Intracranial Pressure

[irvingjohn15]

why does brain herniation related to severe increased icp can lead to cushing's triad? howdoes it affect the heart rate, rr,and bp? i am wondering why does the bp is increased while hr and rr are decreased.. what causes this?

[WonderWomanUS]

why does hyperventilating them with O2 decrease intracranial pressure? Is it because Oxygen is a vasodilator?

[o2demand]

hyperventilation implies breathing down your PaCo2 (carbon dioxide vs oxygen) which creates cerebral vasoconstriction therefore decreasing CBF resulting in a decreased ICP

[WonderWomanUS]

sorry I dont follow you. can you please explain the mechanism of how hyperventilating with 02 helps decrease ICF pressure

[o2demand]

the main concern is carbon dioxide gas tensions (opposed to oxygen gas tensions)

There is a direct correlation to the carbon dioxide gas tension (PaC02) and CBF (cerebral blood flow).

As you decrease PaCo2 ( the gas tension of carbon dioxide) via hyperventilation this decreases your CBF (cerebral blood flow) secondary to cerebral vasoconstriction

As you decrease the CBF, the CBV (cerebral blood volume) decreases which results in a decreased ICP (intracranial pressure)

[WonderWomanUS]

Thank you for that excellent and clear explanation. In a nutshell, if the PaCo2 decreases so does the CBF. We want the CBF to go down to reduce ICP, so we hyperventilate with O2 to displace as much PCo2 as possible, reducing CBF. Thanks

[DJuggz06]

And does the reduced CBF cause reduced Cerebrospinal fluid? is that the reason for the reduction in ICP?

[leader1960]

thanks for your great videos.

but it looks strange to me here!

how could the vasoconstriction reduce the pressure here? while we use the vasodilator drugs to reduce it?

thanks o2demand

[o2demand]

hey leader

two points:

1st point using the Monro-kellie doctrine is that the cranial vault is a fixed rigid structure. Therefore if you increase anything within this fixed vault...the pressure will increase (hence increased intracranial pressure [ICP])

The three possible things which may increase within this cranial vault are: brain tissue (ex. brain mass), CSF, and blood

Therefore by reducing the blood within the cranial vault we hope to reduce the intracranial pressure (ICP)

[o2demand]

We can reduce the cerebral blood flow (CBF) by hyperventilating a patient which decreases the PaCo2 which creates cerebral vasoconstriction therefore a reduction in CBF

We can also provide a barbiturate (ex. thiopental) which also create cerebral vasoconstriction and lead to decreased CBF and reduce the ICP

[o2demand]

2nd point

Cerebral Perfusion Pressure = MAP - ICP

Therefore if we reduce the MAP (using SYSTEMIC [not cerebral] vasodilators ex. NTG)

The decreased MAP will lead to a decreased cerebral perfusion pressure hence decreased CBF and DECREASED ICP...the very thing we want :)

you have to distinguish btn systemic vasodilation (via NTG) and cerebral vasoconstriction (ex. via hyperventilation and thiopental)

[yoda307]

I'll spell it right one of these times lol.

[yoda307]

I mispelled Itracranial hypertension, sorry:)

[sunnybird]

I have a 13 yr old with an intracranial pressure reading of +40. diagnosis is benign intracranial hypertension. Thanks for your explanation of intracranial hypertension...

[o2demand]

always a pleasure. Just want to share some of the things I have come to learn within time and hopefully keep learning from others.

[yoda307]

Hello, I have a friend with hypocranial tension. She had an LP shunt put in a few months ago. She has constant headaches and her medications help but she still gets headaches. She wants a VP shunt or a VA shunt put in badly. She's trying to find a doctor that can put either of these shunts in for her but she hasn't found a doctor thats willing to do the surgery on her so far. She lives in upstate ny. I was wondering if you knew of any doctors that do VP or VA shunts?

[o2demand]

I know many neurosurgeons who place VP shunts when indicated and need to treat patients with intracranial hypertension. I assume the neurosurgeons who are not willing to place the VP shunt are not doing so because they dont find it indicated...meaning maybe her headaches are caused by other reasons other than intracranial hypertension with increased CSF Volume

let us know how your friend does...and if you can provide more info maybe we can help further

best of luck!

[yoda307]

Thank you so much o2demand. Could I email you with the information from her? She was losing her eyesight from the pressure. She got an LP shunt put in and she regained her eyesight that she partially lost in her left eye. So were not sure whats going on inside her. She needs to find someone who is willing to examine her. Thank you very much for the response.

[o2demand]

if you consider the cerebral perfusion pressure CePP = MAP - ICP, then by reducing the increased ICP you hope to re-establish an adequate CePP and therefore an adeduate CBF. By hyperventilating and blowing of PaC02 this creates cerebral vasoconstriction and therefore reduces the cerebral blood volume and therefore reduced ICP. If the reduction of CePP was due to increased ICP opposed to a reduced MAP then we can assume by reducing the ICP the MAP will provide adequate CePP...hope that helps

[mercyde0]

Why hyperventilate?