Diastolic blood pressure and preload

[Thug4]

Hi, yesterday I was in a GI cholonoscopy and after the insertion of the camera, the pt BP dropped. My attending asked me why the diastolic was so decreased. His answer was because diast BP is equal to preload and the patient “needed volume”.
Is this concept right? I searched in the web and Guyton but could not find this correlation
Tks

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[Planktonmd]

Hi, yesterday I was in a GI cholonoscopy and after the insertion of the camera, the pt BP dropped. My attending asked me why the diastolic was so decreased. His answer was because diast BP is equal to preload and the patient “needed volume”.
Is this concept right? I searched in the web and Guyton but could not find this correlation
Tks

How about a vagal response to dilating the colon?

 

[ethilo]

He's probably trying to drive home that you should remember they get a bowel prep that makes them dry and easily get hypotensive. Whether that is diastolic blood pressure related I wouldn't take that leap myself.

 

[Hoya11]

Hi, yesterday I was in a GI cholonoscopy and after the insertion of the camera, the pt BP dropped. My attending asked me why the diastolic was so decreased. His answer was because diast BP is equal to preload and the patient “needed volume”.
Is this concept right? I searched in the web and Guyton but could not find this correlation
Tks

what pressure does the cuff measure?

 

[GassYous]

Unless you have an a line the map is all you measure. The automated cuff gives you a systolic and diastolic pressure that is calculated based on a proprietary algorithm.

 

[Hoya11]

Unless you have an a line the map is all you measure. The automated cuff gives you a systolic and diastolic pressure that is calculated based on a proprietary algorithm.

right - so the true diastolic bp was not even known

 

[vector2]

Hi, yesterday I was in a GI cholonoscopy and after the insertion of the camera, the pt BP dropped. My attending asked me why the diastolic was so decreased. His answer was because diast BP is equal to preload and the patient “needed volume”.
Is this concept right? I searched in the web and Guyton but could not find this correlation
Tks

Saying aortic diastolic pressure is a reflection of preload is a gross oversimplification. More generally, arterial blood pressure is a function of arterial compliance and stroke volume, and there are many factors that go into determining a particular pt's systolic, diastolic, pulse pressure, and mean arterial pressure.

Pointing to a low indirectly calculated diastolic on a non-invasive oscillometric cuff and then proclaiming the pt must be volume-down after induction for a colonoscopy is pure nonsense.

 

[DrOwnage]

After an attending once told me that patients "could still larygospasm when they're paralyzed because its a different muscle" I learned to start self-confirming stuff that sounded like horsecrap. Misinformation is worse than no information. Don't just blindly believe something someone says because they are in a position above you, especially your attending. After you have exhausted other routes and cannot find said explanation, post it here and usually someone knows.

 

[deleted697535]

Most ppl are either stupid or crazy, some both. This attending has declared himself

Low diastolic must mean needs volume? wow.
Nothing else could cause this? sure
I do like hearing these stories, they make me feel like im not an absolute *******

 

[Radetzky]

After an attending once told me that patients "could still larygospasm when they're paralyzed because its a different muscle" I learned to start self-confirming stuff that sounded like horsecrap. Misinformation is worse than no information. Don't just blindly believe something someone says because they are in a position above you, especially your attending. After you have exhausted other routes and cannot find said explanation, post it here and usually someone knows.

Reminds me of the genius who told me blown pupils didn’t mean anything cos the patient was paralysed.

 

[woopedazz]

Unless you have an a line the map is all you measure. The automated cuff gives you a systolic and diastolic pressure that is calculated based on a proprietary algorithm.

That's not quite right. The diastolic is calculated in most automated machines, but both the systolic and MAP are measured. Systolic being slightly less accurate, but still measured.

 

[GassYous]

That's not quite right. The diastolic is calculated in most automated machines, but both the systolic and MAP are measured. Systolic being slightly less accurate, but still measured.

Thought it just measures the maximum amplitude

 

[coffeebythelake]

Thought it just measures the maximum amplitude

Yep, only MAP which corresponds to maximum amplitude. The Oscillometric method does not measure systolic or diastolic.

How trustworthy is automated noninvasive blood pressure monitoring?

Most vital signs are now obtained using automated techniques. We put a lot of stock in these numbers. Just how accurate are they?.

acphospitalist.org

 

[propadope]

Yep, only MAP which corresponds to maximum amplitude. The Oscillometric method does not measure systolic or diastolic.

How trustworthy is automated noninvasive blood pressure monitoring?

Most vital signs are now obtained using automated techniques. We put a lot of stock in these numbers. Just how accurate are they?.

acphospitalist.org

👍Hence the original dynaMAP

 

[MirrorTodd]

Hi, yesterday I was in a GI cholonoscopy and after the insertion of the camera, the pt BP dropped. My attending asked me why the diastolic was so decreased. His answer was because diast BP is equal to preload and the patient “needed volume”.
Is this concept right? I searched in the web and Guyton but could not find this correlation
Tks

Maybe he was thinking of LVEDP?

 

[propadope]

Maybe he was thinking of LVEDP?

Thats still wrong though cause its equal to LVEDV no?

 

[woopedazz]

Yep, only MAP which corresponds to maximum amplitude. The Oscillometric method does not measure systolic or diastolic.

How trustworthy is automated noninvasive blood pressure monitoring?

Most vital signs are now obtained using automated techniques. We put a lot of stock in these numbers. Just how accurate are they?.

acphospitalist.org

That's not true. In current oscillometric methods the systolic BP is measured directly (hence the systolic measurement appearing on the monitor prior to the pressure reaching MAP).

Systolic pressure is determined by the maximum rate of ↑amplitude (change over time). Most machines then adjust the value post-MAP, but it is still a direct measurement. Diastolic can be measured directly in the same way, but it is inaccurate, and therefore normally calculated instead of measured.

Visual representation attached.

 

[GassYous]

That's not true. In current oscillometric methods the systolic BP is measured directly (hence the systolic measurement appearing on the monitor prior to the pressure reaching MAP).

Systolic pressure is determined by the maximum rate of ↑amplitude (change over time). Most machines then adjust the value post-MAP, but it is still a direct measurement. Diastolic can be measured directly in the same way, but it is inaccurate, and therefore normally calculated instead of measured.

Visual representation attached.

So what you're saying is the systolic is a calculated number made by a proprietary algorithm...

 

[propadope]

That's not true. In current oscillometric methods the systolic BP is measured directly (hence the systolic measurement appearing on the monitor prior to the pressure reaching MAP).

Systolic pressure is determined by the maximum rate of ↑amplitude (change over time). Most machines then adjust the value post-MAP, but it is still a direct measurement. Diastolic can be measured directly in the same way, but it is inaccurate, and therefore normally calculated instead of measured.

Visual representation attached.

https://www.flukebiomedical.com/sites/default/files/resources/nibp____tuteng0100.pdf

“Height Method
Figure 4. Height/Slope Interpretations for Determining BP from Pulse Amplitude Data
The peak pulse amplitude is treated as MAP and normalized to a value of 100 %. The cuff pressure at MAP is the MAP pressure. Systole and diastole are fixed percentages based on MAP. The cuff pressure under diastole is the diastolic pressure and the cuff pressure under systole is the systolic pressure.
There is no standard to suggest what the percentages for systole and diastole should be or even that they should be fixed percentages. Manufacturers using height-based algorithms have performed their own clinical trials and drawn their own conclusions about what the percentages should be and whether they are fixed as a function of MAP pressure.
Slope Method
There are many methods employed to determine how many slopes should be drawn and what conclusions can be made about their intersection. As shown in Figure 4, the cuff pressure under the intersection of the slopes is treated as the systolic and diastolic pressures. There is no standard for slope algorithms, just as there is no standard for height algorithms.”

 

[coffeebythelake]

That's not true. In current oscillometric methods the systolic BP is measured directly (hence the systolic measurement appearing on the monitor prior to the pressure reaching MAP).

Systolic pressure is determined by the maximum rate of ↑amplitude (change over time). Most machines then adjust the value post-MAP, but it is still a direct measurement. Diastolic can be measured directly in the same way, but it is inaccurate, and therefore normally calculated instead of measured.

Visual representation attached.

I think you should begin by reviewing the definition of measurement.

 

[propadope]

I think you should begin by reviewing the definition of measurement.

Well I guess it really depends on the monitor/manufacturer. There is some interpretation involved wether they use height vs slope. Who knows how accurate it is. We can assume MAP is.