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CV Perf Tech III > Neurologic Complications- Exam 2 > Flashcards

Neurologic Complications- Exam 2 Flashcards

1
Q

How many cardiac surgical procedures are carried out worldwide?

A

1.4 million

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2
Q

Overt stroke occurs in what percent of all patients?

A

1-5%

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3
Q

Neurologic dysfunction may be present in what percent of patients?

A

25-80%

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4
Q

What is the annual cost for treating neurologic dysfunction patients?

A

Exceeds $2 billion/ year

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5
Q

What are neurologic deficits in adults?

A 
Psychomotor speed
attention
concentration
new learning ability
short term memory
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6
Q

What are some neurologic deficits in pediatrics?

A

Seizures, movement disorders, developmental delays

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7
Q

TIA: Broad or localized?

A

Localized

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8
Q

TIA: Describe onset and recovery.

A

Rapid onset and recovery (minutes to hours)

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9
Q

TIA: What does severity depend on?

A

Collateral flow

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10
Q

RIND

A

Reversible Ischemic Neurologic Deficit

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11
Q

What is reversible ischemic neurologic deficit?

A

Similar to TIA but lasts longer (24-72 hours)

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12
Q

Lacunar Brain Infarct

A

Stroke; specific focal deficit from cerebral artery occlusion
Much more severe, often doesn’t resolve
Hemiparesis/aphasia/sensory

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13
Q

Global Ischemia results from what?

A

Long periods of hypoperfusion or massive embolic load; poor recovery

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14
Q

What percent of global ischemia patients are brain dead and never wake?

A

> 50% are brain dead and never wake

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15
Q

What are the 4 classifications of neurologic deficit?

A
  1. TIA
  2. RIND
  3. Lacunar Brain Infarct (Stroke)
  4. Global Ischemia
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16
Q

What patients experience more serious neurologic morbidity than age, and health matched controls undergoing non-cardiac surgery?

A

Cardiac patients

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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
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18
Q

What incidence of stroke in < 45 y/o?

A

~0.2 % incidence of stroke

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19
Q

What incidence of stroke in <60 y/o?

A

1 % incidence of stroke

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20
Q

What incidence of stroke in 60-70 y/o?

A

3.0% incidence of stroke

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21
Q

What incidence of stroke in >75 y/o?

A

8.0 % incidence of stroke

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22
Q

Avg age at MGH in 1980?

A

56

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23
Q

Avg age at MGH in 1994?

A

67

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24
Q

What percent of patients with stroke show multiple infarcts? How many zones?

A

75%, 6 zones

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25
Q

What percent of stroke in patients with normal aorta?

A

5%

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26
Q

What percent of stroke with large intraluminal plaques?

A

45%

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27
Q

What are embolic events related to?

A

Aortic plaques
Platelet-fibrin and leukocyte aggregates
Bubbles from CPB circuit

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28
Q

What is atherosclerosis/thromboembolic debris often associated with?

A

Specific surgical events

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29
Q

At what point during surgery are the highest instances of embolic events?

A

Highest: Short filling of beating heart
2nd highest: filling again

Highest: Release of cross clamp
Another high pt: release of partial occlusion clamps

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30
Q

What percent of cardiac patients have a history of TIA/stroke?

A

13%

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31
Q

How many times greater risk of new deficit or exacerbation of previous deficit?

A

3x greater

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32
Q

What intracardiac operations are risk factors for neurologic injury and air emboli? What is the risk? How does it compare to CABG alone?

A

Valves, ASD/VSD/ Myxomas

5-13% risk
2x higher than CABG alone

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33
Q

What percent of cardiac surgical patients have hypertension?

A

55% of all cardiac surgery patients

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34
Q

What percent of cardiac surgical patients have diabetes?

A

25% of all cardiac surgery patients

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35
Q

HTN and DM may be due to what?

A

Changes in cerebral autoregulation; narrows arteries penetrating the brain, decrease in collateral blood flow, decrease ischemic tolerance

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36
Q

What percent of cardiac surgery patients have greater than 50% carotid stenosis?

A

15%

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37
Q

What percent stroke rate in asymptomatic patients with carotid disease?

A

9.2%

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38
Q

What percent stroke rate in patients with no carotid disease?

A

1.3%

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39
Q

What percent stroke rate with >75% carotid stenosis?

A

14%

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40
Q

___ of 19 patients with >75% carotid stenosis before carotid endarterectomy had strokes.

A

0

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41
Q

What is the carotid stenosis mechanism?

A

Unclear, whether embolic of decrease in flow, but >50% of strokes occur in immediate postoperative period

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42
Q

How many studies prove higher CPB MAP is beneficial?

A

None

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43
Q

CMRO2

A

Cerebral Metabolic Requirement of Oxygen

44
Q

What is hte normal CMRO2?

A

40-50 ml O2/min

45
Q

What is the normal index of CMRO2?

A

3.0-3.5 ml O2/ 100 g/ min

46
Q

Normal CBF

A

750 ml /min

47
Q

What is the index of CBF? What percent of CO?

A

50-60 ml/100g/min (about 15% CO)

48
Q

Avg brain weight

A

1400 g

49
Q

CBF: CMRO2

A

10-15

50
Q

What is CBF influenced by?

A

CMRO2, PaCO2, Hct, MAP; all may increase or decrease CBF

51
Q

Without bypass; how does Cerebral delivery of oxygen compare to oxygen demand?

A

CDO2 normally exceeds the oxygen demand

52
Q

CDO2

A

Cerebral delivery of oxygen

53
Q

When cerebral delivery of oxygen decreases, how is CMRO2 maintained? What would further decrease in delivery result in?

A

Increasing oxygen extraction; ischemia

54
Q

Autoregulation tries to maintain what?

A

Constant CBF over a wide range of pressures

55
Q

Due to changes in CMRO2, what is different in managing awake patient vs anesthetized patient?

A

different CBFs are maintained over variable MAPs

56
Q

What does autoregulation maintain in awake patients?

A

50-150 mmHg

57
Q

Autoregulation of CBF in anesthetized patients at moderate hypothermia?

A

May have preserved autoregulation down to CPP of 28 mmHg

58
Q

Autoregulation of CBF in anesthetized patients at deep hypothermia?

A

down to 20 mmHg

59
Q

Instrinsic autoregulation strives to maintain what?

A

CBF: CMRO2 coupling

60
Q

What other factors place major roles in maintaining CBF: CMRO2 coupling?

A
  1. Temperature
  2. Carbon Dioxide
  3. Oxygen Tension
  4. MAP
61
Q

What is the primary determinant of CBF?

A

Temperature

62
Q

Flow-Metabolism Coupling

A

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
Q

What happens to coupling at profound levels of hypothermia (<22 C)?

A

“Coupling” Disappears

CBF can become in excess of CMRO2

64
Q

What is a large player in determining CBF in alpha stat?

A

pCO2

65
Q

What happens to pCO2 as CBF is increased?

A

Increases; and vice versa

66
Q

Alpha stat effects are regardless of what?

A

Temperature, MAP, Hct, pO2

67
Q

pH stat acid-base management

A

maintain temperature corrected pH= 7.40 and pCO2 =40 mmHg; by continually adding CO2

68
Q

Alpha-stat acid-base managemnet

A

maintain an uncorrected value of pH= 7.40 and pCO2 = 40 mmHg; keeping the total CO2 constant

69
Q

pH stat management good for pediatric cases

A

adult patients lose cerebral autoregulation

where CBF becomes dependent on CPP; this leads to luxuriant CBF and can have significant neurological side effects

70
Q

Normal Cerebral Tissue pO2

A

35-40 mmHg

71
Q

pO2 <30 mmHg

A

immediate reduction in cerebral vascular resistance

yielding an increase in CBF

72
Q

What can hyperoxia cause ?

A

An increase in cerebral vascular resistance

73
Q

What percent reduction in CBF when PaO2 was increased from 125 to 300 mmHg (all other parameters constant)?

A

15% reduction in CBF

74
Q

With alpha stat: what is constant?

A

CBF over varying mAP

75
Q

Alpha Stat: at mild hypothermia or normothermia, what happens to the safety margin for CDO2 vs CMRO2?

A

Starts to narrow at MAPs < 50 mmHg

76
Q

With pH stat, CBF is dependent on what?

A

MAP

77
Q

pH-stat: High pressures

A

excessive flow

78
Q

pH-stat: Low pressures

A

hypoperfusion

79
Q

Is CPB responsible for cognitive injury?

A

No

80
Q

Cognitive Decline: 3 months post op (on vs off pump)

A

21 % off pump vs 29% on pump

81
Q

Cognitive Decline: 1 year post op (on vs off pump)

A

31% off pump vs 34% on pump

82
Q

Use the epiaortic ultrasounds for hwat?

A

Cannulation, XC, proximal anastomosis sites

83
Q

How to pay attention to the aorta?

A

Epiaortic ultrasounds

Devices to deflect/trap emboli

84
Q

Surgical Management: Attn to Neurological Injury

A

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
Q

What pharmacological agents reduce CMRO2?

A

Thiopental

Propofol

86
Q

Anesthesia Management for Attenuating Neurological Injury

A

Pharmacological agents that reduce CMRo2
Ensure air removed from IVs and arterial lines
Apply manual compression on carotid arteries with XC removal

87
Q

Perfusion Management for Attenuating Neurological Injury

A

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
Q

Why should you avoid hyperglycemia on bypass?

A

Potential for increase CMRO2; may aggravate neurologic ischemic injury

89
Q

If SVC is congested….

A

CPP is diminished

90
Q

NIRS

A

near infrared spectroscopy

Non-invasive transcutaneous assessment of regional brain oxygenation

91
Q

NIRS is sensitive to whta

A

temperature, pCO2, Hct, CPB flow

92
Q

Hgb sat does not indicate what?

A

Tissue utilization

93
Q

What does Transcranial Doppler measure?

A

Blood velocity in middle cerebral artery; correlation to blood flow

94
Q

Transcranial Doppler is sensitive to whta

A

temp, map, pump flow, pco2, hct

95
Q

reliable velocity in transcranial doppler requires what?

A

Constant vessel diameter; not always true on bypass better trending device

96
Q

Transcranial doppler is much more useful in what patient population?

A

Pediatrics; easier to obtain temporal window

97
Q

In adults, transcranial doppler is better at what than indicator of CBF?

A

emboli detection

98
Q

Antegrade Cerebral Perfusion: Pt in what position?

A

Trendelenburg position

99
Q

Describe flow in antegrade cerebral perfusion

A

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
Q

What do you have to do with the venous line in antegrade cerebral perfusion?

A

have ot leave venous line open to drain the heart

101
Q

Cannulation of head vessels in ACP

A

can be direct

102
Q

Flow in ACP

A

10 ml/kg/min

103
Q

What was 1st used as a method to treat massive air embolus?

A

RCP

104
Q

Flow in RCP

A

up the SVC, through the Circle of willis and down the carotid arteries; many variations to do so

105
Q

What is RCP useful for?

A

Deair for aortic surgeries

106
Q

RCP flow

A

<500 ml/min

107
Q

SVC pressure in RCP

A

<25 mmHg

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