Arterial line versus cuff pressure - page 2
Hi there, I would like to know what nurses do when you come on to a patient on various inotropic sgents and the nurse you are following has decided to follow the cuff pressure for the blood pressure... Read More
Aug 23, '08We zero everything at the phlebo axis at my place and everywhere else I've worked. As my understanding goes, that's the current school of thought in most literature (I'm not one of those ppl that has a works cited of books to quote off the top of my head, so Im just shooting from the hip per-se).
And in relation to the other posts on the topic of alines vs cuff...at my place we use the aline if there is a good waveform and good square wave test. We typically follow the aline if there is about 5 - 15 mmHg difference higher than the cuff/nibp. However whats neat about our bedside monitors is that in the cases where one has a good waveform but the darn aline doesnt correlate at all no matter what we do to troubleshoot....we can dial up/down the aline reading in the monitor to make it match better. Not sure if I explained that right or not...Im tired and just got off work :wink2:
Hope that helps!
Aug 23, '08We zero at phlebostatic axis. Did anybody notice the OT is 9 years old? I think this is the oldest thread I've participated in! Amazing how much data is in this website...
As far as cuff vs aline, if there is a big difference between the two, I make sure to get an order as to which one to use for titration (unless it's totally obvious. But, if the Aline is so bad that it's giving me a crappy waveform then maybe we should pull it)
Aug 26, '08I have found many times after inaccurate readings between A-line and cuff pressures that there has been a problem with the art line catheter itself..mostly bent under the skin thus being the cause of the inaccuracy.
To bad I didn't fine this out until the line was dc'ed. Even with the catheter bent I still got the square waveform when it was leveled and calibrated. Also, we always compare the two- art and cuff- at the beginning of each shift , if there is 10% difference we go with the cuff pressure-may still use the art line to draw blood from though.
Sep 6, '08Variance in arterial lines and cuff pressures vary significantly a lot of the time and need to be addressed on a case specific basis...When there is a variance sometimes it's better to go with the cuff... sometimes the arterial line... I didn't see anyone mention arterial line placement... that's a big factor... radial arterial lines aren't as accurate as some other arterial lines (also used are the brachial, femoral, axillary, and dorsalis pedis arteries)... axillary is ideal for pts with PVD, Dorsalis pedis in burn pts or with other massive injuries... Sometimes the french size of the catheter versus the diameter of the lumen will skew your readings thereby making your cuff pressure more accurate...Keep in mind that for every inch the transducer is below the correct level the weight of the fluid on the transducer diaphragm will add 2 mm Hg to the true intravascular or intracardiac pressure, and for every inch above the correct level the reading will be 2 mm Hg less than the actual pressure...You can get a false high from the flush solution flow rate being too fast, or air in the system, or catheter fling... on the other hand sometimes the cuff pressure isn't great if the sizing of the cuff versus the patient's arm isn't optimal...then there is the variance from R arm to L arm... in some cases this can be significant...I just had a situation where my manager barked at me about "Hey, do you know where your pressure is going?" I said "Of course I do, it's 170s... but my cuff is 147/71" She went on to bite my head off saying "I don't care what your cuff pressure is..." I said, "Well, I do... and I've spoken with the physician twice in the last 40 minutes and we're not doing anything about it until tonight depending on the trend" ... She continued to bark and the surgeon happened to walk onto the unit as well as the intensivist... She tried to make me look stupid at which point the intensivist pointed out that the radial art line, in this case, despite the good square wave and waveform was not as reliable as the cuff because of the pressure skew between cathether french size and the size of the radial lumen where it was placed... Sure felt good after that! Surgeon told her he was perfectly fine with the pressure and that I notified him twice in the last hour (basically that I was always on top of it and to back off)! Anyway... I like the post that suggests to confirm which pressure the physician wants to titrate by and documenting that... good idea... and we often go by MAP vs. SBP... but sometimes we have an intensivist that gives parameters for both SBP and DBP... with our CEAs our order set goes by MAP...I haven't seen any literature about leveling at the line site...but that makes perfect sense... why would you level the transducers for your SGC readings at the phlebostatic axis where the catheter sensors are and then level the transducer for radial art line at that same location rather than where the pressure is reading from the arterial line catheter sensors? Anyone have info on this or literature/references?.... Hey you all, guess what? I just passed CCRN last week!!!! Yahooooooo!!!!!
Sep 7, '08I tried to get some information on transducer referencing... phlebo or cathether level...I called Edwards... but it's the weekend... and the tech support available is supposed to be for emergencies only... I'll call them during the week and ask the manufacturer directly... by the way... Edwards.com has phenomenal inservice materials of all sorts on all their products available for free... check it out...it's where I learned a lot of my equipment... I'm often citing manufacturer recommendations... drives people crazy... but whatever...
Sep 7, '08It doesn't matter where you zero the transducer, because you are zeroing it to atmospheric pressure. When you zero you are isolating the transducer from the pt and opening it to atmospheric pressure.
Also with the a-line you are directly measuring pressure. With the cuff you are indirectly measuring flow. The first sound you hear (Korotkoff) is generated by flow. If your a-line has a good square wave test and the pt doesn't have vascular impedence or a compliance issue you should use the a-line. Although I agree it should be pt specific.
Also when you coorelate the two you should use the map. Your systolic and diastolic may differ, but your map should be the same through out your arterial system. If both maps are coorelating your deviation is just the diff between wherever the catheter is and the cuff located.
Of course I'm not this smart, most of this was paraphrased from "The ICU Book" by Marino. You should google book it, it's a great read.
I wasn't 100% sure but after going to the Edwards site the phlebostatic axis is the measurement point for measuring aortic and intra cardiac pressures.Last edit by Soonstudent on Sep 7, '08
Sep 7, '08Referencing is different than zeroing... you zero to atmospheric via the fluid-air interface, correct... but you reference as stated above in a previous post of mine... which is why you can rereference after position changes without having to rezero... make sense?
Sep 27, '08I am a student nurse in my last semester of nursing school. My clinical preceptorship is on a med/surg ICU floor. My second shift one of my patients has this problem, a huge discrepancy between the aline and the NIBP. The nurse used the "return to flow method" to determine which bp was actually accurate. Does anyone else use this? Basically, you inflate the manual cuff, watch the monitor for the aline to go flat which indicates no blood flow, then you slowly release the manual cuff watching the montior for when the wave form comes back on the aline. This number is the actual systolic pressure and depending on the number, this is how one decides which BP measurement is the most accurate. Does this make sense to anyone?
Sep 27, '08Doesn't make sense to me - if the art line is inaccurate, it'll just give you an inaccurate # when the flow returns. If you go to the trouble of getting out a manual cuff, you could just take a manual BP and you'd know that was accurate.
Oct 10, '08I thought we are supposed put it at the level of phlebostatic axis...? Can you say more about this?
Also, at my teaching facility, the new group of anesthesia docs sometimes use brachial based on research that says brachial is more accurate than radial, although brachial art lines infect & clot more easily....
Nov 11, '08We never take the initiative to choose which one we want to titrate to. If there is an a-line, that is what we must use. If there is a discrepancy, the MD will have to right for us to titrate to NBP if that is what he/she desires, but we would then typically d/c a-line if it's not accurate.
Nov 15, '08Steps of troubleshooting: a) ensure properly inflated pressure bag b) level transducer at phlebostatic axis c) re-zero d) ensure a-line is not "positional" (catheter is not stuck against vessel wall, kinked, etc.) e) if necessary, aspirate near insertion site to r/o air within catheter and/or ensure good blood return f) ensure good waveform with dicrotic notch; if need be, adjust scale on your monitor based on current blood pressure (If your scale is set to 150 and your BP is only 90, your waveform can appear dampened)
In our unit, we will use a cuff pressure just as a reference point. I have never seen anyone zero the transducer at the insertion site. We only use the phlebostatic axis because this is used as a reference point for the level of the heart. Bottom line, if you are visualizing a good waveform, your a-line will be the most accurate.
Nov 23, '08I work in a surgical ICU, and when I first come on, I make sure the a line is leveled and zero'd, trouble shoot for little things like positioning, and making sure the pressure bag is inflated enough.
ultimately what i'm worried about though is that the mean arterial pressures match up because that determines how i'll titrate my drips. so a little variation between them isn't the end of the world for us as long as the MAPs match up closely.