BP Cuff Readings vs. Arterial BP

Specialties MICU

Published

Specializes in Hospice, Critical Care.

Disagreement at work yesterday. Which do you use:

Left radial artery SBP reading: 70 (I don't remember diastolic)

Right brachial non-invasive cuff SBP reading: 109

Which one do YOU use to base therapy on? This was repeated several times, using the cuff on both arms, and the same range of differences was obtained (~30 mmHg each time).

Pt. was on neo at 200 and dopamine at 20. 82-year-old female, s/p cardiac arrest. Sinus tachycardia on monitor, heart rate ~110. Blood pressure cuff used was the appropriate size for the patient's arm.

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There are many things to consider-->

1. Was there a good wave form on the art line? Did it flush ok? What is the map, compared to the manual bp cuff? How old was the art line?

2. Was the manual BP accurate? Was it the right size cuff for the patient? Was the patient obese or skinny? False readings can be obtained. The MAP should on both your aline/manual cuff.

3. Why so much Neo??? 200 mcg/min What is your facility max? Why was another vasopressor started if you're maxed on 2?

4. Would the patient have benefitted from a Swan??? Then you would better be able to adjust your gtts...I'm assuming...which you should never do...patient was in cardiogenic shock s/p cardiac arrest? What about IABP insertion to decrease oxygen demands and decrease the workload of the heart? Or possibly a gtt to decrease SVR?

5. What was the patient's pH? If acidotic you will find that pressors tend to be ineffective.

6. What was the patient's fluid volume status? Was a CVP available to use as a reference. Renal Status...BUN/Cr?

7. Patient's co-morbidities have a huge impact on pressor therapy.

Just a couple questions to think about...but I probably would have believed the cuff if it was the correct size and fit for the patient.

LCRN

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I think LCRN covered it.

I would say take the a-line if it has a good waveform and flushes well.

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Comparing arterial bp and noninvasive bp is like comparing an apple to an orange. Everything I've read in current critical care texts is to follow the

arterial pressure if has been accurately zero'ed (leveled at the phlebostatic

axis) and if it has an accurate square wave without damping.

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Specializes in Home Health, Primary Care.

And we can't forget the transducer being at the level of the phlebostatic axis!!!

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Specializes in Home Health, Primary Care.

You beat me to it Robred!!!

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Specializes in Critical Care.

NIBPs are good measuring devices, even if ABP is the 'gold standard'. There could be a natural difference in the BPs between the arms. In that case, the NIBP WOULD probably be a better indicator of systemic pressure. I would have checked the NIBP on the left arm (ABP arm) for a more direct comparison.

Several of our docs say to use the 'highest' measurement. But only because it saves them on phone calls at night. Of course, my 'best practice' isn't based on their convenience.

But documentation with an art line, you should always document the correlation between NIBP and ABP at the beginning of your shift and which measurement you are actually documenting. IF YOU SWITCH measurements for some reason (you were documenting the ABP until it dropped to 70 and then switched to NIBP because it was higher) you have to document that you switched and why.

And if that were the justification for switching (NIBP was higher), that's just inviting legal scrutiny. I wouldn't think it would be so much if the reverse is true, because then you would be switching to the 'gold standard'. (But I'd make sure there wasn't a whip in that art line, in that case.) If the ABP waveform is correct, it is the gold standard, and I'm sure a defense lawyer could find a 'prudent' nurse to back that up.

In my facility, neo can be titrated to effect so the 200 doesn't bother me, but I agree with another poster, why didn't you add Levophed. Levophed is back in good graces in the last few years . . . we don't say 'leave 'em dead' anymore - or, we're not supposed to, anyway.

~faith,

Timothy.

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Specializes in Hospice, Critical Care.

Thank you for your input. What I really wanted was: which is the one you would use when there are significant variances: arterial or cuff with all things being equal -- the cuff was the proper size (as stated), the arterial line was in proper position with a good waveform, flushed well and had the appropriate square wave response--it was not over- or under-dampened. BPs were checked in BOTH arms several times.

I appreciate the input regarding the various pressors to use but the cardiologist on this case (by phone only, I might add) was explicit in his instructions regarding use of desired pressors. IF the pressure was via the arterial line, he wanted Levophed. If it was the NIBP pressure, then he didn't. So which one to use? (ALSO: This wasn't my patient, I was part of the discussion and said I was going to do look into it.)

The patient was basically dead already (I don't mean to sound callous but it's true--she had NO protectives, had been down for an undetermined amount of time before found, had an extended resuscitation period in the field AND got to us on a Friday night with no docs around--who's coming in to put in a Swan in this patient?! She didn't even have a central line.)

SO -- all things being equal -- which pressure would YOU use to guide therapy? I was taught that the arterial line (with everything zero'd,leveled, yada yada yada) was a direct measurement and therefore the most accurate.

(The RN did ask the physician in a phone call which one he wanted her to use and, of course, you know HIS answer -- "use the NIBP" (and stop calling me all night--the implied message).

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Specializes in Critical Care.

All things being equal, the ABP is the 'gold standard'.

~faith,

Timothy.

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Hey Y'all

I agree with the Art Line being the 'gold standard' if properly used, kind of 'by definition'. But I really understand the questioning of it. A while back I opened a question on the Nurse Anesthetists forum here about NBPs cause I had a problem with some of the ways they were being used in the ICU where I worked at the time. I found out a few things about 'em: 1. They actually 'feel' pressure from the arterial wave--not sound like we once listened to as the systolic/diastolic markers. And 2. they actually 'record' the MAP--and the SBP and DBP are calculated by the machine. (I have no idea how THAT works--but it's what the goggling and searching the internet that I did seemed to indicate. If anyone has a better way to understand NBP's--I'd really love to hear from 'em.)

So if the A-line and NBP have the same MEAN BP--they're doing what they're 'sposed to do--except the SBP and DBP were wrongly calculated by the NBP. (I guess that's not MUCH help--but it's the best I can do after looking into as deep as I could for a couple of hours on the 'net.)

Two ways to check the system: Dopler the BP the old fashioned way--with a manual cuff and a dopler. And watch other indicators of perfusion--like a swan, as someone mentioned--or the foley.

Still--pretty confusing to see those different numbers.

Papaw John

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Specializes in Hospice, Critical Care.

Good point about the MAP, Papaw John. I wasn't involved enough to take a better look at that. I'd love, now, to go back and see how they compared. I saw the patient's obituary in the paper today so I won't be able to look back at the record.

If anyone DID have references for this subject, I'd love to see them. I can find articles an accuracy of either ABPs or NIBPs but not a comparison of the two!

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Definitely the cuff pressure, even better take it with a manual cuff and you stethoscope, that would be the right BP.

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