I'm a fairly new nurse and have to print off/analyze ECG and CVP strips on a regular basis. I have been through critical care class and have many references, but I'm still not clear on something.
When taking the mean of the A-wave, at what point is diastole if there is a C-wave present?
I come down from the ECG P-wave, and on the CVP tracing the next pos deflection is A-wave. So the top of the A-wave is systolic, but then there's a C-wave "bump" on the downslope before it bottoms out and leads into the V-wave. Where do I read diastole - valley before C-wave?
Nov 20, '10
Couldn't you just go 1/2 way up from the baseline preceding the a-wave and the peak of the a wave? Do you actually do that every time you document a CVP? just curious
Nov 20, '10
Actually I do this every time I have someone with a central line setup, so almost every shift. Usually I'm OK with it because it's pretty clear, however when the darned C-wave is present it throws me off (luckily it's not that common).
Technically I could get away with using the Z-point but since I'm new I want to play by the rules and do it right. If there is a p-wave present on the ECG, we're supposed to mean the A-wave. We have to mark, sign and post the strips in the chart q-shift.
I do plan to talk to one of my CNS's, but I've been doing evening shifts and by the time I'm up and running they're already gone. That's why I'm posting here on the CCU forum - figured you cardiac folks could help me out (I'm in a MICU).
Nov 20, '10
I should've also commented that I have never heard of the method you mentioned - is that common?
Nov 21, '10
I have no idea if it's common. I never do either way, it's not required at my facility. I realize that it is the "gold standard" but I just dont see the point. I watch the trend on the monitor display and combine that knowledge with the clinical picture to figure out what my volume status is. Unless there's marked variability in the waveform with the respiratory cycle then I suppose it would be better to mark it out on paper to find the mean of the a wave at end expiration but I just have never found the need to do that. Besides, what would marking the mean of the a-wave q shift accomplish? Seems pointless. And I'm not knocking you btw, just saying that it really doesn't seem necessary.
Funny you should ask about this because there's an article in this months American Journal of Critical Care about it.
"In this study, we found no significant differences in mean pressures measured via 3 different methods (end-expiration graphic recording, monitor cursor line display, and monitor digital display) for measurement of CVP and PAP."
I don't feel like writing out the full reference all official-like but the name of the article is "Evaluation of the monitor cursor line display method for measuring pulmonary artery and central venous pressures" AJCC, nov 10, vol 19, No. 6. Page 511-521.
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