Can anyone explain to me a couple things about CVP??

  1. 1)
    First of all, what is so significant about the number? What is a normal number for someone healthy? What does that number mean??


    2)
    Now, can anyone expalin to me, step-by-step, how to get a CVP reading?
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  2. 22 Comments

  3. by   ZASHAGALKA
    Quote from raindrop
    1)
    First of all, what is so significant about the number? What is a normal number for someone healthy? What does that number mean??


    2)
    Now, can anyone expalin to me, step-by-step, how to get a CVP reading?
    Normal is (corrected again - 2-6mmHg). It is Central Venous Pressure or the pressure of the veins in the Vena Cava as they enter the heart.

    You get the measurement by having a line in place along that route and transducing the pressure within the vena cava. The two most common examples of such lines are Swan-Ganz catheters or subclavian/IJ central lines.

    A pressure tranducer system is connected to the Swan or to one of the central line ports (I was always taught the distal (brown) port, but our anesthesiologists always seem to hook them up to the medial (blue) port.) Once that line is connected to the patient, it is 'transduced' - the pressure is carried through a transducer to a connection on a critical care/OR monitoring system to the monitor and the monitor interprets that data.

    The transducer system has to be under pressure, so it is attached and primed with fluid (we use 1000units/heparin in 500ml NS but some places just use 500ml of NS). Then a pressure bag is inflated around the fluid to 250-300mmHG pressure.

    The actual transducer (a little smaller than a credit card) has to be 'leveled' to the patient. We level it at the phlebostatic axis (the midway point between between the how do I say, height and width of the chest. Think midway along the ribs between the width of the body at about the nipple line). It is usually attached to a transducer holder mounted on an IV pole that is attached to the bed.

    The higher the pressure, generally speaking the greater the amount of fluid in the vein. It gives information about vascular volume. We don't want just to know how much fluid you have inside you - we can discover that by measuring I&Os. We want to know how much fluid is circulating in your vascular system.

    A low CVP is probably consistent with low BP. If we know its due to low circulating volume, we can replace with fluids. Low BP with a high CVP probably involves other factors and so would first be treated with pressors.

    The first rule of pressors, generally, is to replace volume first. It does little good to press down on an empty system. So CVP is important in knowing how to treat BP.

    CVP is also used in the calculation of other Swan readings, such as SVR (systemic vascular resistance) and those reading provide a more direct picture of how the heart is doing, including an indirect measure of Left Ventricular End Diastolic Pressure (how the left heart - the side that pumps reoxygenated blood to the major organs - is doing). Knowing the 'hemodynamics' of the heart gives you a better idea of what kind of treatment will aid the heart instead of hinder.

    Basically, our medications either beat the heart to work harder (using more oxygen) or it relaxes the heart so that it uses less oxygen (but works less). There is a tradeoff - doing one complicates the other and vice versa. Knowing what the status of the heart is to determine the best treatment is essential.

    CVP is an essential measure of that. The heart is a pump. CVP gives an idea of how 'primed' the pump is. CVP is a measure of preload.

    As an aside, balloon pumps do both - make the heart work more efficiently AND provide better oxygenation - that is why they are sometimes preferable to meds.

    ~faith,
    Timothy.
    Last edit by ZASHAGALKA on Sep 26, '05
  4. by   raindrop
    Quote from ZASHAGALKA
    Normal is 2 to 15. It is Central Venous Pressure or the pressure of the veins in the Vena Cava as they enter the heart.

    You get the measurement by having a line in place along that route and transducing the pressure within the vena cava. The two most common examples of such lines are Swan-Ganz catheters or subclavian/IJ central lines.

    The higher the pressure, generally speaking the greater the amount of fluid in the vein. It gives information about vascular volume. We don't want just to know how much fluid you have inside you - we can discover that by measuring I&Os. We want to know how much fluid is circulating in your vascular system.

    A low CVP is probably consistent with low BP. If we know its due to low circulating volume, we can replace with fluids. Low BP with a high CVP probably involves other factors and so would first be treated with pressors.

    The first rule of pressors, generally, is to replace volume first. It does little good to press down on an empty system. So CVP is important in knowing how to treat BP.

    CVP is also used in the calculation of other Swan readings, such as SVR (systemic vascular resistance) and those reading provide a more direct picture of how the heart is doing, including an indirect measure of Left Ventricular End Diastolic Pressure (how the left heart - the side that pumps reoxygenated blood to the major organs - is doing). Knowing the 'hemodynamics' of the heart gives you a better idea of what kind of treatment will aid the heart instead of hinder.

    Basically, our medications either beat the heart to work harder (using more oxygen) or it relaxes the heart so that it uses less oxygen (but works less). There is a tradeoff - doing one complicates the other and vice versa. Knowing what the status of the heart is to determine the best treatment is essential.

    CVP is an essential measure of that. The heart is a pump. CVP gives an idea of how 'primed' the pump is.

    As an aside, balloon pumps do both - make the heart work more efficiently AND provide better oxygenation - that is why they are sometimes preferable to meds.

    ~faith,
    Timothy.
    Wow Time that was a beautiful explanation. So, if someone has a Central Line, you should always be able to get a CVP reading then?

    When I asked how you do it, believe it or not, I was being serious. I am a new grad on ICU precepting with the grouchiest nurses on earth. In report, I always hear them ask what the pt's CVP reading was and when we give report, everyone wants to know what it was on our shift. My preceptor showed me one time how to get it, but she went thru it so fast, and it was a multi-step process, that there is no way I can remeber how to do it. I asked her to write it down, step-by-step for me, and I got a dirty look. I plan on asking her to show me again, but if someone here can type it so I can "study" it, that will help me alot.

    I remeber that the bed is suppose to be low, and that the "thing" is suppose to be at axillary level for th reading. That is all I remember. Are the IVF's suppose to be off when getting the reading? What is the "thing" called.

    Why is it usually hooked with a bag of fluid, and what is that white air-filled balloon?
  5. by   ZASHAGALKA
    Quote from raindrop
    Wow Time that was a beautiful explanation. So, if someone has a Central Line, you should always be able to get a CVP reading then?

    When I asked how you do it, believe it or not, I was being serious. I am a new grad on ICU precepting with the grouchiest nurses on earth. In report, I always hear them ask what the pt's CVP reading was and when we give report, everyone wants to know what it was on our shift. My preceptor showed me one time how to get it, but she went thru it so fast, and it was a multi-step process, that there is no way I can remeber how to do it. I asked her to write it down, step-by-step for me, and I got a dirty look. I plan on asking her to show me again, but if someone here can type it so I can "study" it, that will help me alot.

    I remeber that the bed is suppose to be low, and that the "thing" is suppose to be at axillary level for th reading. That is all I remember. Are the IVF's suppose to be off when getting the reading? What is the "thing" called.

    Why is it usually hooked with a bag of fluid, and what is that white air-filled balloon?
    reread, i edited the above and added more explanation on the how to.

    No they aren't off, the pressure from the bag normally instill about 3 ml/hr into the patient. But is should be 'zeroed' before taking the measurement. You open (uncap) the stopcock on the transducer, turn the stopcock to let it open to the atmosphere (turn it up). you relevel at the phlebostatic axis, and then you push and hold the zero button on the transducer module on the monitor for 3 seconds or until it beeps and reads across the top that it is zeroing that module. When the monitor reports that it is zeroed, you turn the stopcock back to the middle position, re cap it and I normally pull the pigtail to flush a ml or so to make sure nothing is occluded, but that's me.

    It is very important not to let air get into the system, because air in the transducer will mess up the reading, so, when you connect the bag to the tubing, make sure the fill chamber at the top is completely filled.

    ~faith,
    Timothy
    Last edit by ZASHAGALKA on Sep 25, '05
  6. by   raindrop
    Quote from ZASHAGALKA
    reread, i edited the above and added more explanation on the how to.

    ~faith,
    Timothy
    Ahhh,aaa I'm starting to get it now.

    Now, on the transducer, what way/direction means it is "off" to the pt, etc, etc. Is it towards the yellow? What direction should it be when taking a reading, or inflating the Pressure bag? Most importantly, what way should it be all the time if your not getting a reading, etc, etc?

    With CL's in general, is it safe to always clamp the port that you aren't using?
  7. by   NRSKarenRN
    a normal cvp reading in a spontaneously breathing patient is 5-10 cmh2o
    http://www.hku.hk/anaesthe/learnet/index.htm

    central venous lines
  8. by   ZASHAGALKA
    Maybe I was thinking normal ICP readings with the 2-15 number, eh? Sorry, I don't normally 'teach'.

    OK, I'll buy 5-10.

    ~faith,
    Timothy.
  9. by   ZASHAGALKA
    Quote from raindrop
    Ahhh,aaa I'm starting to get it now.

    Now, on the transducer, what way/direction means it is "off" to the pt, etc, etc. Is it towards the yellow? What direction should it be when taking a reading, or inflating the Pressure bag? Most importantly, what way should it be all the time if your not getting a reading, etc, etc?

    With CL's in general, is it safe to always clamp the port that you aren't using?
    there are three ways you can move the stopcock. up is off to the the patient (because the fluid from the bag actually enters the bottom of the tranducer and goes up through the transducer to the patient).

    the middle position opens the patient reading through to the monitor (and the pressure from the bag keeps blood from backflowing). Down is off to the monitor. I never have a reason to turn it down if I am actively using the transducer. Down takes out the pressure from the system and could lead to backflow/bleeding from the patient.

    I always clamp non used ports. When I flush them I clamp as I end the flush. Think about a straw. If you clamp/aka put your finger on the top of the straw, the fluid in place, stays in place. If you clamp as you flush, you hold that fluid in the line, decreasing the chance that blood will backflow and clot.

    unclamped lines risk clotting off.

    If you are taking a constant CVP however, that is not an unused line, if you clamp it, it doesn't work.

    And you should zero a pressure transducer system every 4 hrs, or according to your policy. Q4 is ours.

    Transducing an art line works the same general way, btw. Except, never turn off the alarms on an art line transducer, if the line disconnects, the alarm would tell you that you have a line in the pt's artery gushing out blood. (ABP disconnect alarm). It can't tell you that if it's off.

    ~faith,
    Timothy.
  10. by   ZASHAGALKA
    At my last hospital, turning of the alarms on an ABP monitor was considered a major safety infraction and, if repeated, cause for termination.

    Even if the line is 'dampened' and not working, turn down the bp parameters for alarming, not the alarm off itself.

    ~faith,
    Timothy.
  11. by   raindrop
    So, is the "yellow" knob called the stopcock, or is the stopcock what you actually turn up/across/down?

    The yellow thing twists off, right?


    Here is what I thinkg the steps are from what you have told me...

    1) Lie pt flat.

    2) Twist off the yellow thing.

    3) put the lever up

    4) lie the transducer mid-axillary

    5) Zero the monitor, wait for it to beep...

    6) Read the CVP

    Am I quasi?
  12. by   ZASHAGALKA
    Quote from raindrop
    So, is the "yellow" knob called the stopcock, or is the stopcock what you actually turn up/across/down?

    The yellow thing twists off, right?


    Here is what I thinkg the steps are from what you have told me...

    1) Lie pt flat.

    2) Twist off the yellow thing.

    3) put the lever up

    4) lie the transducer mid-axillary

    5) Zero the monitor, wait for it to beep...

    6) Read the CVP

    Am I quasi?
    Sorry, was chatting w/ my neighbor.

    The yellow thing is the cap? Our caps are blue. the stop cock is actually the lever that moves in three positions. And the little pull thing we call a 'pig-tail' that actually lets you flush the line when the stop cock is in the middle position.

    You have to remove the cap with zeroing to allow the pressure to 'zero' or become equivalent to the atmosphere. (And you have to turn the stopcock up so that the monitor is open to the atmosphere - up blocks off to the patient because the fluid comes in from the bottom and goes to the patient from the top).

    Oh, when you open the transducer to the atmosphere, pull a bit on the pigtail so that 1ml or so of fluid flows through the transducer and out the open port.

    After you zero, you have to replace the cap and put the stopcock in the middle position.

    And you don't have to leave the patient flat to monitor, just make sure as you adjust the patient by moving up HOB, that you adjust the transducer holder so that the transducer is at the phlebostatic axis.

    ~faith,
    Timothy.
  13. by   ZASHAGALKA
    there are single tranducer kits, double and triple.

    You'd use a single to monitor 1 feature, ABP or CVP by itself.

    A double has two transducer so you can monitor both (the holder lets you put four on I think)

    A triple would be both the ABP,CVP and the Pulmonary Artery Pressure (PAP) of a swan.

    If all three are running, they are going to each have their own pressure module and each would be zeroed independently.

    If you don't need one anymore, I normally turn the stopcock down to shut it off to the monitor, and remove the tubing above the transducer and replace it with a needleless cap to - cap it off. That way you can keep the transducer set up without using the now 'extra' tranducer.

    btw, the tranducer tubing is 'pressure' tubing. It's hard - not the same as regular IV tubing and not interchangeable.

    ~faith,
    Timothy.
  14. by   raindrop
    Okkkk, I think I am getting there. Slowly, but surely. You are helping me out greatly.



    1) HOB Down (I'm just going to keep it down. That is how I see the other nurses do it)

    2) Place stopcock up
    3) Remove cap.

    3) Give a little flush via pigtail

    5) Place transducer at phlebostatic axis

    6) Zero it out

    7) Read.

    Now, how does that look?

    If it looks correct, I want to make a cheat sheet out if it.
    Last edit by raindrop on Sep 25, '05

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