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Advanced Principles II > Anesthesia for Neurosurgery > Flashcards

Anesthesia for Neurosurgery Flashcards

1
Q

What arteries supply blood flow to the brain?

A

Internal carotid artery and the Vertebral arteries

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2
Q

Where do the two vertebral arteries arise?

A

Branches of the subclavian artery and enter the base of the skull through the foramen magnum

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3
Q

What are the three branches of the internal carotid artery?

A

Middle cerebral artery
Posterior communicating artery
Anterior cerebral artery

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4
Q

Where is the circle of willis located?

A

At the base of the brain and forms an anastomotic ring that includes vertebral and internal carotid flow

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5
Q

What is the purpose of the circle of willis?

A

If one portion of cerebral blood flow becomes obstructed, other blood flow will compensate and give collateral flow

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6
Q

What artery supplies majority of the blood flow to the brain?

A

Internal carotid artery 85%, supplies anterior 2/3 surface of the brain

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7
Q

What is normal cerebral blood flow?

A

50mL/100gm brain tissue/min (750mL/min or 15-20% total cardiac output)

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8
Q

Decreasing blood flow to the brain by how much will cause cerebral impairment?

A

Decreased flow by 50% (20-25mL/100gm/min)

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9
Q

Decreasing blood flow to the brain by how much will cause isoelectric EEG?

A

Flow 6-15mL/100gm/min

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10
Q

Decreasing blood flow to the brain by how much will cause neuronal death?

A

Less than 6mL/100gm/min

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11
Q

How is cerebral perfusion pressure calculated?

A

CPP = MAP - ICP

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12
Q

What is normal CPP?

A

80-100mmHg

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13
Q

What is CPP dependent on in a healthy individual?

A

MAP because ICP is usually less than 10mmHg

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14
Q

At what ICP does CPP become significantly compromised?

A

ICP greater than 30mmHg

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15
Q

What metabolic factors regulate CBF?

A

Hydrogen ion (pH of blood)
Carbon dioxide
Oxygen tension

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16
Q

What is the most potent determinant of CBF?

A

Carbon dioxide

Blood flow increases 1-2mL/100gm/min for every 1mmHg change in PaCO2

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17
Q

Why isn’t hyperventilating a patient for increased ICP always the best decision?

A

Once PaCO2 less than 20mmHg there is no further vasoconstriction effects, may cause cerebral impairment

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18
Q

How does oxygen tension affect CBF?

A

Only affected by marked changes in PaO2 less than 50mmHg will cause vasodilation and increase CBF

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19
Q

How is CBF impacted by temperature?

A

CBF changes 5-7% per 1C

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20
Q

At what temperate will an EEG become isoelectric?

A

20C

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21
Q

What is optimal Hct for CBF?

A

30-34%

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22
Q

What ANS control is predominately in cerebral circulation?

A

Extensive SNS innervation

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23
Q

At what MAPs is CBF auto regulated extremely well?

A

50-150mmHg, beyond these limits CBF become pressure dependent

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24
Q

How does chronic HTN cerebral auto regulation?

A

Cerebral auto regulation curve is shifted to the right so higher presses are necessary to maintain CBF

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25
Q

How does the metabolic rate of the brain differ than that of the rest of the body?

A

Overall metabolic rate of brain is 7 times greater than the average metabolic rate of the body

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26
Q

Why isn’t the brain able to sustain anaerobic glycolysis when no oxygen is present?

A

Metabolic rate of neurons is too great

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27
Q

What becomes a source of energy in the brain when glucose stores are depleted?

A

Ketone bodies

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28
Q

How does hyperglycemia contribute to global hypoxic brain injury?

A

Accelerates cerebral acidosis and cellular injury

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29
Q

What is the major function of the CSF?

A

Protect the CNS against trauma

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30
Q

About how much CSF is produced in a day?

A

21mL/hr (500mL/day) –> Total CSF volume is only about 150mL

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31
Q

What is a normal ICP?

A

5-15mmHg

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32
Q

What are the three components of the cranial vault?

A

Blood
Brain tissue
CSF

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33
Q

What is the first mechanism to compensate for an increase in ICP?

A

Displacement od CSF from cranial to the spinal compartment

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34
Q

What ICP is considered mild, moderate and severe intracranial HTN?

A

Mild: 12-25mmHg
Moderate: 25-40mmHg
Severe: greater than 40mmHg

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35
Q

Why is normal ICP said to have high compliance?

A

Small increases in volume can be tolerated without an increase in pressure

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36
Q

What are the three components of cushings triad?

A

HTN
Bradycardia
Irregular respirations

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37
Q

What medications can be given to a patient for increased ICP?

A

Mannitol, Lasix and Corticosteroids

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38
Q

What is a target PaCO2 if hyperventilation for increased ICP?

A

30-35mmHg

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39
Q

What anesthetic interventions have a Robin hood effect on CBF?

A

Barbiturates and Hyperventilation (good for focal ischemia or tumors)

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40
Q

What is the most important mechanism for protecting the brain during focal and global ischemia?

A

Hypothermia

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41
Q

What are strategies for cerebral protection?

A

Avoid hyperglycemia
Maintain normocarbia
Maintain O2 carrying capacity
Maintain normal or slightly increased BP

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42
Q

What should be considered if a patient undergoing neurosurgery is on anticonvulsants?

A

Anesthetic drug requirement
Therapeutic level of drug
Continue drug intraoperatively

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43
Q

Why is it important for the provider to have a smooth induction and emergence in neurosurgies?

A

To avoid swings in ICP

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44
Q

What are the types of mass lesions?

A

Congenital
Neoplastic
Infectious
Vascular

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45
Q

What are typical presentations for brain lesions?

A

HA
Seizures
Neurological decline
Focal neurologic deficits

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46
Q

What are the three tissue types of primary intracranial tumors?

A

Glial cells
Ependymal cells
Supporting tissues

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47
Q

What are secondary intracranial tumors?

A

They evolve from lesions that metastasize from primary cancers in the lungs, breast or skin

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48
Q

What are three major considerations in managing patients with intracranial lesions?

A

Tumor location (blood loss, hemodynamic changes)
Growth rate and size
ICP elevation

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49
Q

Why shouldn’t you monitor TOF on the hemiplegic side with an intracranial lesion?

A

May end up overdosing paralytic

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50
Q

Why do we zero the arterial line at the external auditory meatus in neurosurgical procedures?

A

It approximates the MAP at the level of the circle of willis

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51
Q

What is a major risk in neurosurgical procedures since the bed is turned 90-180 degrees away?

A

Unrecognized disconnects (vent, IV) may be increased

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52
Q

Why should PEEP be avoided in neurosurgical procedures?

A

Could potentially increase ICP

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53
Q

What is the best anesthetic technique if cerebral edema is present?

A

TIVA

54
Q

How should fluid be managed in patients undergoing neurosurgical procedures?

A

Normovolemia, fluids replacements will be below calculated maintenance
Replace blood loss with blood or colloids

55
Q

Why isnt using volatiles an effective method in controlling blood pressure in patients with elevated ICP?

A

BP is centrally mediated

56
Q

What complications can occur if bucking or coughing happens during extubation?

A

Intracranial hemorrhage or worsening cerebral edema

57
Q

What are the components of the posterior fossa?

A

Cerebellum
Brainstem
Cranial nerves
Large venous sinuses

58
Q

What nerve is responsible for stimulating cushing’s reflex?

A

Trigeminal nerve (HTN and Bradycardia)

59
Q

Stimulation of which cranial nerves causes bradycardia and HoTN?

A

Vagus and Glossophsryngeal

60
Q

What are concerns for anesthesia in patients with posterior fossa lesions?

A

Risk injury to cranial nerves, respiratory centers and circulatory centers

61
Q

What cranial nerves control the pharynx and larynx?

A

IX, X, XI

62
Q

What is the preferred position for a posterior fossa lesion for the surgeon?

A

Sitting position

63
Q

Why is the sitting position not preferred to used in posterior fossa lesions?

A

Most detrimental to physiologic status due to a lack of perfusion

64
Q

What are cardiac complications are associated with the sitting position?

A

Postural hypotension, arrhythmias and venous pooling

65
Q

What precautions can be taken to avoid CV compromise in the sitting position?

A 
Light anesthesia during positioning
Paralysis
Volume/Vasopressors
SCDs
Move to sitting position slowly
66
Q

How does a pneumocephalus occur?

A

Open dura and CSF leakage causes air to enter

67
Q

What can occur if the air is not evacuated prior to closing the cranium?

A

The air can act as a mass lesion as CSF reaccumulates

68
Q

What is the treatment for a tension pneumocephalus?

A

Burr holes

69
Q

What are the symptoms of the pneumocephalus?

A

Delayed awakening, HA, lethargy and confusion

70
Q

What are nerve injuries associated with the sitting position?

A

Ulnar compression
Sciatic nerve stretch
Lateral peroneal compression
Brachial plexus stretch

71
Q

What can be done to prevent ulnar nerve compression and brachial plexus stretch in the sitting position?

A

Arms across abdomen, pad elbow and under the arms to support the shoulders

72
Q

What can be done to avoid sciatic nerve stretch and lateral peroneal compression?

A

Place a pillow under the knees and pad the knees appropriately

73
Q

When does a venous air embolism occur?

A

When the pressure within an open vein is sub atmospheric and the incision is greater than the level of the heart

74
Q

What occurs when there is slow entrainment of air into the veins?

A

Small bubbles enter and travel to the heart
PVR increased from air lodging in capillary beds
Gas eventually diffuse into the alveoli and are excreted

75
Q

When does pulmonary artery pressure begin to rise from small bubble entering the circulation?

A

When the amount of entrained air exceeds pulmonary clearance

76
Q

What occurs when air is rapidly entrained in the veins?

A

Large bubbles enter and lodge into the SVC, RA and RV
Impedes flow through the right heart
Slow increase in PAP, CV collapse

77
Q

What is a paradoxical air embolism?

A

Air enters the left side of the heart and travels to systemic circulation

78
Q

What vessels are most at risk with a paradoxical air embolism?

A

Coronary and cerebral circulations

79
Q

What causes a paradoxical air embolism to occur?

A

When the right heart pressure is greater than the left

80
Q

What population is a paradoxical air embolism common?

A

Patients with PFOs

81
Q

What are signs and symptoms of a VAE?

A 
Mill wheel murmur
Decreased ETCO2/ Increased PaCO2
Detection of ET nitrogen
Dysrhythmias 
HoTN
Sudden appearance of vigorous spontaneous ventilation
82
Q

What tool can be used for early detection of a VAE?

A

Precordial doppler most common
Capnography
CVP/PA line

83
Q

What should be used to confirm diagnosis of VAE?

A

Do NOT rely n only one monitor alone to diagnose, used 2-3 monitors of varying sensitivity to confirm diagnosis

84
Q

What is the most sensitive indicator of a VAE?

A

TEE

85
Q

Where should the precordial doppler be positioned to detect VAE?

A

Over right atrium

86
Q

What is the treatment for a VAE?

A

100% O2
Have surgeon flood field or pack the wound
Call for help
Aspirate CVP line
Volume/inotropes
Position in LLD with slight trendelenberg

87
Q

What is the leading cause of non traumatic intracranial hemorrhage?

A

Cerebral aneurysms

88
Q

Where do cerebral aneurysms occur?

A

At a brand of a large cerebral artery (most turbulent blood flow)
Located in the base of the brain in the anterior circle of willis

89
Q

What treatment should be given to patient with a ruptured cerebral aneurysm to avoid vasospasm?

A

Triple H therapy
Hemodilution
HTN (SBP 160-200)
Hypervolemia CVP greater than 10

90
Q

Why is triple H therapy beneficial in preventing vasospasm after an aneurysm rupture?

A

It is intended to increase CBF to areas in the brain that become ischemia due to intense vascular narrowing

91
Q

Why is it that in vasospasm increasing CBF will help prevent ischemia?

A

With a vasospasm the vascular beds become passive

92
Q

What are the treatment goals of Cerebral aneurysm?

A

Diagnose early, airway management, control ICP, hemodynamic stabilization and seizure prophylaxis

93
Q

What grading system is used with subarachnoid hemorrhage?

A

Hunt and Hess Gradin System (ranges from 0-5)

94
Q

What is the most common method of treating an aneurysm?

A

Microsurgical clip ligation, clips it off from circulation

95
Q

When might circ arrest be required for an aneurysm clipping?

A

Greater than 2.5cm

96
Q

How should fluids be managed in a patient undergoing an iracranial aneurysm repair?

A

Run patient dry, expand blood volume with colloid (no glucose in fluids)

97
Q

When are the most likely times an aneurysm will rupture?

A

Dural incision
Excessive brain retraction
Aneurysm dissection
During clipping or releasing clip

98
Q

What should be done if an aneurysm ruptures intra operatively?

A

Immediate fluid resuscitation

Decrease MAP to decrease blood loss

99
Q

What kind of anesthetic should be provided for endovascular therapy?

A

GETA with complete muscle paralysis

100
Q

What is an arteriovenous malformation?

A

Congenital abnormality that involves a direct connection from an artery to a vein without a pressure modulating capillary bed

101
Q

What are the treatment options for an AV malformation?

A

Intravascular embolization
Surgical excision
Radiation

102
Q

How should the AV malformation be managed?

A

Similar to aneurysms however potential for larger amounts of blood loss, need multiple IV access

103
Q

What is the leading cause of death in individuals less than 24 years old?

A

Head trauma

104
Q

What are the determining factors of the significance of the head injury?

A

The extent of irreversible neuronal damage at the time of injury
Occurrence of of secondary insult

105
Q

What is the goal of anesthetic and surgical intervention of head trauma?

A

Prevention of the secondary insult

106
Q

If a skull fracture is present, what other injury is likely present?

A

Intracranial lesion

107
Q

What type of skull fracture is associated with subdural and epidural hematoma?

A

Linear skull fracture

108
Q

What are symptoms associated with basilar skull fracture?

A

CSF rhinorrhea
Pneumocephalus
Cranial nerve palsies

109
Q

What type of skill fracture is associated with a brain contusion?

A

Depressed skull fracture

110
Q

What type of injuries produce coup contra coup injuries?

A

Deceleration injuries

111
Q

What is the range of the Glasgow coma scale?

A

3-15

112
Q

What is the general rule of thumb of controlling an airway based on a score?

A

Less than 8, intubate

113
Q

What are the three components that make up the Glasgow coma scale?

A

Eye opening
Verbal responses
Motor response

114
Q

How should the airway be manipulated in a trauma patient?

A

In line stabilization to maintain the head in a neutral position

115
Q

When is a blind nasal contraindicated in a trauma patient?

A 
Basilar skull fracture
   Raccoon Sign (ecchymosis into periorbital)
   Battle Sign (ecchymosis behind ears)
116
Q

Why might HoTN be seen in a spinal cord injury?

A

Sympathectomy associated with spinal shock and bradycardia id the cardia accelerator center

117
Q

What should the provider be assessing for if there is pituitary insult?

A

Urine output for DI

118
Q

How do VP shunts function?

A

One way pressure dependent valves to regulate flow of CSF

119
Q

How should the provider control ventilation for placing a VP shunt?

A

Avoid hyperventilation and hypocarbia because they make the cannulation of the ventricle more difficult

120
Q

When is an awake craniotomy indicated?

A

Epilepsy surgery

Resection of tumors in frontal and temporal lobe (speech and motor assessed intraoperatively

121
Q

What is a major challenge of the anesthetic provider for an awake craniotomy?

A

Technique that provides adequate sedation, analgesia and respiratory and hemodynamic control but also awake and cooperative for neurological testing

122
Q

What is the most common non endocrine symptom of enlarging pituitary tumors?

A

Frontal or temporal HA

123
Q

When do pituitary tumors become apparent?

A

With mass effect or Hypersecretion of pituitary hormones

124
Q

What hormones are commonly secreted by functional pituitary tumors?

A

Prolactin (lactation)
Growth hormone (acromegaly)
ACTH (adrenal hyperplasia)

125
Q

When is a transphenoidal approach appropriate for pituitary surgery?

A

Tumor under 10mm in diameter

126
Q

What can the anesthetic provider do to optimize the view for the surgeon resecting a pituitary tumor?

A

Avoid hyperventilation because reductions in ICP result in retraction of pituitary into the sella tursica making access difficult

127
Q

What vascular structures are close to the suprasellar area when resecting a pituitary tumor?

A

Carotid arteries lie adjacent to the supra stellar area

128
Q

What anesthetic agent should be avoided in pituitary surgery?

A

Halothane

129
Q

What are Epi and Cocaine used for in pituitary surgery?

A

Topical to vasoconstrictor vessels, may produce HTN and dysrhythmias

130
Q

What is a common complication that occurs after pituitary surgery?

A

Diabetes insipidus, usually self limiting and resolves within 7-10 days

131
Q

What can DI be treated with?

A

DDAVP and vasopressin

132
Q

Why might you need to d/c nitrous for pituitary surgery?

A

The surgeon may wish to inject air or saline to delineate suprasellar margins

Advanced Principles II (8 decks)

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