map & dbp question

chaosRN, ASN, RN · May 5, 2006

What was the bun/cr before surgery? If your art line sys/dia is OK and the mean is suspect (but your wavefrom is ok and you are properly zero/balanced), with a suspected high CVP (presumed decent vascular volume) - and the only s/s you are seeing is low uop - is that really a problem?
All that extra fluid, not just the liter plus YOU gave, but the 4-6 liters given in the OR tend to cause nice (um, not so) little fluid shifts that can have a tendency to decrease UOP in the immediate hours post up while his/her body is trying to figure out what the h^%# to do with all this fluid.
Our CV surgeons don't even want to know UOP over night POD#1: "We'll fix it later with diuretics."
Normal renal fuction, as measured by previous bun/cr, in my experience, requires little intervention in the first 12 hrs post op Open Heart - unless there are other s/s as well.
I understand the suspicion that low MAP = low UOP - but in fresh Open Hearts, this is not automatically the case. Or at least, to the extent that it IS, keeping those freshly minted needle jobs safe and happy at a lower BP than those renals are used to: well that take a much higher priority.
I would be more concern w/ mental status: if that checks out, I'd likely just keep watching - or if you don't have docs that specifically write not to bother them about UOP the first night: then I'd go ahead and report the
~faith,
Timothy.

Hey all, thanks for the replies! Hearing others opinions really make me think!!

Timothy, I guess you're right about the worry about the uop later. Our post op orders do say notify MD if UOP is

I don't remember pts bun/cr preop. The art line was functioning properly - I kept checking it, zeroing, flushing, good waveform.

hrtprncss - yes, I was attempting to titrate the nipride off.

I too, wish this patient had a swan, but we don't see those much anymore.

Speaking of left & right sided heart failure..remember right side likes fluid - give lasix for the left. But you know that!! So.......

A little more information about said patient.....

The patient actually had a small ASD repaired, and a redo partial tricuspid repair. I probably should have said all that at first.

The way Papaw John thinks about any Post Op Pt is that the hormone-release related to shock (cortisol) turns our Pt's tissue into a sponge. Altho you gave 750ml of Albumin (which is in short supply!!) and blood products, you STILL could be barely keeping up with loss of circulating volume into tissues. If you think of the high Pulm Vasc Resistance as a 'choke-point' or 'bottle-neck' that only allows a limited amount of fluid to pass thru it, you have the picture.

So in the ICU--we're not gonna worry about Lower Extremity Edema, are we? If the alternative is bad renal perfusion and low urine output--no, we're going to pour fluids in with the thought that a HIGH CVP actually helps push blood thru the Pulm Circulation and into the Left Side and arterial circulation. So--to paraphrase Commodore Perry in the War Between the States--"Damn the CVP!!! Full speed ahead!!!

So really more albumin (or fluid) should have been given to keep up.

Interesting discussion..:wink2:

ZASHAGALKA, RN · May 5, 2006

So really more albumin (or fluid) should have been given to keep up.

Our post op orders allow for 500ml hespan x 2 (liter total) at will and 250ml Plasminate q6 hr prn after that. So, I'm loaded for bear w/ colloids if I need them.

I don't know, however, if I would have treated the low MAP in the abstract, absent a corresponding low sys/dia and on the basis of low UOP in a fresh heart (I don't think I'd use UOP as a criteria for intervention, as it's something I normally 'expect' in any case).

I agree w/ the idea of 'Dang the CVP, full speed ahead', if warranted. I'm not sure that UOP alone would have been enough to 'warrant' it, in my opinion.

But in times like that, I usually evaluate the science, and then make an effort to evaluate the 'art' of my science. This and this = that. But finally, what does my gut tell me?

And obviously, your 'gut' was telling you something. So, in that case, I might indeed have 'launched some hespan'.

~faith,

Timothy.

Trauma · May 12, 2006

I was going through all the post and I can only think of a couple of tidbits to add that may or may not be responsible for the low DBP but I'll share my experience.

The first thing that caught my eye was that this pt was on Dobutrex. Being a Beta 1 agonist stimulating the beta cells found in the heart, it also stimulates the vascular smooth muscle cells causing a slight vasodilation. It has been my experience that when Cardiologists order Dobutrex to increase B/P, I see the B/P remains where it is rather than increase.

The second thing comes to mind is how long has this patient been out of surgery? As we know the Bypass machine triggers an acute inflammatory response with massive amounts of histamines,prostaglandins and bradykinins being released which lead to vasodilation and increased capillary permeability causing a third space shift and hypovolemia. It could be that the patient has lost vascular tone and the compensatory mechanism of a catecholamine release has not yet occurred due to the general anesthesia he is still under. This would explain the wide pulse pressure.

I agree fluid would be my first suggestion, however, if true hypovolemia is the culprit(Hematocrit of 40 or higher) I would use NS instead of Albumin. The reason is Albumin works by increasing plasma osmotic pressure drawing fluid from the interstitium and the cells. The last thing we want is to further dehydrate the cells. Without a Swan Ganz catheter to monitor wedge and PA/RA pressures, fluid challenges will be a closely monitored process depending on the pre-op EF%.(Can the muscle handle all this volume?) One thing with valve replacements is that they all require extremely high filling pressure for the first few months until the muscle reverses the hypertrophy created in order to open the faulty valve.I have seen a PAD of low 30's needed to maintain UOP, CO/CI, and B/P.

Off topic. Another reason I dislike using Albumin in post mechanical valve patients if their albumin level is normal is that Coumadin is 99% bound to albumin with about 1% in circulation. If we increase the patients Albumin levels above the normals then it takes a ton of Coumadin to get them therapeutic. Then when they go home, their albumin levels return to normal and all this Coumadin is released causing potential problems.

That is all I have to add. I appreciate the knowledge that was displayed in the previous posts. Its nice to see other RNs out there who take their job serious and realize that the greater the understanding we have of the human body and its interactions, the better care we can give.

Sugah Britches · May 12, 2006

:thankya: :thankya: :thankya: :thankya: :thankya: :thankya:

This is an awesome thread. The knowledge and exchange of ideas is inspiring.

chaosRN, ASN, RN · May 12, 2006

I was going through all the post and I can only think of a couple of tidbits to add that may or may not be responsible for the low DBP but I'll share my experience.
The first thing that caught my eye was that this pt was on Dobutrex. Being a Beta 1 agonist stimulating the beta cells found in the heart, it also stimulates the vascular smooth muscle cells causing a slight vasodilation. It has been my experience that when Cardiologists order Dobutrex to increase B/P, I see the B/P remains where it is rather than increase.
The second thing comes to mind is how long has this patient been out of surgery? As we know the Bypass machine triggers an acute inflammatory response with massive amounts of histamines,prostaglandins and bradykinins being released which lead to vasodilation and increased capillary permeability causing a third space shift and hypovolemia. It could be that the patient has lost vascular tone and the compensatory mechanism of a catecholamine release has not yet occurred due to the general anesthesia he is still under. This would explain the wide pulse pressure.
I agree fluid would be my first suggestion, however, if true hypovolemia is the culprit(Hematocrit of 40 or higher) I would use NS instead of Albumin. The reason is Albumin works by increasing plasma osmotic pressure drawing fluid from the interstitium and the cells. The last thing we want is to further dehydrate the cells. Without a Swan Ganz catheter to monitor wedge and PA/RA pressures, fluid challenges will be a closely monitored process depending on the pre-op EF%.(Can the muscle handle all this volume?) One thing with valve replacements is that they all require extremely high filling pressure for the first few months until the muscle reverses the hypertrophy created in order to open the faulty valve.I have seen a PAD of low 30's needed to maintain UOP, CO/CI, and B/P.
Off topic. Another reason I dislike using Albumin in post mechanical valve patients if their albumin level is normal is that Coumadin is 99% bound to albumin with about 1% in circulation. If we increase the patients Albumin levels above the normals then it takes a ton of Coumadin to get them therapeutic. Then when they go home, their albumin levels return to normal and all this Coumadin is released causing potential problems.
That is all I have to add. I appreciate the knowledge that was displayed in the previous posts. Its nice to see other RNs out there who take their job serious and realize that the greater the understanding we have of the human body and its interactions, the better care we can give.

Just to answer your question: the patient was immediate post op. I began having this trouble within the first 1-2 hours. (More info: Hct was fine & so was EF)

I did not know that about coumadin. Very interesting, we occaisionally get patients on long-term Coumadin tx.

Thanks for all the responses!! I learn something new every day!!

~Chaos~

ghmccart · May 18, 2007

how do the labs look? na+, h/h, bun, etc? help w/fluid status and r side consideration. :saint: w/2 vaso dilators running maybe only one would be able to manage sbp while allowing for an improved dbp. i would like to know what a good assessment looked like. how did the pt say they felt?

TopherSRN · May 18, 2007

keeping those freshly minted needle jobs safe and happy at a lower BP than those renals are used to: well that take a much higher priority.

To the graft comment,I was talking with one of our surgeons who fellowed under one of the most renowned CV surgeons when a Precedex rep approached us trying to sell him on it. He said something along the lines of 'snow them so they don't wake and blow your graft surtures'. The surgeon just looked at him and asked him 'What made him think that he didn't sew grafts well enough that couldn't withstand a little increased pressure?' He then kept berating him about his grafts.

While I like a pressure between 80-130, there are many factors other than just the SBP or MAP to consider. I've seen immediate post op pts with SBP 220s+ (not sustained) and many, many with refractory HTN that hovers in the 160s-170s, never seen a graft blow.

While typically I (and our surgeons) are fine with anything a SBP > 80torr. A hypotensive patient with unremarkable Cr that isnt making urine does tend to make me think. One of our surgeons runs his cases dry as a chip ( no routine fluids post-op, MAYBE 2-2.5L of crystalloids in the OR), in his patients puny, yet sufficient UOP (20-25/hr) doesnt concern me that much. We joke with him about what he thinks the iSTAT Hct will be on admission. Ive seen immediate post of CABGs with Hcts of 37 and 40.

Our other surgeons tank them in the OR, as well as run RTNs, so I'd expect a greater UOP.

The fluid shift that usually starts to happen early POD1 of course will make them pee buckets.