Leveling art line to tragus for cpp???

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    Hello all. I am taking a class that stated in a sitting/semi-fowlers patient that we have concerns with CPP, we should level the art line at the tragus (or where every you would level your ICP monitor). I have never done that in any of my neuro units. Art was at phleb axis and ICP at tragus and we used those numbers to calculate the CPP. That big of a difference would give you about a 20-30 mmhg difference (lower) pressures. These are huge differences. Anyone doing this? Does it modify your reference numbers for goal cpp?

    Jimmy

    The only articles I am able to find are ones from journals that state that the transducer should not be leveled to insertion site. I am shocked because I thought that was old news but the research based ones are from 2001 in CHEST. I was practicing back then but it was never taught to me as anything other that the phleb axis.
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    cpp= map-cvp or icp (whichever is higher and both are normally under 10mm hg). therefore, cpp is primarily dependent on map. a normal cpp is around 80 to 100mmhg. map at the phleb axis does not equal map in the brain (especially in a sitting or semi sitting position). the reason the tragus is chosen is because that roughly approximates the circle of willis. the circle of willis is fed via the internal carotids and vertebral arteries that branch from the subclavian artery. typically in healthy individuals the brain will autoregulate between a map of 60 to 150mmhg. in sick dudes that are chronically hypertensive, that curve shifts to the right requiring higher pressures.

    knowing this allows you to put everything together. dudes with high icps, chronic hypertension or anything to disrupt the cpp will need higher maps to perfuse the brain. getting your map from the tragus allows you to more closely monitor actual cpp without breaking out the really cool and expensive monitors.
    Jlocke7 and Skeletor like this.
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    So why not level the transducer at the kidneys if your main concern is renal perfusion? The MAP I have always seen used for such a calculation was based on the Central or aortic pressures, Hence why it is leveled at the phleb axis. NO NICU I have worked for has leveled the artline in any position other than the phleb axis and that is the MAP we used to calculate the CPP. Is anyone leveling to the tragus or circle of willis? I understand the rational and anatomy behind using this but I have not seen anyone doing it. If this is the correct method, my unit was WAY off because that would create huge differences.
    This class was not a neuro class nor taught by someone well versed in neuro. This is why I have to question it. I am also unable to find any research or articles supporting this. I find it hard that the different neuro units I have worked on missed something so basic with such large ramification.
    Hmmm, just ran into an article that talks about maintaining the transducer at the tragus. Maybe those units just sucked, or this is a newer thing to do. It was a few years ago I worked neuro. Guess this might not be any different from the last CVICU that kept leveling the IABP transducer at the femoral insertion site............
    experienceawareness likes this.
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    http://journals.lww.com/ccmjournal/C...ion_in.51.aspx <--- anyone have acesess to this??????
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    Quote from jimmy_hat
    So why not level the transducer at the kidneys if your main concern is renal perfusion? The MAP I have always seen used for such a calculation was based on the Central or aortic pressures, Hence why it is leveled at the phleb axis. NO NICU I have worked for has leveled the artline in any position other than the phleb axis and that is the MAP we used to calculate the CPP. Is anyone leveling to the tragus or circle of willis? I understand the rational and anatomy behind using this but I have not seen anyone doing it. If this is the correct method, my unit was WAY off because that would create huge differences.
    This class was not a neuro class nor taught by someone well versed in neuro. This is why I have to question it. I am also unable to find any research or articles supporting this. I find it hard that the different neuro units I have worked on missed something so basic with such large ramification.
    Hmmm, just ran into an article that talks about maintaining the transducer at the tragus. Maybe those units just sucked, or this is a newer thing to do. It was a few years ago I worked neuro. Guess this might not be any different from the last CVICU that kept leveling the IABP transducer at the femoral insertion site............

    Hey man, I could not access your link from home. I'll take a look tomorrow. Back to the circle of willis thing....Look in a physiology book. Basically, for each cm above the phlebostatic axis the BP will decrease by 0.7-.75mm Hg. This means that in a healthy individual in a sitting position the BP will typically be approx 20-30 points lower in the circle of willis. Again, in a healthy dude that autoregulates between 60-150mm Hg has normal RAP and ICP, this will not be an issue as CPP will be maintained. In a sick dude this change can be pretty significant. Hence, if CPPs are in issue, put your arterial transducer at the ear.

    Of course, you could also argue that circle of willis perfusion is only normal in roughly 50 percent of the population and therefore the only way to really measure the adequacy of cerebral perfusion is with a cerebral oximeter. As expected though, cerebral oximetry has its pitfalls and doubts as well. That is another argument though.
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    i understand the A&P of doing it. My question I guess is does your unit level thier tranducers there when calculating the CPP in patients with ICP monitoring? (the ones i have worked for did not, but still used the same documented reference range for treatment and such)
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    Quote from jimmy_hat
    i understand the A&P of doing it. My question I guess is does your unit level thier tranducers there when calculating the CPP in patients with ICP monitoring? (the ones i have worked for did not, but still used the same documented reference range for treatment and such)
    For most patients that I put to sleep that are going to be placed in a beach chair position whether it be a shoulder replacement or craniotomy I will put the transducer at the tragus if I place an arterial line. Especially if it is some old gomer that gets by on a systolic >200. I have noticed quite a few of the Neuro ICUs doing the same in hospitals that I have worked in.

    If you are putting your ICP monitor level with the ear and your arterial transducer level with the right atrium and the patient is in a semi-fowlers or sitting position then your documented CPPs are going to be off.
    IckuRN likes this.
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    From your comments I assume you are a CRNA. That is the lecture I heard this from, but had never seen this actually done in any of my ICUs including the NICUs. Just caught me by surprise. Thanks for your comments. I am curious if any bedside RNs in the NICU are doing this.
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    I've never heard of doing this and have worked at some large hospitals with neuro ICUs. Very interesting.
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    http://www.baccnconference.org.uk/do...n-practice.pdf

    Seems like the UK has noticed these discrepancies. They did a survey in 2006 and found that 6 out of 20 leveled at the tragus. But all used the same calculations to monitor CPP. This seemed to spark debate about the wide variation in practice.
    In 2009 they did a lit review to establish a standard of practice. They found conflicting data and no agreement on where the transducer should be placed.
    The Brain Trauma Foundation Guidelines 2007 has no recommendations on placement.

    It seems that everyone agrees that only one way is correct. But there does not seem that there is agreement. I have been unable to find a standard of practice on this. Either the aortic root is overestimating CPP or the tragus is underestimating it. It can not be both.
    CRNAs and Anesthesiologist are taught to level at the tragus as law, but as I said before, I have never seen this performed on a unit.
    Here is a very detailed letter about CPP. I have not read it all to varify the math or rational behind it.
    http://www.apsf.org/resource_center/...alculation.htm

    Anyone have any literature to back up one practice vs another? Anyone seen any SOP of a major nursing organization?


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