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

Topic 6: Neurological Complications Flashcards by Rachel ramella

Overt stroke occurs in what % of all pts?

1-5%

How well did you know this?

Not at all

Perfectly

Neurologic dysfunction may be present in what % of pts.

25-80%

How well did you know this?

Not at all

Perfectly

Annual cost for treating these pts. exceeds what cost?

$2billion/ yr

How well did you know this?

Not at all

Perfectly

Neurologic Deficits Include:

Psychomotor speed
Attention
Concentration
New Learning Ability
Short term memory

How well did you know this?

Not at all

Perfectly

Neurologic Deficits in pediatrics include?

Seizures, Movement disorders,

developmental delays

How well did you know this?

Not at all

Perfectly

Transient Ischemic Attack (TIA)

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

How well did you know this?

Not at all

Perfectly

Reversible Ischemic Neurologic Deficit (RIND)

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

How well did you know this?

Not at all

Perfectly

Lacunar Brain Infarct (stroke)

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

How well did you know this?

Not at all

Perfectly

Global Ischemia

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

How well did you know this?

Not at all

Perfectly

Cardiac patients experience more serious

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

than age, and health matched controls

How well did you know this?

Not at all

Perfectly

Risk factors for having a neurological event

Advanced Age
Atherosclerosis
History of previous neurologic incident
Intracardiac operation
Hypertension and Diabetes
Carotid Stenosis
Other

How well did you know this?

Not at all

Perfectly

•<45 years old- % incidence of stroke

~ 0.2% incidence of stroke

How well did you know this?

Not at all

Perfectly

<60 years old–% incidence of stroke

How well did you know this?

Not at all

Perfectly

60-70 years old- % incidence of stroke

3.0%

How well did you know this?

Not at all

Perfectly

> 75 years old- % incidence of stroke

8.0%

How well did you know this?

Not at all

Perfectly

Age is an easy identifier due to what?

comorbidities

How well did you know this?

Not at all

Perfectly

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

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

How well did you know this?

Not at all

Perfectly

Risk Factor Atherosclerosis/ Thromboembolic debris

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

6 zones

How well did you know this?

Not at all

Perfectly

Atherosclerosis/ Thromboembolic debris

Embolic events related to: (3)

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

How well did you know this?

Not at all

Perfectly

History of previous Neurologic Incident

•13% of cardiac patients have a history of?

TIA/Stroke

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

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

Valves, ASD/VSD, Myxomas, etc.

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

How well did you know this?

Not at all

Perfectly

Hypertension–what % of cardiac surgical patients

55%

How well did you know this?

Not at all

Perfectly

Diabetes–what % of cardiac surgical patients

25%

How well did you know this?

Not at all

Perfectly

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

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

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

carotid stenosis

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

MAP

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

immediate postoperative period

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

~40-50mL of O2/min 3.0-3.5

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

~ 750mL/min 50-60mL/100g/min (about 15% CO)

Average brain weighs about what?

1400g

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

10-15

CBF is influenced by what 4 things?

CMRO2, PaCO2, Hct, MAP | All may increase or decrease cerebral blood flow

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

exceeds increasing oxygen extraction Further decrease in delivery will result in ischemia

Autoregulation of CBF Awake patients Maintain autoregulation at what pressures?

from 50-150mmHg ***This does not take into consideration other comorbidities***

Autoregulation of CBF | Anesthetized patients at moderate hypothermia may have preserved autoregulation

down to CPPressue of 28mmHg ***This does not take into consideration other comorbidities***

Autoregulation of CBF | Deeper Hypothermia maintain autoregulation at what pressure?

down to 20mmHg ***This does not take into consideration other comorbidities***

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

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

Temperature is the #1 determinant of what?

CBF

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

disappears in excess of CMRO2

↑CBF as pCO2 ?

↑pCO2 and vice versa Effects are regardless of Temperature, MAP, Hct, pO2

pH-stat acid-base management Maintains what?

temperature corrected pH= 7.40 and pCO2 = 40mmHg | By continually adding CO2

Alpha-stat acid-base management maintain what?

an uncorrected value of pH = 7.40 and pCO2 = 40mmHg | Keeping the total CO2 constant

Normal cerebral tissue pO2 =

35-40mmHg

Hyperoxia causes an increase in what?

cerebral vascular resistance

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?

constant <50mmHg

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

dependent yield excessive flow yield hypoperfusion

that there is what effect of CPB on cognitive | decline

was no effect

Attenuation of Neurological Injury–Surgical Management

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

What attention can be paid to the aorta

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

Pharmacologic agents that reduce CMRO2 (2)

Thiopental | Propofol

Attenuation of Neurological Injury–Anesthesia Management

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

Attenuation of Neurological Injury–Perfusion Management

-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

Attenuation of Neurological Injury–Perfusion Management | -Monitor warming/cooling gradients

- Slow rewarm is better - Better cognitive performance 6 weeks postop - Avoid Hyperthermia

Attenuation of Neurological Injury (3)

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???

hyperglycemia affect on CMRO2?

potential for↑CMRO2 | May aggravate neurologic ischemic injury

If SVC is congested,

CPP is diminished

Near Infrared Spectroscopy is sensitive to what? (4)

Sensitive to temperature, pCO2, Hct, CPB flow | Hgb sat does not indicate tissue utilization

Transcranial Doppler --Measures what?

blood velocity in middle cerebral artery | Correlation to blood flow

Transcranial Doppler -- sensitive to what?

Temperature, MAP, pump flow, pCO2, Hct

Transcranial Doppler in Adults is actually better detector of what?

Adults–better at emboli detection than indicator of CBF

Transcranial Doppler in Pediatrics is more useful do to what?

much more useful–easier to obtain temporal window

Transcranial Dopplers reliable velocity requires what?

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

Antegrade Cerebral Perfusion -- how do you do it? steps - 5 flow path?

- 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

Antegrade Cerebral Perfusion Flow?

10ml/kg/min

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

massive air embolus

Retrograde Cerebral Perfusion flow path?

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

Retrograde Cerebral Perfusion | Flow ? SVC?

Flow 500 ml/min | SVC Pressure of <25mmHg