Exam 3 Study Guide Critical Care
NEURO
o Cerebral circulation requires oxygen and glucose.
o Three components normally determine ICP
Brain substance (80%)
CSF (10%)
Blood (10%)
o Risk factors for increased ICP:
Increased Brain Volume: Tumors or injury with cerebral edema
Increased CSF: hydrocephalus, obstruction, Excess production of CSF fluid
Increased blood: Loss of autoregulation, hemorrhage, vasodilation, Hypercapnia, Increased metabolic demands,
Obstruction of venous outflow
1
,Exam 3 Study Guide Critical Care
Secondary causes: (extracranial) Hypotension, HTN, increased intrathroacic pressure (sneezing and coughing),
hyponatemia, seizures
o Normal ICP is 5-15 mm Hg
o Factors that change Cerebral Blood Flow
Acidosis (increased PaCO2) and hypoxia cause cerebrovascular vasodilation
Alkalosis causes cerebrovascular vasoconstriction
Increased metabolic rate increases CBF
Decreased metabolic rate decreases CBF
Outside the MAP limits, CBF becomes dependent on the perfusion pressure
o Cerebral Perfusion Pressure is an estimate of CBF
CPP = MAP – ICP
Normal CPP = 60-100 mm Hg
Intracranial hypertension = > 20 mm Hg
Increased ICP reduces CPP and brain is less well-perfused (CBF decreases)
Anytime CPP is less than 60, blood flow in brain is diminished or compromised.
o A GCS of 3 to 8 is an indication of ICP monitoring!
Intraventricular: CSF measurement and drainage; risk of bleeding/infection. This is the most reliable and
common way of monitoring CSF. You can also give intrathecal meds.
2
, Exam 3 Study Guide Critical Care
o GCS:
o Remember, decerebate posturing is WORSE than decorticate posturing. Think: DeCOREticate….. holding onto the core.
o Assessment of IICP:
1. Early Response:
Altered LOC
Papilledema
Unilateral pupil dilation
Headache
Vomiting
2. Late Response:
Paralysis/paresthesia
Cushing’s triad: systolic hypertension, widening pulse pressure, bradycardia, hyperventilation (Cheyne stokes)
3. Major complication is brainstem herniation
o Increased ICP Nursing Care:
Monitor carefully
Avoid actions that increase ICP: coughing, straining, suctioning, PEEP; hip flexion, pain, abdominal/bladder
distention
Avoid actions that impair cerebral venous drainage: supine position, head low, neck twisted
Minimize external stimuli
Ensure patent airway
HOB elevation 30 degrees
3
NEURO
o Cerebral circulation requires oxygen and glucose.
o Three components normally determine ICP
Brain substance (80%)
CSF (10%)
Blood (10%)
o Risk factors for increased ICP:
Increased Brain Volume: Tumors or injury with cerebral edema
Increased CSF: hydrocephalus, obstruction, Excess production of CSF fluid
Increased blood: Loss of autoregulation, hemorrhage, vasodilation, Hypercapnia, Increased metabolic demands,
Obstruction of venous outflow
1
,Exam 3 Study Guide Critical Care
Secondary causes: (extracranial) Hypotension, HTN, increased intrathroacic pressure (sneezing and coughing),
hyponatemia, seizures
o Normal ICP is 5-15 mm Hg
o Factors that change Cerebral Blood Flow
Acidosis (increased PaCO2) and hypoxia cause cerebrovascular vasodilation
Alkalosis causes cerebrovascular vasoconstriction
Increased metabolic rate increases CBF
Decreased metabolic rate decreases CBF
Outside the MAP limits, CBF becomes dependent on the perfusion pressure
o Cerebral Perfusion Pressure is an estimate of CBF
CPP = MAP – ICP
Normal CPP = 60-100 mm Hg
Intracranial hypertension = > 20 mm Hg
Increased ICP reduces CPP and brain is less well-perfused (CBF decreases)
Anytime CPP is less than 60, blood flow in brain is diminished or compromised.
o A GCS of 3 to 8 is an indication of ICP monitoring!
Intraventricular: CSF measurement and drainage; risk of bleeding/infection. This is the most reliable and
common way of monitoring CSF. You can also give intrathecal meds.
2
, Exam 3 Study Guide Critical Care
o GCS:
o Remember, decerebate posturing is WORSE than decorticate posturing. Think: DeCOREticate….. holding onto the core.
o Assessment of IICP:
1. Early Response:
Altered LOC
Papilledema
Unilateral pupil dilation
Headache
Vomiting
2. Late Response:
Paralysis/paresthesia
Cushing’s triad: systolic hypertension, widening pulse pressure, bradycardia, hyperventilation (Cheyne stokes)
3. Major complication is brainstem herniation
o Increased ICP Nursing Care:
Monitor carefully
Avoid actions that increase ICP: coughing, straining, suctioning, PEEP; hip flexion, pain, abdominal/bladder
distention
Avoid actions that impair cerebral venous drainage: supine position, head low, neck twisted
Minimize external stimuli
Ensure patent airway
HOB elevation 30 degrees
3
