Critical Care Theory (Neuro)- Help!

[StudentOfHealing]

I have an exam this Thursday over Neuro. We are discussing tumors and my notes say that when there is a tumor in the brain, vascular volume/CSF increase, and ICP also increases. I'm told this a compensatory mechanism, it's called autoregulation.

OK- I think I may be completely off but here's my shot at understanding this.

For some reason the presence of the tumor activates this mechanism to increase cerebral perfusion. Increased CSF will have to go back into circulation, correct? I found a diagram that said:

> CSF = > Central venous pressure through the Jugular Vein.

So basically it's increasing venous return? increasing CO? increasing cerebral perfusion?

GAH! I refuse to just memorize what the notes say )=

Then my notes say autoregulation can lost due to injury from the tumor itself.

CO2 will relax smooth muscle (vasodilation) basically will increase the CBF.

I scavenged by book and notes for this ... but is there a way we can control CO2 for desired outcomes. Are there circumstances in which patients are at risk for cerebral ischemia in where we can control this? Is it the ventilator settings?

(also does the vasodilation happen only at the cerebral level)? How could vasodilation improve CBF (cerebral blood flow) is vessels were peripherally vasodilated?

I have here that acidosis can cause vasodilation and thusly a decrease in autoregulation, so I imagine this vasodilation is peripheral?

Also, autoregulation can be both bad and good?

I would appreciate your help.

Thank You

[Esme12, ASN, BSN, RN]

or it can't respond/auto-regulate fast enough

[nurseprnRN, BSN, RN]

Autoregulation also involves blood vessel diameter, respiratory drive center management, carotid sinus BP management, and others. All of these can be wildly unstable in head injury/CVA/etc.

If we waited for autoregulation to fix squashed brains, we'd save a lot of money on ICU beds because the patients would be out of them and into the morgue fast. :)

[StudentOfHealing]

Right! When I was researching it I saw there's a lot of controversy! I see the brain is pretty complex and we yet have a lot to really understand about it. I completely see how the CVA & BP applies! Hemorrhagic strokes you would NOT exactly want a super high BP ... depending on the MD? With ishemic stroke you want to keep it in a nice Elevated safe zone to Perfuse. Seems very circumstancial! But ALL of it seems that way. My professor (who happens to be an NP- and an awesome one) was talking to us about shock and why we treat them all differently.

Wow. Thanks guys. Always appreciate it. It takes a bit more effort than just memory learning but having a grasp on this stuff helps me in the end!