Prodigy Flashcards
Which of the following values most accurately represents the normal average total cerebral blood flow?
About 15 percent of the cardiac output goes to the brain, or about 50 mL/100g/min.
During a craniotomy, a patient’s blood pressure decreases from 120/80 to 60/30. Which of the following would happen?
A. Cerebral vessels would dilate and CBF would increase
B. Cerebral vessels would dilate and CBF would decrease
C. Cerebral vessels would constrict and CBF would increase
D. Cerebral vessels would constrict and CBF would decrease
B. Cerebral vessels would dilate and CBF would decrease.
In response to a decreased MAP, cerebral vessels dilate. Between MAPs of 60 and 160 this mechanism is able to keep CBF constant, but outside of this range CBF becomes pressure dependent. The MAP decreased to 40, therefore CBF would decrease despite compensatory mechanisms.
In normal patients, an increase in the blood pressure from 120/45 to 180/90 results in: A: Cerebral vasoconstriction B: Cerebral vasodilation C: An increase in cerebral blood flow D: A decrease in cerebral blood flow
A: Cerebral vasoconstriction
In this patient, the MAP increased from 70 to 120. Normally, the CBF remains constant between MAPs of 60 to 140 mmHg. As the MAP increases within this range, the cerebral vessels constrict to keep CBF constant.
For every 1 degree Celsius that the core body temperature decreases, the cerebral metabolic rate of oxygen consumption
A: decreases 1%
B: decreases 5%
C: decreases 8%
D: increases 10%
C: decreases 8%
A decrease in the core temperature by 1 degree Celsius is associated with a 8% decrease in CMRO2. Hypothermia between 12 and 20 degrees Celsius has been shown to protect against ischemia for 30 to 60 minutes. Mild hypothermia (33-35 degrees Celsius) has not been shown to provide significant protection.
Which of the following interventions will not help decrease intracranial pressure?
A: Ventriculostomy
B: Hypoventilation
C: Administration of mannitol
D: 30 degree head-up position
B: Hypoventilation
The most effective method to rapidly decrease intracranial pressure is via a lumbar cerebrospinal fluid drain or a ventriculostomy. Hyperventilation and the administration of drugs such as corticosteroids, diuretics, mannitol, and barbiturates also help decrease the intracranial pressure.
What is the formula for cerebral perfusion pressure (CPP)?
A: CPP = ICP-CVP
B: CPP = MAP-ICP
C: CPP = MAP-HR
D: CPP = ICP-PAP
B: CPP = MAP-ICP
The formula for cerebral perfusion pressure is CPP = MAP-ICP. If the CVP is higher than the ICP, then it is used in place of the ICP.
Which of the following values most accurately represents the normal average total cerebral blood flow?
A: 10% of cardiac output
B: 50 mL/100g/min
C: 1500 mL/min
D: 20 mL/100g/min
B: 50 mL/100g/min
About 15 percent of the cardiac output goes to the brain, or about 50 mL/100g/min.
You are preparing to induce a patient with uncorrected hydrocephalus for placement of a ventriculoperitoneal shunt. Which of the following agents would be least appropriate for this patient?
A: Spironolactone
B: Isoflurane
C: Desflurane
D: Acetazolamide
C: Desflurane
Desflurane can increase cerebrospinal fluid production and could potentially increase cerebrospinal fluid pressure prior to placement of the shunt. Acetazolamide, isoflurane, sevoflurane, furosemide, corticosteroids, spironolactone, and vasoconstrictors all decrease CSF production.
Which of the following statements regarding respiratory gas tension and cerebral blood flow (CBF) is true?
A: CBF decreases in response to hypocapnia
B: CBF is not related to carbon dioxide tension
C: CBF is directly proportional to PaO2 between tensions of 50 and 100 mmHg
D: PaO2 tension has no effect on CBF
A: CBF decreases in response to hypocapnia
Hypocapnia decreases cerebral blood flow. This effect usually lasts for about 4-6 hours. PaO2 has little effect on CBF until it reaches a tension of 50 mmHg at which point it dramatically increases CBF.
Intracranial hypertension is defined as a sustained increased in intracranial pressure above:
A: 6-8 mmHg
B: 10-15 mmHg
C: 20-25 mmHg
D: 35-40 mmHg
B: 10-15 mmHg
The definition of intracranial hypertension can be consistently found as a sustained pressure above 15 mmHg.
THIS SOURCE IS CLAIMING NAGELHOUT, BUT SHE SAYS NAGELHOUT SAYS ABOVE 20-25MMHG
Solve for cerebral perfusion pressure with the following values: BP: 180/100; HR: 95; O2 Sat: 99%; RR: 24; ICP: 29 Calculate your answer in mm Hg to the nearest whole number.
98.
Cerebral Perfusion Pressure= MAP-ICP If you are provided with the CVP and it is higher than the ICP, then you should use it instead. The formula to determine MAP = SBP + 2(DBP)/3 Filling in our values, we get MAP: (180 + 2(100))/3 = 126.6. Therefore the CPP: 126.6-29= 97.6 or 98.
Which of the following will decrease intracranial pressure?
A: Dexmedetomidine
B: Hyperventilation
C: Droperidol
D: Midazolam
B: Hyperventilation
Hyperventilation (to a PaCO2 of no lower than 22-25 mmHg) results in respiratory alkalosis and vasoconstriction. As the degree of vasoconstriction increases, the blood flow to the brain decreases, thus decreasing the volume of the intracranial compartment.
A patient has been diagnosed with an ischemic stroke. Which agent should be avoided in the care of this patient?
A: Glucose
B: Labetolol
C: Tissue plasminogen activator
D: Heparin
A: Glucose
Hyperglycemia is associated with poor outcomes in patients with ischemic stroke. Intravenous administration of glucose should be avoided in stroke patients. Labetolol is often used to control blood pressure in these patients. Tissue plasminogen activator and heparin may be used in the treatment of an ischemic stroke.
In normal patients, a decrease in blood pressure from 120/60 to 90/60 results in:
A: Cerebral vasoconstriction
B: Cerebral vasodilation
C: An increase in cerebral blood flow
D: A decrease in cerebral blood flow
B: Cerebral vasodilation
In this patient, the MAP has decreased from 80 to 70. Normally, the CBF remains constant between MAPs of 60 to 140 mmHg. As the MAP decreases within this range, the cerebral vessels dilate to keep CBF constant.
Which of the following will decrease cerebrospinal fluid production?
A: Etomidate
B: Isoflurane
C: Fentanyl
D: Meperidine
A: Etomidate
Isoflurane has no effect on the secretion of CSF but does increase the absorption rate. Desflurane increases the secretion of CSF, and etomidate decreases the secretion of CSF. Fentanyl increases the absorption of CSF.
