APPLIED PHYSIOLOGY | The Brain and Anesthesia Flashcards
Intracranial hypertension is defined as a sustained increase in intracranial pressure (ICP) above
A. 5 to 10 mm Hg
B. 15 to 20 mm Hg
C. 25 to 30 mm Hg
D. 30 + mm Hg
A. 5 to 10 mm Hg
The normal ICP is 5 to 15 mm Hg (or 7-20 cm H2O)
- In patients with elevated ICP, premedication must be carefully titrated, or AVOIDED completely.
What is the normal CPP?
80-100 mm Hg
CPP progressively decreases as ICP or CVP increases. Likewise, CPP decreases as MAP decreases.
CPP less than 50 mm Hg shows slowing on EEG, CPP of 25-40 mm Hg shows flat EEG, and CPP sustained at less than 25 mm Hg results in irreversible brain damage.
The normal CMRO2 is:
A. 3 - 3.8 mL/100g/min
B. 5 mL/100g/min
C. 2 mL/100g/min
The cerebral metabolic rate of oxygen consumption (CMRO2) is normally **3 to 3.8 mL/100 g/min. **
The brain glucose consumption is approximately 5 mg/100 g/min.
Normal cerebral blood flow is:
A. 50 mL/100 g/min
B. 450 mL/min
C. 35 mL/100g/min
A. 50 mL/100 g/min or 750 mL/min
What is the effect of sitting position during neuroanesthesia?
Increase risk of VAE
Calculate cerebral perfusion pressure (CPP) from the following data:
Blood pressure (BP) 100/70
Heart rate (HR) 65 beats/min
Cardiac output 5 L/min,
CVP of 5 cm/H2 O
ICP 15 mm Hg
A. 60 mm Hg
B. 65 mm Hg
C. 70 mm Hg
D. 75 mm Hg
B. 65 mm Hg
CPP is equal to mean arterial pressure (MAP) minus the ICP or CVP, whichever is greater.
In some institutions, CVP and/or ICP is measured in cm H2 O; to convert from cm H2 O to mm Hg, multiply the amount of cm of H2 O by 0.74 (i.e., 10 cm H2 O pressure = 7.4 mm Hg).
CPP = MAP − (ICP or CVP, whichever is greater)
MAP equals the diastolic blood pressure + 1/3 of the pulse pressure. Pulse pressure equals the systolic blood pressure minus the diastolic blood pressure.
In this case the Pulse pressure is (100 mm Hg -70 mm Hg) / 3 = 10 mm Hg. Thus the MAP = 70 mm Hg = 10 mm Hg = 80 mm Hg.
Since the ICP is greater than the CVP the CPP = 80 mm Hg (MAP) − 15 mm Hg (ICP) = 65
Which of the following intravenous (IV) anesthetic induction agents is relatively contraindicated in patients with intracranial hypertension?
A. Propofol
B. Etomidate
C. Ketamine
D. Thiopental
C. Ketamine
Barbiturates (such as thiopental or methohexital), propofol, and etomidate all decrease CMR, CBF,
CBV, and ICP and can be used for IV anesthesia in patients with elevated ICP.
A 62-year-old patient is scheduled to undergo resection of a large frontal lobe intracranial tumor under general anesthesia. Preoperatively, the patient is alert and oriented, and has no focal neurologic deficits. Within what range should Paco 2 be maintained during surgery?
A. 15 and 20 mm Hg
B. 30 and 35 mm Hg
C. 40 and 45 mm Hg
D. 45 and 50 mm Hg
C. 40 and 45 mm Hg
To help prevent an increase in ICP, mild hypocarbia is often induced. With severe hypocarbia (i.e., Paco 2 reduced below 20 mm Hg), cerebral ischemia
has been reported in both normal humans and laboratory animals.
When the Paco 2 is < 20 mm Hg, it is likely that cerebral ischemia is caused by a leftward shift of the oxyhemoglobin dissociation curve (produced by the severe respiratory alkalosis) and possibly by intense cerebral vasoconstriction.
Why do we AVOID premedication on a patient with elevated ICP?
Benzodiazepines and opioids, even in small doses, can depress respiration, leading to elevated PaCO2 and subsequent exacerbation of intracranial hypertension.
Depressed ventilation > Elevation of PCO2 > Elevation of ICP!
Also, in patients with preexisting or resolved motor deficits, even sedative doses of common anesthetic drugs, especially those with significant GABA-ergic activity, have been shown to exacerbate or “unmask” these deficits.
Hemodynamic GOAL when inducting a patient with elevated ICP EXCEPT:
A. Avoid hypertension
B. short-acting opioid and lidocaine (1.5 mg/kg) intravenously to blunt the sympathetic response to laryngoscopy is recommended
C. Succinylcholine is an absolute contraindication
D. Avoid hypoventilation
E. Avoid hypercapnia
C. Succinylcholine is an absolute contraindication - NOT AN ABSOLUTE contraindication
Succinylcholine should be used with caution in patients with preexisting motor deficits as upregulation of nicotinic receptors at the neuromuscular junction can lead to increased risk of hyperkalemia. Also, succinylcholine can increase ICP but this effect is of short duration.
Dose of mannitol for ICP control?
A. 0.5 - 1.5 g/kg
B. 500 mcg/kg
C. 2.5mg/kg
D. 10mg/kg
A. 0.5 - 1.5 g/kg
For intracranial surgeries, ICP control is
paramount until the dura mater is opened.
To this end, once Mayfield fixation of the head and positioning are safely completed, mannitol (0.5 to 1.5 g/kg) may be administered if ICP control is needed, as are steroids (e.g., dexamethasone 10 mg) and, in some cases, a prophylactic anticonvulsant.
MAC of __ may interfere with neuromonitoring:
A. 2.0 MAC
B. 1.0 MAC
C. more than 0.5 MAC
> 0.5 MAC
For patients with elevated ICP, volatile anesthetics are often limited to 0.5 MAC, if used at all, to minimize the degree of cerebral vasodilation and inhibition of autoregulation that can result.
more than 0.5 MAC of volatile agent may interfere with SSEP and MEP monitoring.
A 1°C decrease in core temperature will decrease the CBF to ___
A. 5 - 10%
B. 10 - 15%
C. 6 - 7%
D. 2 -3 %
C. 6 - 7%
Temperature is also an important determinant of CBF, with a 6% to 7% decrease in CBF per 1°C
decrease in core temperature.
CBF changes by approximately __ of baseline for each 1 mmHg change in PaCO2:
A. 2%
B. 3%
C. 7%
D. 5%
B. 3%
Maximum peak pressure in the setting of SAH or increased ICP:
A. 40 mmHg
B. 20 mmHg
C. 10 mmHg
D. 8 mmHg
A. 40 mmHg
For patients undergoing an intracranial procedure, tidal volume should be maintained at 6 to 8 mL/kg to minimize potential inflammatory injury to the lungs, with peak pressures kept at less than 40
cmH2O.
Which of the following is INACCURATE in terms of the fluid management in intracranial surgeries?
A. The goal of fluid management should be to keep the patient euvolemic
B. Hypotonic solutions can be used on patients with TBI
C. Glucose containing solutions are generally avoided
D. Hypertonic saline (3%) supplementation is indicated in moderate to severe hyponatremic states
E. Rapid rises in serum sodium (more than 3 to 4 mEq/L/h) must be avoided as this poses a risk for central pontine myelinolysis
B. Hypotonic solutions can be used on patients with TBI
Neurosurgical patients having nonurgent surgery should have a platelet count over:
A. 145,000
B. 80,000
C. 100,000
C. 100,000/mm
Serum glucose during neurosurgical procedures should be maintained between:
A. 90 to 180 mg/dL
B. 140 - 180 mg/dL
C. 80 - 120 mg/dL
A. 90 to 180 mg/dL
Intraoperative hyperglycemia >180 mg/dL has also been associated with an increase in postoperative infections after craniotomy.
TRUE or FALSE
Dexamethasone should also be avoided following pituitary surgery.
Why?
TRUE!
No dexamethasone in post-pituitary surgery!
Dexamethasone should also be avoided following pituitary surgery as it can suppress the
hypothalamic–pituitary–adrenal axis and significantly increase the false positive rate for diagnosis of postoperative hypopituitarism.
Which of the following statements concerning air embolism during intracranial operations is true?
(A) It does not occur in supine patients
(B) It is prevented by positive end-expiratory pressure
(C) It is confined to the right side of the heart and the pulmonary vasculature
(D) It is detectable by measurement of end-tidal nitrogen
(E) It is most efficiently treated by aspiration from a pulmonary artery catheter
(D) It is detectable by measurement of end-tidal nitrogen
An infarct involving the hypothalamus would most likely result from occlusion of which artery?
A. Anterior spinal artery
B. Vertebral artery
C. Anterior cerebral artery
D. Middle cerebral artery
E. Posterior cerebral artery
C. Anterior cerebral artery
The anterior portion of the hypothalamus, which consists largely of the preoptic region, obtains its blood supply from branches of the anterior cerebral arteries, where they lie above the optic nerves. There may be an element of blood supply
from the anterior communicating artery as well.
Cerebral perfusion pressure (CPP), in the absence of intracranial pathology, is MOST closely correlated with which parameter?
A. Intracranial pressure (ICP)
B. Central venous pressure (CVP)
C. Cerebral blood volume (CBV)
D. Mean arterial blood pressure (MAP)
D. Mean arterial blood pressure (MAP)
CPP = MAP—ICP or CVP, whichever is greatest.
Because the ICP (and CVP) is usually less than 10 mm Hg, CPP is primarily determined by MAP. Normal CPP is approximately 80-100 mm Hg.
CPP progressively decreases as ICP or CVP
increases. Likewise, CPP decreases as MAP decreases. CPP less than 50 mm Hg
shows slowing on EEG, CPP of 25-40 mm Hg shows flat EEG, and CPP sustained
at less than 25 mm Hg results in irreversible brain damage. CBV refers to cerebral
blood volume.
Which of the following situations has the least significant effect on cerebral blood flow (CBF)?
A. PaCO2 of 80
B. Temperature of 34°C
C. Increased blood viscosity
D. Acute metabolic acidosis
D. Acute metabolic acidosis
Acute metabolic acidosis has little effect on CBF because hydrogen ions cannot readily cross the blood-brain barrier.
Paco2 affects CBF. CBF increases approximately 1-2 mL/100 g/min per mm Hg increase in Paco2. This effect is thought to be due to CO2 diffusing across the blood-brain barrier and inducing changes in the pH of the CSF and the cerebral tissue. CBF changes 5%-7% per 1°C change in temperature.
Hypothermia decreases both CMR and CBF, whereas hyperthermia has the reverse effect. The most important determinant of blood viscosity is hematocrit.
A decrease in hematocrit decreases viscosity and can improve CBF though probably not to an appreciable extent. Conversely, elevated
hematocrit increases blood viscosity and can reduce CBF to an appreciable extent.
All of the following medications can be used to decrease elevated ICP EXCEPT which one?
A. Hypertonic saline
B. Furosemide
C. Propofol
D. Ketamine
E. Acetazolamide
D. Ketamine
IV induction agents generally decrease CBF. Ketamine is the only exception in that it increases CBF.
Which of the following agents can cause an increase in CBF and CMRO2?
A. Nitrous oxide
B. Desflurane
C. Halothane
D. Sevoflurane
A. Nitrous oxide
Volatile anesthetics increase CBF at greater than or equal to 1 MAC. Halothane produces the greatest increase in blood flow, whereas sevoflurane produces the least.
(halothane > desflurane > isoflurane > sevoflurane).
While increasing CBF, volatile
anesthetics also cause a decrease in the CMRO2.
Nitrous oxide, however, is an exception. When combined with IV agents, nitrous oxide has minimal effects on CBF, CMR, and ICP. Adding this agent to a volatile anesthetic, however, can further
increase CBF. When given alone, nitrous oxide causes mild cerebral vasodilation and an increase in both CBF and CMRO2.
Which of the following inhalational agents facilitates CSF absorption?
A. Halothane
B. Isoflurane
C. Sevoflurane
D. Desflurane
A. Halothane
Volatile anesthetics affect both formation and absorption of CSF. Halothane impedes absorption of CSF but only causes a minimal decrease in CSF formation
Which of the following inhaled agents has the highest propensity to elevate CBF (cerebral blood flow)?
A. Desflurane
B. Sevoflurane
C. Halothane
D. Isoflurane
C. Halothane
Volatile-inhaled anesthetics increase CBF at greater than or equal to 1 minimum alveolar concentration (MAC).
(halothane > desflurane = isoflurane > sevoflurane).
Which of the following statements most accurately describes the Monro- Kellie doctrine?
A. Given the non-distensible cranial vault, the volume of blood, CSF, and brain tissue must be in equilibrium to maintain ICP and CPP.
B. The cranial vault is distensible; therefore, there is adequate room for a space-occupying lesion without altering ICP.
C. Given the non-distensible cranial vault, brain tissue and CSF must remain in equilibrium to maintain ICP. CSF volume has no impact.
D. There is no relationship between brain tissue, CSF, and CBV and ICP.
A. Given the non-distensible cranial vault, the volume of blood, CSF, and brain tissue must be in equilibrium to maintain ICP and CPP.
The Monro-Kellie doctrine refers to the fact that the cranial vault is nondistensible; thus, CBV, CSF, and brain tissue must be in equilibrium to maintain ICP and CPP.
Efforts to decrease ICP can focus on decreasing CBV (elevating the head of the bed to allow drainage), decreasing brain tissue (through diuresis), and decreasing CSF volume (through drainage).
Which of the following is most appropriate diagnostic value for screening for acromegaly?
A. FSH
B. GH
C. ACTH
D. IGF-1
D. IGF-1
It is not growth hormone. GH is ‘diurnal’ which is less like reliable.
TRUE or FALSE
Glucocorticoids are generally avoided in Acromegaly post-operatively.
Why?
TRUE
It will affect subsequent endocrine evaluation post-operatively such as serum cortisol which are clinically taken 2-3 days post-operatively.
Which is NOT associated with a high risk of cerebral aneurysm rupture?
A. age over 40 years
B. female sex
C. cigarette smoking
D. systemic hypertension
E. male sex
E. male sex
The development of cerebral aneurysms and their likeliness to rupture is associated with age over 40 years, female sex, cigarette smoking, systemic
hypertension, and connective tissue disorders.
Which artery has the lowest occurrence of cerebral aneurysm?
A. MCA
B. Basilar artery
C. ACA
D. PCOM
C. ACA
Cerebral aneurysms most commonly occur at the anterior communicating arteries (40%), PCOMs (25%), and MCA (25%), with only 10% arising from the vertebro-basilar system.
ACA> PCOM > MCA > others
The score in Hunt and Hess Grading Scale for aneurysms is based on:
A. radiographic findings
B. GCS
C. clinical symptoms
C. clinical symptoms
A 54 year old male ASA II for smoking came in the ER with the following symptoms: severely obtunded, hemiparesis, early decerebrate posturing. BP 160/90 HR 90 O2 sat 92%
Based on the Hunt and Hess grading scale, the patient should have a score of:
A. 2
B. 3
C. 4
D. 5
C. 4
Which of the following assessment tool utilizes GCS and motor deficit in evaluating aneurysm?
A. Fisher grading system
B. Hunter and Hess grading system
C. World Federation of Neurological Surgeons Grading Scale
C. World Federation of Neurological Surgeons Grading Scale
This size of aneurysm clinically requires surgical treatment:
A. at least 3mm
B. at least 6mm
C. at least 20mm
D. at least 12mm
B. at least 6mm
“Small” aneurysms are less than 10 mm in diameter, “large” aneurysms are 10 to 24 mm in diameter, and “giant” aneurysms are more than 24 mm in diameter. Rupture risk increases with aneurysm diameter, with those larger than 6 mm generally requiring
treatment.
This is the only pharmacologic intervention that decreases risk for cerebral vasospasm:
A. Nimodipine
B. Mannitol
C. Dexamethasone
D. Rosuvastatin
A. Nimodipine
What is the IV bolus dose of PROPOFOL to accomplish burst suppression relative to aneurysm clipping?
A. 1-2 mcg/kg
B. 1-2 mg/kg
B. 1-2 mg/kg
Burst suppression can be accomplished with propofol administered as a 1- to 2-mg/kg bolus
followed by infusion of 100 to 150 μg/kg/min. Additional vasopressor may be required during this time to maintain CPP.
Which of the following drugs can be given to allow for a transient circulatory arrest during aneurysm clipping?
A. Adenosine
B. Propofol
C. Amiodarone
D. Labetalol
A. Adenosine
What dose of Adenosine can be given to transiently cause a circulatory arrest to allow clip application during aneurysm clipping?
A. 0.3 - 0.4mg/kg
B. 3 - 4 mg/kg
C. 0.5 mg/kg
A. 0.3 - 0.4mg/kg
Alternatively, when temporary clips are anatomically difficult to place, Adenosine 0.3 to 0.4 mg/kg may be safely given as a bolus to cause a transient (3- to 5-second) circulatory arrest allowing safe permanent clip application.
Cerebral blood flow is __ percent of cardiac output:
A. 20 -25%
B. 10%
C. 15%
D. 40%
A. 20 -25%
Chronic hypertension shifts the autoregulation curve to the:
A. Right
B. Left
C. Unchanged
A. Right
TRUE or FALSE
The higher the ICP (or CVP), the lower the CPP, if the MAP remains stable
TRUE
Which of the following is NOT an indication of decompressive craniectomy:
A. midline shift less than 5mm
B. basal cistern compression
C. refractory ICP elevation
D. acutely expanding intracranial hemorrhage
E. skull fracture
A. midline shift less than 5mm - Should be more than 5mm
INDICATION of Decompressive craniectomy:
Depressed skull fractures
Dural breech
* Midline shift more than 5 mm
Basal cistern compression
Refractory ICP elevation
Acutely expanding intracranial hemorrhage, including subdural and epidural hematomas
In the anesthetic management of TBI, hyperventilation should not continue beyond:
A. 1 - 2 hrs
B. 2 - 3 hrs
C. 2 - 6 hrs
C. 2 - 6 hrs
Hyperventilation should not continue beyond 2 to 6 hours, as its effect to decrease ICP may not be
durable after this time.
After this acute phase of hyperventilation, a PaCO2 of 30 to 35 mmHg is desirable.
what is the CPP target in the context of TBI anesthetic management:
A. above 60 - 70 mmHg
B. below 60 mmHg
C. above 90 mmHg
A. above 60 - 70 mmHg
Of particular importance for TBI management,
CPP should always be kept above 60 mmHg, and perhaps above 70 mmHg, to maintain cerebral perfusion.
In the context of TBI, a 70 year old should have an intraoperative systolic blood pressure maintained at:
A. systolic BP of ≥ 90 mmHg
B. systolic BP of ≥ 110 mmHg
B. systolic BP of ≥ 110 mmHg
Attention must be paid to hemodynamics, as systolic blood pressure should be maintained at
at ≥100 mmHg for patients aged 50 to 69 y.o.
at ≥110 mmHg for patients aged 15 to 49 y.o. or ABOVE 70 y.o.
Which anatomical location is responsible for vegetative regulation?
A. Precentral gyrus
B. Postcentral gyrus
C. Diencephalon
D. Brainstem
C. Diencephalon
The intracranial cavity is made up of brain parenchyma, CSF, and cerebral blood volume. Under normal physiologic condition, CBV is approximately ___
A. 150 mL
B. 120 mL
C. 200 mL
Intracranial VAULT:
Brain parenchyma (1,400 mL)
CSF (150 mL)
Cerebral blood volume (CBV) (150 mL)
Dexamethasone is effective at decreasing ONLY what type of cerebral edema?
A. Vasogenic edema
B. cytotoxic edema
C. interstitial edema
A. Vasogenic edema
Dexamethasone is effective at decreasing only vasogenic edema, due in part to its effect at upregulating expression of proteins responsible for the integrity of the tight junctions between endothelial cells in the brain
What type of cerebral edema has the characteristic of increased extracellular fluid in the setting of an INTACT blood brain barrier:
A. Vasogenic edema
B. cytotoxic edema
C. interstitial edema
C. interstitial edema
What type of cerebral edema has the characteristic of increased INTRACELLULAR water:
A. Vasogenic edema
B. cytotoxic edema
C. interstitial edema
B. cytotoxic edema
Cytotoxic edema is characterized by increased intracellular water. This commonly occurs in the setting of cerebral ischemia, where failure of membrane ionic pumps leads to accumulation of ions, and thus water, within cells.
What type of cerebral edema has the characteristic of increased EXTRACELLULAR water and loss of integrity of the blood brain barrier:
A. Vasogenic edema
B. cytotoxic edema
C. interstitial edema
A. Vasogenic edema
In vasogenic edema, there is loss of integrity of the BBB, leading to accumulation of extracellular water.
Vasogenic edema commonly occurs in regions of brain surrounding tumors, abscesses, or contusions.
The most important factor regulating blood flow to ischemic cerebral tissue is:
(A) systolic blood pressure
(B) PaO2
(C) cerebral perfusion pressure
(D) PaCO2
(E) cerebral oxygen consumption
(C) cerebral perfusion pressure
A 50-year-old man is scheduled to undergo emergency craniotomy for evacuation of an epidural hematoma. His Glasgow Coma Scale score is 6; heart rate is 54 bpm, and blood pressure is 190/110 mmHg. The most appropriate initial management is administration of which of the following agents?
(A) Atropine
(B) Mannitol
(C) Nimodipine
(D) Sodium nitroprusside
(E) Thiopental
(E) Thiopental
Which of the following drugs best facilitates management of cerebral vasospasm after subarachnoid hemorrhage?
(A) Nifedipine
(B) Nimodipine
(C) Nitroglycerin
(D) Nitroprusside
(E) Thiopental
(B) Nimodipine
In a patient who is to undergo clipping of a cerebral aneurysm, an advantage of isoflurane over nitroprusside for induction of hypotension is
(A) better maintenance of cardiac output
(B) better maintenance of cerebral blood flow
(C) greater decrease in cerebral oxygen consumption
(D) greater decrease in afterload
(E) more rapid titration of systemic blood pressure
(C) greater decrease in cerebral oxygen consumption
Depression of cerebral oxygen requirements below the level required to create an isoelectric EEG can be achieved by
(A) administration of isoflurane
(B) administration of nimodipine
(C) barbiturate coma
(D) hyperventilation
(E) hypothermia
(E) hypothermia
In patients with blunt head trauma, cerebral perfusion pressure is determined by the gradient between
(A) diastolic pressure and central venous pressure
(B) intracranial pressure and central venous pressure
(C) mean arterial pressure and central venous pressure
(D) mean arterial pressure and intracranial pressure
(E) systolic pressure and intracranial pressure
(D) mean arterial pressure and intracranial pressure
Which of the following drugs increases cerebral blood flow while decreasing cerebral metabolic rate?
(A) Etomidate
(B) Fentanyl
(C) Isoflurane
(D) Lidocaine
(E) Midazolam
(C) Isoflurane
Which of the following provides the most definitive diagnosis in a patient with suspected brain death?
(A) Absent bilateral somatosensory evoked potentials
(B) Absent cerebral blood flow during four-vessel contrast cerebral arteriography
(C) Intracranial pressure greater than mean arterial pressure
(D) Score of zero on Glasgow Coma Scale
(E) Two isoelectric electroencephalograms
(B) Absent cerebral blood flow during four-vessel contrast cerebral arteriography
Which of the following detects the smallest volume of venous air embolization?
(A) Changing the precordial Doppler ultrasound signal
(B) Decreasing PetC02
(C) Decreasing Sp02
(D) Increasing central venous pressure
(E) Increasing pulmonary artery pressure
(A) Changing the precordial Doppler ultrasound signal
