chapter 11. quiz 2. Regulation of Cerebral Blood Flow
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Questions and Answers

What is the lower limit of autoregulation (LLA) for cerebral blood flow in normal humans?

  • 90 mm Hg
  • 70 mm Hg (correct)
  • 60-65 mm Hg
  • 80-85 mm Hg

    • What is the upper limit of autoregulation (ULA) for cerebral blood flow in normal humans?

  • 190-195 mm Hg
  • 170 mm Hg
  • 180 mm Hg
  • 150 mm Hg (correct)

    • What is cerebral perfusion pressure (CPP) defined as?

  • Difference between LLA and ULA
  • Autoregulation limits
  • Cerebral blood flow resistance
  • MAP minus intracranial pressure (ICP) (correct)

    • How is autoregulation affected by rapid changes in arterial pressure?

    <p>It causes a transient alteration in CBF</p> Signup and view all the answers

    How does the autoregulatory mechanism respond to an increase in mean arterial pressure (MAP) concerning cerebral blood flow (CBF)?

    <p>It counteracts by narrowing vessel radius and increasing resistance.</p> Signup and view all the answers

    Which proposed mechanism of autoregulation involves a myogenic response of vascular smooth muscle to pressure changes?

    <p>Myogenic mechanism</p> Signup and view all the answers

    Why is autoregulation of cerebral blood flow considered significant clinically?

    <p>It prevents excessive perfusion and hypoperfusion injuries.</p> Signup and view all the answers

    What is the primary function of autoregulation of cerebral blood flow?

    <p>To maintain a constant level of perfusion pressure</p> Signup and view all the answers

    when the CBF become pressure-dependent (pressure-passive) and linearly varies with CPP.

    <p>Above and below the autoregulatory plateau</p> Signup and view all the answers

    According to the myogenic hypothesis, changes in CPP lead to direct changes in

    <p>tone of vascular smooth muscle</p> Signup and view all the answers

    What is the relationship between increased neuronal activity and local brain metabolism in terms of cerebral blood flow (CBF)?

    <p>Increased neuronal activity results in increased local brain metabolism, leading to an increase in CBF.</p> Signup and view all the answers

    Which factors are involved in the regulation of cerebral metabolic rate (CMR)?

    <p>A combination of metabolic, glial, neural, and vascular factors</p> Signup and view all the answers

    What is the traditional view of neurovascular coupling?

    <p>It is based on a feed-forward mechanism where neuronal activity directly increases CBF.</p> Signup and view all the answers

    Which by-products of metabolism are implicated in mediating neurovascular coupling?

    <p>K+, H+, lactate, adenosine, and ATP</p> Signup and view all the answers

    What is the role of glutamate release due to increased synaptic activity in relation to cerebral blood flow?

    <p>Glutamate release enhances CBF by affecting vascular tone.</p> Signup and view all the answers

    How are regional cerebral blood flow and metabolism typically coupled?

    <p>They are tightly coupled and involve a combination of various factors.</p> Signup and view all the answers

    What is the role of Glutamate in neurovascular coupling?

    <p>Results in the synthesis and release of NO</p> Signup and view all the answers

    How does glutamate activation of metabotropic glutamate receptors (mGluR) in astrocytes affect cerebral blood flow?

    <p>Promotes prostaglandin and epoxyeicosatrienoic acids generation</p> Signup and view all the answers

    What contributes to vascular dilation in the setting of reduced oxygen tension at the tissue level?

    <p>Release of adenosine</p> Signup and view all the answers

    Which neurotransmitter released by nerves innervating cerebral vessels is NOT mentioned as potentially involved in neurovascular coupling?

    <p>Dopamine</p> Signup and view all the answers

    How is the net result on vascular tone determined in neurovascular coupling?

    <p>By the relative contribution of multiple signaling pathways</p> Signup and view all the answers

    What can influence CMR according to the text?

    <p>Functional state of the nervous system</p> Signup and view all the answers

    How do anesthetic drugs generally affect cerebral metabolic rate (CMR)?

    <p>Suppress CMR</p> Signup and view all the answers

    What happens to the CMR when plasma concentrations of certain anesthetics like propofol increase?

    <p>CMR decreases proportionally</p> Signup and view all the answers

    Which component of cerebral metabolic rate (CMR) remains unaffected by anesthetic drugs?

    <p>Housekeeping component for cellular integrity</p> Signup and view all the answers

    What is the effect of increasing general anesthetics on CMRO2 when EEG suppression is completely achieved using any anesthetic agent?

    <p>CMRO2 remains similar</p> Signup and view all the answers

    In what scenario does the CMR increase extremely ?

    <p>epileptic activity</p> Signup and view all the answers

    What sets ketamine and nitrous oxide apart from other anesthetic drugs regarding their impact on CMR?

    <p>They do not affect CMR</p> Signup and view all the answers

    What is a distinguishing feature of the effects of barbiturates compared to isoflurane and sevoflurane on cerebral blood flow (CBF) and cerebral metabolic rate (CMR)?

    <p>with barbiturates, Uniform reduction in CBF and CMR throughout the brain</p> Signup and view all the answers

    At what approximate concentration of isoflurane associated with a burst-suppression pattern are cortical somatosensory evoked responses to median nerve stimulation difficult to elicit?

    <p>~1.5 MAC</p> Signup and view all the answers

    Why does a further decrease in cerebral metabolic rate (CMR) occur with temperature reduction beyond that at which EEG suppression first occurs?

    <p>Due to decreased energy utilization associated with both electrophysiological function and cellular integrity maintenance</p> Signup and view all the answers

    What happens to cerebral blood flow (CBF) between 37°C and 42°C?

    <p>Increases</p> Signup and view all the answers

    What effect does hyperthermia above 42°C have on cerebral oxygen consumption?

    <p>Dramatic reduction</p> Signup and view all the answers

    What is the primary difference between the effects of anesthetic drugs and hypothermia on cerebral metabolic rate (CMR)?

    <p>Hypothermia decrease both electrophysiological function and energy utilization associated with cellular integrity maintenance</p> Signup and view all the answers

    How do the EEG characteristics of burst-suppression states differ among anesthetic drugs?

    <p>They differ among anesthetic drugs</p> Signup and view all the answers

    What is the relevance of the EEG characteristics of burst-suppression states among anesthetic drugs?

    <p>They may provide insights into differences in the neuroprotective potential of the drugs</p> Signup and view all the answers

    What is the approximate decrease in cerebral metabolic rate (CMR) per degree Celsius of temperature reduction?

    <p>6% to 7%</p> Signup and view all the answers

    At what temperature range can hypothermia lead to complete suppression of the EEG?

    <p>18°C-20°C</p> Signup and view all the answers

    What effect can hypothermia have on EEG when the temperature drops below 20-18°C?

    <p>Complete suppression</p> Signup and view all the answers

    How does a decrease in temperature impact cerebral metabolic rate (CMR)?

    <p>Decreased CMR</p> Signup and view all the answers

    How does mild hypothermia affect the cerebral metabolic rate of oxygen (CMRO2) at 18°C compared to normothermic control values?

    <p>It decreases to less than 10%</p> Signup and view all the answers

    What explains the brain's tolerance for moderate periods of circulatory arrest at temperatures around 18°C and colder?

    <p>Decrease in CMRO2 below 10% of normothermic control values</p> Signup and view all the answers

    What is the primary effect of hypothermia on the basal component of the cerebral metabolic rate?

    <p>Suppresses it</p> Signup and view all the answers

    How does the cerebral metabolic rate respond as the temperature drops below the point where EEG suppression first occurs?

    <p>It decreases further</p> Signup and view all the answers

    What is the relationship between cerebral metabolic rate and tolerance to circulatory arrest at colder temperatures?

    <p>Lower metabolic rate leads to better tolerance</p> Signup and view all the answers

    How does cerebral blood flow (CBF) respond to hypocapnia when resting CBF is increased?

    <p>The reduction in CBF is more intense</p> Signup and view all the answers

    What happens to the cerebrovascular response to changes in Paco2 during severe hypotension?

    <p>No response is observed</p> Signup and view all the answers

    How does moderate hypotension affect the response of cerebral blood flow (CBF) to hypercarbia?

    <p>The increase in CBF is reduced</p> Signup and view all the answers

    What is the effect of modest hypotension on hypocapnia-induced vasoconstriction?

    <p>Slightly affects vasoconstriction</p> Signup and view all the answers

    How do anesthetic drugs that increase resting CBF impact the response of the cerebral circulation to CO2?

    <p>They enhance the response to CO2</p> Signup and view all the answers

    What happens to the cerebrovascular response to changes in Paco2 under normal circumstances?

    <p>It increases with increasing Paco2 values</p> Signup and view all the answers

    What happens to cerebral blood flow (CBF) when there is hypercarbia?

    <p>CBF increases significantly.</p> Signup and view all the answers

    Which factor mediates the vasodilatory response to hypercapnia?

    <p>Nitric oxide (NO)</p> Signup and view all the answers

    What effect does acute systemic metabolic acidosis have on cerebral blood flow (CBF)?

    <p>It has little immediate effect on CBF.</p> Signup and view all the answers

    What happens to cerebrospinal fluid (CSF) pH and CBF levels after a sustained period of hyperventilation and Acute restoration of a normal Paco2 value ?

    <p>CBF increases while CSF pH decreases.</p> Signup and view all the answers

    How does acute restoration of a normal Paco2 value affect cerebrospinal fluid (CSF) pH after a sustained period of hypoventilation ?

    <p>It leads to CSF alkalosis.</p> Signup and view all the answers

    What is the theoretical risk associated with an acute restoration of a normal Paco2 value after hypercapnia?

    <p>Risk of cerebral ischemia.</p> Signup and view all the answers

    What is the theoretical risk associated with an acute restoration of a normal Paco2 value after hypocapnia?

    <p>increased CBF with a concomitant increase in ICP</p> Signup and view all the answers

    With hypercarbia, cerebral autoregulatory response is?

    <p>response to hypertension is attenuated</p> Signup and view all the answers

    how much CBF changes for each 1 mm Hg change in Paco2 around normal Paco2 values?

    <p>1 to 2 mL/100 g/min</p> Signup and view all the answers

    when the CBF response to Paco2 is attenuated

    <p>Paco2 of 75 to 80 mm Hg</p> Signup and view all the answers

    How does the rostral ventrolateral medulla (RVLM) respond to hypoxia?

    <p>By increasing cerebral blood flow (CBF)</p> Signup and view all the answers

    What is the effect of high Pao2 values on cerebral blood flow (CBF)?

    <p>CBF decreases modestly</p> Signup and view all the answers

    What is the theoretical risk associated with hypercapnia followed by an acute restoration of a normal Paco2 value?

    <p>Risk of ischemia</p> Signup and view all the answers

    What effect does a reduction in Pao2 below 60 mm Hg have on cerebral blood flow (CBF)?

    <p>Rapidly increases CBF</p> Signup and view all the answers

    Which of the following variables leads to a more significant increase in cerebral blood flow (CBF) according to the text?

    <p>Hypoxemic hypoxia</p> Signup and view all the answers

    What mediates cerebral vasodilation during hypoxia, as mentioned in the text?

    <p>Both neurogenic effects and local humoral influences</p> Signup and view all the answers

    What role does deoxyhemoglobin play in hypoxia-induced increases in cerebral blood flow (CBF)?

    <p>Releasing NO and ATP</p> Signup and view all the answers

    What happens to cerebral oxygen delivery during hypoxia when arterial content is equivalently reduced by hypoxia or hemodilution?

    <p>Cerebral oxygen delivery better maintained during hypoxemic hypoxia</p> Signup and view all the answers

    How does opening of ATP-dependent K+ channels in vascular smooth muscle impact cerebral blood flow?

    <p>Increases CBF</p> Signup and view all the answers

    what is The relationship between oxyhemoglobin saturation, as evaluated by pulse oximetry, and CBF?

    <p>is inversely linear</p> Signup and view all the answers

    the greatest neurogenic influence appears to be exerted on ?

    <p>larger cerebral arteries</p> Signup and view all the answers

    Which nuclei are likely to give rise to intraaxial pathways influencing cerebral blood flow?

    <p>Fastigial nucleus</p> Signup and view all the answers

    What effect does hemorrhagic shock, characterized by high sympathetic tone, have on autoregulation of cerebral blood flow?

    <p>Shifts the lower end of the autoregulatory curve to the right</p> Signup and view all the answers

    How does sympathetic denervation impact cerebral blood flow during hemorrhagic shock?

    <p>Increases cerebral blood flow</p> Signup and view all the answers

    Activation of cerebral sympathetic innervation result in ?

    <p>shifts the ULA to the right</p> Signup and view all the answers

    What effect does anemia have on cerebral vascular resistance and cerebral blood flow (CBF)?

    <p>Reduces resistance and increases CBF as a compensatory response to reduced oxygen delivery</p> Signup and view all the answers

    What is the impact of hypoxia compared to hemodilution on cerebral blood flow?

    <p>Hypoxia significantly increases CBF compared to hemodilution</p> Signup and view all the answers

    In patients with acute ischemic stroke, why is viscosity manipulation not beneficial in reducing cerebral injury?

    <p>Reducing viscosity does not affect CBF in ischemic areas</p> Signup and view all the answers

    How does a hematocrit of 30% to 34% impact oxygen delivery in patients with focal cerebral ischemia?

    <p>It results in maximal oxygen delivery</p> Signup and view all the answers

    Why is viscosity not a target for manipulation in patients at risk due to cerebral ischemia?

    <p>Viscosity reduction does not enhance oxygen delivery</p> Signup and view all the answers

    In focal cerebral ischemia, why is reducing viscosity through hemodilution significant for increasing CBF?

    <p>It further dilutes the blood, improving CBF in ischemic territories</p> Signup and view all the answers

    What effect does the administration of epinephrine have on cerebral blood flow (CBF) under hypotensive epidural anesthesia?

    <p>Maintains CBF</p> Signup and view all the answers

    reduction in cardiac output (CO) by approximately 30% results in a decrease in CBF by about:

    <p>10%</p> Signup and view all the answers

    What is the primary factor that influences cerebral blood flow (CBF) according to the provided text?

    <p>perfusion pressure</p> Signup and view all the answers

    In which disease states does augmentation of cardiac output NOT increase cerebral blood flow (CBF) according to the text?

    <p>Traumatic head injury</p> Signup and view all the answers

    What is suggested by the relationship between cardiac output (CO) and cerebral blood flow (CBF) based on the available data?

    <p>The influence of CO on CBF varies depending on the clinical scenario</p> Signup and view all the answers

    Which factor is increasingly being recognized as an important determinant of cerebral blood flow (CBF)?

    <p>Cardiac output</p> Signup and view all the answers

    How do medications like β-antagonists and α2-agonists impact autoregulation according to the text?

    <p>By modulation of sympathetic nervous system activity</p> Signup and view all the answers

    How does congestive heart failure affect the capacity of autoregulatory mechanisms to maintain CBF in response to hypotension?

    <p>limit the capacity of autoregulatory mechanisms to maintain CBF in response to hypotension</p> Signup and view all the answers

    What role does the sympathetic nervous system play in the cerebrovascular response to hypotension?

    <p>Decreases vasodilatory capacity of cerebral vessels</p> Signup and view all the answers

    How do hypercarbia and hypoxia affect autoregulation according to the text?

    <p>Attenuate autoregulation</p> Signup and view all the answers

    What is a major determinant of cerebral blood flow (CBF) according to the text?

    <p>MAP (perfusion pressure)</p> Signup and view all the answers

    What is the primary focus of anesthetics in modulating autoregulation according to the text?

    <p>Suppression of autonomic neural activity</p> Signup and view all the answers

    What factor is deemed to render the static representation of cerebral autoregulation invalid?

    <p>Multitude of factors affecting perfusion pressure</p> Signup and view all the answers

    In the context of autoregulatory curves, what is suggested to be more accurate than a single static curve?

    <p>A family of autoregulatory curves</p> Signup and view all the answers

    What is recommended as a key part of anesthetic management concerning cerebral perfusion in individual patients?

    <p><strong>Maintenance of circulatory volume</strong> and cardiac output consideration</p> Signup and view all the answers

    How do medications like CCB, nitrates, ARB, ACEI impact autoregulation according to the text?

    <p>direct reduction of vasomotor tone</p> Signup and view all the answers

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