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Perf Tech III (Exam 2) > Topic 6: Neurological Complications > Flashcards

Topic 6: Neurological Complications Flashcards

1
Q

Overt stroke occurs in what % of all pts?

A

1-5%

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2
Q

Neurologic dysfunction may be present in what % of pts.

A

25-80%

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3
Q

Annual cost for treating these pts. exceeds what cost?

A

$2billion/ yr

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4
Q

Neurologic Deficits Include:

A 
Psychomotor speed
Attention
Concentration
New Learning Ability
Short term memory
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5
Q

Neurologic Deficits in pediatrics include?

A

Seizures, Movement disorders,

developmental delays

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6
Q

Transient Ischemic Attack (TIA)

A
  • Localized event
  • Rapid onset and recovery (minutes to hours)
  • Severity depends on collateral flow
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7
Q

Reversible Ischemic Neurologic Deficit (RIND)

A

•Similar to TIA but lasts longer (24-72hrs)

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8
Q

Lacunar Brain Infarct (stroke)

A
  • Specific focal deficit from cerebral artery occlusion.
  • Much more severe, often doesn’t resolve
  • Hemiparesis/aphasia/sensory
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9
Q

Global Ischemia

A
  • Results from long periods of hypoperfusion or massive embolic load
  • Poor recovery. >50% are brain dead and never wake
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10
Q

Cardiac patients experience more serious

neurologic morbidity than what matched controls undergoing non-cardiac surgery?

A

than age, and health matched controls

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11
Q

Risk factors for having a neurological event

A
  1. Advanced Age
  2. Atherosclerosis
  3. History of previous neurologic incident
  4. Intracardiac operation
  5. Hypertension and Diabetes
  6. Carotid Stenosis
  7. Other
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12
Q

•<45 years old- % incidence of stroke

A

~ 0.2% incidence of stroke

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13
Q

<60 years old–% incidence of stroke

A

1%

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14
Q

60-70 years old- % incidence of stroke

A

3.0%

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15
Q

> 75 years old- % incidence of stroke

A

8.0%

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16
Q

Age is an easy identifier due to what?

A

comorbidities

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17
Q

Is there a continued trend of older people coming to surgery?

A

Continued trend of older patients coming to surgery. At MGH, average age was 56 in 1980 up to 67 in 1994

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18
Q

Risk Factor Atherosclerosis/ Thromboembolic debris

•75% of pts with stroke show multiple infarcts, with an average of how many zones?

A

6 zones

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19
Q

Atherosclerosis/ Thromboembolic debris

Embolic events related to: (3)

A

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

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20
Q

History of previous Neurologic Incident

•13% of cardiac patients have a history of?

A

TIA/Stroke

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21
Q

If there is a history of previous Neurologic Incident there is a ____x greater risk of new deficit or exacerbation of previous deficit

A

3X

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22
Q

Intracardiac types of operation that have increased risk of air emboli? how much more risk?

A

Valves, ASD/VSD, Myxomas, etc.

Risk (5-13%) is 2X higher than CABG alone

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23
Q

Hypertension–what % of cardiac surgical patients

A

55%

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24
Q

Diabetes–what % of cardiac surgical patients

A

25%

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25
Q

DM and HTN may be risk factors for neurological incidents due to what?
3 main things?

A

May be due to changes in cerebral autoregulation
•Narrows arteries penetrating the brain
•Decrease in collateral blood flow
•Decrease ischemic tolerance

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26
Q

15% of cardiac surgery patients have greater than 50% what?

A

carotid stenosis

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27
Q

No studies prove higher what on CPB is beneficial for patients with carotid stenosis

A

MAP

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28
Q

Mechanism is unclear, whether embolic or ↓Q, but >50% of strokes occur when??

A

immediate postoperative period

29
Q

Cerebral Metabolic Requirement of Oxygen
(CMRO2)
CMRO2 ____mL of O2/min
Indexed at ____ mL of O2/100g/min

A

~40-50mL of O2/min

3.0-3.5

30
Q

Cerebral Blood Flow (CBF)
CBF ____mL/min
Indexed at ____ mL/100g/min (about 15% CO)

A

~ 750mL/min

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

31
Q

Average brain weighs about what?

A

1400g

32
Q

CBF:CMRO (Cerebral Metabolic Requirement of Oxygen) 2 is typically

A

10-15

33
Q

CBF is influenced by what 4 things?

A

CMRO2, PaCO2, Hct, MAP

All may increase or decrease cerebral blood flow

34
Q

Without bypass:
Cerebral delivery of oxygen (CDO2) normally ____ the oxygen demand
When delivery decreases, CMRO2 is maintained by what?

A

exceeds

increasing oxygen extraction

Further decrease in delivery will result in ischemia

35
Q

Autoregulation of CBF
Awake patients
Maintain autoregulation at what pressures?

A

from 50-150mmHg

This does not take into consideration other
comorbidities

36
Q

Autoregulation of CBF

Anesthetized patients at moderate hypothermia may have preserved autoregulation

A

down to CPPressue of 28mmHg

This does not take into consideration other
comorbidities

37
Q

Autoregulation of CBF

Deeper Hypothermia maintain autoregulation at what pressure?

A

down to 20mmHg

This does not take into consideration other
comorbidities

38
Q

While intrinsic autoregulation strives to maintain a CBF:CMRO2 coupling, there are other factors that play major roles: (4)

A
  1. Temperature
  2. Carbon Dioxide
  3. Oxygen Tension
  4. Mean Arterial Pressure
39
Q

Temperature is the #1 determinant of what?

A

CBF

40
Q

At profound levels of hypothermia (<22°C) “coupling” does what?
CBF can become in excess of

A

disappears

in excess of CMRO2

41
Q

↑CBF as pCO2 ?

A

↑pCO2 and vice versa

Effects are regardless of Temperature, MAP, Hct, pO2

42
Q

pH-stat acid-base management Maintains what?

A

temperature corrected pH= 7.40 and pCO2 = 40mmHg

By continually adding CO2

43
Q

Alpha-stat acid-base management maintain what?

A

an uncorrected value of pH = 7.40 and pCO2 = 40mmHg

Keeping the total CO2 constant

44
Q

Normal cerebral tissue pO2 =

A

35-40mmHg

45
Q

Hyperoxia causes an increase in what?

A

cerebral vascular resistance

46
Q

With alpha-stat:
CBF is relatively ____ over varying MAP.
At mild hypothermia or normothermia, the safety margin for CDO2 vs. CMRO2 starts to narrow at what MAP’s?

A

constant

<50mmHg

47
Q

With pH-stat
CBF is ____ on MAP
High pressures can ?
Low pressures can ?

A

dependent

yield excessive flow
yield hypoperfusion

48
Q

that there is what effect of CPB on cognitive

decline

A

was no effect

49
Q

Attenuation of Neurological Injury–Surgical Management

A

Attention to Aorta
Pre-op carotid studies in older patients and those
with a history of TIA/ Stroke/ Carotid Dz.
Minimize aortic manipulations
Flood chest cavity with CO2
Use care during de/cannulation
Utilize TEE to ensure de-airing prior to XC removal

50
Q

What attention can be paid to the aorta

A

Use the epiaortic ultrasound (versus “feel”) for cannulation, cross clamp, and proximal anastamosis sites
Devices to deflect / trap emboli

51
Q

Pharmacologic agents that reduce CMRO2 (2)

A

Thiopental

Propofol

52
Q

Attenuation of Neurological Injury–Anesthesia Management

A

-Pharmacologic agents that reduce CMRO2
-Ensure air removed from IV’s and arterial lines
-Apply manual compression on carotid arteries
with XC removal?

53
Q

Attenuation of Neurological Injury–Perfusion Management

A

-Use of arterial line & cardiotomy filter
-Ensure proper de-airing of circuit (CO2 flush)
-Maintain adequate anticoagulation
-Monitor warming/cooling gradients
-Communicate with surgeon and understand
surgical sequence of events
-Alpha-stat acid-base management

54
Q

Attenuation of Neurological Injury–Perfusion Management

-Monitor warming/cooling gradients

A
  • Slow rewarm is better
  • Better cognitive performance 6 weeks postop
  • Avoid Hyperthermia
55
Q

Attenuation of Neurological Injury (3)

A

Check arterial line post CPB prior to transfusion of volume
Avoid hyperglycemia (potential for↑CMRO2) —May aggravate neurologic ischemic injury
Discuss venous drainage problems.

↓pCO2 during embolic periods???
Avoid excessive pO2???

56
Q

hyperglycemia affect on CMRO2?

A

potential for↑CMRO2

May aggravate neurologic ischemic injury

57
Q

If SVC is congested,

A

CPP is diminished

58
Q

Near Infrared Spectroscopy is sensitive to what? (4)

A

Sensitive to temperature, pCO2, Hct, CPB flow

Hgb sat does not indicate tissue utilization

59
Q

Transcranial Doppler –Measures what?

A

blood velocity in middle cerebral artery

Correlation to blood flow

60
Q

Transcranial Doppler – sensitive to what?

A

Temperature, MAP, pump flow, pCO2, Hct

61
Q

Transcranial Doppler in Adults is actually better detector of what?

A

Adults–better at emboli detection than indicator of CBF

62
Q

Transcranial Doppler in Pediatrics is more useful do to what?

A

much more useful–easier to obtain temporal window

63
Q

Transcranial Dopplers reliable velocity requires what?

A

Reliable velocity requires a constant vessel diameter
Not always true on bypass
Better trending device

64
Q

Antegrade Cerebral Perfusion – how do you do it? steps - 5

flow path?

A
  • Patient put in Trendelenburg position
  • Flow up the axillary artery to the innominate artery, to the head via the right common carotid artery.
  • Thru the Circle of Willis and down the jugular veins to the SVC/ Atrium.
  • Have to leave venous line open to drain the heart
  • Can also do via direct cannulation of the head vessels
65
Q

Antegrade Cerebral Perfusion Flow?

A

10ml/kg/min

66
Q

Retrograde Cerebral Perfusion 1st used as a method to treat what?

A

massive air embolus

67
Q

Retrograde Cerebral Perfusion flow path?

A

Flow up the SVC through the Circle of Willis and down the carotid arteries
Many variations to do so
Useful to deair for aortic surgeries

68
Q

Retrograde Cerebral Perfusion

Flow ? SVC?

A

Flow 500 ml/min

SVC Pressure of <25mmHg

Perf Tech III (Exam 2) (6 decks)

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