Intracranial Pressure

Question 1

Intracranial Pressure (ICP)

Answer 1

• The pressure inside the cranial vault
• ICP is the result of interaction btwn the brain, CSF, & blood
• ICP is what mean arterial pressure (MAP) must overcome to get blood to the brain
• Normal ICP: 5-15 mmHg

Question 2

Cerebral Perfusion Pressure (CPP)

Answer 2

• The pressure necessary for perfusing the brain & nervous tissues to achieve adequate metabolic function
• CPP = MAP - ICP
• Normal CPP: 50-70 mmHg

Question 3

Normal ICP doesn’t always equal normal cerebral perfusion

Answer 3

• Pts w/ higher ICP & lower MAP
  > EX: MAP of 60 & ICP of 15; CPP = 45, not enough pressure to get blood to underlying tissues; this is when ischemic events occur

Question 4

Autoregulation

Answer 4

• Maintenance of cerebral blood flow even w/ changes in arterial pressure
  > the physiologic process tht refers to the capacity of cerebral circulation to adjust its resistance to maintain a cerebral bloodflow regardless of changes in the systemic blood pressure acheived through different compensatory mechanisms

Question 5

Compensatory Mechanism

Answer 5

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

Question 6

Cerebral Compliance

Answer 6

• The ability of cranial content to accomodate volume variations while preventing a rise in intracranial pressure
  > vol variations refers to volume of blood in intracranial vault, CSF, cerebral edema, or a mass, etc

Question 7

Cerebral Ischemia

Answer 7

The result of dcrd brain perfusion secondary to incrd ICP

Question 8

Components of ICP

Answer 8

• Brain: 80%
  > contains 75% water
  > when vol incrs it’s referring to water, not brain tissue
• Arterial & Venous Blood: 10%
  > cerebral blood vol as a whole
  > 15% of cardiac output goes to brain
  > 20% of glucose metabolized by brain; requires blood flow bc brain does not store glucose
• Cerebral Spinal Fluid (CSF): 10%
  > continuous made & reabsorbed
  > shock absorber

Question 9

Etiology of Incrd ICP

Answer 9

• Incr in brain tissue or mass
• Incr in blood volume
• Alterations in CSF

Question 10

Incrd ICP - Brain Tissue or Mass

Answer 10

• Cerebral Edema
  > trauma
  > surgery
  > hyper/hypo Na
• Space-Occupying Masses
  > hematomes
  > abscesses
  > neoplasms
  > aneurysms

Question 11

Incrd ICP - Blood Volume

Answer 11

• Incrd cerebral blood flow during hypercarbia
• Aneurysms, AVMs, intracranial hemorrhage
• Venous stasis from venous sinus thrombosis
• Elevated central venous pressures
  > HF; affects fluid vol all around & how blood enters & exists brain
  > incrd intraabdominal pressure
  > incrd intrathoracic pressure; for these 2, blood gets into brain easily but cannot exit d/t affected venous return = more blood in head
  > meds tht dilate arteries or veins” nitroglycerin causing headahces bc veins dilate in head

Question 12

Incrd ICP - Alterations CSF

Answer 12

• Incr in CSF (altered production)
  > inflammation of the arachnoid villa causes incrd production of CSF
  > choroid plexus tumor
• Dcrd reabsorption of CSF
  > obstructive hydrocephalus; still producing CSF but obstruction causing accumulation = ventricles dilating
  > meningeal inflammation or granulomas; can’t reabsorb

Question 13

Incrd ICP - Nursing Care

Answer 13

• Prevent further ICP & maintain homeostasis
• Position
  > elevate HOB
  > head in neutral position
• Fluid Management
  > I&Os
  > fluid restriction
• Avoidance of vomiting
  > antiemetics
• Avoidance of fever
  > incrs metabolic demand
  > tylenol, motrin, cooling blankets
• Comfort & support
• Promote arterial oxygenation
  > airway & breathing
• Avoid incring metabolic demand
  > htn, anxiety, pain, elevated temp)
  > PRN PO/IV benzodiazepines
  > titrate continuous IV sedation
• Assess for comps
  > infection, corneal abrasions, injury
• Stool softeners

Question 14

If intracranial pressure is not maintained

Answer 14

Normal pressure > incrd ICP > intracranial HTN > herniating brain > possible death