Rock_shoes,
First, thanks for the response. I appreciate the time people with experience like you take to answer questions from people like me who are in the process of starting out. I have no idea why I find all this so fascinating, but I do.
Unfortunately, I'm not sure I understand your point - I'm still just a student without a single ride to my name yet searching for a class that's open during COVID without much success. Can you check my analysis below and tell me if I'm right?
The Monro-Kellie Doctrine (which was a new one for me; thanks!) says that if any one of the 3 volumes of brain, blood, or CSF increases then another volume must decrease and ICP will rise. That makes sense intuitively to me, and is why an intracranial bleed 2/2 head trauma would cause an rise in ICP. But why is morphine contraindicated here? I would think morphine would decrease BP, therefore decreasing cranial blood volume proportional to the brain's arterial compliance, therefore decreasing ICP, and therefore improving things. So from that, morphine is good.
Cerebral perfusion pressure (yet another thing I hadn't heard of before; thanks!) says the greater the differential between the MAP and ICP, the greater perfusion. Also makes sense intuitively. From that I see that the drop in BP from morphine combined with the increase in ICP if there is a brain bleed or post-traumatic swelling would be bad; it would decrease the pressure gradient and therefore decrease neural cellular respiration. So from that morphine is bad.
Combining those two things, the takeaway is that, in practice, the damage that morphine does from decreasing cerebral perfusion is worse than the improvement it does by reducing ICP, so don't use it.
Is that right?