Week 2

Question 1

What are causes of Cerebral Edema?

Answer 1

Cerebral infections - encephalitis, meningitis
Head injuries and brain surgery - contusion, hemorrhage, post-traumatic brain swelling
Mass lesions - brain abscess, brain tumor (primary, metastatic), hematoma (intracerebral, subdural, epidural), hemorrhage (intracerebral, cerebellar, brainstem)
Toxic or Metabolic Encephalopathies - Hepatic encephalopathy, Lead or arsenic intoxication, uremia
Vascular Insult - anoxic and ischemic episodes, cerebral infarction (thrombotic or embolic), venous sinus thrombosis

Question 2

What are the three types of cerebral edema?

Answer 2

Vasogenic, cytotoxic, and interstitial

Question 3

What is Vasogenic cerebral edema?

Answer 3

It results from disruption of the blood-brain barrier. This allows large molecules (protein, blood products) to enter brain tissue. This exposes brain cells to toxic products from the blood and results in an osmotic gradient that causes fluid to flow from the intravascular to extravascular space. The result is an increase in the extracellular fluid volume.

Question 4

What is Cytotoxic cerebral edema?

Answer 4

Cytotoxic cerebral edema results from disruption of the integrity of the cell membranes. It develops from destructive lesions or trauma to brain tissue, resulting in cerebral hypoxia or anoxia and syndrome of inappropriate antidiuretic hormone (SIADH) secretion. In this type of edema, the blood-brain barrier stays intact. Cerebral edema occurs from fluid and protein shifts from the extracellular space directly into the cells, with subsequent swelling and loss of cellular function.

Question 5

What is interstitial cerebral edema?

Answer 5

Interstitial cerebral edema is usually a result of hydrocephalus. Hydrocephalus is a buildup of fluid in the brain. It is manifested by ventricular enlargement. It can be due to excess CSF production, obstruction of flow, or an inability to reabsorb the CSF.

Question 6

What is the most sensitive and reliable indicator of neurological status?

Answer 6

LOC

Remember: A change in consciousness may be dramatic (as in coma) or subtle (e.g., flattening of affect, change in orientation, decrease in level of attention).

Question 7

What are Early signs of Increased ICP?

Answer 7

Restlessness/ agitation then changes in LOC - lethargy
HA
Decrease in GCS
Changes in speech
Sluggish or unequal pupils; ptosis
Motor/ sensory (early to late)

Question 8

What are late signs/ symptoms of increased ICP?

Answer 8

Changes in GCS - posturing - decerebrate or decorticate, reacts only to pain
Change in V/S - abnormal respirations (rate, depth, pattern)
Cushing triad - Systolic HTN with widening pulse pressure, Profound bradycardia with bounding pulse, Altered/ irregular respirations
Projectile vomiting
Cardiac changes - Arrythmias
Hemiplegia - early to late)
Hyperthermia
Fixed/ dilated pupils
Loss of corneal reflex
Loss of gag reflex

Question 9

What is the normal pressure range of ICP?

Answer 9

5-15 mmHG

Question 10

What is considered an abnormal ICP?

Answer 10

Sustained pressure greater than 20 mm Hg

Question 11

What is the normal range of Cerebral Perfusion Pressure (CPP)?

Answer 11

70-90 mm Hg (60 - 100 mm Hg in Lewis)

Question 12

What is the normal range for MAP?

Answer 12

70-90 mm Hg

Question 13

What is the lower limit of systemic arterial pressure for cerebral autoregulation?

Answer 13

MAP of 70 mm Hg.

Question 14

What happens to cerebral blood flow (CBF) below a MAP of 70 mm Hg?

Answer 14

CBF decreases → symptoms of cerebral ischemia (e.g., syncope, blurred vision).

Question 15

What is the upper limit of systemic arterial pressure for cerebral autoregulation?

Answer 15

MAP of 150 mm Hg.

Question 16

What happens when MAP exceeds 150 mm Hg?

Answer 16

Vessels are maximally constricted → further vasoconstrictor response is lost.

Question 17

What is the normal range for paCO2?

Answer 17

35-45 mm Hg (or 30 mm Hg)

Question 18

What is the normal paO2 range?

Answer 18

80 - 100 mm Hg

Question 19

What cerebral perfusion pressure (CPP) is associated with ischemia and neuron death?

Answer 19

CPP < 50 mm Hg.

Question 20

What cerebral perfusion pressure (CPP) is incompatible with life?

Answer 20

CPP < 30 mm Hg. Severe ischemia → complete loss of perfusion → neuronal death.

Question 21

What is the formula for calculating cerebral perfusion pressure (CPP)?

Answer 21

CPP = MAP − ICP.

Question 22

Which two pressures determine CPP?

Answer 22

Mean arterial pressure (MAP) and intracranial pressure (ICP).

Question 23

What is the normal pH of blood?

Answer 23

7.35 - 7.45

Question 24

What is the calculation for MAP?

Answer 24

MAP = DBP + 1/3 (SBP - DBP)
OR
MAP = SBP + 2 (DBP) / 3

Question 25

Factors that influence ICP:

Answer 25

Arterial pressure Venous pressure Intra-abdominal pressure and intra-thoracic pressure Posture Temperature Blood gases (particularly CO2)

Question 26

What is auto-regulation in regards to cerebral blood flow?

Answer 26

When the brain vasoconstricts or dilates cerebral blood vessels to maintain consistent CPP

Question 27

What medications are used to treat elevated ICP?

Answer 27

Mannitol (Osmotic diuretic) Hypertonic saline Antiseizure drugs (e.g., phenytoin) Corticosteroids for brain tumors, bacterial meningitis Histamine (H2)-receptor antagonist (e.g., cimetidine) or proton pump inhibitor (e.g., pantoprazole to prevent GI ulcers and bleeding caused by stress and/ or steroids)

Question 28

What is Metabolic-Auto regulation in the brain?

Answer 28

it is a balance of acid/base & oxygenation which causes vasoconstriction or vasodilation of cerebral vessels to increase or decrease blood supply to brain and rid the brain of waste products as needed