they'll be looking to you to manage it (had this happen for a lap chole with someone with RCC on chemo)

I'd need to look it up, but you may have answered part of your question. Pretty sure you shouldn't use it with RCC