Brain 3 Flashcards
Anesthetic management for the patient with an ICP of 25 mmHg undergoing craniotomy for tumor resection includes (select 3):
a. PaCO2 30 mmHg
b. nitroprusside
c. D5LR
D. dexamethasone
E. phenylephrine
F. PEEP 10 cmH2O
a. PaCO2 30 mmHg
D. Dexamethasone
E. Phenylephrine
What are the four strategies to reduce ICP?
reduce cerebral blood volume
reduce CSF
reduce cerebral edema
reduce cerebral mass
How can we reduce cerebral edema?
administer diuretics and steroids (dexamethasone and methylprednisolone)
How can we reduce cerebral mass?
surgical debulking or evacuation of a hematoma
How can we reduce cerebrospinal fluid?
drain with an intraventricular catheter or VP shunt or
administer acetazolamide or furosemid
How can we reduce cerebral blood volume?
provide mild hyperventilation
avoid hypoxemia
avoid vasodilators and employ cerebral vasoconstrictors
elevate head >30 degrees and avoid neck flexion
reduce intrathoracic pressure
Steroids should NOT be used for
traumatic brain injury or a functional pituitary adenoma
Corticosteroids cause ________ which in the setting of cerebral ischemia is associated with worse outcomes.
hyperglycemia
Loop diuretics reduce cerebral edema by
inducing diuresis and decreasing the rate of CSF production
Osmotic diuretics (i.e. mannitol) increase
serum osmolarity and “pull” water across the blood-brain barrier
The high tonicity of 3% sodium chloride can also
reduce ICP by “pulling” water across the BBB
If the BBB is disrupted and mannitol is given,
mannitol can enter the brain and increase cerebral edema
The following drugs can reduce CSF production:
acetazolamide
furosemide
Draining CSF is most useful when there’s an
obstruction to CSF flow such as in the case of hydrocephalus
Describe how mild hyperventilation can decrease cerebral blood flow.
mild hyperventilation (PaCO2 30-35 mmHg) constricts the cerebral vessels–> increased cerebral vascular resistance–> decreased cerebral blood flow–> decreased ICP
Lowering PaCO2 <30 mmHg increases the risk of
cerebral ischemia due to vasoconstriction and shifting the oxyhemoglobin dissociation curve to the left
PaO2 <50-60 mmHg greatly increases
CBF and ICP
_____ is a good choice to maintain cerebral perfusion pressure.
phenylephrine
What positions should be avoided in the setting of increased ICP?
head <30 degrees- does not facilitate venous drainage from the brain
neck flexion or extension can compress the jugular veins and reduce outflow
the Trendelenburg position increases CBV and ICP
The following vascular structures exist as pairs EXCEPT the:
a. posterior communicating artery
b. vertebral artery
c. basilar artery
d. middle cerebral artery
C. basilar artery
The primary function of the circle of Willis is to provide
redundancy of blood flow in the brain
What are the two cerebral circulations?
anterior and posterior circulations
What supplies the anterior circulation?
internal carotid arteries
What supplies the posterior circulation?
vertebral arteries
enter through the foramen magnum
The cerebral venous circulation can be divided into
two separate circulations
Venous blood from the cerebral cortex and cerebellum drain via the
superior sagittal sinus & the dural sinuses
Venous blood from the basal brain structure drains via the
inferior sagittal sinus, the vein of Galen, and the straight sinuses
All venous blood exits the brain via the
paired jugular veins
Within how many hours can IV recombinant tissue plasminogen activator be given after a patient exhibits symptoms of an acute ischemic stroke?
4.5 hours
_____ is the first therapy in patients with acute ischemic stroke
PO aspirin
We can classify the type of CVA as
ischemic or hemorrhagic
_______ strokes are more common
Ischemic
A transient ischemic attack or “mini-stroke” is a
focal neurologic deficit that spontaneously resolves within 24 hours
_____________ should be determined prior to treatment because
The type of CVA b/c a thrombolytic should not be given to a patient with a hemorrhagic stroke
________ is common after ischemic CVA
Hypertension
An elevated BP in the setting of ischemic stroke supports
CPP & cerebral oxygenation
The blood pressure should be kept under ______ in the setting of an ischemic stroke
185/110 mmHg
During cerebral hypoxia, glucose is converted to
lactic acid; cerebral acidosis destroys brain tissue and is associated with poor outcomes
Risk factors for ischemic stroke include
Hypertension (most important)
smoking
DM
HLD
excessive alcohol intake
elevated homocysteine levels
Since the etiology of CVA cannot be determined by clinical criteria alone, the patient should receive an
emergent non-contrast CT
