Neurosurgery Flashcards
(170 cards)
1
Q
Percent of brain volume?
A
80%
2
Q
Percent of blood volume in head?
A
12%
3
Q
Percent of CSF?
A
8%
4
Q
Normal ICP:
A
15mmHg or less
5
Q
Adult brain weighs how much?
A
1400g
6
Q
Adult brain is how much of total body weight?
A
2%
7
Q
What is the oxygen consumption of the brain?
A
3.3ml/100g/min
50ml/min total
8
Q
Oxygen consumption is how much of the total body consumption?
A
20%
9
Q
Normal cerebral BF and what percent of CO?
A
50ml/100g/min
15%
10
Q
Cerebral perfusion pressure is dependent on what?
A
Pressure gradient between arteries and veins (difference between MAP and the mean cerebral venous pressure)
11
Q
Normal CPP and equation?
A
~80mmHg
MAP-(ICP or CVP, whichever is GREATER)
12
Q
7 things that cerebral BF depend on?
A
- Those affecting cerebral perfusion pressure
- Those affecting the radius of cerebral blood vessels
- PaCO2
- PaO2
- Anesthetic agents
- Temp
- Cerebral metabolic rate for O2 (CMRO2)
13
Q
CBF is proportional to what?
A
CMRO2
14
Q
CBF and CMRO relationship is unaffected and affected by what?
A
Unaffected: IV agents
Affected: uncoupled by inhalation agents
15
Q
Cerebral steal (luxury perfusion): nonischemic and ischemic brain BF and vessel diameter
A
Nonischemic brain: increase BF and vessel diameter
Ischemic brain: decrease and no change to vessel diameter
16
Q
Inverse steal (Robin Hood, reverse steal): nonischemic and ischemic brain BF and vessel diameter
A
Nonischemic brain: decrease BF and vessel diameter
Ischemic brain: increase BF and no change in vessel diameter
17
Q
1mmHg change in PaCO2 produces what change in CBF and time frame?
A
1ml/100g/min
6-8hrs
18
Q
PaCO2 from 40 to 35 reduces CBF by what?
A
5ml/100g/min or 70ml/min
19
Q
For normal ICP, CBF maintain low; what should PaCO2 be?
A
30-35mmHg
20
Q
How to lower PaCO2?
A
Hyperventilate
21
Q
CBF decreased by how much if PaCO2 is 20mmHg?
A
50%
22
Q
PaO2 of what causes significant increase in BF?
A
<50mmHg
23
Q
Changes in CBF and metabolism tend to what?
A
Follow each other
24
Q
Local/global increases in metabolic demand are met rapid by what in CBF and substrate delivery?
A
Increase
25
7 vasoactive metabolic mediators thought to control:
1. Hydrogen ions
2. Potassium
3. CO2
4. Adenosine
5. Glycolytic intermediates
6. Phospholipid metabolites
7. Nitric oxide (NO)
26
Cerebral metabolism can be decreased by (2)
1. Hypopyrexia
| 2. Some anesthetic agents
27
Cerebral metabolism can be increased by (2)
1. Hyperpyrexia
| 2. Seizures
28
CBF changes how much per 1 degree change?
5-7%
29
Hypothermia does what (2)
Decreases CMR and CBF
30
At 27 degrees C, CBF is approximately what?
50% of normal
31
At 20 degrees C, CBF is about what?
10% of normal
32
Auto regulation keeps CBF relatively constant as long as CPP is between what?
50-150mmHg
33
Lower limit of auto regulation causes (3)
1. Cerebral vasodilation is maxed
2. Below this level the vessels collapse
3. CBF falls passively with falls in MAP
34
Upper limit of auto regulation causes (4)
1. Vasoconstriction is maxed
2. Elevated intraluminal pressure force vessels to dilate
3. Elevated intraluminal pressure leading to increase in CBF
4. Elevated intraluminal pressure DAMAGE blood-brain-barrier
35
Auto regulation impaired by (6)
1. Brain tumor
2. Subarachnoid hemorrhage
3. Stroke
4. Head injury
5. Damage of control system (cerebral vessels)
6. Damage to the feedback mechanism involved in brain’s hemodynamic control (impaired CBF become pressure dependent)
36
Does inhalation anesthetics impair auto regulation?
NO
37
Increased radius (vasodilation) causes (4)
1. Increase in cerebral BF
2. Increase ICP
3. Reduce CPP
4. Balance must be reached
38
Balance is maintained by 4 primary factors:
1. Cerebral metabolism
2. CO2
3. O2
4. Auto regulation
39
Sympathetic nerves to radius of cerebral blood vessels:
Vasoconstriction protects the brain by shifting the auto regulation curve to the right in HTN
40
Parasympathetic nerves to radius of cerebral blood vessels:
Contribute to vasodilation and may play a part in hypotension and reperfusion injury
41
7 signs of increased ICP:
1. N/V
2. Personality change
3. Altered level of consciousness
4. Altered pattern of breathing
5. Papilledema
6. Seizures, abductees nerve or Abdul ent
7. Cushing’s triad
42
What is cushing’s triad?
1. Increased systolic BP
2. Widened pulse pressure
3. Bradycardia
43
Breathing is rapid for a period and then absent for a period
Kussmaul, Cheyne-stokes/biot’s respiration
44
Patients with normal BP retain normal alertness with ICP of what? (Unless tissue shifts at the same time)
25-40 mmHg
45
Only when ICP exceeds to what do CPP and cerebral perfusion decrease to a level that results in loss of consciousness and further elevations will lead to brain infraction and brain death?
40-50 mmHg
46
What part of infants heads bulge when ICP gets too high?
Fontanels (soft spot)
47
What predominantly affects obese women of childbearing age and has an unknown etiology?
Idiopathic intracranial HTN (IIH)
48
What deals with most important neurological manifestation is papilledema and may lead to secondary progressive optic atrophy, visual loss, and possible blindness?
Idiopathic intracranial HTN (IIH)
49
3 consequences of raised ICP?
1. Cerebral ischemia due to reduction of cerebral perfusion pressure
2. Brain shifts
3. Brain herniation
50
Diplopia (double vision) with increased ICP and papilledema is usually what and rarely what?
```
Usually horizontal (due to nonlocalizing 6th nerve palsy)
Rarely vertical
```
51
Lowering ICP first tier treatment steps (8)
1. General physiologic homeostasis
2. Head of bed elevation 30 degrees
3. Analgesia and sedation
4. NMB
5. CSF drainage
6. Hyperventilate
7. Osmotic diuretics
8. Steroids (dexamethasone)
52
What 3 drugs are used for sedation?
1. Propofol
2. Etomidate
3. Midazolam
53
What 2 drugs are used for analgesia and antitussive effect?
1. Morphine
| 2. Alfentanil
54
Hyperventilate historically to what but new update says what?
Used to: 25-30
| New to: no lower than 35
55
What happens if you hyperventilate to <20mmHg?
Vasoconstriction and risk of cerebral ischemia
56
PaCO2 form 40 to 15… CBF reduced by what?
25ml/100g/min or 50% reduction
57
Osmotic diuretics drug to lower ICP?
Mannitol blouses at .25-1g/kg or continuous infusion
58
How does steroid lower ICP?
Decreases the amount and duration of plateau waves
59
Lowering ICP 2nd tier treatment steps (3)
1. Barbiturate coma
2. Hypothermia
3. Decompressive craniectomy
60
What 3 drugs can be used for barbiturate coma?
1. Pentobarbital
2. Pentothal
3. Propofol
61
Barbiturate coma infusion dose rate of barbiturates is increased under monitoring by electroencephalograph until what?
Burst suppression or cortical electrical silence (isoelectric “flatline”) is attained
62
Cooling to what can be effective in lowering refractory intracranial HTN but is associated with a relatively high rate of complications including pulmonary, infectious, coagulation, and electrolyte problems?
34 degrees Celsius
63
When performing a barbiturate coma, what monitor should be used and what should it read?
BIS and 40-50
64
12 goals for ideal neuro anesthetic agents:
1. Rapid onset and rapid offset
2. Maintains hemodynamic stability
3. Does not increase CBF
4. Does not alter CSF production or reabsorption
5. Decrease ICP
6. Maintains CO2 reactivity
7. Maintains cerebral auto regulation
8. Allows EEG/EP monitoring
9. Does not increase cerebral metabolic rate
10. Anticonvulsant
11. Decrease edema
12. “Protects” the brain
65
4 best agents for neuroanesthetic?
1. Propofol
2. Des
3. Sevo
4. Remifentanil
66
What is special about remifentanil?
Reduces MAC by up to 50%
67
All IV drugs except what decreases CBF and CMRO2?
Ketamine
68
- decreases CMRO2, CBF, and ICP, MAP, CPP
- cerebral autoregulation and vascular response to CO2 remain unaltered
- prevention of large increases in BG
- anti-oxidative effects
Propofol
69
- decrease CMRO2, CBF, ICP
| - increase EEF activity
Etomidate
70
- increases CMRO2 and CBF
| - anti-oxidative effects
Ketamine
71
How does opioids affect the brain?
Increase PaCO2=increase CBF and ICP
| -depress LoC
72
What does lidocaine do to brain?
Decrease CBF
73
- potent cerebral vasoconstrictor
- decreases CMRO2, CBF, ICP
- produce reverse steal or Robin Hood syndrome
- facilitate absorption of CSF
Thiopental
74
What kind of correlation is there between CBF and CMRO2 when using propofol?
Strong linear
75
What does N2O do to CBF and CMRO2?
Increase
76
Cerebral vasodilation can be countered by what?
Hyperventilation
77
- 40-60 years of age
- s/s reflecting increasing ICP
- adult onset seizure disorder
- confirmed with CT or MRI
Intracranial tumors
78
Positioning for suprtentorial tumor?
Supine
79
Positioning for infratentorial tumor?
Prone or sitting
80
Why should you beware with sitting position for brain tumors?
Increases risk of venous air embolism
81
Tissue is benign
Grade 1
82
Tissue is malignant
Grade 2
83
Anaplastic-malignant cells are actively growing
Grade 3
84
Malignant cells look most abnormal, tend to grow quickly
Grade 4
85
Tumor arises from star-shaped glial cells called astrocytes. Can be any grade. In adults, most often arises in the cerebrum/
Astrocytoma
86
Tumor arises in meninges. Can be grade 1,2 or 3. Usually benign (grade 1) and grows slowly.
Meningioma
87
Tumor arises from cells that make the fatty substance that covers and protects nerves. Usually occurs in the cerebrum. Most common in middle-aged adults. Can be grade 2 or 3.
Oligodendroglioma
88
Usually arises in cerebellum. Sometimes called primitive neuroectodermal tumor. Grade 4.
Medulloblastoma
89
Low-grade tumor occurs anywhere in brain.
Grade 1 or 2 astrocytoma
90
Most common astrocytoma among children is what?
Juvenile pilocytic astrocytoma (grade 1)
91
Arises from cells that line the ventricles or the central canal of the spinal cord. Most commonly found in children and young adults. Can be grade 1, 2 or 3.
Ependymoma
92
Occurs in the lowest part of the brain. Can be low grade or high grade.
Brainstem glioma
93
4 diagnostic studies for raised ICP:
1. Skull radiography- beaten silver or lacunar skull
2. Angiography- slowing circulation
3. CT scan-edema
4. ICP monitoring
94
Maintenance of what IV fluid for fluid and electrolyte balance?
Mild hyperosmolality (NS or LR)
95
No glucose for how long when considering fluid and electrolyte balance?
First 4 hrs
96
Do you ignore 3rd space and NPO for neurosurgery?
YES
97
Adults and peds maintain how much deficit?
Adults: maintain 500-1000cc
Peds: 0
98
What is the most common hypertonic solution used to provide relaxed brain at surgery?
Mannitol
99
How does mannitol relax the brain?
By cerebral dehydration and decreasing the ICP
100
What are the 3 adverse effects of mannitol?
1. Adverse dehydration, hyponatremia, hypokalemia, renal failure
2. Transient increase in ICP before diuresis
3. Exaggeration of brain shifts with unilateral lesions
101
What is the dosage of mannitol?
.25-2g/kg bolus and administer bolus over 15-20 min before opening the dura
102
What are the 4 goals for cerebral tumors?
1. Reducing the brain bulk
2. Providing easy access to the surgical lesion
3. Monitor urine output, serum osmolality and electrolytes
4. Carefully monitor IV volume
103
Sitting position has what 2 most common threatening complications?
1. Venous air-embolism
| 2. Severe hypotension
104
Acute flex ion of the neck may cause (3)
1. Airway obstruction
2. Obstruction to cerebral venous outflow
3. Intraop brain swelling
105
Elevation of the head above the heart risk what 2 things?
1. Cerebral venous drainage
| 2. Venous air embolism from open veins
106
What are the 4 premed risk:
1. Depression of consciousness
2. Airway obstruction
3. Hypoxia and hypercapnia
4. Increased ICP
107
Pts without evidence of raised ICP may be given what to allay anxiety?
Small doses of benzodiazepines
108
4 things to limit stimulation during induction and intubation:
1. Liberal doses of thiopental or propofol combined with narcotics
2. Mild to moderate hyperventilation with mask before intubation
3. IV lidocaine bolus
4. To help prevent dangerous increases in ICP, AVOID nitrous oxide and inhalational anesthetics
109
Does TIVA provide bette operating conditions than inhalational anesthesia?
Maybe
110
5 definitive measures used for decreasing brain bulk:
1. Hyperventilation
2. Mannitol
3. Continuous infusion of IV anesthetic agents
4. CSF diversion through ventriculostomy catheter
5. Moderate hypothermia (extreme cases only)
111
What 3 things increase the chances of postop hematoma and edema?
HTN, coughing, and asynchrony
112
Does the pt need to be fully awake at the time of extubation?
Yes so the neurological exam can be performed
113
Benefits of delayed extubation (3):
1. Reduced risk of hypoxemia
2. Better respiratory and hemodynamic control
3. Lower incidence of postop hematoma formation
114
4 things that warrant delaying extubation:
1. Obtunded consciousness and inadequate airway
2. Intraop brain swelling
3. Hemostasis problems during surgery
4. Major postop hemostatic disturbances
115
Blood flow to ischemic region of brain is dependent upon what?
CPP
116
Bleed between the arachnoid membrane and pia mater
Subarachnoid hemorrhage
117
Subarachnoid hemorrhage is most caused by what?
Ruptured aneurysm then trauma, hemorrhagic tumors
118
HHH stands for?
Hypervolemia, HTN, and hemodilution
119
2 things that come with HHH?
1. Reduce HCT and lower viscosity (HCT 27-30)
| 2. Increases CPP
120
CPP goal for intracranial aneurysm?
>70 mmHg
121
5 additional monitors for intracranial aneurysm:
1. 2 large bore IV catheters
2. A line
3. ICP monitor
4. Foley
5. CVP catheter
122
Induction of anesthesia for intracranial aneurysms (5)
1. Propofol or etomidate
2. Muscle relaxant (avoid sux becuase raises ICP)
3. More Propofol, opioids &/or lidocaine 1-2 min prior to DL
4. Ventilate to PaCO2 25-30
5. NO PEEP bc increase ICP
123
What do you avoid in patients with elevated ICP before the dura is opened?
Vasodilators (nitroprusside, nitroglycerine)
124
4 ways to handle cerebral swelling:
1. Mannitol (.25-1g/kg)
2. Furosemide (.5-1mg/kg)
3. Propofol/thiopental
4. Head up position (30degrees)
125
What to do for aneurysm clipping:
Facilitate exposure (shrink brain) and reduce transmural pressure in the aneurysm prior to clipping
126
Temporary clipping of the feeding vessel will require what?
Normal to increase BP to maintain collateral flow
127
IV fluids for intracranial aneurysm (4)
1. Restrict 1-3ml/kg/hr
2. Glucose NOT recommended (may increase cerebral edema and hyperglycemia worsens cellular ischemic injury)
3. Isotonic crystalloids
4. Colloids are controversial
128
Avoid N2O during emergence why?
May cause tension pneumocephalus
129
If delayed return to consciousness or neurological deterioration then what test should be completed?
CT or MRI
130
2 cautions to get venous air embolism:
1. Head >5cm above heart
| 2. Transecting veins in cut edge of bone or dura and may not collapse
131
8 detections for venous air embolism (VAE):
1. Per ordinal Doppler near R upper sternal
2. Trans-esophageal
3. Increase in ET nitrogen
4. Sudden decrease in EtCO2
5. PaCO2 decrease
6. CVP
7. ECG/esophageal stethoscope
8. Gasping, hypotension, dysrhythmias, cyanosis, chest pain (awake)
132
8 treatment options for venous air embolism:
1. Irrigate operative site with fluid
2. Apply occlusive material to bone edges
3. Gently compress internal jugular veins
4. Head down position
5. Aspirate air through RA catheter
6. Discontinue N2O
7. Inotropes may be needed
8. CPR
133
Depression is what?
TCA’s (tricyclic antidepressants)
134
Depression has exaggerated response to what?
Stimulation and indirect acting vasopressors
135
What 4 things to avoid in pts with depression:
1. Pancuronium
2. Demerol (meperidine)
3. Ketamine
4. Epinephrine
136
- results in temporary loss or depression of all or most spinal reflex activity below the level of injury
- hypotension due to loss of sympathetic tone
Spinal shock
137
Spinal cord reflex arcs immediately where?
Above the level or injury may be severely depressed
138
Phase 1
0-1day
Areflexia/hyporeflexia
Loss of descending facilitation
139
Phase 2
1-3days
Initial reflex return
Denervation supersensitivity
140
Phase 3
1-4weeks
Hyperreflexia (initial)
Axon-supported synapse growth
141
Phase 4
1-12months
Hyperreflexia, spasticity
Soma-supported synapse growth
142
Cercival lesions have total loss of what and resolve in what time frame?
```
Sympathetic innervation (Vasovagal hypertension and Brady)
3-6 weeks
```
143
What happens if acute spinal injury above T6?
Autonomic dysreflexia may occur and parasympathetic is preserved
-synergy between sympathetic and parasympathetic system is LOST
144
What happens below T6 or T7 acute spine injury?
Sacral parasympathetic loss
145
Innveration to the heart
T1-4
146
How long can spinal shock last?
1-3 weeks or longer
147
If vasopressors don’t work for acute c-spine injuries, what should be used?
High dose corticosteroids
148
Inability to regulate core body temp (cold blooded)
Poikilothermic
149
Can pts sweat below level or injury with complete spinal cord injuries?
NO
150
For chronic spine injury, what does suctioning causes?
Bradycardia
151
What is permanent for chronic spine injury?
Autonomic dysreflexia; occurs form phase 4 and onwards
| Remember cyto’s
152
What puts chronic spine injury pts at greater risk (2)?
1. Duration of surgery
| 2. Operations greater than 4 cervical levels or involving C2
153
Pts with neurogenic bladder dysfunction as a result of spinal cord injury can lead to what bladder functions (5)?
1. UTI
2. Stone disease
3. Bladder cancer
4. Autonomic dysreflexia
5. Renal dysfunction
154
Is a standard x-ray reliable for an acute c spine injury?
NO
155
Airway control with sux:
NO sux for 24hrs - 6months and risk of hyperkalemia
156
Autonomic hyperreflexia may include (5):
1. Change in HR (bradycardia)
2. Excessive sweating
3. HTN
4. Muscle spasms
5. Skin color changes (pale, red, blue-gray)
157
Pts with lesions above where have AH?
T6
158
AH is confused with what 4 other things?
Thyroid storm, carcinoid syndrome, serotonin syndrome, MH
159
2 prevention of AH?
Spinal anesthesia MOST EFFECTIVE (epidural not as good)
| Deep general
160
2 treatments for AH?
1. Arterial vasodilators (nitroprusside)
| 2. Vasodilators (hydralazine)
161
Other 2 considerations for AH?
1. AVOID sux 24 hours after injury until 6months
| 2. Temp monitoring with lesion above T1
162
Flexed prone positions causes what 6 things:
1. Excessive compression to IVC (decrease preload)
2. Restriction of diaphragm (increase PIP)
3. Brachial plexus may be stretched
4. Ulnar nerve not properly padded
5. Eye damage from pressure
6. Nose pressure
163
What table is used for prone position, maintains flexed position, and intrabdominal pressure may be increased if supporting pads are not properly placed?
Wilson frame
164
Table for prone position, frame based table, allows abdomen and chest to hang freely, and may allow 180degree rotation?
Jackson table
165
POVL (postop visual loss) related to spine surgery in what position?
Prone
166
6 postop vision loss risk factors:
1. Atherosclerotic disease
2. Hypotension
3. Anemia
4. Excessive blood loss (>1000ml)
5. Long duration of surgery (>6hrs)
6. Head dependent positioning
167
What does venous air embolus respond to normally if not massive?
Fluid therapy
168
Up to how much air can stop lungs?
1cc/kg
169
How much air in the cerebral circulation can be fetal?
2ml
170
How much air into a coronary artery can cause cardiac arrest?
.5ml
