Neurologic Complications- Exam 2 Flashcards
1
Q
How many cardiac surgical procedures are carried out worldwide?
A
1.4 million
2
Q
Overt stroke occurs in what percent of all patients?
A
1-5%
3
Q
Neurologic dysfunction may be present in what percent of patients?
A
25-80%
4
Q
What is the annual cost for treating neurologic dysfunction patients?
A
Exceeds $2 billion/ year
5
Q
What are neurologic deficits in adults?
A
Psychomotor speed attention concentration new learning ability short term memory
6
Q
What are some neurologic deficits in pediatrics?
A
Seizures, movement disorders, developmental delays
7
Q
TIA: Broad or localized?
A
Localized
8
Q
TIA: Describe onset and recovery.
A
Rapid onset and recovery (minutes to hours)
9
Q
TIA: What does severity depend on?
A
Collateral flow
10
Q
RIND
A
Reversible Ischemic Neurologic Deficit
11
Q
What is reversible ischemic neurologic deficit?
A
Similar to TIA but lasts longer (24-72 hours)
12
Q
Lacunar Brain Infarct
A
Stroke; specific focal deficit from cerebral artery occlusion
Much more severe, often doesn’t resolve
Hemiparesis/aphasia/sensory
13
Q
Global Ischemia results from what?
A
Long periods of hypoperfusion or massive embolic load; poor recovery
14
Q
What percent of global ischemia patients are brain dead and never wake?
A
> 50% are brain dead and never wake
15
Q
What are the 4 classifications of neurologic deficit?
A
- TIA
- RIND
- Lacunar Brain Infarct (Stroke)
- Global Ischemia
16
Q
What patients experience more serious neurologic morbidity than age, and health matched controls undergoing non-cardiac surgery?
A
Cardiac patients
17
Q
What are some risk factors for neurologic injury?
A
Advanced Age Athersclerosis Hx of previous neurologic incident Intracardiac operation Hypertension and diabetes carotid stenosis
PVD Alcohol Abuse IABP MI Prolonged HTN Arrhythmias CHF Gender Decreased Cardiac Output
18
Q
What incidence of stroke in < 45 y/o?
A
~0.2 % incidence of stroke
19
Q
What incidence of stroke in <60 y/o?
A
1 % incidence of stroke
20
Q
What incidence of stroke in 60-70 y/o?
A
3.0% incidence of stroke
21
Q
What incidence of stroke in >75 y/o?
A
8.0 % incidence of stroke
22
Q
Avg age at MGH in 1980?
A
56
23
Q
Avg age at MGH in 1994?
A
67
24
Q
What percent of patients with stroke show multiple infarcts? How many zones?
A
75%, 6 zones
25
What percent of stroke in patients with normal aorta?
5%
26
What percent of stroke with large intraluminal plaques?
45%
27
What are embolic events related to?
Aortic plaques
Platelet-fibrin and leukocyte aggregates
Bubbles from CPB circuit
28
What is atherosclerosis/thromboembolic debris often associated with?
Specific surgical events
29
At what point during surgery are the highest instances of embolic events?
Highest: Short filling of beating heart
2nd highest: filling again
Highest: Release of cross clamp
Another high pt: release of partial occlusion clamps
30
What percent of cardiac patients have a history of TIA/stroke?
13%
31
How many times greater risk of new deficit or exacerbation of previous deficit?
3x greater
32
What intracardiac operations are risk factors for neurologic injury and air emboli? What is the risk? How does it compare to CABG alone?
Valves, ASD/VSD/ Myxomas
5-13% risk
2x higher than CABG alone
33
What percent of cardiac surgical patients have hypertension?
55% of all cardiac surgery patients
34
What percent of cardiac surgical patients have diabetes?
25% of all cardiac surgery patients
35
HTN and DM may be due to what?
Changes in cerebral autoregulation; narrows arteries penetrating the brain, decrease in collateral blood flow, decrease ischemic tolerance
36
What percent of cardiac surgery patients have greater than 50% carotid stenosis?
15%
37
What percent stroke rate in asymptomatic patients with carotid disease?
9.2%
38
What percent stroke rate in patients with no carotid disease?
1.3%
39
What percent stroke rate with >75% carotid stenosis?
14%
40
___ of 19 patients with >75% carotid stenosis before carotid endarterectomy had strokes.
0
41
What is the carotid stenosis mechanism?
Unclear, whether embolic of decrease in flow, but >50% of strokes occur in immediate postoperative period
42
How many studies prove higher CPB MAP is beneficial?
None
43
CMRO2
Cerebral Metabolic Requirement of Oxygen
44
What is hte normal CMRO2?
40-50 ml O2/min
45
What is the normal index of CMRO2?
3.0-3.5 ml O2/ 100 g/ min
46
Normal CBF
750 ml /min
47
What is the index of CBF? What percent of CO?
50-60 ml/100g/min (about 15% CO)
48
Avg brain weight
1400 g
49
CBF: CMRO2
10-15
50
What is CBF influenced by?
CMRO2, PaCO2, Hct, MAP; all may increase or decrease CBF
51
Without bypass; how does Cerebral delivery of oxygen compare to oxygen demand?
CDO2 normally exceeds the oxygen demand
52
CDO2
Cerebral delivery of oxygen
53
When cerebral delivery of oxygen decreases, how is CMRO2 maintained? What would further decrease in delivery result in?
Increasing oxygen extraction; ischemia
54
Autoregulation tries to maintain what?
Constant CBF over a wide range of pressures
55
Due to changes in CMRO2, what is different in managing awake patient vs anesthetized patient?
different CBFs are maintained over variable MAPs
56
What does autoregulation maintain in awake patients?
50-150 mmHg
57
Autoregulation of CBF in anesthetized patients at moderate hypothermia?
May have preserved autoregulation down to CPP of 28 mmHg
58
Autoregulation of CBF in anesthetized patients at deep hypothermia?
down to 20 mmHg
59
Instrinsic autoregulation strives to maintain what?
CBF: CMRO2 coupling
60
What other factors place major roles in maintaining CBF: CMRO2 coupling?
1. Temperature
2. Carbon Dioxide
3. Oxygen Tension
4. MAP
61
What is the primary determinant of CBF?
Temperature
62
Flow-Metabolism Coupling
Brian regulated flow in response to its O2 demand
Is maintained at autoregulatory state
When there is an increase or decrease in CMRO2, CBF is adjusted accordingly
**Temerpature
63
What happens to coupling at profound levels of hypothermia (<22 C)?
"Coupling" Disappears
| CBF can become in excess of CMRO2
64
What is a large player in determining CBF in alpha stat?
pCO2
65
What happens to pCO2 as CBF is increased?
Increases; and vice versa
66
Alpha stat effects are regardless of what?
Temperature, MAP, Hct, pO2
67
pH stat acid-base management
maintain temperature corrected pH= 7.40 and pCO2 =40 mmHg; by continually adding CO2
68
Alpha-stat acid-base managemnet
maintain an uncorrected value of pH= 7.40 and pCO2 = 40 mmHg; keeping the total CO2 constant
69
pH stat management good for pediatric cases
adult patients lose cerebral autoregulation
| where CBF becomes dependent on CPP; this leads to luxuriant CBF and can have significant neurological side effects
70
Normal Cerebral Tissue pO2
35-40 mmHg
71
pO2 <30 mmHg
immediate reduction in cerebral vascular resistance
| yielding an increase in CBF
72
What can hyperoxia cause ?
An increase in cerebral vascular resistance
73
What percent reduction in CBF when PaO2 was increased from 125 to 300 mmHg (all other parameters constant)?
15% reduction in CBF
74
With alpha stat: what is constant?
CBF over varying mAP
75
Alpha Stat: at mild hypothermia or normothermia, what happens to the safety margin for CDO2 vs CMRO2?
Starts to narrow at MAPs < 50 mmHg
76
With pH stat, CBF is dependent on what?
MAP
77
pH-stat: High pressures
excessive flow
78
pH-stat: Low pressures
hypoperfusion
79
Is CPB responsible for cognitive injury?
No
80
Cognitive Decline: 3 months post op (on vs off pump)
21 % off pump vs 29% on pump
81
Cognitive Decline: 1 year post op (on vs off pump)
31% off pump vs 34% on pump
82
Use the epiaortic ultrasounds for hwat?
Cannulation, XC, proximal anastomosis sites
83
How to pay attention to the aorta?
Epiaortic ultrasounds
| Devices to deflect/trap emboli
84
Surgical Management: Attn to Neurological Injury
Attention to Aorta
Pre-op carotid studies in order patients and those with a Hx of TIA/stroke/ Carotic Dz
Minimize Aortic manipulations
Flood chest cavity with Co2
Use care during de/cannulation
utilize TEE To ensure de-airing prior to Xc removal
85
What pharmacological agents reduce CMRO2?
Thiopental
| Propofol
86
Anesthesia Management for Attenuating Neurological Injury
Pharmacological agents that reduce CMRo2
Ensure air removed from IVs and arterial lines
Apply manual compression on carotid arteries with XC removal
87
Perfusion Management for Attenuating Neurological Injury
Use of art line and cardiotomy filter
proper de-airing of circuit (CO2 flush)
maintain adequate anticoagulation
monitor warming/cooling gradients (slow rewarming better)
Avoid hyperthermia
communicate with surgeon and understand surgical sequence of events
alpha-stat and acid-base management
check art line post CPB prior to transfusion of vol
avoid hyperglycemia
discuss venous drainage problems
88
Why should you avoid hyperglycemia on bypass?
Potential for increase CMRO2; may aggravate neurologic ischemic injury
89
If SVC is congested....
CPP is diminished
90
NIRS
near infrared spectroscopy
| Non-invasive transcutaneous assessment of regional brain oxygenation
91
NIRS is sensitive to whta
temperature, pCO2, Hct, CPB flow
92
Hgb sat does not indicate what?
Tissue utilization
93
What does Transcranial Doppler measure?
Blood velocity in middle cerebral artery; correlation to blood flow
94
Transcranial Doppler is sensitive to whta
temp, map, pump flow, pco2, hct
95
reliable velocity in transcranial doppler requires what?
Constant vessel diameter; not always true on bypass better trending device
96
Transcranial doppler is much more useful in what patient population?
Pediatrics; easier to obtain temporal window
97
In adults, transcranial doppler is better at what than indicator of CBF?
emboli detection
98
Antegrade Cerebral Perfusion: Pt in what position?
Trendelenburg position
99
Describe flow in antegrade cerebral perfusion
Flow up the axillary artery to the innominate artery, to the head via the right common carotid artery through the circle of willis nad down the jugular veins to the SVC/atrium
100
What do you have to do with the venous line in antegrade cerebral perfusion?
have ot leave venous line open to drain the heart
101
Cannulation of head vessels in ACP
can be direct
102
Flow in ACP
10 ml/kg/min
103
What was 1st used as a method to treat massive air embolus?
RCP
104
Flow in RCP
up the SVC, through the Circle of willis and down the carotid arteries; many variations to do so
105
What is RCP useful for?
Deair for aortic surgeries
106
RCP flow
<500 ml/min
107
SVC pressure in RCP
<25 mmHg
