ICP

Question 1

The pressure inside the cranial vault. ICP is the result of the interaction between the brain, CSF, and blood.
Pressure inside skull

Answer 1

ICP

Question 2

ICP is what mean arterial pressure (MAP) must overcome to get blood up to the brain.
MAP must be higher than ICP to get blood to underlying structures
Direct measurement inside skulls with specific tools
Normal ICP: 5-15 mmHg

Answer 2

Pressure inside skull

Question 3

The pressure necessary for perfusing the brain and nervous tissues to achieve adequate metabolic function.
Brain and underlying structures
Not waveform
Not direct measurement
Calculation: CPP = MAP - ICP
Normal CPP: 50 - 70 mmHg
Just because normal ICP not mean norm CPP - seen pts higher ICP and lower MAP; if lower - not enough blood getting to tissues and if not addressed when get lower perfusion pressures = ischemic events

Answer 3

Cerebral perfusion pressure (CPP)

Question 4

Maintenance of cerebral blood flow even with changes in arterial pressure. - big concept with ICP; physiologic process which refers to capacity of cerebral circ to adjust its resistance to maintain consistent cerebral blood flow regardless of BP = achieved through diff comp mechanisms

Answer 4

Autoregulation:

Question 5

An action taken by the body to continue physiological function despite an alteration in natural function.

Answer 5

Compensatory mechanism:

Question 6

The ability of cranial content to accommodate volume variations while preventing a rise in intracranial pressure. - ability intracranial content to compensate for variations to maintain intracranial pressure; volume variations: increase volume blood, CSF, cerebral edema, or mass

Answer 6

Cerebral Compliance:

Question 7

The result of decreased brain perfusion secondary to increased ICP.

Answer 7

Cerebral ischemia:

Question 8

Depends on Intracranial volumes - inside intracranial vault
Brain (80%) - 75-80% water and some brain tissue - Volumes increasing - more water increasing or cerebral edema and how brain expands to affect volumes
Arterial and Venous Blood (10%) - cerebral blood volume as whole - brain takes 15% CO - 20% oxygen consumed by brain; 25% glucose metabolised by brain - brain does not store glucose
Cerebral spinal fluid (10%) - continuously made and reabsorped; 10% what inside skull; shock absorber

Answer 8

Components of ICP

Question 9

To keep the intracranial pressure within normal limits, any change in volume of one of the intracranial contents must be accompanied by a change in one or two of the other components.
If increase in one or something else introduced (mass), components should be in skull - blood volume, CSF, brain = will compensate; CSF reabsorped higher rate in arachnoid villi/lymphatic sys - decrease CSF production thereby decreasing volume; venous volume - decrease: pressure pushing on it so lumen smaller and volume less; brain: not want compensate because sponge - squish it down and whatever squished not func; preserve art volume - need O2, glucose, perfusion; brain and art volume last to compensate
How compliant intracranial vault components are
Initial stage (stage 1):
Transition stage (stage 2):
Ascending stage (stage 3): Stay compliant: interventions: meds, extra catheter and drains

Answer 9

Monro-kellie Hypothesis/Doctrine

Question 10

This is the stage dominated by high compliance and low ICP. Despite the increase in volume, there is scarcely any increase in ICP (CSF and CBV absorb the increase in volume).
Intracranial contents compliant
Small tumor or subdural hematoma but brain able to autoregulate
CSF - decreasing volume in intracranial space and venous decreasing in intracranial space
ICP staying within normal limits

Answer 10

Initial stage (stage 1):

Question 11

This stage is characterized by low compliance and low ICP, but the latter starts to increase slowly.
Compliance not present and/or low - part of autoregulation - failing in vault
ICP begins to increase
Need start intervention immediately to get back into compliant state
Autoregulation not enough = must help pt

Answer 11

Transition stage (stage 2):

Question 12

Stage of low or null compliance and high ICP (beginning decompensation). Compensatory mechanisms stop working and small changes in volume elicit high increases in pressure.
Not get ICP under control - no compliance at all; ICP hypertension present
Salvageable
Able to get ICP down - pt very symptomatic - global, focal, or neuro - must fix it - pressure cont climbing until brain squished inside cranial vault and only option to relieve that pressure - herniation out forman magnum - not reversible and deadly
Autoregulation not enough = must help pt

Answer 12

Ascending stage (stage 3):

Question 13

Focus on three structures in intracranial vault - brain, blood, CSF
Increase in brain tissue or mass
Increase in blood volume
CSF volume

Answer 13

Etiology of increased ICP

Question 14

Cerebral edema
Space-occupying masses

Answer 14

Increase in brain tissue or mass

Question 15

Head Trauma
Surgery - tissue manipulated have edema as part of healing process
hypo/hypernatremia
Hypercarbia
Anoxic brain injury
No different colors of gray - no endulation - class brain structures gone; edematous and swollen - not getting adequate perfusion and increases ICP - occupies more space

Answer 15

Cerebral edema

Question 16

Tumor gets surrounded by edema as well; tumor not func as not brain; causes pressure and increases ICP - brain trying to be compliant and make room and have midline shift - squishes ventricles sometimes - where CSF goes before in spinal column - affects flow; takes up space and causes cerebral edema around it increasing ICP and moves structures around - can affect CSF being reabsorbed
Hematomas
Abscesses
Neoplasms
Aneurysms

Answer 16

Space-occupying masses

Question 17

Increase amount of blood in intracranial vault - aneurysm rupture or AVM
Increased cerebral blood flow during hypercarbia
Aneurysms, AVM’s, intracranial hemorrhage
Venous stasis from venous sinus thrombosis - causes blood to be able to get intracranial vault - exit through jugular veins - sluggish = mor blood retained in skull therefore occupying more space
Meds - dilate out arteries, veins - nitro: get headache: partially because low BP and veins dilated - increase amount blood in intracranial vault increasing ICP
Elevated central venous pressures

Answer 17

Increase in blood volume

Question 18

Heart failure - affects fluid volume, how blood enters and exits intracranial vault
Increased intraabdominal pressure - blood into brain easily - venous return not have heart beat or not feel pulse on vein side - depends on gravity; impeded outflow affected so more blood in head
Increased intrathoracic pressure - blood into brain easily - venous return not have heart beat or not feel pulse on vein side - depends on gravity; impeded outflow affected so more blood in head

Answer 18

Elevated central venous pressures

Question 19

CSF - continuously made and reabsorped in arachnoid space - alter production or reabsorption - increase ICP
Increase in cerebrospinal fluid
Decreased reabsorption of CSF

Answer 19

CSF volume

Question 20

Increased production of CSF - typ made choroid plexus: 0.3-0.35 mL/min; increased due to inflammation arachnoid villa
Choroid plexus tumor

Answer 20

Increase in cerebrospinal fluid

Question 21

Obstructive hydrocephalus - something occluding flow of CSF - narrow point between foramen, monroe and third ventricle - plug and CSF not flow like should so not reabsorped; cont produce: start accumulating more and more - ventricles dilate
Meningeal or arachnoid space inflammation (inflammation in part of brain that reabsorbs it) or granulomas
CSF volume can be altered

Answer 21

Decreased reabsorption of CSF

Question 22

Aware of interventions in place to prevent sudden increases ICP further
Focused on homeostasis in intracranial vault so adequate blood flow to brain
Positioning
Fluid management
Stool softener - increases ICP
Aggressive about controlling cough - every time cough - increase ICP secondary intrathoracic pressure affecting venous return down from brain
Avoidance of vomiting - increases intracranial pressure - Nausea - antiemetics - prevent increase ICP with vomiting can cause death, expand hemorrhage
Avoidance of fever - increases metabolic demand.
Comfort & emotional support
Promote arterial oxygenation (airway & breathing)
Avoid increasing metabolic demand (htn, anxiety, pain, elevated temp., infection, seizures)
Assess for complications: infection, corneal abrasions, injury

Answer 22

Nursing care of pts with increased ICP

Question 23

↑ HOB
Head in neutral position

Answer 23

Positioning

Question 24

I & O
Fluid restriction

Answer 24

Fluid management

Question 25

Source identified and treated effectively
Aware metabolic demand
Based on neuronal demand affects metabolic rate
May administer sedation
PRN P.O./IV benzodiazepines
Titrate continuous IV sedation

Answer 25

Avoid increasing metabolic demand (htn, anxiety, pain, elevated temp., infection, seizures)

Question 26

3 major components: Brain tissue, blood, cerebral spinal fluid
Have to have Homeostasis; Homeostasis can be disrupted if the amount of brain tissue, blood, or CSF is higher than normal; aka autoregulation and compliance - must be maintained; cannot change amount of components
The cranial vault is not expandable. As one of the major components increases, one of the other must compensate.
Fail to do so - go from norm ICP to increased ICP to ICP HTN to herniating brain and death
When the brain is no longer able to compensate for an increased volume of brain tissue, blood, or CSF the intracranial pressure becomes elevated.

Answer 26

ICP summary