🎙️ Episode 22: Pressure in the Cranium: ICP Demystified

🧠 Core Concept:

Cerebral perfusion pressure (CPP) = MAP – ICP.

Normal ICP = ~10 mmHg; threshold for concern >20 mmHg.

🧰 Management Strategies:

Elevate head of bed (30°), ensure neck is midline.

3% hypertonic saline preferred over mannitol in AKI.

Short-term hyperventilation (↓ PaCO₂ → vasoconstriction).

Consider sedation or decompressive craniectomy in refractory cases.

External ventricular drain (EVD) for CSF removal and monitoring.

🧩 Clinical Takeaway:

Managing ICP is about protecting perfusion.

Monitor trends closely — especially in trauma, hemorrhage, hepatic encephalopathy.

Chapters

• 0:22 Introduction to Intracranial Pressure
• 1:14 Brain Anatomy and Space Constraints
• 2:06 Reducing Brain Volume and CSF
• 3:29 Position and Sedation Strategies
• 5:02 Final Thoughts on Management

Transcript

Speaker 1: 0:12

let's do a little quick neural short on intracranial pressure, because this always learners struggle with this and it can make it harder to manage a patient. So, management of intracranial pressure the goal is to reduce intracranial pressure and maintain cerebral perfusion pressure, cpp. And the formula for CPP is very simple. It's MAP mean arterial pressure. Remember what is this? One Two-thirds diastolic minus one-third systolic minus. That's your MAP. Remember your BP cuff? It gets the MAP. Did you know that when you're doing an automated BP cuff it gets the MAP and it calculates and interprets with the systolic blood pressure and diastolic blood pressure is from that. So CCP equals MAP minus intracranial pressure.

Speaker 1: 1:02

Now what is in the brain? First, you got the helmet, the skull and we're talking about adults, not children and roughly the brain is about 1400 milliliters and CSF is 150 milliliters in the skull and blood is about 150 milliliters in the skull. Remember, you got that helmet there and it can't. The brain can't expand anywhere outside the helmet, the helmet in most cases the skull is not going to expand outward. In an adult that's something weird, is going on 99.9% of patients. The helmet is not going to expand out. So it's a helmet, it's on there at the skull and if it doesn't, if it expands out, it doesn't like it and it causes injury.

Speaker 1: 1:45

So what can we use? So sedation, decompressive craniotomy and steroids all these things can help us and we'll talk about each one kind of individually. Remember, cerebral perfusion pressure. It's a measurement of pressure gradient that drives blood flow to the brain. So this is super important. Remember we talked about perfusion from the heart. Now we're talking about perfusion for the brain and here again it's calculated for making a difference between the mean arterial pressure minus the intercranial pressure.

Speaker 1: 2:17

So how can we reduce in brain? How can we reduce? We can't just chop out the brain. So you can do a decompressive craniotomy. So if the brain swells out, you let the brain swell and then you put the cranium back on. This is a neurosurgeon's going to do this. You're not going to do this bedside.

Speaker 1: 2:33

But we can use hyperosmolar therapy and there's two main ones. We use mannitol and 3% saline. Mannitol's kind of gone out of favor because it can do what it can cause problems with our kidneys. It can cause problems with our kidneys. So 3% is becoming more in favor.

Speaker 1: 2:53

Now how do we decrease CSF? How do we decrease this as part of the items that are in here. So we talked about brain decompressor, cradiotomy and CSF. How do we decrease CSF? Well, we can do a lumbar puncture if we had to. That'd be emergently, those aren't critical cases. But we can have our neurosurgery colleagues place internal ventricle drain which allows for continuous drainage, and you may have seen those bedside before Now. How about cerebral blood volume? And we talked about that over here. How can we decrease that? How can we decrease it?

Speaker 1: 3:31

Hyperventilation, now, this is short-term, very, very short-term, very controversial. Not always works great, but this is just a short-term thing. You're just trying to get through the next half hour to hour. Hyperventilation these patients are probably going to be on the vent, which induces hypocapnia, low carbon dioxide levels, causing cerebrovasoconstriction, therefore decreasing blood flow to the brain and reducing cerebral blood volume. This is rapid and it's emergent situations.

Speaker 1: 4:03

Only. This is hey, we're not going to do well right now, just like in hyperosmolar therapy, there's another one that you can do. It's very high dose mannitol. Another one that you can do is very high dose mannitol. Now, what's another way we can decrease cerebral blood volume? Very simple, and this should be on all your ventilated patients and this should be in all your heads. We'll call them Position the patient's head at a slightly elevated angle usually 30% can help reduce venous drainage and lower ICP. Lower ICP Reduces venous drainage resistance and lowers ICP. What's another thing we can do? Sedation Propylthol for said, can decrease cerebral metabolism and potentially reducing cerebral blood volume. So this is just a quick little snippet of how to manage a very difficult topic and something that a lot of people don't get exposure to unless it's too late.