Arterial Line Question - page 2

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... Read More

  1. Visit  NotReady4PrimeTime profile page
    1
    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.
    Hawkeye-RN likes this.
  2. Visit  BellaInBlueScrubsRN profile page
    0
    We have a policy to re-zero all of our lines q4h.
  3. Visit  NotReady4PrimeTime profile page
    1
    What is the rationale? How much does the atmospheric pressure change in 4 hours? Are you in a storm belt then?
    Hawkeye-RN likes this.
  4. Visit  BellaInBlueScrubsRN profile page
    0
    Nope, just the midwest! We've had some late night discussions on the real point of zeroing often. Whats your policies on zeroing?
  5. Visit  NotReady4PrimeTime profile page
    2
    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.
    Hawkeye-RN and ghillbert like this.
  6. Visit  resumecpr profile page
    0
    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.
  7. Visit  BellaInBlueScrubsRN profile page
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    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!
  8. Visit  txdude35 profile page
    0
    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.
  9. Visit  TakeBack profile page
    0
    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.
  10. Visit  getoverit profile page
    0
    Quote from TakeBack
    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?
  11. Visit  TakeBack profile page
    0
    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.
  12. Visit  txdude35 profile page
    0
    I hadn't seen that either, learn something new every day. A couple observations though.
    1. the efficacy of reverse trendelenberg has been pretty much dismissed in all the literature I've seen and in my clinical practice so I really don't use it.
    2. the conclusions state that there was a difference but not statistically significant in the trendelenberg position but then goes on to say "significant errors occur when subjects are in nonsupine positions." So... which is it?
    3. Is the slight difference between the position of the aortic root and the phlebo axis going to be clinically significant?
  13. Visit  TakeBack profile page
    0
    Quote from txdude35
    I hadn't seen that either, learn something new every day. A couple observations though.
    1. the efficacy of reverse trendelenberg has been pretty much dismissed in all the literature I've seen and in my clinical practice so I really don't use it.
    2. the conclusions state that there was a difference but not statistically significant in the trendelenberg position but then goes on to say "significant errors occur when subjects are in nonsupine positions." So... which is it?
    3. Is the slight difference between the position of the aortic root and the phlebo axis going to be clinically significant?
    If you are referring to the use of reverse-T for BP management, I routinely see that it works for short term management- an acutely hypertensive pt will get some BP benefit from the venous pooling.That study shows more sig differences in reverse T than others.Re: the signfiicance of the difference:Circulation. 1995 Oct 1;92(7):1994-2000.Anatomically and physiologically based reference level for measurement of intracardiac pressures."CONCLUSIONS: External fluid-filled transducers should be used with the goal of removing hydrostatic pressure and other influences so that the presence of subatmospheric pressure during diastole in any of the cardiac chambers is accurately measured. To achieve this goal, intracardiac pressure should be referenced to an external fluid-filled transducer aligned with the uppermost blood level in the chamber in which pressure is to be measured. The current practice of referencing the zero level of LV diastolic pressure to an external fluid-filled transducer positioned at the midchest level results in systematic overestimation due to hydrostatic effects and produces physiologically significant error in the measurement of diastolic intracardiac pressure."

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