Monitoring and Neurosurgery Flashcards
1
Q
What are the two monitoring modalities?
A
nervous system blood flow and function
2
Q
What are the three way to monitor blood flow?
A
cerebral oximetry, transcranial doppler, jugular bulb venous O2 saturation
3
Q
What are the five ways to monitor nervous system function?
A
EEG, SSEP, BAEP, VEP, MEP
4
Q
What is NIRS?
A
monitors CBF in relation to CMRO2
5
Q
NIRS monitoring is based off of what Law?
A
Beer Lambert
6
Q
What does NIRS monitor estimate?
A
brain tissue saturation
7
Q
Which monitoring modality most closely resembles the pulse oximeter?
A
NIRS
8
Q
If your patient is going to be monitored with NIRS what should you do before they go to sleep?
A
get a baseline reading before induction
9
Q
What can decrease the accuracy of a NIRS monitor?
A
changes in BP, PaCO2, Hgb, regional BV, peripheral oxygenation of the scalp
10
Q
The risk of cerebral ischemia is reduced if your NIRS monitor says within which range of baseline?
A
75% of baseline or greater
11
Q
What is a normal value for NIRS?
A
60-80%
12
Q
What is a limitation of NIRS?
A
only measures regional blood flow, not global, electrocautery interferes with reading
13
Q
What is spatial resolution?
A
depth of tissue measured for the actual cerebral oxygenation is directly proportional to the distance between the light emitting diodes and the sensors
14
Q
What monitor uses ultrasound waves to measure blood flow velocity of the brain?
A
Transcranial doppler
15
Q
Which monitor assesses the integrity of the circle of willis?
A
transcranial doppler
16
Q
Where is transcranial doppler placed?
A
temporal bone
17
Q
transcranial doppler most likely monitors which circle of willis vessel?
A
middle cerebral artery
18
Q
Does transcranial doppler measure blood flow or velocity?
A
blood flow velocity
19
Q
Transcranial doppler provides information specifically about what measurements?
A
flow direction, peak systolic and end-diastolic flow velocity, flow acceleration time, intensity of pulsatile flow, and detection of microemboli
20
Q
What does SjVO2 measure?
A
global cerebral O2 extraction
21
Q
SjvO2 measures blood from which segments of the brain?
A
blood draining from both cerebral hemispheres
22
Q
What vessel drains cortical blood, and subcortical blood?
A
dominant internal jugular vein drains cortical (usually right), non dominant drains subcortical (usually left)
23
Q
The jugular bulb receives how much blood from the contralateral and ipsilateral sides?
A
70% ipsilateral hemisphere - RIJV 30% contralateral - LIJV
24
Q
Is inter cranial mixing of blood complete or incomplete?
A
incomplete, therefore we only measure from one side and not both.
25
Where is a blood sample drawn from to measure SjvO2?
1 cm below and 1 cm anterior to the mastoid process
26
Where is SjvO2 monitoring useful?
cerebral ischemia with increased ICP
27
What value of SjvO2 is considered normal?
55-75%
28
What does a SjvO2 reading below 55% suggest?
inadequate O2 delivery to the cerebral tissues or increased consumption.
29
What does a SjvO2 reading above 75% suggest?
hyperemia or stroke
30
What does EEG measure?
difference of electrical potentials between groups of neurons
31
Does EEG measure cortical or subcortical structures or both?
cortical - outer 3mm
32
What are the three basic components of the EEG?
frequency, amplitude, and morphology
33
What is frequency of EEG?
rate and duration of impoulses
34
What is amplitude of EEG?
peak to peak measurements
35
What is morphology of EEG?
shape of the waveform due to amplitude and frequency of wave appearance.
36
What is the frequency of gamma waves?
32-100 Hz
37
What do gamma waves represent?
heightened perception, learning, problem solving tasks, cognitive processing
38
What is the frequency of beta waves?
15-30 Hz
39
What do beta waves represent?
awake, alert consciousness
40
What is the frequency of alpha waves?
10-15 Hz
41
What do alpha waves represent?
physically and mentally relaxed
42
What is the frequency of theta waves?
5-10 Hz
43
What do theta waves represent?
dreams, meditation, light sleep
44
What is the frequency of delta waves?
0.5-5 Hz
45
What do delta waves represent?
deep sleep
46
What is frequency of EEG waves?
speed of impulses
47
What is amplitude of EEG?
height of waveform
48
What is the progression of EEG waveforms as a result of ischemia?
Increased Beta -\> amplitude increases -\> theta -\> delta waves
49
What does Delta waves on EEG likely represent?
increased ischemia
50
When delivered in equal doses, do IV or Inhalation anesthetics cause more EEG depression?
inhalation anesthetics
51
Inhalation agents have the most effect on which EEG waves?
Beta waves
52
How do gases change amplitude and frequency?
increase frequency decrease amplitude
53
Which IV anesthetics increase Beta wave frequency and decrease amplitude?
Propofol, Etomidate, and ketamine
54
At 1 MAC which waves are seen?
delta, and theta
55
As the patient enters stage 3 of anesthesia which waves are demonstrated on EEG?
low frequency, high amplitude
56
After giving Ketamine what types of EEG waves are expected?
high oscillation waves, no theta or delta
57
If you induce with high doses of induction agents what is commonly seen on EEG?
burst suppression
58
What is burst suppression?
pattern of high frequency activity, and periods of electrical suppression with variable duration
59
At what MAC levels will burst suppression be seen on EEG?
1.2-1.5
60
At what MAC does Iso, Sevo and Des cause burst suppression?
Iso 1.5 Sevo, Des 1.2
61
Which volatile does not cause burst suppression?
N2O
62
What volatile requires the highest MAC to cause burst suppression?
Iso
63
What does the BIS value signify?
anesthetic depth
64
To prevent recall you would titrate your anesthetic to a BIS value of what?
\<60
65
If you are a good CRNA you would keep your BIS value above what level to prevent increased mortality?
40
66
If your BIS falls below 40, make a change within what time frame?
5 minutes
67
What does Ketamine do to BIS values?
falsely elevates them
68
What BIS value will be consistent with burst suppression on EEG?
20
69
What is an evoked potential?
electrical potential in response to a stimulus and are used to warn of current or impending neurological dysfunction and ischemia
70
What are the four types of evoked potentials?
motor, brainstem auditory, somatosensory, visual
71
What are the sensory evoked potentials?
BAEP, SSEP, VEP
72
Motor evoked potentials are derived from which area of the brain?
Precentral gyrus
73
Sensory evoked potentials are derived from which area of the brain?
Postcentral gyrus
74
What things affect evoked potentials?
anesthetics, hypothermia, hypotension, anemia, positioning
75
What is the amplitude of a Evoked Potential?
intensity of the evoked potential (height)
76
What is latency of evoked potentials?
period of time until evoked response is measured (time)
77
What changes in amplitude and latency are consistent with ischemia?
50% decrease in amplitude and 10% increase in latency
78
How do SSEP's detect localized injury to specific areas of the neural axis?
assessing cortically generated waves
79
SSEPs are a non specific indicator of what?
cerebral O2 delivery
80
SSEP specifically monitors what part of the brain and spinal cord?
Faciculus Cuneatus and Gracillis tracts of the dorsal lemniscal system
81
If ischemia occurs what happens to SSEP impulses?
they are reduced
82
SSEPs monitor the integrity of which cortex?
somatosensory
83
What sensations does the dorsal lemniscal system transmit?
touch (fine, discrete), vibration, and proprioception
84
The Fasciculus gracilis is more ____ and transmits sensation from ___ and ___ regions?
medial, lumbar, sacral
85
The Fasciculus Cuneatus is more ____ and transmits sensation from ___ and ___ regions?
lateral, thoracic, cervical
86
Trace the dorsal lemniscal system pathway from first order to third order neurons.
First Order fibers enter from the dorsal horn into the fasciculus gracilis or cuneatus, ascending to the medulla, then synapse with their second order neurons in the nucleus gracilis or nucleolus cuneatus. Then traveling to the thalamus to synapse with a third order neuron.
87
Which nerves are most frequently stimulated with SSEP's?
posterior tibial and median nerves
88
Where are stimulating and detecting SSEP electrodes placed?
stimulating placed peripherally detecting placed centrally
89
Where is an alternative SSEP detecting lead placed for the lower extremity?
common perineal nerve
90
Where is an alternative SSEP detecting lead placed for the upper extremity?
ulnar nerve
91
If we were to stimulate the left posterior tibial nerve. Where would the central electrode be placed on the brain?
postcentral gyrus, right side, midline
92
Where would you place a peripheral electrode on the lower extremity to ensure stimulation is adequate for SSEP?
iliac crest
93
Where would you place a peripheral electrode on the upper extremity to ensure stimulation is adequate for SSEP?
Erbs point
94
SSEP latency increases how much for every 2 degrees Celsius decrease in temperature?
3ms
95
Hyperthermia suppresses SSEP amplitude by how much?
15%
96
In general how do anesthetics affect latency and amplitude?
increase latency and decrease amplitude of SSEP
97
How does etomidate and ketamine affect SSEP amplitude?
increase amplitude 200-600%
98
How can we optimize SSEP readings?
not making changes to gas or IV drugs
99
What nerve does BAEP monitor?
vestibulocochlear (CN8)
100
What procedures are BAEP's monitored?
inner ear and auditory cortex
101
Which evoked potential monitor is least sensitive to anesthetics?
BAEP
102
How does hypothermia affect BAEPs?
increases latency
103
While monitoring BAEP's what happens to amplitude as temperature increases?
amplitude decreases
104
What does electromyography monitor?
the facial nerve also 3, 4, 10, 11, 12
105
What is the standard of care monitor for acoustic tumor surgery?
electromyography
106
Does electromyography monitor ischemia?
no. only mechanical and thermal damage
107
What is electromyography very sensitive to?
muscle relaxation. Avoid
108
What monitor is used for the visual pathway for everything from the retina to the occipital cortex?
VEP
109
Where are VEP electrodes placed?
visual cortex
110
What do MEPs monitor?
motor cortex and descending tracts (corticospinal tracts)
111
Where are detecting and stimulating electrodes placed in MEP's?
detecting electrodes peripherally stimulating electrons centrally
112
What suppresses MEP's?
inhalation agents and NMB
113
What is the goal MAC when using MEP's?
0.5 MAC
114
What is the most appropriate way to give NMB's during MEPs?
infusion
115
What is the order of sensitivity to anesthetic gases of evoked potentials?
VEP\>MEP\>SSEP\>BAEP Visual very, Motor moderately, Sensory somewhat, Brain barely
116
What is the first compartment to decrease in response o increased ICP?
CSF
117
What begins to occur as volume compensation mechanisms reach exhaustion?
local and focal ischemia
118
ICP has a direct relationship with what?
herniation risk, mechanical injury, & ischemia
119
ICP has a indirect relationship with what?
CPP
120
Sustained elevations in ICP lead to what?
catastrophic herniation of the brain
121
What are the four locations herniation can occur?
- the cingulate gyrus under the falx cerebri
- uncinate gyrus through the tentorium cerebelli
- cerebellar tonsils through the foramen magnum
- any area beneath a defect in the skull
122
Name the Herniations
1. Subfalcine 2. Transtentorial (uncal) 3. Tonsilar 4. Transcalvarial
123
Pressure on the brainstem, rostral to caudal. altered consciousness, ocular and sight reflex issues, respiratory and cardiac dysfunction are symptoms of which type of herniation?
transtentorial
124
What are symptoms of uncal herniation?
pupillary dilation, ptosis, deviation of ipsilateral eye
125
What causes a tonsilar herniation?
increased infratentorial pressure -\> compression on the medulla
126
What does a tonsilar herniation lead to?
cardio-respiratory instability
127
What is the gold standard for ICP monitoring?
intraventricular catheter
128
What is a major advantage of the ventriculostomy?
allows CSF drainage
129
Where is a ventriculostomy zeroed?
jugular foramen (tragus)
130
Draining CSF in a patient with brain tumor can lead to what?
tonsilar herniation
131
what is the most common complication of ICP monitoring?
infection
132
What is the most effective and rapid way of lowering ICP?
ventriculostomy, intraventricular catheter or lumbar subarachnoid
133
What do the ICP waveforms signify?
P1: percussion, highest, arterial compliance P2: tidal wave, cerebral compliance P3 dicrotic wave, aortic valve closure, the dicrotic notch
134
What does a P2 wave is greater than P1 wave signify?
intercranial hypertension
135
What maintains ICP?
inter cranial elastance
136
What is elastance the inverse of?
compliance
137
What is a plateau ICP wave called?
Lundberg A wave
138
How long does a Lundberg A wave last and what is the range of ICP?
20 minutes ICP of 20-100
139
What does Lundberg A waves tell you about brain elastace and compliance?
increased elastance or decreased compliance
140
Cushings Triad is common with Lundberg A waves? What is cushings triad?
HTN, tachycardia, irregular respirations
141
How long to Lundberg B Waves last and what is the typical ICP?
.5-2 minutes ICP 20-50
142
What does Lundberg B waves tell you about elastance and compliance?
increased elastance decrease compliance
143
Intracranial hypertension occurs with a sustained increase in ICP above what?
20
144
What are signs of increased intracranial pressure?
HEADACHE, nausea, vomiting, papilledema, blurred vision, neurological deficits, ventilatory deficits, decreasing consciousness, seizures, and coma
145
What happens to CBF when ICP exceeds 30?
CBF decreases -\> brain edema -\> increased ICP -\>ischemia
146
What happens if increased ICP is not corrected?
herniation
147
What does expanding tissue mass, fluid mass, CSF absorption interference, excessive CBF, or systemic disturbances promoting brain edema lead to?
inter cranial HTN
148
How do brain tumors increase ICP?
size, edema formation, obstruction of CSF flow
149
What causes aqueductal stenosis?
obstructive hydrocephalous
150
How are the third and fourth ventricle affected by aqueductal stenosis?
enlarged 3rd ventricle, normal 4th ventricle
151
How is aqueductal stenosis treated?
ventricular shunt
152
Lack of cerebral lesions, and increased ICP with no known cause is called what?
benign intercranial HTN
153
Benign intracranial HTN is most common in which population?
obese women with autoimmune irregularities
154
What are potential symptoms of benign intracranial HTN?
Headache and bilateral visual disturbances
155
What is the treatment for benign intracranial HTN?
removal of CSF and administration of acetazolamide and corticosteroids
156
What can acetazolamide cause?
acidemia d/t hydrogen ion secretion by renal tubules
157
what is the anesthetic management of benign intracranial HTN?
avoid hypoxia and hypercarbia.
158
What is the safest type of anesthetic for someone with benign intracranial HTN?
general
159
What type of anesthesia should be avoided in someone with benign intracranial HTN?
Epidural
160
Which of the 4 intracranial sub compartments can anesthetists control?
CSF, fluid and blood. We can't alter cellular compartment
161
It is not recommended to remove CSF in patients with increased risk of which types of herniation?
transtentorial (uncal) or tonsillar herniation
162
Which intracranial subcompartment can anesthesia rapidly alter?
blood
163
Does the venous or arterial system more likely increase ICP?
venous due to obstruction of drainage or increased intrathoracic pressure
164
How do volatile anesthetics affect ICP, CBV and CBF?
increase ICP, CBV, CBF by decreasing cerebrovascular dilation
165
What affect does gases have on CPP?
decreases CPP by decreasing MAP
166
What affect does gases have on auto regulation and CMRO2?
CMRO2 decreased, impaired autoregulation
167
CMRO2-CBF coupling becomes impaired at what MAC level?
0.6-1 MAC
168
Which gases cause the greatest increase in CBF and ICP?
Des \> Sevo \> Iso
169
Which gas increases absorption of CSF?
Iso
170
Are volatile agents beneficial in focal or global ischemia?
global. Focal causes steal
171
With a MAC above 1.5 which gas causes the greatest increase in CBF?
Iso
172
Gases cause activation of ATP-dependent potassium channels, up-regulation of nitric oxide synthase, reduction of excitotoxic stressors and CMR, augmentation of peri-ischemic CBF, and up-regulation of anti-apoptosis factors leading to what?
neuroprotection during ischemic insults
173
Does N2O affect auto regulation?
not on its own, but it does in combination with other gases
174
How does N20 affect CBF and CMRO2?
increase both
175
What happens to CBF at 0.5 MAC?
doubles
176
How does N2O affect ICP?
increase due to cerebral vasodilation
177
megaloblastic anemia, leukopenia, impaired fetal development, and a depressed immune system can be caused by what?
accumulation of metabolic breakdown products
178
Which gas should be avoided in patients with pneumocephalus, craniofacial trauma, recent craniotomy?
N2O
179
Which anesthetic is great for awake craniotomy?
Dexmedetomidine
180
What induction agent causes myoclonia, thrombophlebitis, nausea/vomiting, and suppression of the adrenal corticoid response to stress?
Ketamine
181
Which induction agents decrease CMRO2, CBF, and ICP?
all but ketamine
182
Which induction agent decreases production and enhances absorption of CSF?
etomidate
183
which induction agent activates seizure foci in patients with a history of epilepsy?
etomidate
184
which induction agent maintains CPP better than propofol due to lower decrease in MAP?
etomidate
185
Which induction agent is the most widely used for neurosurgery?
propofol
186
How do opioids affect cerebral vasculature, CMRO2, ICP, and CPP?
mild cerebral vasoconstrictors, mild effects on CMRO ICP CPP
187
Which opioid activates seizure foci in patients with epilepsy, but produces the greatest decreases in MAP and CPP?
Alfentanil
188
Which opioid should be avoided because it can enduce seizures?
Meperidine
189
Do Benzos decrease or incresae CBF, CMRO2, ICP, and CPP?
decrease
190
Which Benzo in large doses may activate seizures?
flumazenil
191
Is ketamine OK in multisystem trauma?
yes
192
Why is ketamine undesirable in neuroanesthesia?
Dissociative anesthesia and rocky emergence
193
How does Ketamine affect CBF, ICP, and CSF?
Increases CBF, ICP, and resistance to CSF reabsorption
194
If Ketamine is used in neuroanesthesia should it be used independently or in combination?
combination with a GABA agonist
195
How do NMBs affect CBF or CMRO2?
Nondepolarizers have little to no effect on CBF or CMRO2
196
How does Succinylcholine affect ICP, CBF, and CMRO2?
transient elevations in ICP, CBF, and CMRO2
197
How much does Succ increase ICP?
10-15 for 5-8 minutes
198
Muscle spindle activity for succinylcholine is caused by what?
jugular venous stasis
199
Why do histamine releasing NMB’s increase ICP and reduce CPP?
vasodilation
200
What medication could cause herniation if ICP already high?
nitrates
201
How do vasodilators affect cerebral vasculature and CBF?
induce cerebral vasodilation and increase CBF
202
CBV increases and can increase ICP in patients with decreased intracranial ... compliance or elastance?
compliance
203
What two vasodilators are considered unsafe in someone with abdnormal cerebral elastance?
NTP and NTG
204
What are some benefits of hypnocapnia in neurosurgery?
reduces ICP by promoting cerebral vasoconstriction thereby increasing cerebral vascular resistance, reducing CBF and CBV
205
What are the two considerations for hyperventilation?
hypocapnia may cause ischemia, beneficial effects are not sustained
206
What are 1st and 2nd line PaCO2 goals?
30-35 1st line, 25-30 2nd line
207
What happens to the pH of CSF and brain ECF with hyperventilation?
they increase
208
How long does it take carbonic anhydrase to return pH to normal?
6-12 hours
209
What is the goal of CPP during CNS insults and neurosurgery?
normal to high normal
210
What happens to areas of the brain with compromised autoregulatory responses during HoTN?
pressure dependent
211
Which medications reduce edema and the increased BBB permeability that is seen with tumors?
steroids
212
If you want the benefits of steroids intraoperatively when should they be initiated?
24 hours. up to 72 hours for ICP reduction
213
Which steroid type can cross the BBB and increase edema?
glucocorticoids
214
Steroids are contraindicated for which patients due to negative effects?
TBI
215
Steroids alter which lab value?
blood glucose
216
What medications are useful to reduce brain intracellular contents?
hyperosmolar and diuretics
217
what medication can decrease water content in the brain?
mannitol
218
What medication works by creating an osmotic gradient and can cross a nonintact BBB and actually make edema worse?
Mannitol
219
Mannitol can cause problems in which patient population?
heart failure
220
What electrolyte derangements does mannitol cause?
plasma hyperosmolarity, hypokalemic hypochloremia metabolic alkalosis
221
What is the most commonly used intraoperative agent due to its rapid and effective reduction in brain volume?
mannitol
222
How much fluid does mannitol remove from the brain, time to decrease ICP, max effect, duration, UO in 1 hour?
~ 100 mL fluid from brain, decreases ICP in 30 min, max effect 2 hours, duration 6 hours, UO 1-2 L within 1 hour
223
Which diuretics decrease the rate of CSF formation?
loop diuretics
224
Which medication has an osmotic effect (similar to mannitol) but remains outside of the BBB
3% NS
225
How does 3% affect circulating plasma volume, ABP and CPP?
increases
226
Side effects of which drug cause natriuresis, hemodilution, immunomodulation, improved pulmonary gas exchange, cardiac failure, bleeding diathesis (bruise/bleed easily), vesicant
3%
227
Giving large volumes of 3% rapidly can cause what?
central pontine myelinolysis
228
serum Na+ should not be raised more than ___ in 24 hour period?
9mEq
229
What is the goal serum osmolarity when giving 3%?
\< 320 mmol
230
TBI, SAH, cortical incisions, brain surface irritation can cause what?
seizures
231
What medications are used to induce coma in patients with increased ICP that is refractory to other treatment options?
barbiturates
232
Which medications decrease CMRO2 scavenging free radicals, hyperthermia (d/t ischemia) and prevents convulsions?
barbiturates
233
What is first and second line treatment HoTN caused by barbiturates?
1st: VOLUME EXPANSION 2nd: vasopressors
234
What signifies propofol infusion syndrome?
high anion gap metabolic acidosis
235
What is BG goal levels during neurosurgery?
140-180
236
Which patient should not have tight glucose control?
TBI and SAH
237
What causes injured brains to become hypoglycemic and suffer metabolic distress?
localized hyperglycolysis
238
What levels should BG be kept in patients with TBI or SAH?
treat if \>250 and keep below 200
239
Which patients is intraoperative permissive hypothermia best utilized?
high risk for intraoperative ischemia
240
What are the risks of hypothermia?
coagulopathies and dysrhythmias?
241
What is the fluid management goal during neurosurgery?
maintain normovolemia/MAP during surgery
242
What are the most frequency used fluids in neurosurgery?
LR and NS
243
Which common fluid is slightly hyperosmolar (308 mOsm/L) and has the disadvantage that large volumes can cause hypercholremic metabolic acidosis?
NS
244
Which common fluid is slightly hypo-osmolar (274 mOsm/L) and in large quantities could produce cerebral edema by lowering serum osmolarity?
LR
245
What does reduced serum osmolarity lead to?
edema formation in normal/abdnormal brains
246
What is normal plasma osmolarity?
280-295
247
What is the goal UO during neurosurgery?
0.5-1 mL/kg/h
248
Hct should be maintained above ___ in neurosurgery?
28%
249
Reduced colloid oncotic pressure w/out change in osmolarity leads to what?
cerebral edema
250
In traumas that require large fluid administration, which fluids should be used?
Crystalloid/colloid combination
251
Which fluid should be used cautiously in neurosurgery due to dilutional reduction in coagulation factors, and direct inhibition of platelets and factor VIII?
Hetastarch
252
Which fluid interferes with platelet function?
Dextran
253
Which fluid should be avoided when the BBB is not intact?
albumin
254
What is the other name for the semi lateral position?
Janetta
255
If the patient is in supine or any position what is very important to avoid?
neck flexion
256
What does neck flexion do to cerebral blood volume and ICP?
increases
257
An axillary roll is used in the lateral position to prevent injury to what?
brachial plexus
258
What is another name for prone position?
concorde position
259
POVL, pressure necrosis, IVC compression, airway/tongue injury area ll risk factors for which position?
prone
260
What is the most frequent cause of POVL (post-operative vision loss)?
ION - ischemic optic neuropathy
261
Cortical ischemia, central retinal vessel occlusion (2/2 orbital compression) can also cause what?
POVL
262
Wilson frame, low ABP/Hct, males, obesity, lengthy surgery and Large IVF resusctitation are risk factors for what?
POVL
263
compression of the IVC directs blood to the ___ leads to increased risk of bleeding.
epidural space
264
Cervical/posterior fossa surgery requires neck flexion , how can you avoid injury in the mouth?
avoided excess equipment in the mouth, soft bite block
265
While in the sitting position where should the A-line transducer be placed?
external auditory canal
266
An A-line transducer placed at the ear, measures the BP where?
circle of willis
267
What is the formula to calculate the pressure difference in the BP cuff due to height?
1cm difference in height = 0.78 mmHg change in BP
268
Prepositioning hydration, compression stockings, and slow incremental table adjustments are ways to prevent what?
hypotension
269
What is the goal CPP in normal healthy patients?
60
270
In sicker patients should CPP be kept higher or lower?
higher
271
What is necessary for a patient in the sitting position?
A-line
272
What can occur as a result of edema formation in the pharyngeal structures, soft palate, and tongue?
Upper airway obstruction
273
This can occur secondary to stretching or compression of the cervical spinal cord while in the sitting position?
Unexplained quadriplegia
274
What position is contraindicated in those with intracardiac shunts (PFO, VSD) and relatively contraindicated in significant degenerative disease of the cervical spine and/or cerebral vascular disease?
sitting
275
What evoked potential monitor is potentially used for patients undergoing procedures in the sitting position?
SSEP
276
What is a common complication of posterior fossa surgeries in the head up position?
pneumocephalus
277
When does pneumocephalus typically occur?
after cranial closure
278
What is a potential cause of delayed or non-awakening after posterior fossa or supratentorial surgery?
pneumocephalus
279
VAE is principally a concern with which procedures?
posterior fossa and upper cervical spine procedures Super high risk if also in sitting position
280
What results from a negative pressure gradient between the operative site and the right side of the heart?
VAE
281
Does spontaneous or mechanical ventilation increase the risk of air entrainment?
spontaneous
282
Should pins be removed when the patient is in the sitting or supine position?
supine
283
What are the most common sites of critical VAE?
sigmoid and saggital sinus
284
What are the 4 pathways a VAE can travel?
R heart to lungs
R-\>L heart through a shunt
collect at SVC and RA junction
transverse the p. capillaries and enters circulation
285
Increased PAP & CVP, decreased CO, hypotension, dysrhythmias, up to cardiac arrest are S/S of what?
VAE
286
What develops with entry of air into the systemic circulation through an existing anatomic connection between the right and left heart?
paradoxical air embolus
287
Is the venous or arterial circulation the preferred route for a VAE?
venous
288
What should you avoid in a patient with a known VAE and R-\>L shunt?
PEEP
289
What position is contraindicated with a known VAE?
sitting
290
In VAE Endothelial mediators produce a reflex pulmonary vasodilation or constriction
constriction
291
Pulmonary vasoconstriction from VAE has what affects on the lungs?
Pulmonary HTN, hypoxemia, CO2 retention, dead space ventilation, ↓ETCO2
292
Air that enters the pulmonary artery in VAE can trigger reflex broncho\_\_\_\_\_\_?
bronchoconstriction
293
Entry of air into the alveoli from VAE may be detected by presence of what?
end tidal nitrogen
294
This amount of entrained air cause decreased ETCO2, increased ETN2, oxygen desaturation, altered mental status, wheezing?
\<0.5 mL/kg
295
This amount of entrained air cause difficulty breathing, wheezing, hypotension, ST changes, peaked P waves, JVD, myocardial and cerebral ischemia, bronchoconstriction, pulmonary vasoconstriction?
0.5-2mL/kg
296
This amount of entrained air causes chest pain, RHF, CV collapse, pulmonary edema?
\>2mL/kg
297
What is the most sensitive monitor for VAE?
TEE
298
What is the most sensitive noninvasive monitor, and earlier detector for VAE?
precordial doppler
299
What are late signs of VAE?
hypotension, tachycardia, dysrhythmias, cyanosis
300
precordial doppler can a detect a VAE this size?
0.002mL/kg/min
301
Where is a precordial doppler placed?
right side of the heart (right sternal border between 3rd/6th ICS
302
a 10mL bolus of saline through a CVC helps confirm proper placement of what?
precordial doppler
303
What is a late sign of air entrainment with precordial or esophageal stethoscope?
mill wheel murmur
304
Is a PAC or EtCO2 more sensitive for VAE?
PAC
305
What is an early indication for potential VAE in a intubated patient?
gasp reflex
306
What is the treatment of VAE?
Stop, wax bone edges 100% FiO2, stop N2O Jugular vein compression Trendelenburg
307
What is another name for the left lateral position?
Durrant position
308
What are no longer treatments for VAE?
PEEP and valsalva
309
What is the most common induction agent for neurosurgery?
propofol
310
Which induction agent does not increase ICP?
propofol
311
NDNMB or DNMB for neurosurgery?
NDMB
312
Does risk of VAE increase by using N2O?
No
313
What is maintained due to risk of elevated ICP, increased surgical bleeding, and direct brain or head injury from sudden patient movement?
Paralysis
314
Monitoring a TOF in a paralyzed extremity leads to an increased or decreased TOF response?
Increased response in the paralyzed extremity.
315
What does coughing, straining, and arterial hypertension cause during emergence?
bleeding and edema formation
316
How can you manage HTN during the final stages of craniotomy?
lidocaine 1.5mg/kg, labetalol, esmolol, and dexmedetomidine
317
Should emergence occur during dressings application or suture placement?
dressing
318
What are the most common types of supratentorial tumors?
gliomas and meningiomas
319
Seizures, hemiplegia, headaches, & aphasia are s/s of which type of tentorial mass?
supratentorial
320
Cerebellar dysfunction (ataxia, nystagmus, dysarthria) and brainstem compression (cranial nerve palsies, altered LOC, abnormal respiration) are s/s of which type of tentorial mass?
intratentorial mass
321
What. indicates the presence of intracranial HTN?
brain edema
322
What medication class should not be given in patients with large mass lesions, midline shift, and abnormal ventricular size?
Benzos
323
What do benzos and opioids cause?
respiratory depression and hypercapnia
324
To control ICP the head of the bed should be kept at what degree in preop holding and during transport to the OR?
15-30 degrees
325
Some tumors may require excision around the hypothalamus and thus may result in postoperative what?
DI, within 12-24 hours
326
What approach to craniotomy may leave a patient with disturbed consciousness in the immediate postop period resulting in lethargy, disinhibition, or delayed emergence?
Subfrontal
327
What is the term used to describe lethargy, disinhibition, or delayed emergence?
Frontal Lobey
328
What type of craniotomy is reserved for patients in which a seizure foci may be suppressed by general anesthesia or surgical manipulation is adjacent to an area of eloquent cortical function?
Awake craniotomy
329
What is the single most important element of a successful awake craniotomy is what?
highly motivated, well informed patient
330
Who is allowed to talk to the patient with an awake craniotomy?
Surgeon and CRNA
331
What are common induction agents for awake craniotomy?
Fent, Prop, Dex
332
What medications do we give to induce seizure foci?
etomidate, methohexitol 0.03mg/kg, hyperventilation
333
What are the most common complications of awake craniotomy?
pain, seizures, nausea, confusion
334
What are abnormal, localized dilations of intracranial arteries?
cerebral aneurysms
335
What type of aneurysm is the most common cause of SAH?
berry or saccular
336
Where do cerebral aneurysms typically occur?
middle cerebral artery of Circle of Willis
337
Which diagnostic is best for localizing the site of a bleeding aneurysm?
CT scan
338
What typically presents as an abrupt, intense headache, in most patients with transient loss of consciousness in up to half?
SAH
339
What is meningismus (pseudo meningitis)?
Triad of nucal rigidity, photophobia, headache
340
What often accompanies acute SAH secondary to autonomic hyperactivity which can increase transmural pressure in the aneurysm?
HTN
341
How do you calculate transmural pressure?
MAP- ICP
342
What is the stress applied to an aneurysm sac called?
transmural pressure
343
What is the BP goal before aneurysm clipping?
120-150
344
What EKG changes are common after SAH?
T wave, ST, U wave, Qt prolongation, dysrhythmias
345
What is a life threatening complication of a previous ruptured aneurysm with a current SAH?
rebleeding
346
What is minimized by early surgical clipping, antifibrinolytics, and bp control during SAH/cerebral aneurysm?
Rebleeding
347
What is reactive narrowing/contraction of cerebral arteries after SAH?
vasospasm
348
What does cerebral vasospasm increase the risk of?
stroke and death
349
What is used as a treatment for vasospasm and is ideally done in those who have had aneurysm clipped?
angioplasty
350
Which medication is used to treat cerebral vasospasm?
Nimodipine
351
What is initiated by the release of oxyhemoglobin and related to free radicals, lipid peroxidation, and endothelin-1?
cerebral vasospasm
352
What is the most consistently effective treatment for cerebral vasospasm?
HHH therapy
Hypervolemia, HTN, hemodilution
353
What is the goal CVP in treating cerebral vasospasm?
10
354
What are the BP goals pre and post aneurysm clipping?
post 160-200 pre 120-150
355
What are the most commonly used vasopressors for HHH therapy in cerebral vasospasm?
Dopamine and phenylephrine
356
What is the goal Hct for HHH therapy for cerebral vasospasm?
27-30%
357
What medication is used to combat large urine output from HHH therapy?
Vasopressin
358
If urine output exceeds 200mL/hr during HHH therapy what is the medication you give and dose?
5 units IM vasopressin
359
In order to keep the HR 80-120 during HHH therapy what medication should you give and dose?
1mg Atropine Q4
360
How long is HHH therapy utilized?
3-7 days
361
What is the best indicator of survival for a SAH?
gross neurological condition preop
362
When is open surgery for SAH preferred?
Day 1-3
363
Patients with what grade of SAH often have procedures delayed to resolve vasospasm and improve preoperative neurologic status?
Grade 3 or worse
364
What are pulmonary complications of SAH?
pneumonia, atelectasis, and pulmonary edema
365
When should preoperative sedation for SAH be given?
in the OR
366
Which evoked potential is used for an anterior circulation SAH?
SSEP (median and posterior tibial nerve)
367
Which evoked potential is used for an posterior circulation SAH?
SSEP and BAEP
368
Correlation between alterations in what two things, with transient electrophysiologic changes corresponding to good outcomes and permanent changes to postoperative deficits
electrical signals and CBF
369
EEG monitoring is used to titrate anesthetics to what to decrease cerebral oxygen requirements during aneurysm clipping?
burst suppression
370
How can we avoid hypertensive responses to laryngoscopy in SAH?
propofol, opioid (5-10 mcg/kg fentanyl or 1-2 mcg/kg sufentanil, and lidocaine
371
What can Succs produce in comatose head injuried patients and SAH?
hyperkalemia
372
After a SAH, how long should hyperventilation be avoided?
24 hours
373
What position will the patient be in for a aneurysm in the anterior part of the circle of Willis?
supine
374
What position will the patient be in for an aneurysm arising from the posterior aspect of the basilar artery?
lateral
375
What position will the patient be in for an aneurysm in the vertebral artery or from lower basilar artery ?
sitting or prone
376
Does intraoperative hypothermia improve the neurologic outcome for patients with good grade SAH?
no
377
BP during cerebral aneurysm surgery should be kept within what percentage of baseline?
40%
378
What medications are most commonly used to induce controlled HoTN during cerebral aneurysm surgery?
NTP or gases
379
How should residual opioid side effects be reversed after cerebral aneurysm surgery?
small doses with Narcan
380
What is postoperative care after aneurysm repair aimed at?
avoid vasospasm
381
What is the MAP goal after aneurysm repair?
80-120
382
Changes in LOC after aneurysm repair are usually signs of what?
vasospasm
383
If a aneurysm ruptures during surgery what is your MAP goal?
40-50
384
How long can carotid arteries be occluded to prevent bleeding in a ruptured cerebral aneurysm?
3 minutes
385
Do Arteriovenous malformations autoregulate blood flow?
No
386
What is characterized by sudden engorgement and swelling of brain with protrusion through cranium?
perfusion pressure breakthrough
387
What is a AVM?
arteries flow directly into veins, no capillaries
388
AVM leads to what symptoms caused by steal?
bleeding, seizures, or ischemia
389
Preventing secondary insults to brain is an anesthetic goal of what?
head trauma
390
What physiologic derangements accompany head trauma?
hypercapnia, hypotension, and elevated ICP
391
What value of ICP leads to irreversible brain edema?
\>60
392
All patients must be assumed to have what until proven otherwise by radiography?
cervical spine instability
393
Which NMB is best avoided in closed head injury?
succ
394
Name the brain hematoma.
.
395
Those with hypoventilation, absence of gag reflex, or GCS less than what require intubation?
8
396
What route of intubation is avoided in basilar skull fractures?
nasal
397
What breathing abnormality is characterized by crescendo-descrendo breathing from pattern followed by apnea, persists in sleep?
Cheyne-stokes
398
What breathing abnormality is characterized by irregular respiratory rate, rhythm and amplitude?
ataxia
399
What breathing abnormality is characterized by prolonged inspiration with a 2-3s pause then expiration?
apneusis
400
What breathing abnormality is characterized by irregular clusters of breaths followed by apnea episodes of variable duration?
cluster breathing
401
What breathing abnormality is characterized by loss of autonomic respiration during sleep?
central neurogenic hypoventilation, Ondines curse
402
What breathing abnormality is characterized by sustained hyperventilation \>40?
central neurogenic hyperventilation
403
Maintaining ICP less than 20, preventing or reversing herniation, minimizing retractor pressure, and facilitating surgical access are important goals of what surgical treatment?
head trauma
404
What are essential monitors for head trauma?
ICP and a-line
405
What is goal CPP when performing fluid resuscitation for head trauma?
CPP \>60
406
How long should hyperventilation be avoided post TBI?
24 hours
407
Which type of fluid is avoided in any patient undergoing neurosurgery?
Fluids with Dextrose
408
Which fluid decreases serum osmolarity can aggravate cerebral swelling?
anything with dextrose
409
Are steroids used in TBI?
no
410
Which type of subdural hematoma occurs slowly over time, usually not detected right away?
chronic SDH
411
chronic NSAID use, heavy alcohol use, anticoagulants, and blood disorders and risk factors for what?
chronic SDH
412
Patients with chronic SDH often have what lab value elevated?
INR
413
What is the preferred agent to reverse Warfarin?
prothrombin concentrate. vitamin K and FFP also reverse it
414
SDH & TBI increase the risk of what due to the release of tissue thrmoboplastin & activation of the complement system?
DIC and ARDS
415
What does Idarucizumab (praxbind) reverse?
dabigatran
416
What does platelet therapy reverse?
ASA and clopidogrel
417
The infratentorial space is contained in which cranial fossa?
posterior
418
Posterior fossa surgery includes things located around what?
cerebellum & brainstem
419
Neuropathology within this fossa can result in impaired airway control, respiratory dysfunction, cardiovascular dysfunction, autonomic dysfunction, and impaired consciousness?
Posterior
420
What is the preferred position for posterior fossa surgeries?
Sitting
421
Increased ICP is ___ common in infratentorial lesions?
less
422
Obstructive hydrocephalus is ___ common in infratentorial lesions?
more
423
Quadriplegia, macroglossia, pneumocephalus, VAE, and PAE are all potential risks of what position?
sitting
424
CSF outflow is typically obstructed where?
Aqueduct of sylvius (cerebral aqueduct) or 4th ventricle
425
What is the treatment of choice for intraoperative VAE during posterior fossa surgery?
mechanical ventilation
426
What nerves are common damaged during posterior cranial fossa surgery?
9, 10, 12
427
Damage to what cranial nerves can result in loss of airway patency and swelling of the brainstem could cause impairment of CN function or respiratory drive?
9, 10, 12
428
A small amount of intercranial neoplasms are found where?
pituitary gland
429
Pituitary gland neoplasms often compress which cranial nerve?
Optic - CN 2
430
What are the most common nonendocrine symptoms of a pituitary neoplasm?
frontotemporal headache and bitemporal hemianopsia (half vision)
431
If a patient has acromegaly do you size up or down the ETT?
size down
432
What hormone causes acromegaly, CAD, HTN, cardiomyopathy, and hyperglycemia?
growth hormone
433
What disease is associated with HTN, DM, osteoporosis, fragile skin/connective tissue and obesity?
Cushing's disease
434
What is the preferred approach for pituitary surgery?
transphenoidal
435
Risk of panhypopituitarism & permanent diabetes insipidus is reduced with this pituitary surgery approach?
transphenoidal
436
What is avoided in pituitary surgery because decreased ICP may result in retraction of the pituitary gland into the sella turcica (access becomes more difficult)?
hyperventilation
437
What arteries lie close to the suprasellar area and can be inadvertently injured in pituitary surgery?
carotids
438
What is Diabetes Incipidus treated with?
\*\*desmopressin (DDAVP)\*\* or vasopressin.
439
During pituitary surgery what is the max of cocaine and epi?
Don’t exceed 200 mg cocaine, or 10 ml of 1:100,000 epi in 10 min in 70kg adult
440
What does cocaine block that leads to HTN and dysrhythmias?
catecholamines
441
Name the respiratory pattern characterized by the waveform.
A. Cheynes Stokes
B. Central Neurogenic Hyerventialtion
C. Apneusis
D. Cluster Breathing
E. Ataxia
442
Label the EEG waves.
