73 Questions
What happens to CBV during cerebral ischemia?
Increases
What occurs when autoregulation is impaired?
CBF and CBV increase in parallel
How does the cerebral circulation respond to a decreasing MAP?
CBV increases progressively
What compensatory adjustments occur in normal subjects with initial CBV increases?
CSF is translocated to extracerebral vessels
What can an increase in CBV lead to when intracranial compliance is reduced?
Herniation
How do CBF and CBV typically vary when autoregulation is functioning normally?
Varies independently
In neuroanesthesia, why is control and manipulation of CBF important?
To manage Intracranial Pressure (ICP)
What is the approximate normal CBV in mL/100g of brain?
5 mL/100g
For an adult brain weighing approximately 1400g, how much can the total CBV change for a Paco2 range of 25 to 55 mm Hg?
20 mL
Why are there few data on CBV compared to CBF, especially in humans?
CBV is more difficult to measure
which of the following statements are correct
the magnitude of change in CBV is less than the magnitude of change in CBF
50% increase in CBF can lead to
20 % increase in CBV
What effect does Ketamine have on cerebral metabolic rate (CMR) and cerebral blood flow (CBF) compared to most intravenous anesthetics?
Ketamine increases both CMR and CBF.
How do intravenous anesthetics typically affect neurovascular coupling and cerebral blood flow (CBF)?
Intravenous anesthetics maintain neurovascular coupling with parallel changes in CMR leading to changes in CBF.
What is the net effect on cerebral blood flow (CBF) at the point of EEG suppression when barbiturates are administered?
Vasoconstriction and a substantial decrease in CBF
What is the general effect of intravenous anesthetics on autoregulation during their administration?
Autoregulation remains preserved during the administration of intravenous anesthetics.
What effects do intravenous anesthetics have on vascular tone?
direct effects on vascular tone
What is the approximate reduction in cerebral blood flow (CBF) and cerebral metabolic rate (CMR) with large doses of thiopental causing complete EEG suppression?
50% to 60%
What is the major effect of nontoxic doses of depressant anesthetics on cerebral metabolism, based on the observations?
Reduction in neurophysiologic activity
In patients with severe head injury maintained in barbiturate coma for 72 hours, what happens to the blood concentration of thiamylal required to maintain EEG burst suppression over time?
Increases steadily
During deep pentobarbital anesthesia, what is the effect on autoregulation and CO2 responsiveness?
Both are maintained
What effect do further increases in barbiturate dose have on cerebral metabolic rate (CMR) beyond a certain point?
They have no additional effect on CMR
What effect does propofol have on regional cerebral blood flow (CBF) in healthy volunteers?
Decreased CBF by 53% to 79%
During propofol administration, what effect does hypocapnia have on cerebral blood flow (CBF)?
Reduction in the magnitude of CBF decrease during hypocapnia
In what way are CO2 responsiveness and autoregulation affected in humans during propofol administration?
Preserved even during doses that produce burst suppression of the EEG
Why does the reduction in cerebral blood flow (CBF) during hypocapnia decrease with propofol administration?
Cerebral vasoconstriction induced by suppression of cerebral metabolic rate (CMR)
How do propofol's effects on cerebral metabolism impact cerebral blood flow (CBF) and intracranial pressure (ICP)?
Reductions in CMR lead to secondary decreases in CBF, CBV, and ICP
What is the approximate reduction in cerebral blood flow (CBF) with a dose of etomidate sufficient to produce EEG suppression?
34%
How does the cerebral metabolic rate (CMR) suppression caused by etomidate differ from barbiturates?
Predominantly in forebrain structures
In what scenario is etomidate ineffective in reducing intracranial pressure (ICP)?
When EEG activity is suppressed
What effect does etomidate have on cerebral perfusion pressure (CPP) in patients with intracranial tumors or head injuries?
dose not Reduce CPP
What is the general trend of cerebral metabolic rate (CMR) suppression achievable with etomidate compared to isoflurane and barbiturates?
Less profound
What effect did the administration of morphine as the sole drug have on global CBF and CMRO2 in humans?
No effect on CBF and decreased CMRO2
What was the observed effect of administering morphine (1 mg/kg and 3 mg/kg) with 70% N2O on CBF and CMR?
No significant change in either CBF or CMR
What can histamine release caused by morphine lead to in terms of cerebral vasculature?
Increase in CBV a CBF effect that will vary, depending on BP
What was the impact of autoregulation between MAP values of 60 and 120 mm Hg in human volunteers anesthetized with a combination of morphine and N2O?
Autoregulation remained intact
What was the general finding regarding net changes in awake control measurements of CBF and CMR with large doses of morphine?
A small-to-moderate depressive effect on CBF and CMR
What effect does fentanyl have on CBF and CMR in the normal quiescent brain?
Reduces both CBF and CMR
How does high dose fentanyl (100 μg/kg) combined with diazepam affect CBF?
Reduces CBF by 25%
What is the effect of sedative doses of fentanyl (1.5 μg/kg) on CBF in various brain areas?
Increases CBF in some areas and decreases it in others
What remains unaffected by fentanyl according to the text?
CO2 responsiveness and autoregulation
What was observed in human subjects after the infusion of small doses of remifentanil?
Increases in CBF in the prefrontal and supplementary motor cortices
Which area showed reductions in CBF when larger doses of remifentanil were administered?
Cerebellum
What impact does the administration of 15 mg of diazepam have on cerebral blood flow (CBF) and cerebral metabolic rate (CMR) in patients with head injuries?
25% decrease in CBF and CMR
What effect did the administration of midazolam have on cerebral blood flow (CBF) in awake healthy human volunteers?
decrease in CBF and increase CMR
How does the extent of maximal reductions in cerebral blood flow (CBF) and cerebral metabolic rate (CMR) caused by benzodiazepines compare to narcotics and barbiturates?
Greater than narcotics but less than barbiturates
What are the effects on cerebral blood flow (CBF) and cerebral metabolic rate (CMR) observed when diazepam are administered?
Both CBF and CMR decrease
What effect did flumazenil have on cerebral blood flow (CBF) when administered to nonanesthetized human volunteers?
No effect on CBF
In patients with severe head injury and uncontrolled intracranial pressure (ICP), what side effect was observed when flumazenil was administered?
Increase in ICP
What unexpected phenomenon was observed regarding cerebral blood flow (CBF) and intracranial pressure (ICP) levels after flumazenil administration?
CBF overshoot and ICP overshoot
Why should flumazenil be cautiously used to reverse benzodiazepine sedation in patients with impaired intracranial compliance?
Potential for uncontrolled CBF fluctuations
What is the likely effect of droperidol on cerebral blood flow (CBF) and cerebral metabolic rate (CMR) in humans?
No effect on CBF and CMR
What do occasional increases in intracranial pressure (ICP) observed with droperidol administration most likely reflect?
Autoregulation-mediated vasodilation in response to decreased MAP
What effect is droperidol likely to have on cerebral metabolic rate (CMR) based on the provided information?
No effect on CMR
What effect does the (R)-ketamine enantiomer have on the cerebral metabolic rate (CMR) compared to the (S)-ketamine enantiomer?
Decreases CMR in the cerebellum
How does ketamine affect global cerebral blood flow (CBF) at subanesthetic doses?
Increases CBF by 14%
Which brain areas in humans show the greatest increase in cerebral metabolic rate (CMR) after ketamine administration?
frontal and anterior cingulate cortex
What is the observed effect anesthetic doses of ketamine on global cerebral blood flow (CBF)?
Increase by 36%
How does autoregulation behave during ketamine anesthesia according to the majority of investigations?
Maintained
What is the effect of large anesthetic doses of ketamine in patients with head injuries who are sedated with propofol?
Decrease in intracranial pressure (ICP)
Which statement best explains the effect of ketamine on intracranial pressure (ICP) in patients receiving adjunctive sedative drugs?
Ketamine decreases ICP when administered with sedatives.
What is the likely impact of concurrent administration of sedative agents on the effects of ketamine on cerebral blood flow (CBF) and intracranial pressure (ICP)?
Blunt or eliminate the increases in CBF or ICP associated with ketamine
In what scenario might ketamine be best avoided as the sole anesthetic drug due to concerns about intracranial compliance?
Patients with impaired intracranial compliance
What effect does lidocaine have on cerebral metabolic rate (CMR) and CBF in nonanesthetized human volunteers?
reductions in CBF and CMR
What effect did large doses of lidocaine have on the cerebral metabolic rate of oxygen (CMRO2) in dogs on cardiopulmonary bypass?
Reduced CMRO2 more than large-dose barbiturates
How did the reduction in intracranial pressure (ICP) compare between bolus doses of thiopental and lidocaine in patients undergoing craniotomies?
Both were equally effective in reducing ICP
What is a reasonable adjunct for preventing or treating acute increases in intracranial pressure (ICP) based on the text?
Lidocaine
What serum concentration range of lidocaine should be maintained to avoid seizures in awake humans?
<5-10 μg/mL
What was the observed effect of large doses of lidocaine on seizures in anesthetized humans?
No effect on seizures in anesthetized humans
What changes in cerebral blood flow (CBF) and cerebral metabolic rate (CMR) were observed after the administration of a 5 mg/kg dose of lidocaine in nonanesthetized human volunteers?
24% reduction in CBF and 20% reduction in CMR
What was the observed peak serum concentration range after a 2-mg/kg bolus of lidocaine?
6.6 to 8.5 μg/mL
which of the following drugs has the greatest reduction in CMR?
Thiopental
which of the following drugs has the greatest reduction in CBF?
propofol
Explore how anesthetic drugs impact cerebral blood flow (CBF) and cerebral metabolic rate. Understand the significance of CBF in energy substrate delivery and neuronal outcomes, particularly in ischemic conditions. Delve into the management of intracranial pressure (ICP) through control and manipulation of CBF.
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