chapter 11. quiz 8. Considerations Relevant to Focal Ischemia and Anesthesia

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in cases of focal ischemia, anesthesia is considered being ?

harmful

has no clinical effect

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protective (correct)

Which mechanism is attributed as the principal reason for the protective efficacy of barbiturates in focal cerebral ischemia?

Increase in free radicals

Suppression of CMR (correct)

Promotion of CBF redistribution

Enhancement of CMR

What role does CMR suppression play in brain regions affected by focal ischemia?

Leads to flat EEG readings

benefit to brain regions in which oxygen delivery is inadequate (correct)

Increases oxygen consumption

Induces abnormal EEG patterns

What is an expected benefit of CMR suppression in areas affected by focal ischemia?

sufficient to allow energy consumption by some ongoing electrophysiologic activity Signup and view all the answers

Why should readers be cautious when reviewing the protection-by-anesthetics literature?

Anesthetics exaggerate injury in a high-stress state Signup and view all the answers

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. Signup and view all the answers

When should barbiturate-induced EEG suppression be considered as a logical therapy?

When dealing with temporary focal ischemia (temporary occlusion during aneurysm surgery) Signup and view all the answers

Why have barbiturates traditionally been administered to produce maximal reduction of the CMR?

Presumed to have a protective effect by reducing CMR. Signup and view all the answers

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. Signup and view all the answers

In what scenario did methohexital and thiopental demonstrate a similar reduction in injury?

In an animal model of focal ischemia. Signup and view all the answers

What is the proposed neuroprotective mechanism of action for xenon?

Noncompetitive blockade of NMDAR Signup and view all the answers

Which statement accurately reflects the comparison between different volatile anesthetics regarding their neuroprotective efficacy?

All volatile anesthetics have similar neuroprotective efficacy Signup and view all the answers

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 Signup and view all the answers

isoflurane is considered ?

neuroprotective Signup and view all the answers

Which type of ischemia models has shown isoflurane to be neuroprotective?

Hemispheric, focal, and nearly complete ischemia models Signup and view all the answers

What observation was made about the sustainability of isoflurane's neuroprotective efficacy in a preclinical investigation?

The protection diminishes by 14 days Signup and view all the answers

In what circumstances has sevoflurane been found to reduce ischemic injury in animal models?

focal and hemispheric ischemia Signup and view all the answers

What has research shown regarding the impact of propofol on cerebral infarction in comparison with awake animals?

Significantly reduced Signup and view all the answers

In direct comparison to pentobarbital, what similarity in cerebral injury was observed with propofol after focal ischemia in animals?

Similar Signup and view all the answers

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 Signup and view all the answers

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 Signup and view all the answers

How does propofol protection compare to volatile anesthetics based on initial investigations?

Protection is not sustained Signup and view all the answers

Which calcium channel antagonist is established for clinical use after subarachnoid hemorrhage (SAH)?

Nimodipine Signup and view all the answers

What is the proposed mode of action for the neuroprotective effect of nimodipine after SAH?

Cellular effect Signup and view all the answers

Which statement is true about the use of calcium channel blockers (CCBs) after neurologic stroke?

Not all investigations have confirmed the benefits of nimodipine Signup and view all the answers

What is the recommended use of CCBs in the management of blood pressure?

Administering CCBs for blood pressure management is reasonable Signup and view all the answers

What is the recommended range for maintaining the mean arterial pressure (MAP) in most patients with cerebral ischemia?

70 to 80 mm Hg Signup and view all the answers

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 Signup and view all the answers

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 Signup and view all the answers

What effect does hypotension have on cerebral blood flow (CBF) in patients with cerebral ischemia?

Reduces CBF Signup and view all the answers

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 Signup and view all the answers

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 Signup and view all the answers

What is the recommended blood pressure augmentation for patients with SAH-induced vasospasm?

A systolic pressure of approximately 180 mm Hg Signup and view all the answers

What is the recommended CPP range for patients with traumatic brain injury?

A CPP of 60 to 70 mm Hg Signup and view all the answers

What is the primary goal of blood pressure augmentation in patients with SAH-induced vasospasm and traumatic brain injury?

To increase cerebral blood flow Signup and view all the answers

What is the recommended systolic BP in patients with SAH-induced vasospasm ?

systolic pressure of approximately 180 mm Hg Signup and view all the answers

What is the recommended CPP in patients with traumatic brain injury?

60 to 70 mm Hg Signup and view all the answers

What is the impact of hypocapnia on intracerebral perfusion?

It has not generally proved effective in either laboratory or clinical settings. Signup and view all the answers

What is the recommended practice regarding the manipulation of Paco2 in the absence of a means to verify perfusion response?

Normocapnia should be maintained. Signup and view all the answers

What is the potential consequence of hypercapnia on intracerebral perfusion?

It may cause intracerebral steal and worsen intracellular pH. Signup and view all the answers

What is the relevance of the 'Robin Hood' or inverse steal effect in the context of Paco2 manipulation?

not generally proved effective Signup and view all the answers

What is the primary cerebral protective technique for circulatory arrest procedures?

Hypothermia induction Signup and view all the answers

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 Signup and view all the answers

What benefit is associated with hypothermia initiation in the immediate postischemic period?

Enhanced protective effect Signup and view all the answers

What advantage of hypothermia use in the surgical setting is highlighted by its proponents?

Ease of achievement and rewarming Signup and view all the answers

What was observed in hypothermic patients undergoing intracranial aneurysm clipping based on pilot study results?

Trend toward improved outcome Signup and view all the answers

hypothermia is not recommended for neuroprotection in ?

focal ischemia Signup and view all the answers

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 Signup and view all the answers

Why is avoiding hyperthermia crucial in patients at risk of cerebral ischemia?

To prevent cerebral injury Signup and view all the answers

What effect can a 1°C increase in body temperature have on ischemic injury?

It dramatically aggravates injury Signup and view all the answers

What is a common complication associated with induced hypothermia in stroke patients?

Bradycardia Signup and view all the answers

What side effects are frequently associated with induced hypothermia in stroke patients?

Thrombocytopenia, bradycardia, ventricular ectopy Signup and view all the answers

What is the rationale behind withholding glucose-containing solutions in situations where cerebral ischemia may occur?

To aggravate neurologic injury Signup and view all the answers

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 Signup and view all the answers

What has long-term outcome studies shown about the impact of hyperglycemia on patients with stroke?

Hyperglycemia is an independent predictor of poor outcome Signup and view all the answers

What is the recommended range for maintaining blood glucose levels in clinical settings?

140 to 180 mg/dL Signup and view all the answers

At what blood glucose level is suppression of the EEG observed?

20 mg/dL Signup and view all the answers

What happens to CMR and CBF during sustained seizure activity?

Increase dramatically Signup and view all the answers

What is a significant consequence of hypoglycemia with a level of 20 mg/dL or lower?

Increased seizure activity Signup and view all the answers

What effect does a shift in EEG frequencies toward delta and theta have on cerebral injury?

Increases injury Signup and view all the answers

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. Signup and view all the answers

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%. Signup and view all the answers

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. Signup and view all the answers

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. Signup and view all the answers

What is the threshold Pao2 that leads to an increase in mortality in patients who have sustained cardiac arrest?

Greater than 300 mm Hg Signup and view all the answers

In which situation does hyperoxia improve cerebral metabolism?

In regions of the brain where metabolism has been significantly reduced Signup and view all the answers

What is the potential adverse effect of hyperoxia in the injured brain?

All of the above Signup and view all the answers

What is the potential consequence of excessive Pao2 (>487 mm Hg) in hyperoxic patients?

Worse outcomes Signup and view all the answers

What is the recommended Pao2 range to avoid increased mortality in patients who have sustained cardiac arrest?

Between 100 and 300 mm Hg Signup and view all the answers

Which anesthetics have been found to potentially reduce ischemic injury?

Volatile anesthetics, barbiturates, propofol, xenon, and ketamine Signup and view all the answers

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 Signup and view all the answers

What should efforts for brain protection primarily focus on?

Maintenance of physiologic parameters Signup and view all the answers

What is the recommended delay before performing Carotid Endarterectomy (CEA) after a stroke?

6 weeks Signup and view all the answers

How long does it take for regional CBF and CMR to stabilize after a stroke?

2 weeks Signup and view all the answers

When do BBB abnormalities, as reflected by the accumulation of CT contrast material or brain scan isotopes, resolve after a stroke?

4 weeks Signup and view all the answers

What is the primary risk associated with delaying carotid endarterectomy (CEA) after a stroke?

Increased risk of complete carotid occlusion Signup and view all the answers

In which group of stroke patients is early CEA generally preferable?

Patients with small cerebral infarctions and resolved neurologic symptoms Signup and view all the answers

What is the risk of intracerebral hemorrhage when performing early CEA after stroke?

Increased risk Signup and view all the answers

When does the occurrence of adverse cardiovascular events, including new stroke and myocardial infarction, stabilize after a stroke?

9 months Signup and view all the answers

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 Signup and view all the answers

What type of patients may be candidates for early CEA after a stroke?

Patients with ipsilateral carotid artery stenosis and resolved neurologic symptoms Signup and view all the answers

What percentage of patients with stroke experience loss of normal vasomotor responses beyond 2 weeks?

A small percentage Signup and view all the answers

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 Signup and view all the answers

In patients who have sustained a stroke, the incidence of a second stroke is approximately ?

12% Signup and view all the answers

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 Signup and view all the answers

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 Signup and view all the answers

What effect have ACE inhibitors been shown to have on the LLA in both normotensive and hypertensive subjects?

Decrease LLA acutely Signup and view all the answers

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 Signup and view all the answers

What is the average reduction in MAP that brings both normotensive and hypertensive patients to the LLA?

25% reduction Signup and view all the answers

What happens to CBF values as the reduction in the MAP exceeds 25% of baseline?

CBF values become below normal Signup and view all the answers

What is the impact of a 50% reduction in MAP in nonanesthetized patients?

It produces reversible symptoms of cerebral hypoperfusion Signup and view all the answers

What type of edema is often associated with intracranial tumors?

Vasogenic edema Signup and view all the answers

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 Signup and view all the answers

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 Signup and view all the answers

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 Signup and view all the answers

What is the primary cause of edema formation in the peritumoral region?

Plasma protein leakage from the vascular space Signup and view all the answers

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 Signup and view all the answers

What is the primary cause of rebound edema formation with mannitol osmotherapy?

Diffusion of mannitol into the peritumoral space due to a permeable BBB Signup and view all the answers

What is the main effect of dexamethasone treatment on tumor edema?

Reduction in edema formation with little effect on edema reabsorption Signup and view all the answers

What is the role of loop diuretics such as bumetanide in reducing rebound edema?

Reduce the accumulation of idiogenic osmoles significantly Signup and view all the answers

What factors contribute to the formation of tumor edema?