Section 2: Increased ICP Pathophysiology - Stroke & Increased Intracranial Pressure

NUR 433: Adult Health 2; MCUSON; Mrs. Cooper

_____ _____ is the pressure exerted by everything inside the rigid skull

intracranial pressure (ICP)

a sustained ICP above ___ mm Hg is intracranial hypertension and puts the patient at risk for ischemia and herniation

20

what is normal ICP for adults

5-15 mm Hg

what is normal ICP for children

3 - 7 mm Hg

what is normal ICP for infants

1.5-6 mm Hg

Monro-Kellie doctrine: the skull holds three things in fixed space: _____ _____ (78%), _____ (12%), and _____ (10%). if one increases, one or both of the others must decrease, or ICP rises. think of the skull as a closed jar: add volume and the pressure goes up.

brain tissue, blood, CSF

_____ is the pressure that pushes blood into brain tissue

CPP (cerebral perfusion pressure)

what is the formula to calculate CPP

CPP = MAP - ICP

normal CPP is _____-_____ mm Hg

60-100

the treatment goal is CPP at least _____-_____ mm Hg (Sole)

60-70

CPP < _____ mm Hg leads to ischemia and neuron death

50

CPP < _____ mm Hg id incompatible with life

30

***Worked example: MAP 90, ICP 25 → CPP = 65 mm Hg. If ICP rises to 40, CPP falls to 50: the brain is now ischemic

normal cerebral blood flow (CBF) is ___-___ mL/100 g of brain tissue per minute

50-55

_____ is when the brain changes vessel diameter to keep CBF steady even when systemic BP changes

autoregulation

_____ autoregulation is when high BP leads to cerebral vessels constricting and low blood pressure leads to the vessels dilating

pressure

_____ (metabolic) autoregulation is when CO2, lactic acid, an other by-products dilate vessels

chemical

_____ is the most potent cerebral vasodilator

CO2

***↑ PaCO₂ → vasodilation → ↑ CBF → ↑ ICP

***↓ PaCO₂ → vasoconstriction → ↓ CBF → ↓ ICP

***once autoregulation fails, CBF passively follows BP and ICP can rise uncontrollably

***Common causes of increased ICP

Everyday activities such as sneezing, coughing, bending, sitting up and bearing down for a bowel movement briefly raise _____. A healthy brain compensates easily; an injured brain may not.

ICP

Compensation, then decompensation

The brain protects cortical neurons, which are the most oxygen-sensitive, in this order:

1. CSF shifts. CSF is pushed into the spinal subarachnoid space and absorption increases.

2. Blood volume falls. Cerebral vessels constrict to reduce blood volume.

3. Oxygenation drops. As perfusion falls, oxygen delivery to neurons falls.

4. Ischemia and damage. Prolonged hypoxia causes cell death and more edema, which raises ICP further. This is the vicious cycle you are trying to interrupt