Arterial Line Question

Specialties CCU

Published

I'm precepting in CVICU which so far has been great. I'm curious about how an arterial line works. I understand what it's for, but don't understand how it works. Is pressure going through the line to keep the vessel open?

found this thread in a search. I know it's a bit of an oldie, but I found it very helpful.

A couple of questions about zeroing. How often do I need to re-zero? Should I re-zero when the patient is transferred to PACU from the OR? And also after I use the line to take bloods?

Thanks in advance :)

Specializes in NICU, PICU, PCVICU and peds oncology.

When you're zeroing your pressure lines you're calibrating them to the atmosphere. You should zero them when you take over care of the patient, whether from the previous shift or from the OR/PACU/ER etc, for your own assurance that it has been done. You'd rezero if the cable has been disconnected for any reason, because the monitor will probably not give you a number value, just a wave. And you should rezero if there's a sudden dramatic change in your patient's pressures without an obvious or discernible reason. Take a cuff pressure and troubleshoot your lines and then if you're still not sure you can rezero. The atmospheric pressure in the room is only going to change if the weather changes (or there's an explosion somewhere), so rezeroing when you reposition or when you draw labs is not really necessary.

We have a policy to re-zero all of our lines q4h.

Specializes in NICU, PICU, PCVICU and peds oncology.

What is the rationale? How much does the atmospheric pressure change in 4 hours? Are you in a storm belt then?

Nope, just the midwest! We've had some late night discussions on the real point of zeroing often. Whats your policies on zeroing?

Specializes in NICU, PICU, PCVICU and peds oncology.

That's a great question. Our nurse educator, who incidentally can't tell you what she's doing when she zeros or why exactly she's doing it, has been teaching new staff that they are to rezero EVERY time they reposition their patient. Not just level but also rezero. So when I'm precepting I ask the newb how exactly rolling a person from supine to banked on their right side has changed the pressure in the room and they give me a blank stare. Of course you want your pressure lines to be zeroed to the atmosphere at the beginning of the shift so you're sure they're giving you accurate information. But every time you reposition? Come on. I've looked all over for a policy that gives a frequency and we don't have one. We have one for EVDs (q4h) and the pressure pods on our ECMO circuits (q6h), but nothing for art, LA, RA or CVP lines. (We don't use PA lines.) AACN and many hospitals (such as Stanford) have a policy to recal q12h and/or when there has been a change in caregiver (verifying accuracy for oneself!), when the tubing is changed (no choice there!) or if there's a sudden change in readings that cannot be explained.

Specializes in ED, ICU, Education.

I'm going to be relocating to the Sierra Nevada Mountain region and was wondering if there will be a difference in my a-line procedures and my lab values.

Speaking of Art lines, ALWAYS make sure your alarms are on! I was standing at my patients bedside that I had just received from PACU with a labile BP. I look up and the pressure went from 100/60 to 69/30. No alarming! Good thing I was standing there. Although I should have checked my alarms when getting the room ready, I know! And the PACU nurse (bless her soul!) told me that when they received him, the ART was reading systolic in the 40s. What?! I was like "was it a good waveform?" "Oh no it wasn't" she replied. Always make sure that the wave looks crisp before you start treating it!

Great info here but not one mention of where the transducer needs to be. Curious. Can't tell you how many times I've been called in to a room by a new nurse in a panic over a pressure reading just to find the transducer hanging off the bed.

The answer, of course, is the phlebostatic axis-mid axillary line, 4th intercostal space (ie, in line with the heart). Many folks use armbands to hold the transducer and that's fine but keep in mind that if you turn the patient the reading is false- if the transducer is lower than the heart the reading is falsely high, higher than the heart reads falsely low.

Central venous pressure is zeroed to the phlebostatic axis.

Art lines are zeroed to the level of the aortic root- best done a bit more anterior.

Specializes in ER/ICU/Flight.
TakeBack said:
Central venous pressure is zeroed to the phlebostatic axis.

Art lines are zeroed to the level of the aortic root- best done a bit more anterior.

Interesting. In almost 20 years I've never heard of leveling to the aortic root.

I did a google search of it and after looking at the first 20-30 hits, every single one of them said to level the a-line to the phlebostatic axis. It's all I've ever done and I wonder how much of an actual difference it would make?

Effect of Variable Transducer Level, Catheter Access, and Patient PositionCHEST October 2001 vol. 120 no. 4 1322-1326 Measurements and main results: For each transducer level, five systolic and diastolic pressures were measured and used to calculate five corresponding mean arterial pressures (MAPs) at each access site. When transducers were at the aortic root, MAP corresponding to aortic root pressure was obtained in all positions regardless of catheter access site. When transducers were moved to the level of catheter access, as current recommendations suggest, significant errors in aortic MAP occurred in the reverse Trendelenburg position. The same trend for error was noted in the Trendelenburg position but did not reach statistical significance. Conclusions: (1) Current recommendations that suggest placing the transducer at the level of catheter access regardless of patient position are invalid. Significant errors occur when subjects are in nonsupine positions. (2) Valid determination of direct arterial BP is dependent only on transducer placement at the level of the aortic root, and independent of catheter access site and patient position.

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