Respiratory Acidosis and cerebral vascular dilation? I'm so confused.

[scubanurse]

Ok, I've been reading and researching this correlation but can't seem to find much on it. In our ABG lecture notes it was mentioned that patients in respiratory acidosis wil have increased cerebral vascular dilation. I'm so terribly confused.

Is this why we used to want to hyperventilate brain trauma patients? Hyperventilation can cause respiratory alkalosis which I'm guessing can cause constriction of cerebral vasculature? I've tried to find some scholarly articles on this to help me get it but am so turned around and lost.

Why does acidosis increase vascular dilation? What's the physiology behind this?

Sorry, I'm just so turned around on this and ABG's and we have our final tomorrow so I'm trying to understand it at a physiological level so maybe I can critically think through the questions.

Thanks!

[chbare]

The physiology is ill defined but a general metabolic theory exists where it appears that cells release vasoactive substances in the presence of metabolic by-products. Clearly, acids are by-products. The exact mechanisms are not well known but if I had to guess, I'd say that it probably begins with conformational changes of proteins and may involve metabotropic or ionotropic (perhaps both) channels/receptors. We also know that changes in protein conformation directly effect physiological processes with conformational changes. Acid levels and the Bohr effect at the tissue level being an example of a normal process based on such changes.

[scubanurse]

So I'm not just an idiot... Thanks chbare! I was trying to find info that apparently just isn't out there!

[DFIB]

So I'm not just an idiot... Thanks chbare! I was trying to find info that apparently just isn't out there!

I have perhaps a simplistic view of acidosis/alkalosis and head trauma. Since the host of metabolites cannot be tracked and measured in the field, I focus on the things that I can measure and regulate. Carbon Dioxide is a strong vasodilator that can be measured and often times controlled by regulating the ventilation rate.

So yea, you are most definitely on the right track. You might try investigating the relationship between CO2, Acidosis, arterial vasodilation, and heat trauma.

Happy Hunting!!

[chbare]

I think Kate is wanting to go beyond what is traditionally taught. For example, is CO2 it's self a vasodilator? Given that most of the CO2 is transported in the form of bicarbonate ions and Hydronium ions, it's reasonable to ask what are the things that actually cause vasidilation. Is it CO2 by its self, pH changes, release of other substances, an amalgamation of processes or something ill defined?

[DFIB]

I think Kate is wanting to go beyond what is traditionally taught. For example, is CO2 it's self a vasodilator? Given that most of the CO2 is transported in the form of bicarbonate ions and Hydronium ions, it's reasonable to ask what are the things that actually cause vasidilation. Is it CO2 by its self, pH changes, release of other substances, an amalgamation of processes or something ill defined?

True. Those things are ill defined and not measurable in the field.

EDIT: Do you have one of your videos about this? Would love to see one!

Edited February 18, 2013 by DFIB

[scubanurse]

Thanks Chbare & DFIB Ch is right... I'm looking deeper into this for nursing. And do you have a video?? Everyone in my class is struggling with blood gases and I get those on the basic level and can ID the different ones but it's the why that is bugging me

[Kiwiology]

I have always wondered if CO2 itself is a vasodialator seeing as how most is carried in HC03/H2CO3 (if memory serves) with only a tiny amount actually dissolved in the blood plasma

[systemet]

http://www.nda.ox.ac.uk/wfsa/html/u08/u08_015.htm

This is a nice page that speaks to the role of CO2 in cerebral autoregulation.