Neurosurgery Flashcards
(98 cards)
1
Q
Brain metabolism (% of O2 consumption)
A
20%
2
Q
What is CMRO2?
A
Cerebral Metabolic Rate of O2 consumption
3
Q
What is the CMRO2 of the average brain?
A
3-3.8mL/100g/min or 50mL/min
4
Q
Where is the the CMRO2 the highest and why
A
Grey matter because the myelin sheath is present
5
Q
Why is the brain so sensitive to hypoxia?
A
No O2 reserves
6
Q
What is CBF?
A
Cerebral blood flow
7
Q
What is the average CBF?
A
15-20% of CO
8
Q
Circle of Willis Anatomy
A
9
Q
What is CPP?
A
Cerebral Perfusion Pressure
10
Q
CPP formula?
A
CPP=MAP-ICP or CVP
Whichever is greater
11
Q
Normal CPP pressure?
A
80-100mmHG
12
Q
What CPP value shows slowing on an EEG?
A
< 50mmHG
13
Q
Autoregulation for the brain?
A
60-160mmHg
14
Q
Relationship with MAP / PaO2 / PaCO2
A
15
Q
Average PaC02 for the brain?
A
20-80mmHG
16
Q
Why doesn’t metabolic acidosis affect CBF?
A
Ions do not cross the BBB but CO2 does
17
Q
A reduction in temp does what two things in the brain?
A
Reduces CBF and CMRO2
18
Q
A decrease in 10°C is a what reduction in CMRO2?
A
50%
19
Q
An increase in 10°C is a what rise in CMRO2?
A
Double the CMRO2
20
Q
Why is blood viscous?
A
The hematocrit
21
Q
An increase in blood viscocity does what?
A
Reduces blood flow
22
Q
What do tight junctions regulate?
A
Size
Charge
Lipid solubility
Protein binding
H2O moves freely throught tight junctions
23
Q
What disrupts tight junctions selectivity?
SHITTSS
A
Severe HTN
Hypercapnia/Hypoxia
Infection
Tumors
Trauma
Stroke
Sustained seizures
24
Q
What is CSF
A
Cerebrospinal Fluid
25
How much CSF is made per day?
500mL
26
Total volume of CSF?
150mL
27
Why do we make more CSF than the total volume?
It is constantly being reabsorbed in the arachnid layer
28
Where is CSF made?
Choroid Plexus
ependymal cells in ventricles
29
The skull is a fixed volume, what are some mechanism to help with increased pressure?
## footnote
4 things
Displacment of CSF into spinal column
Increase in CSF absorption
Decrease in CSF production
Decrease in cerebral blood volume
30
What is considered a significant midline shift?
>0.5cm
31
What is luxury perfusion?
A decrease in CMRO2 and increase in CBF
32
What is circulatory steal phenonmenon?
When there is vasodilation and ischemic areas, blood is shunted or "stolen" away from the narrowed vessels to the dilated ones
33
How can we protect the brain from furthter deline during periods of less O2 delivery?
## Footnote
6 things HAAAAN
* Hypothermia
* Anesthetics
* Adequate CPP
* Avoid hypotension
* Avoid blood sugars of 180mg/dl and above
* Nimodipine (prevents spasms)
34
Neuromonitoring Types: Blood Flow
## Footnote
CIT-JIT
* **Cerebral Oximetry**
* IV Tracer Flow
* Transcranial doppler ultrasound
* Jugular bulb venous O2 saturation
* Invasive tissue blood flow
* Tissue partial pressure of O2
## Footnote
Bold most common and the only one Adam has seen
35
Neuromonitoring Types: Nerve Function
* EEG (Electroencephalogram)
* EP (Evoked Potentials)
36
Different kind of EP's?
1. Sensory (SEPs)
2. Motor (MEPs)
3. Electromyograph (EMG)
37
Different kind of SEPs?
1. Somatosensory Evoked Potentials (SSEPs)
2. Brainstem Auditory Evoked Potentials (BAEPs)
3. Visual Evoked Potentials (VEPs)
38
Different kind of MEPs?
1. Transcranial Motor Evoked Potentials
2. Spinal Motor Evoked Potentials
39
Most common cranial vessel to be involved in an acute stroke?
Middle cerebral artery (MCA)
## Footnote
neuromonitoring done by the transcranial doppler
40
What is the EEG
Electroencephalogram: summation of excitatory and inhibitory postsynaptic potentials of the cerebral cortex
41
Brain Waves: Gamma
## Footnote
IPE
Insight
Peak focus
Expanded consciousness
42
Brain Waves: Beta
## Footnote
ACC
Alertness
Concentration
Cognition
43
Brain Waves: Alpha
## Footnote
CRV
Creativity
Relaxation
Visualization
44
Brain Waves: Theta
## Footnote
MIM
Meditation
Intution
Memory
45
Brain Waves: Delta
## Footnote
DH
Detached awareness
Healing Sleep
46
Why do we care about brain waves in surgery?
* Helps identify inadequate BF
* Guides us reducing cerebral metabolism
* Predictor of neurological outcome
* BIS monitor
47
When it comes to brain waves and ischemia, what are we looking for?
Slowing frequency with preserved amplitude
## Footnote
Height is the same, wave form lengthens
48
What is BIS and what are the two types?
Bispectral Analysis
1. 2 Channel
2. 4 Channel
## Footnote
4 Channel can monitor left and right brain differences
49
BIS Monitor numbers scale
* 100 = Completely awake
* 60-80 = MAC / Sedation
* 40-60 = GA
* 0 = Isoelectric
50
Evoked potentials look for what in a stimulus?
Amplitude: Tall and potent
Latency: Short and fast
51
Can we paralyze if using MEPs?
No, sensory types only
52
Basic rule about anesthetc drugs and evoked potentials
Increased latency and decreased amplitude
53
5 Generalities of anesthetic drugs on evoked potentials
1. IV agents have significantly less effect that equal potent doses of inhalation agents
2. Combination of drug effects are additive
3. Subcortical SEPs are very resistant to the effects of anesthetic agents
4. MEPs are very sensitive to inhaled agents
5. Des has stronger inhibitor effects than Sevo at high doses
54
Types of spine surgeries
## footnote
RSSF-DVT
* Radiculopathy: compression on nerve root
* Spondylosis: wear on bone or cartlidge
* Scoliosis: congenital defect
* Fusions
* Decompression
* Vascular malformations
* Tumor resection
55
Spine surgery pre-op
Always evaluate neurological defecits
Neuromonitoring?
Airway issues? (C-Spine collar?)
multi-modal analgesia
56
Spinal surgery positioning
Usually prone arms out like superman
Difficult line access after positioned
POVL (Perioperative Vision Loss)
Hypotension due to abdominal compression
Facial edema
57
What is POVL
Perioperative Vision Loss
58
What is OIH
Opioid Induced Hyperalgesia
Hyper increase of pain sensation by short acting opiods
## Footnote
Opiods cause an increase in pain
59
Adams Neuromonitoring regiment for spine cases
PO Hydrocodone preop
Propofol infusion
low dose narcotic infusion
ketamine infusion
0.5 gas MAC
60
Neurogenic shock
Low blood pressure, bradycardia, and hypothermia due to disruption of the sympathetic nervous system with preserved parasympathetic activity.
## Footnote
Trauma to T6 and above
61
Neurogenic Shock Pathway
Spinal cord injury above T6
**Decreased sympathetic output** = vasodilation = decreased preload = decreased stroke volume -=decreased CO
**Unopposed parasympathetic output** = bradycardia = decreased CO
both add up to profound hypotension
## Footnote
treat with volume, then Levophed
62
AH and AD (same thing):
Autonomic Hyperreflexia / Dysreflexia
Usually injury to T6 or above
Sympathetic stimulaiton below injury causes increased BP
Above injury baroreceptors decrease HR
Causes high aferload: LV failure, Pulmonary edema, and arryhtmias
## Footnote
reduce affernent stimulus, treat with narcs, vaso dilators or propofol
63
Brain masses or lesions: Supratentorial
| Presentations
## Footnote
Supratentorial = Cerebrum or all the lobes
Increase seizure activity
hemiplegia (weakness or loss of fuction on one side)
Aphasia (inability to understand language or articulate thoughts to language)
64
Brain masses or lesions: Infratentorial
| Presentations
## Footnote
Infratentorial = Cerebellum and brainstem
Cerebellar:
Ataxia (lack of voluntary coordination of muscle movements)
Nystagmus (involuntary eye movements)
Dysarthria (muscle dysfunction in the lips, tongue and other speech muscles making it hard to pronounce words)
Brainstem:
Basic human funtion abnormalities (respiratory, conciousness, cranial nerve sensations)
65
Brain mass or lesion pre-op
ICP?
Neurological assesments
What meds? (steroids, diuretics, anticonvulsants)
Check sodium levels and glucose levels
Avoid pre-op medication, can cause issues post-op for assesments
66
Brain mass or lesion intra-op
ASA Monitors
Foley (diuretic for relaxed brain)
±Neuromonitoring
A-Line
±Central line
EVD (external ventricular drain)
67
What is an EVD and what does it monitor?
External Ventricular Drain
Monitors CSF pressure and allows acces to test and drain CSF
## Footnote
Draining CSF reduces pressure
68
Induction for brain masses
Extra propofol
phenylephrine
esmolol
Avoid succs if not a difficult airway (succs can potentially increase ICP)
69
Crani positioning
Variable but usually in mayfields (aka pinning)
70
When a patient is in mayfields (aka pinned) what do we need to make sure they do not do and how?
Do not let them cough, they can die
Propofol and esmolol at the ready
71
Crani maintenance
Paralyze if you can
limit fluids
avoid hyperglycemia
normocarbia
normotensive
72
**Hypertension** in a crani does what?
Increased brain mass and EBL
73
**Hypotension** in a crani does what?
greater chance of ischemia
74
**Hypercarbia** in a crani does what?
Increase CBF
75
**Hypocarbia** in a crani does what?
Decrease CBF
76
How does an increase/decrease of CBF affect ICP?
Increse/decrease ICP respectivly
77
Hyperventilation will only transceintly decrease CBF and ICP beauce of the bicarb buffering system. How long does this take?
6-8 hours
78
Relaxing the brain can cause what that makes the surgeon annoyed?
Changes in the imgaing when using naviagation
79
Crani emergence
Avoid coughing
rapid wakeup (no precedex, they are slow to emerge) for neuro assesment
Pain should not be too bad, dont over narc
Off to ICU after
80
Brainstem masses disrupt what
breathing
conciousness
BP/HR
Sleep
81
Cheyne-Stokes Respiration?
82
Biot Respiration
83
10 steps to an awake Crani mass
1. ASA Monitors, facemask c̅ O2
2. Sedation
3. Scalp Block by doc (propofol before he starts helps)
4. Pins placed
5. Positioned then woken up
6. Asked about comfort
7. Sedation again, surgery starts
8. Woken up for neural mapping (put back to sleep when done)
9. Mass removed
10. Sedated until emergence
84
Crani mass tidbits
Avoid benzos, slow wakeup
short acting agents
educate patients
lots of local used
Dura manipulations most painful
communication with doc
85
Unruptured aneurysms can be treated what two ways
1. Coiling
2. Clipping
86
Unruptured Aneurysm Pre-op
* Neuro assesment
* Type and Cross
* 4 units PRBC and 4 FFP in room and ready
* Avoid benzos if any altered mental status (othweise beneficial)
87
Unruptured Aneurysm Intra-Op
* Large bore IV
* A-Line
* Central Line
88
Unruptured Aneurysm Induction
Gentle
MAP strict control 60-60 mmHg
ETCO2: 35 mmHg
Propofol
Esmolol
Phenylephrine
Cardene
Labetalol
89
Unruptured Aneurysm Maintenance
Neuromonitoring
possible lumbar drain
if clipping cool patient to 34-35 °C
90
Temporary Clipping
Burst supression just prior to it
Then increase MAP to 90-100 mmHg to test it
After clip removed bring MAP back to 60-80 mmHg
91
Final Clipping
ICG dye to make sure its working
MAP goals of 70-90 mmHg
92
ICG Dye concentration and dosing
25mg in 10mL of normal saline
(2.5mg/1mL)
Dosing is 5mL with rapid saline flush(20mL)
93
Unrupture Aneurysm Emergence
No coughing
Pressors and dilators in line to control BP
Neuro assesment before xfer to ICU
94
Intra-op Aneurysm Rupture
Doc lets room know it busted
Immediate MAP of 40-50
If surgical intervention fails then:
Propofol for decreased CBF
Adenoside (6,12,18 mg)
Xfusion of PRBC
95
Ruptured Aneurysm brought in
Lare bore IV
PRBC stat
Art Line
Brain relaxation (Decadron, Mannitol, Lasix, Hyperventilate)
Keppra
96
What is Keppra
Anticonvolusant
97
What is AVM
Ateriovenous Malformation
98
AVM basic info
Differnet types of abnormalities, may increase or decrease bleeding risk depending on flow rate
Treat similar to unruptured aneurysm
Higher flow rare = higher bleeding risk / surgical risk
