108 Questions
in cases of focal ischemia, anesthesia is considered being ?
protective
Which mechanism is attributed as the principal reason for the protective efficacy of barbiturates in focal cerebral ischemia?
Suppression of CMR
What role does CMR suppression play in brain regions affected by focal ischemia?
benefit to brain regions in which oxygen delivery is inadequate
What is an expected benefit of CMR suppression in areas affected by focal ischemia?
sufficient to allow energy consumption by some ongoing electrophysiologic activity
Why should readers be cautious when reviewing the protection-by-anesthetics literature?
Anesthetics exaggerate injury in a high-stress state
What is the primary concern raised regarding the experiments involving barbiturates and temperature control?
The overestimation of the protective efficacy of barbiturates due to unrecognized cerebral hypothermia.
When should barbiturate-induced EEG suppression be considered as a logical therapy?
When dealing with temporary focal ischemia (temporary occlusion during aneurysm surgery)
Why have barbiturates traditionally been administered to produce maximal reduction of the CMR?
Presumed to have a protective effect by reducing CMR.
What raises the important issue of equivalence among various barbiturates in terms of their protective efficacy?
Recent data suggesting that neuroprotective efficacy varies among barbiturates.
In what scenario did methohexital and thiopental demonstrate a similar reduction in injury?
In an animal model of focal ischemia.
What is the proposed neuroprotective mechanism of action for xenon?
Noncompetitive blockade of NMDAR
Which statement accurately reflects the comparison between different volatile anesthetics regarding their neuroprotective efficacy?
All volatile anesthetics have similar neuroprotective efficacy
What is suggested by the available data regarding anesthesia and its protective effect compared to the awake state?
Anesthesia may have a protective effect compared to the awake state
isoflurane is considered ?
neuroprotective
Which type of ischemia models has shown isoflurane to be neuroprotective?
Hemispheric, focal, and nearly complete ischemia models
What observation was made about the sustainability of isoflurane's neuroprotective efficacy in a preclinical investigation?
The protection diminishes by 14 days
In what circumstances has sevoflurane been found to reduce ischemic injury in animal models?
focal and hemispheric ischemia
What has research shown regarding the impact of propofol on cerebral infarction in comparison with awake animals?
Significantly reduced
In direct comparison to pentobarbital, what similarity in cerebral injury was observed with propofol after focal ischemia in animals?
Similar
What observation was made regarding the protective efficacy of etomidate in an experimental model of focal ischemia?
Volume of injury was significantly larger than the control group
In patients subjected to temporary intracranial vessel occlusion, what effect does the administration of etomidate have on tissue hypoxia and acidosis compared to equivalent desflurane anesthesia?
Greater tissue hypoxia and acidosis
How does propofol protection compare to volatile anesthetics based on initial investigations?
Protection is not sustained
Which calcium channel antagonist is established for clinical use after subarachnoid hemorrhage (SAH)?
Nimodipine
What is the proposed mode of action for the neuroprotective effect of nimodipine after SAH?
Cellular effect
Which statement is true about the use of calcium channel blockers (CCBs) after neurologic stroke?
Not all investigations have confirmed the benefits of nimodipine
What is the recommended use of CCBs in the management of blood pressure?
Administering CCBs for blood pressure management is reasonable
What is the recommended range for maintaining the mean arterial pressure (MAP) in most patients with cerebral ischemia?
70 to 80 mm Hg
What effect does a reduction in blood pressure of 10% to 20% have on patients with acute stroke who are treated with nimodipine?
Increases the probability of an adverse outcome fourfold
In patients treated with thrombolytic agents for stroke, what is the recommended blood pressure range to reduce the incidence of hemorrhage into the ischemic brain?
Less than 180/105 mm Hg
What effect does hypotension have on cerebral blood flow (CBF) in patients with cerebral ischemia?
Reduces CBF
What is the proposed mechanism of action for the adverse impact of blood pressure reduction on an injured brain in patients with cerebral ischemia?
Decreased collateral perfusion
What is the target MAP for patients with cerebral ischemia, based on preexisting blood pressure?
The target MAP should be based on knowledge of a patient’s preexisting blood pressure
What is the recommended blood pressure augmentation for patients with SAH-induced vasospasm?
A systolic pressure of approximately 180 mm Hg
What is the recommended CPP range for patients with traumatic brain injury?
A CPP of 60 to 70 mm Hg
What is the primary goal of blood pressure augmentation in patients with SAH-induced vasospasm and traumatic brain injury?
To increase cerebral blood flow
What is the recommended systolic BP in patients with SAH-induced vasospasm ?
systolic pressure of approximately 180 mm Hg
What is the recommended CPP in patients with traumatic brain injury?
60 to 70 mm Hg
What is the impact of hypocapnia on intracerebral perfusion?
It has not generally proved effective in either laboratory or clinical settings.
What is the recommended practice regarding the manipulation of Paco2 in the absence of a means to verify perfusion response?
Normocapnia should be maintained.
What is the potential consequence of hypercapnia on intracerebral perfusion?
It may cause intracerebral steal and worsen intracellular pH.
What is the relevance of the 'Robin Hood' or inverse steal effect in the context of Paco2 manipulation?
not generally proved effective
What is the primary cerebral protective technique for circulatory arrest procedures?
Hypothermia induction
What effect does mild hypothermia have on electrophysiologic energy consumption and cellular integrity maintenance?
reduction in both electrophysiologic energy consumption and energy utilization related to the maintenance of cellular integrity
What benefit is associated with hypothermia initiation in the immediate postischemic period?
Enhanced protective effect
What advantage of hypothermia use in the surgical setting is highlighted by its proponents?
Ease of achievement and rewarming
What was observed in hypothermic patients undergoing intracranial aneurysm clipping based on pilot study results?
Trend toward improved outcome
hypothermia is not recommended for neuroprotection in ?
focal ischemia
What do recent trials indicate about the induction of hypothermia after successful resuscitation from cardiac arrest?
It results in better neurologic outcomes 6 months post-arrest
Why is avoiding hyperthermia crucial in patients at risk of cerebral ischemia?
To prevent cerebral injury
What effect can a 1°C increase in body temperature have on ischemic injury?
It dramatically aggravates injury
What is a common complication associated with induced hypothermia in stroke patients?
Bradycardia
What side effects are frequently associated with induced hypothermia in stroke patients?
Thrombocytopenia, bradycardia, ventricular ectopy
What is the rationale behind withholding glucose-containing solutions in situations where cerebral ischemia may occur?
To aggravate neurologic injury
What did the results of the randomized clinical trial on insulin administration to stroke patients show?
No change in outcome compared to the control group
What has long-term outcome studies shown about the impact of hyperglycemia on patients with stroke?
Hyperglycemia is an independent predictor of poor outcome
What is the recommended range for maintaining blood glucose levels in clinical settings?
140 to 180 mg/dL
At what blood glucose level is suppression of the EEG observed?
20 mg/dL
What happens to CMR and CBF during sustained seizure activity?
Increase dramatically
What is a significant consequence of hypoglycemia with a level of 20 mg/dL or lower?
Increased seizure activity
What effect does a shift in EEG frequencies toward delta and theta have on cerebral injury?
Increases injury
What is the current practice regarding hemodilution in patients with ischemia associated with vasospasm in SAH?
The current practice is focused on maintaining euvolemia and inducing modest increases in blood pressure rather than on hemodilution.
What is the recommended approach for a procedure where incomplete ischemia might occur, such as CEA, with respect to hematocrit?
Preoperative phlebotomy should be considered when hematocrit is in excess of 55%.
What is the impact of increased hematocrit on cerebral blood flow (CBF) due to viscosity effects?
Increased hematocrit worsens CBF due to increased viscosity effects.
What is the theoretic optimal hematocrit for patients in whom focal ischemia might occur in the surgical unit?
A hematocrit of 30%-35% is the theoretic optimum.
What is the threshold Pao2 that leads to an increase in mortality in patients who have sustained cardiac arrest?
Greater than 300 mm Hg
In which situation does hyperoxia improve cerebral metabolism?
In regions of the brain where metabolism has been significantly reduced
What is the potential adverse effect of hyperoxia in the injured brain?
All of the above
What is the potential consequence of excessive Pao2 (>487 mm Hg) in hyperoxic patients?
Worse outcomes
What is the recommended Pao2 range to avoid increased mortality in patients who have sustained cardiac arrest?
Between 100 and 300 mm Hg
Which anesthetics have been found to potentially reduce ischemic injury?
Volatile anesthetics, barbiturates, propofol, xenon, and ketamine
What is the recommended practice regarding the use of a specific anesthetic for the purpose of brain protection in the clinical setting?
There is no recommended practice for a specific anesthetic
What should efforts for brain protection primarily focus on?
Maintenance of physiologic parameters
What is the recommended delay before performing Carotid Endarterectomy (CEA) after a stroke?
6 weeks
How long does it take for regional CBF and CMR to stabilize after a stroke?
2 weeks
When do BBB abnormalities, as reflected by the accumulation of CT contrast material or brain scan isotopes, resolve after a stroke?
4 weeks
What is the primary risk associated with delaying carotid endarterectomy (CEA) after a stroke?
Increased risk of complete carotid occlusion
In which group of stroke patients is early CEA generally preferable?
Patients with small cerebral infarctions and resolved neurologic symptoms
What is the risk of intracerebral hemorrhage when performing early CEA after stroke?
Increased risk
When does the occurrence of adverse cardiovascular events, including new stroke and myocardial infarction, stabilize after a stroke?
9 months
What is a key factor that should be considered when deciding on the timing of CEA after a stroke?
The location and size of the infarction
What type of patients may be candidates for early CEA after a stroke?
Patients with ipsilateral carotid artery stenosis and resolved neurologic symptoms
What percentage of patients with stroke experience loss of normal vasomotor responses beyond 2 weeks?
A small percentage
What is an important consideration for deferring elective surgery after a cerebral vascular accident, extrapolating from CEA studies?
Deferral for at least 4 weeks and preferably 6 weeks from stable postinsult neurologic state
In patients who have sustained a stroke, the incidence of a second stroke is approximately ?
12%
What was observed in humans regarding the restoration of LLA with antihypertensive therapy?
Partial and incomplete restoration in some patients after 12 months of treatment
What is a suggested unexplored possibility about the restoration of LLA with antihypertensive therapy?
The extent of restoration may be dependent on the type of antihypertensive agent used
What effect have ACE inhibitors been shown to have on the LLA in both normotensive and hypertensive subjects?
Decrease LLA acutely
What is the recommended limit for elective MAP reduction in both hypertensive and normotensive patients for cerebral well-being?
20% to 25% of resting mean levels
What is the average reduction in MAP that brings both normotensive and hypertensive patients to the LLA?
25% reduction
What happens to CBF values as the reduction in the MAP exceeds 25% of baseline?
CBF values become below normal
What is the impact of a 50% reduction in MAP in nonanesthetized patients?
It produces reversible symptoms of cerebral hypoperfusion
What type of edema is often associated with intracranial tumors?
Vasogenic edema
What is the relationship between cerebral blood flow (CBF) and propofol in regions of the brain surrounding the tumor?
Propofol decreases CBF in these regions
What is the impact of changes in Pao2 and Paco2 on vascular responsiveness in patients with gliomas?
Vascular responsiveness to changes in Pao2 and Paco2 is generally preserved in patients with gliomas
Which statement is true regarding the measurement of regional CBF in the area of the tumor?
Measurement of regional CBF in the area of the tumor might be a useful predictor of the grade of intracranial gliomas
What is the primary cause of edema formation in the peritumoral region?
Plasma protein leakage from the vascular space
What is the effect of intracranial tumors on cerebral blood flow (CBF) compared to the normal brain?
Intracranial tumors have lower CBF than the normal brain
What is the primary cause of rebound edema formation with mannitol osmotherapy?
Diffusion of mannitol into the peritumoral space due to a permeable BBB
What is the main effect of dexamethasone treatment on tumor edema?
Reduction in edema formation with little effect on edema reabsorption
What is the role of loop diuretics such as bumetanide in reducing rebound edema?
Reduce the accumulation of idiogenic osmoles significantly
What factors contribute to the formation of tumor edema?
All of the above
How does mannitol osmotherapy affect the reduction of intracerebral pressure (ICP) in the surgical unit?
Reduces ICP but can lead to rebound edema formation in some cases
What physiological adjustment is seen in the CMR during lesions in the reticular activating system?
Normal physiologic reduction
What occurs to cerebral acidosis during prolonged generalized seizure activity?
Systemic and cerebral acidosis increase
How can the development of irreversible neuronal damage be prevented during prolonged seizures?
Muscular relaxation
What is the primary goal of therapy aimed at interrupting seizures?
Restoring balance between CMR and CBF
Which measures are considered important adjuncts during intensive motor and brain activity associated with generalized seizures?
Adequate ventilation and oxygenation
What is the recommended class of medications for interrupting seizures and restoring balance between cerebral metabolic demand and blood flow?
Anticonvulsants
Learn about the protective effects of anesthesia in focal (incomplete) ischemia scenarios and how reducing systemic stress can lead to improved outcomes. Explore the nuances of interpreting the protection-by-anesthetics literature in such experimental settings.
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