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NEUROLOGIC COMPLICATIONS Flashcards

1
Q

amount of cardiac surgical procedures are carried out worldwide

A

1.4 million world wide

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2
Q

Overt stroke occurs in ______ of all patients

A

1-5%

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3
Q

Neurologic dysfunction may be present in _____

of pts.

A

25-80%

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4
Q

Annual cost for treating these pts. with neuro deficits exceeds

A

$2 billion/ yr

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5
Q

Neurologic Deficits Include:

A

 Psychomotor speed  Attention  Concentration
 New Learning Ability
 Short term memory

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6
Q

neuro deficits for peds include

A

Seizures, Movement disorders, developmental delays`

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7
Q

Transient Ischemic Attack (TIA)

A

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

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8
Q

Reversible Ischemic Neurologic Deficit (RIND)

A

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

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9
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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10
Q

Global Ischemia

A

Results from long periods of hypoperfusion or massive embolic load
Poor recovery. >50% are brain dead and never wake.
Symptoms often overlap and share causative mechanism with others

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11
Q

Risk Factors for neuro injuries

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

A

0.2% incidence of stroke

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13
Q

<60 years old

A

1% incidence of stroke

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14
Q

60-70 years old

A

3.0% incidence of stroke

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15
Q

> 75 years old

A

8.0% incidence of stroke

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16
Q

At MGH, average age was _____ in______ and up to ____ in______

A

56 in 1980 up to 67 in 1994.

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17
Q 
Atherosclerosis/ Thromboembolic debris
• •
•
• •
75% of pts with stroke show
A

multiple infarcts, with an average of 6 zones

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18
Q

normal aorta prevalence of stroke

A

5%

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19
Q

stroke rate with large intraluminal plaques

A

45%

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20
Q

Atherosclerosis/ Thromboembolic debris

 Embolic events related to:

A

 Aortic Plaques  Platelet-fibrin and leukocyte aggregates  Bubbles from CPB circuit
 Often associated with specific surgical events

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21
Q

______of cardiac patients have a history of TIA/Stroke

A

13%

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22
Q

______greater risk of new deficit or exacerbation of previous deficit

A

3x

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23
Q

types of intracardiac ops that increase risk for neuro injury

A

Valves, ASD/VSD, Myxomas, etc. • Increased risk of air emboli

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24
Q

risk for neuro injury Valves, ASD/VSD, Myxomas, etc. compared to CABG alone

A

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

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25
percent of cardiac patients that have hypertension
55%
26
percent of cardiac patients with diabetes
25%
27
how diabetes may increase neuro injury
May be due to changes in cerebral autoregulation Narrows arteries penetrating the brain Decrease in collateral blood flow Decrease ischemic tolerance
28
PERCENT OF PATIENTS WITH MORE THAN 50% carotid stenosis
15%
29
stroke rate in asymptomatic patients with carotid disease
9.2%
30
stroke rate in patients with no carotid disease
1.3%
31
stroke rate with >75% Carotid Stenosis
14%
32
>75% Carotid Stenosis before carotid endarterectomy had strokes.
0 of 19 pts.
33
Carotid Stenosis, |  Mechanism is unclear, whether
embolic or ↓Q, but >50% of strokes occur in immediate postoperative period
34
No studies prove higher CPB
MAP is beneficial
35
Risk Factors Other
PVD Alcohol abuse IABP- balloon or preexisting condition?? MI Prolonged hypotension Arrhythmias CHF Gender Decreased Cardiac Output
36
Cerebral Metabolic Requirement of Oxygen (CMRO2)
CMRO2 ~40-50mL of O2/min  Indexed at 3.0-3.5 mL of O2/100g/min
37
Cerebral Blood Flow (CBF)
CBF~ 750mL/min  Indexed at 50-60mL/100g/min (about 15% CO)
38
Average brain weighs about
1400 grams
39
CBF:CMRO2 is typically
10-15
40
CBF is influenced by:
CMRO2, PaCO2, Hct, MAP |  All may increase or decrease cerebral blood flow
41
Without bypass: |  Cerebral delivery of oxygen (CDO2) normally
exceeds the oxygen demand
42
When delivery decreases, CMRO2 is maintained by
increasing oxygen extraction | Further decrease in delivery will result in ischemia
43
Autoregulation tries to maintain a constant
CBF over a wide range of pressures.
44
Due to changes in CMRO2 between an awake patient and an anesthetized patient at hypothermic temperatures,
different CBF’s are maintained over variable MAP’s
45
Awake patients  Maintain autoregulation from
50-150mmHg
46
Anesthetized patients at moderate hypothermia  may have preserved autoregulation down to CPP of
28mmHg. Deeper Hypothermia – down to 20mmHg
47
While intrinsic autoregulation strives to maintain a CBF:CMRO2 coupling, there are other factors that play major roles:
1. Temperature Carbon Dioxide Oxygen Tension Mean Arterial Pressure
48
Primary determinant of CBF  CMRO2 ~ T
low-metabolism “coupling”  Brainregulatesflowinresponsetoit’sO2demand  is maintained in autoregulatory state  When there is an increase or decrease in CMRO2, CBF is adjusted accordingly
49
At profound levels of hypothermia (<22°C)
“coupling” disappears  CBF can become in excess of CMRO2
50
Carbon Dioxide (alpha- stat)
 pCO2 is a large player in determining CBF  ↑CBF as ↑pCO2 and vice versa  Effects are regardless of Temperature, MAP, Hct, pO2
51
pH-stat acid-base management
Maintain temperature corrected pH= 7.40 and pCO2 = 40mmHg  By continually adding CO2
52
Alpha-stat acid-base management
Maintain an uncorrected value of pH = 7.40 and pCO2 = 40mmHg  Keeping the total CO2 constant
53
pH-stat management good for pediatric cases
 Adult patients lose cerebral autoregulation  where CBF becomes dependent on CPP  This leads to “luxuriant” cerebral blood flow and can have significant neurological side effects
54
Normal cerebral tissue pO2
35-40mmHg
55
if cerbral pO2 < 30mmHg
Immediate reduction in cerebral vascular resistance  Yielding an increase in CBF
56
Hyperoxia causes an
increase cerebral vascular resistance.
57
when PaO2 was increased from 125 to 300mmHg (all other parameters constant)
15% reduction in CBF
58
With alpha-stat: map
CBF is relatively constant over varying MAP. |  At mild hypothermia or normothermia, the safety margin for CDO2 vs. CMRO2 starts to narrow at MAP’s < 50mmHg
59
With pH-stat map
CBF is dependent on MAP  High pressures can yield excessive flow  Low pressures can yield hypoperfusion.
60
CPB is not responsible for
cognitive inju
61
neuro injury off pump vs on pump post 3 mo.
 21% off pump vs. 29% on pump
62
neuro injury off pump vs on pump post 1 yr.
 31% off vs. 34% on pump
63
Attenuation of Neurological Injury – Surgical Management
Attention to Aorta  Use the epiaortic ultrasound (versus “feel”) for cannulation, cross clamp, and proximal anastamosis sites  Devices to deflect / trap emboli  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
64
Attenuation of Neurological Injury – Anesthesia Management
 Pharmacologic agents that reduce CMRO2  Thiopental  Propofol  Ensure air removed from IV’s and arterial lines  Apply manual compression on carotid arteries with XC removal???
65
Attenuation of Neurological Injury – Perfusion Management filter/ de airing/
 Use of arterial line & cardiotomy filter  Ensure proper de-airing of circuit (CO2 flush)  Maintain adequate anticoagulation  Monitor warming/cooling gradients  Slow rewarm is better  Better cognitive performance 6 weeks post op  Avoid Hyperthermia  Communicate with surgeon and understand surgical sequence of events  Alpha-stat acid-base management
66
Attenuation of Neurological Injury
 Check arterial line post CPB prior to transfusion of volume  Avoid hyperglycemia (potential for ↑CMRO2)  May aggravate neurologic ischemic injury  Discuss venous drainage problems.  If SVC is congested, CPP is diminished  ↓pCO2 during embolic periods???  Avoid excessive pO2???
67
 Near Infrared Spectroscopy
 Noninvasive transcutaneous assessment of regional | brain oxygenation  Sensitive to temperature, pCO2, Hct, CPB flow  Hgb sat does not indicate tissue utilization
68
Transcranial Doppler
 Measures blood velocity in middle cerebral artery  Correlation to blood flow  Sensitive to Temperature, MAP, pump flow, pCO2, Hct.  Reliable velocity requires a constant vessel diameter  Not always true on bypass  Better trending device  Pediatrics – much more useful – easier to obtain temporal window  Adults – better at emboli detection than indicator of CBF.
69
Antegrade Cerebral Perfusion
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  Flow: 10ml/kg/min
70
Retrograde Cerebral Perfusion
 1st used as a method to treat massive air embolus  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  Flow <25mmHg

Perf tech 3 (14 decks)

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