chapter 11. quiz 4. Effects of Anesthetics on Cerebral Blood Flow

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What happens to CBV during cerebral ischemia?

Decreases

Remains constant

Increases (correct)

Varies independently

What occurs when autoregulation is impaired?

CBF decreases while CBV increases

CBV decreases while CBF increases

CBF and CBV decrease in parallel

CBF and CBV increase in parallel (correct)

How does the cerebral circulation respond to a decreasing MAP?

CBF decreases progressively

CBV decreases progressively

CBV increases progressively (correct)

CBF increases progressively

What compensatory adjustments occur in normal subjects with initial CBV increases?

CSF is translocated to extracerebral vessels Signup and view all the answers

What can an increase in CBV lead to when intracranial compliance is reduced?

Herniation Signup and view all the answers

How do CBF and CBV typically vary when autoregulation is functioning normally?

Varies independently Signup and view all the answers

In neuroanesthesia, why is control and manipulation of CBF important?

To manage Intracranial Pressure (ICP) Signup and view all the answers

What is the approximate normal CBV in mL/100g of brain?

5 mL/100g Signup and view all the answers

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 Signup and view all the answers

Why are there few data on CBV compared to CBF, especially in humans?

CBV is more difficult to measure Signup and view all the answers

which of the following statements are correct

the magnitude of change in CBV is less than the magnitude of change in CBF Signup and view all the answers

50% increase in CBF can lead to

20 % increase in CBV Signup and view all the answers

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. Signup and view all the answers

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. Signup and view all the answers

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 Signup and view all the answers

What is the general effect of intravenous anesthetics on autoregulation during their administration?

Autoregulation remains preserved during the administration of intravenous anesthetics. Signup and view all the answers

What effects do intravenous anesthetics have on vascular tone?

direct effects on vascular tone Signup and view all the answers

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% Signup and view all the answers

What is the major effect of nontoxic doses of depressant anesthetics on cerebral metabolism, based on the observations?

Reduction in neurophysiologic activity Signup and view all the answers

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 Signup and view all the answers

During deep pentobarbital anesthesia, what is the effect on autoregulation and CO2 responsiveness?

Both are maintained Signup and view all the answers

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 Signup and view all the answers

What effect does propofol have on regional cerebral blood flow (CBF) in healthy volunteers?

Decreased CBF by 53% to 79% Signup and view all the answers

During propofol administration, what effect does hypocapnia have on cerebral blood flow (CBF)?

Reduction in the magnitude of CBF decrease during hypocapnia Signup and view all the answers

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 Signup and view all the answers

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) Signup and view all the answers

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 Signup and view all the answers

What is the approximate reduction in cerebral blood flow (CBF) with a dose of etomidate sufficient to produce EEG suppression?

34% Signup and view all the answers

How does the cerebral metabolic rate (CMR) suppression caused by etomidate differ from barbiturates?

Predominantly in forebrain structures Signup and view all the answers

In what scenario is etomidate ineffective in reducing intracranial pressure (ICP)?

When EEG activity is suppressed Signup and view all the answers

What effect does etomidate have on cerebral perfusion pressure (CPP) in patients with intracranial tumors or head injuries?

dose not Reduce CPP Signup and view all the answers

What is the general trend of cerebral metabolic rate (CMR) suppression achievable with etomidate compared to isoflurane and barbiturates?

Less profound Signup and view all the answers

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 Signup and view all the answers

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 Signup and view all the answers

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 Signup and view all the answers

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 Signup and view all the answers

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 Signup and view all the answers

What effect does fentanyl have on CBF and CMR in the normal quiescent brain?

Reduces both CBF and CMR Signup and view all the answers

How does high dose fentanyl (100 μg/kg) combined with diazepam affect CBF?

Reduces CBF by 25% Signup and view all the answers

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 Signup and view all the answers

What remains unaffected by fentanyl according to the text?

CO2 responsiveness and autoregulation Signup and view all the answers

What was observed in human subjects after the infusion of small doses of remifentanil?

Increases in CBF in the prefrontal and supplementary motor cortices Signup and view all the answers

Which area showed reductions in CBF when larger doses of remifentanil were administered?

Cerebellum Signup and view all the answers

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 Signup and view all the answers

What effect did the administration of midazolam have on cerebral blood flow (CBF) in awake healthy human volunteers?

decrease in CBF and increase CMR Signup and view all the answers

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 Signup and view all the answers

What are the effects on cerebral blood flow (CBF) and cerebral metabolic rate (CMR) observed when diazepam are administered?

Both CBF and CMR decrease Signup and view all the answers

What effect did flumazenil have on cerebral blood flow (CBF) when administered to nonanesthetized human volunteers?

No effect on CBF Signup and view all the answers

In patients with severe head injury and uncontrolled intracranial pressure (ICP), what side effect was observed when flumazenil was administered?

Increase in ICP Signup and view all the answers

What unexpected phenomenon was observed regarding cerebral blood flow (CBF) and intracranial pressure (ICP) levels after flumazenil administration?

CBF overshoot and ICP overshoot Signup and view all the answers

Why should flumazenil be cautiously used to reverse benzodiazepine sedation in patients with impaired intracranial compliance?

Potential for uncontrolled CBF fluctuations Signup and view all the answers

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 Signup and view all the answers

What do occasional increases in intracranial pressure (ICP) observed with droperidol administration most likely reflect?

Autoregulation-mediated vasodilation in response to decreased MAP Signup and view all the answers

What effect is droperidol likely to have on cerebral metabolic rate (CMR) based on the provided information?

No effect on CMR Signup and view all the answers

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 Signup and view all the answers

How does ketamine affect global cerebral blood flow (CBF) at subanesthetic doses?

Increases CBF by 14% Signup and view all the answers

Which brain areas in humans show the greatest increase in cerebral metabolic rate (CMR) after ketamine administration?

frontal and anterior cingulate cortex Signup and view all the answers

What is the observed effect anesthetic doses of ketamine on global cerebral blood flow (CBF)?

Increase by 36% Signup and view all the answers

How does autoregulation behave during ketamine anesthesia according to the majority of investigations?

Maintained Signup and view all the answers

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) Signup and view all the answers

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. Signup and view all the answers

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 Signup and view all the answers

In what scenario might ketamine be best avoided as the sole anesthetic drug due to concerns about intracranial compliance?

Patients with impaired intracranial compliance Signup and view all the answers

What effect does lidocaine have on cerebral metabolic rate (CMR) and CBF in nonanesthetized human volunteers?

reductions in CBF and CMR Signup and view all the answers

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 Signup and view all the answers

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 Signup and view all the answers

What is a reasonable adjunct for preventing or treating acute increases in intracranial pressure (ICP) based on the text?

Lidocaine Signup and view all the answers

What serum concentration range of lidocaine should be maintained to avoid seizures in awake humans?

<5-10 μg/mL Signup and view all the answers

What was the observed effect of large doses of lidocaine on seizures in anesthetized humans?

No effect on seizures in anesthetized humans Signup and view all the answers

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 Signup and view all the answers