IABP

CABG patch kid, BSN, RN · Feb 24, 2010

Is it common to have a negative afterload reduction on an IABP? Had my first balloon pump this week and the 2nd night I had him, his numbers were coming out negative. (The assisted diastolic was higher than the unassisted). Isn't that making the heart work harder? I called the doc and he had me change it from 1:1 to 1:2, but they were still negative.

I'm not understanding the problem. You're saying the assisted diastolic was higher than the unassisted, but that's the expected result with IABP therapy. Remember the basics here: when the heart ejects blood in the systolic phase, the balloon will be deflated, creating a "sucking" motion (forget the technical term) making it easier for the heart to eject blood, which decreases afterload and will make your systolic lower, a lot of time.

Ok now during diastole: when the aortic valve is closed and the heart is filling with blood, this is when the majority of your coronary perfusion takes place. This is also when the balloon is inflated, pushing blood up through the coronary sinuses, increasing perfusion to the coronary arteries. This is the reason why we want to ASSIST diastole. So of course your assisted diastolic will be higher than your unassisted. That is the whole point of the therapy. In fact if your pt is on pressors, you should be titrating to assisted diastolic, NOT systolic. There will be times when your assisted diastolic is NOT higher than your systolic, there are a variety of factors that can affect your numbers; basically anything that reduces your cardiac output will reduce your ability to assist, giving you a lower number. That's when you should be critically thinking: what's going on with my pt!!

So I'm not sure how else your numbers would be negative or what exactly that verbiage means, unless your just using the word "negative" to mean "bad".

Also I'm curious: Did you take a class on the IABP before being assigned that pt? And do you have a good support system in place at your job? You should have a minimum of at least one resource person every shift to assist you with things like this!

allnurses Guide · Feb 27, 2010

Your question doesn't make sense to me. You said "negative afterload reduction" but then said the assisted diastole is higher than the unassisted.

Afterload = what the systolic pressure needs to overcome, not the diastolic. IAB therapy reduces the systolic pressure by deflating right before the heart ejects, so it's essentially pushing into a lower pressure and doing less work. This is afterload reduction which reduces myocardial oxygen demand.

The other benefit is increasing diastolic pressure. When the heart is at rest, the IAB blows up and pushes blood to the head, kidneys, and coronary arteries to assist with perfusion. This is the elevated "augmented diastole" - which results in increased myocardial oxygen supply.

So increased supply and reduced demand = less work and more oxygen for the heart.

You should not be taking care of IABP patients unless you at a minimum can interpret their balloon and arterial waveforms.

cvicxena · Feb 27, 2010

As someone who teaches IABP classes some of my best advice to you is that if you don't understand what you are reading and are curious as to why the numbers aren't as expected is the call the IABP company's 1-800 number. They will always be more helpful than physicians who are many times not as comfortable interpreting those numbers as you would imagine them to be . . . The clinicians on the other end of the 1-800 number are trained health care professionals and experts on the IABP.

Assisted pressures are always ideally lower than unassisted and that is how you verify that you are reducing the patient's afterload. If they are higher it is likely that you should consider adjusting the deflation timing to attempt to reduce them. Changing the frequency as they physician instructed you . . . will not make the assisted numbers lower.

Augmented diastolic pressures are the diastolic numbers that should be higher, but not the assisted. So you were right in your initial assessment that something wasn't quite right.

clementinern · Mar 7, 2010

I think the way you worded your question made it a little tricky to understand what you were asking. You didn't actually have a "negative afterload reduction", but you are correct in saying that you were making the pts heart work harder. You actually were increasing the pts afterload. Did you have a measurement of what their SVR was?

The problem was most likely with the timing of the balloon. Do you have self timing IABP's? Even if you do, sometimes deflation needs to be adjusted. Most of the time, if your assisted diastole is higher than your unassisted diastole, you are deflating too late. Put the pt in 1:2 if they can tolerate it. Try moving the deflation a little earlier, and see what happens. Watch your numbers as you change the timing, and for another minute or so as long as they are stable in 1:2. If you see some but not enough change in the numbers, time it to deflate even earlier. If you start to lose your augmented pressure, you are deflating too early (not allowing the balloon to stay inflated long enough, which therefore decreases your augmented pressure. make sense)? Your goal is to have the lowest possible assisted numbers while at the same time maintaining your augmented diastolic pressure preferably at least 10 or so points higher than your systolic.

Clearly you don't have much support with your IABP's, and the doctor should be ashamed of himself for not telling you to check the timing; until you are completely comfortable with timing, and that takes a while, bring a cheat sheet into the room that shows exactly what incorrect timing looks like and what the hemodynamic results will be with improper timing. Datascope makes a great handheld laminated cheat sheet. If you don't have one, go to the datascope website and print something up. IABP's are serious business and proper timing is essential!!!

Good luck in the future! Do you have a critical care educator that can help you learn more about IABP timing?

clementinern · Mar 7, 2010

Also, I think the first person to respond to your post- CABG patch kid- maybe have been confusing augmented diastolic with assisted diastolic. You WERE correct that assisted diastole should be lower. Augmented pressure, however, should be higher.

cvicxena · Mar 7, 2010

I agree with everything clementinern has said, she has given you great advice!

I will tell you that in my varied experience with IABPs . . . unfortunately many physicians themselves are not comfortable with the assisted/unassisted/augmented pressure interpretations either. Many times the in-house perfusionists or the people on the other end of the 1-800 are the best resources - - especially if you should encounter any IABP alarms you aren't familiar with troubleshooting.

BellaInBlueScrubsRN · May 4, 2010

Resurrecting this post! I'm sorry that my question was so muddy. I am trying my hardest to figure out exactly what I wanted to know.

On the paper we chart the numbers:

Assisted systole

Diastolic Augmentation

Assisted end diastolic pressure

Unassisted Systole

Unassisted end diastolic

Then figure the afterload reduction. Which is where I got confused.

Unassisted end diastolic-Assisted end diastolic = Afterload Reduction

You want the assisted end diastolic to be LOWER than the unassisted end diastole, coming to the Afterload reduction. Should the Afterload reduction number be a NEGATIVE number or a POSITIVE? Mine were negative. So a negative number for the AFTERLOAD REDUCTION number would actually meant that I was increasing the afterload. Right?? Like a double negative.

It just drew my attention to it because the ones for previous shifts had been positive. I was mainly just concerned about the number I was charting. I wish I would have included numbers in my example from that night, because I realize that my question is very muddy.

The goal is 5-15mmHg of Afterload reduction. So the number would should positive. Correct?

Now I have a headache! And yes, I have taken the class. However, the first balloon pump will make anyone nervous I think!

BellaInBlueScrubsRN · May 4, 2010

To quote from ICUFAQS.ORG

Now look at the place where the pressure in the aorta is lowest, at the end of balloon deflation – this is called the BAEDP: the “Ballooned Aortic End-Diastolic Pressure”. Say that three times fast. This point should always be lower than the patient’s own diastolic pressure – which on the diagram is the bottom arrow on the left. See how the one is lower than the other? This is the second goal of proper timing – to lower the diastolic resistance in the arteries. Both pressure components are lowered, decreasing the SVR.

No, I didn't have my SVR Thanks for all your posts though! So maybe it was a timing issue?

allnurses Guide · May 5, 2010

Yes it should be a positive number of afterload reduction. Anything >0 = afterload reduction. Negative number = afterload increase.

Could be due to many things, timing is the most common and easily fixed.

cvicxena · May 6, 2010

Bella I can see why you are confused with the way you have to document. In my head (and I'm a balloon pump educator) afterload reduction would be documented as a (-) Negative number and increase in afterload would be documented as a (+) positive number.

Maybe you should try to find the policy on IABP for your facility to help you clarify how you document.

No matter how you have to document: You are correct in your understanding that assisted pressures are ideally lower than unassisted pressures. If the assisted pressures are higher than unassisted pressures afterload has been increased.

When you notice there is an increase in afterload it is usually due to a deflation (late) timing error. You may also see this sometimes if the patient is in an irregular rhythm and the balloon pump is in "A-Fib" mode or "Auto R Wave Deflation" (depending on the manufacturer of pump) because deflation is automatically adjusted to occur later than it typically occurs.

suanna · May 6, 2010

Yep- you had a timing issue. The newer balloon pumps are supposed to have "automatic" timing. As operators we can get lulled into believing the pump knows what it's doing. I dosen't. I never run my pump in full automatic mode, and I check my timing constantly. If the pump is 1:1 I check at least every 2 hrs or with any chang in VS, CO or SV02.