Mean Arterial Pressure

[eaetaylor]

When working in the ICU, we are always sure to monitor a patient's MAP, and work to keep it above 60 to ensure proper vital organ perfusion. I was wondering why, we as nurses (and doctors) are so wrapped up in only systolic BP? We titrate medicines such as dopamine and neosynephrine based on SBP parameters. I was wondering why diastolic pressures are not thought of as importantly? When calculating a MAP, I found that a BP of 120/80 gives a MAP of 93.3 mmHg. If the systolic is changed by 10 to a BP of 130/80, the MAP changes to 96.7 mmHg. BUT, if the diastolic is changed by 10, to 120/90 the MAP changes to 100.0 mmHg.

It only seems logical to me that we should be equally concerned with keeping their diastolic pressure up as their systolic. Am I missing something? I'm fairly new, so any education would be helpful.

Thanks!

[deeDawntee, RN]

You are absolutely correct. Where I work we titrate to MAP and SBP. We keep MAP >65 and SBP >90. You are right though, with patient's with a wide pulse pressure, many times they have lost alot of their vascular tone and then titrating to the MAP becomes essential to perfusing organs.

Good insight.....

[joeyzstj, LPN]

We titrate pressors to keep MAP> 65 mmHg in most cases. You are correct. Diastolic pressure, as you know is the period when the coronary arteries are perfused, so it is very important.

[ghillbert, MSN, NP]

I work in a CT/Cardiology focused area, and we DEFINITELY rely mostly on MAP. Depending on the inotrope/medication and how it acts, we may titrate to SBP, MAP or DBP. You only have to look at an IABP pt to see the importance of diastolic pressure.

[NoviceToExpert]

I agree with all posts on here... but remember, it all depends on pt Dx... if you are talking about certain myopathies and diastolic dysfunction the picture changes, if you are talking about CABG pts, you have to worry about grafts with high pressures... what if you titrate to your MAP and your systolic goes out of range based on that pt's particular hemodynamics?... Sometimes it's a problem keeping both parameters above the prescribed low end if one rise too high, especially as your circulating volume changes in relation to your preload and/or SVR treatment... then, in addition, there is the issue of watching trends in parameters... widening or decreasing pulse pressures (maybe if you are only watching your MAP you won't notice these if the MAP remains fairly stable)... pulsus paradoxus, tamponade, etc. etc... You have to keep an eye on all three parameters SBP, DBP and MAP and consider those in relation to the pt's condition to guide your assessment, titration and plan. Watching these trends all will help you catch difficulties early. I commonly have orders that specify for titration to both SBP and MAP as mentioned above in another post... I sometimes have order sets on stent pt's to watch SBP and MAP and when I call the physician because the MAP is under 60 for a certain time interval I get asked what the pressure is and am told "don't bother me with the MAP if the SBP is over 100," (go figure....this physician didn't even know the order set he signed... he's an invasive cardiologist, so what does he care about the kidneys?...not like he gave his pt contrast or anything and the kidney perfusion is important...argh!)...then there is titrating to the AUG on an IABP...I wouldn't go by one parameter across the board of the pt conditions we handle on our unit... it is all case specific...and I try to keep in mind that generalizing may get me and my pt into trouble...

[anurseuk]

In my unit it is rare that we'll titrate drugs on the SBP and nearly always it is on the MAP; therefore the SBP and DBP are accounted for in the MAP.

I work in a cardiothoracic critical care and usually we'll aim for MAP's between 60-80 post surgery as too low a pressure and perfusion is poor and above you risk increased bleeding and ruptuing a new graft site. :)

[NursesAreCool]

When is MAP considered too high?

[ghillbert, MSN, NP]

Depends on the patient's issues.

[registeredin06]

Through my experience, the SBP will be elevated and concern you before the MAP follows, or occurs at the same time. Only a time or two have I observed the MAP too high and SBP WNL.

I personally, and this could be entirely wrong (feel free to correct me), find myself using the SBP when concerned with hypertension and the MAP for hypotension. I'm sure this isn't textbook accurate, but it seems to be how we practice. And, of course, some pt.'s are the exception.

[eaetaylor]

Now that you say that, I find it to be true. I know in my facility we worry about a SBP that is too elevated, but are concerned about perfusion if the MAP falls below 60.

[ghillbert, MSN, NP]

http://www.nhlbi.nih.gov/guidelines/hypertension/jnc7full.htm

Hypertension is diagnosed by both systolic and diastolic numbers. A DBP of >80 is called "prehypertension" and >90 is hypertension. The numbers that you worry about in a patient are totally dependent on their particular conditions and pathophysiology. It's not as simple as looking at MAP for hypotension and SBP for hypertension.

[registeredin06]

No, definitely not that simple. Is anything in nursing??

We just tend to do it this way. Most of the time, of course not all of the time, in our CVICU we pay little attention to DBP. Some CV surgeons completely ignore it. And nine times out of ten, when you call on a SBP in 80's, they'll ask what your MAP is. If it's >60, they're fine with it. Same goes if you call with a MAP >80, they want to know what your SBP is, and if it's