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553 - Monitoring & CV Patient > Exam 9 - O2 Monitoring & Brain Protection > Flashcards

Exam 9 - O2 Monitoring & Brain Protection Flashcards

1
Q

Health depend’s on bodies ability to:

A
  • deliver appropriate amount of O2 to each cell

- for each cell to uptake and consume oxygen

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2
Q

Normal oxygen consumption

A

200-250 ml O2/min

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3
Q

70 kg adult consumes:

A

10 quintillion molecules of O2 per second

10,000,000,000,000,000,000

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4
Q

Final cause of death

A
  • always ends up being tissue hypoxia
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5
Q

Aerobic

A
  • 1 mole glucose = 36 ATP

- glucose -> 2 pyruvate -> acetyl CoA

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6
Q

Anaerobic

A
  • 1 mole glucose = 2 net ATP
  • 97% reduction in energy plus lactic acid waste build up
    - lactic acid later sent to liver for conversion
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7
Q

C3H6O3

A

Lactic acid

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8
Q

C3H5O3 + H

A

Lactate

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9
Q

CaO2

A
  • Oxygen content of venous and arterial
  • 2% dissolved in plasma
  • 98% carried by hemoglobin
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10
Q

Arterial O2 content

A

17-20 ml/100ml blood

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11
Q

Venous O2 content

A

12-15 ml/100 ml blood

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12
Q

A-V O2 difference

A

4-6 ml O2/100 ml blood

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13
Q

Biggest factor of O2 content

A

Hemoglobin

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14
Q

DO2

A
  • oxygen delivery
  • available oxygen x delivery rate
  • arterial content x CO
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15
Q

Normal O2 delivery

A

950-1150 ml O2/min

Index: 550-650 ml O2/min/m2

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16
Q

VO2

A
  • Oxygen consumption
  • CO x (Ca-Cv)
Ca = arterial O2 content 
Cv = venous O2 content
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17
Q

Normal O2 consumption

A

200-250 ml O2/min

Index: 120-160 ml O2/min/m2

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18
Q

RO2

A
  • oxygen reserve
  • O2 left AFTER consumption
  • built in buffer in time of need
  • what is in venous blood
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19
Q

Normal O2 reserve

A

700-800 ml O2/min

Index: 450 ml O2/min/m2

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20
Q

Anaerobic respiration kicks in at:

A

< 32% O2

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21
Q

Factors increasing O2 consumption

A
  • Patient conditions
    ~surgery/fever/agitation/fast breathing/infection/trauma
    ~biggest are shivering and sepsis….50-100% increase
  • Medications
    ~NE/Dopamine/Dobutamine/Epi
  • Procedures
    ~dressing change/exam/visitors/turning/nasal intubation/trach suction
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22
Q

Factors decreasing O2 consumption

A
  • Hypothermia (up to 50% at 7 degrees)
  • Morphine IV
  • Anesthesia
  • Assist/control ventilation
  • Neuromuscular blocking agents
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23
Q

Conditions that compromise tissue O2

A
  • ischemic hypoxia
    - hypoperfusion / peripheral vascular disease / thrombosis
  • hypoxemic hypoxia
    - bad O2 transfer in lungs / CO poison / methemoglobinemia
  • anemic hypoxia
    - less Hgb molecules
  • toxic hypoxia
    - body cells can’t uptake or use O2 / sepsis / cyanide / ethanol
  • excessive tissue requirements
    - demand > supply / fever / SIRS / hypermetabolism / thyroid
  • impaired O2 unloading
    - at cap level / alkalemia / hypocarbia / excessive bank blood
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24
Q

Compensatory mechanism for low O2

A
  • Increase CO - primary
    - can get to 15-25 L/min
  • draw on venous reserve
    - extract more O2
  • Polycythemia
    - increase amount of Hgb and RBC mass….takes weeks
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25
Q

Arterial and mixed venous gases from central lab

A
  • lag time between sample and results
  • intermittent
  • cannot detect acute/severe hypoxemia
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26
Q

POC blood gas analyzers

A

Pros: been around/measures a lot/portable/small volume required/self calibrating/disposable cartridges

Cons: expensive and labor intensive quality control
- like the i-STAT

27
Q

Non-invasive pulse oximetry

A
  • 2 LEDs w/ red and infrared light
  • Saturated Hb absorbs infrared
  • Desaturated Hb absorbs red
  • placed on finger / toe / earlobe / nose bridge
  • +/- 4% (need above 50% O2 and less reliable below 70%)
  • Does NOT guarantee O2 is being delivered
28
Q

Factors causing underestimation w/ pulse oximetry

A
  • nail polish
  • dark skin
  • IV dyes
  • Lipid infusions
  • Anemia
  • Venous pulses
  • movement
29
Q

Factors overestimating pulse oximetry

A
  • elevated carboxyhemoglbin (CO poisoning)
  • elevated methemoglobin
  • intense surgical light
30
Q

SpO2 ranges

A

Normal: 96-99%
Mild hypoxia: 85-90%
Hypoxia: 75-85%

31
Q

Normal SvO2

A

60-80%

-cells extract about 25%

32
Q

Invasive mixed venous saturation

A
  • fiber optic pulmonary artery catheter
  • uses reflectance spectrophotometry
  • read manufactures guides
  • calibration required
  • do not bend or kink
  • away from wall of artery
  • old accuracy 4%….now higher
  • Cannot tell difference between carboxy/methem from oxy
33
Q

Continuous in dwelling arterial and venous gases

A
  • CDI 500

- needs gas calibration

34
Q

Transcutaneous measurement of local tissue saturation

A
  • NIRS

- can measure at specific depths

35
Q

Causes of brain injury

A
  • Ischemia - biggest factor
  • hypoxia
  • seizures
  • hypoglycemia
  • hyperglycemia
  • improperly calculating CaCl2 dose
36
Q

Neurological injury

A

Combo of patient at risk with surgical stresses for which vascular system cannot compensate

37
Q

Pathophysiology of cerebral ischemia

A
  • buildup of ADP and lactate
  • K buildup causes vasospasms
  • buildup of Ca causes lipolysis / proteolysis / high consumption
  • Platelet activation and vascular obstruction
  • free radical build up
  • receptor dysfunction
  • Apoptosis
38
Q

Type I Neuro outcome

A
  • cerebral death
  • non-fatal strokes
  • New TIAs (no permanent damage from TIA)
  • Predictors: Age (biggest factor)…. >70 is 4-9% risk
    Aortic atherosclerosis
    History of neuro events
    Carotid stenosis
    # of GMEs
39
Q

Type II Neuro outcome

A
  • New intellectual deterioration
  • New seizures upon discharge
-Predictors:  Low CO / hypotensive
                      GME
                      Atrial arrhythmias
                      Hypertension 
                      Diabetes
                      Pulmonary disease
                      Alcoholism
40
Q

Post op delirium

A
  • If LOS longer…..more effects (20-25 vs <10)

- 10-60%

41
Q

Neuro impairment

A
  • 6.1%

- strokes / coma / poor intellectual function / seizure / memory

42
Q

Incidence of neurological dysfunction

A
  • almost always with CV surgery

- Permanent complications: 1.6-23%

43
Q

Most surgical stress happens when:

A
  • Short filling of beating heart
    - bubbles on tissue of heart flow to brain
  • any filling of heart
44
Q

Surgical techniques to prevent GME

A
  • Epiaortic ultrasound
  • single XC
  • no touch technique
  • pay attention
45
Q

How perfusionists contribute to injury

A
  • Focal:
    • Embolisms
    • Hypoperfusion
    • Inflamation
  • Global:
    • Complete cardiac arrest
    • Complete DHCA
    • Incomplete hypotension
    • Inadequate CPB flow
46
Q

RSO2

A

Regional SO2….uses on brain….NIRS

47
Q

EEG

A
  • electroencephalogram
  • activity on surface of brain only
  • electrodes cover 2.5 cm2
48
Q

Alpha and Beta waves

A
  • patient awake waves
  • normal waves
  • Alpha = relaxed
  • beta = alert
49
Q

Theta and delta waves

A
  • patient asleep
  • Theta = sleeping
  • delta = coma / deep sleep / anesthesia / cerebral ischemia
  • 15% of pop may show evidence of old brain injury
    • if seen during awake
50
Q

EEG uses

A
  • EPILEPSY / brain tumors / stroke
  • diagnosis of coma / brain death
  • monitor depth of perfusion
51
Q

EEG disadvantages

A
  • complex analysis
  • large equipment
  • distracting
  • electrically sensitive
52
Q

BIS

A
  • Bispectral index
  • one number and graph tells us how alert
  • non-invasive
  • continuous / direct / real time
  • refresh every 10-15 seconds
  • 1-100 (100 is fully awake)
53
Q

BIS based on

A
  • degree of high frequency activation
  • degree of low frequency synchronization
  • degree of nearly suppressed periods of EEG
  • degree of fully suppressed periods of EEG
  • uses algorithm plus above and turns into one number
54
Q

BIS ranges

A
  • 100 = awake
  • 80 = light/moderate sedation
  • 60 = general anesthesia
  • 40 = deep hypotonic state
  • 20 = burst suppression
  • 10 = flat line EEG

> 70….patient will remember

55
Q

BIS benefits

A
  • reduction in anesthesia use
  • decrease in patient awakening
  • reduction in LOC and recovery
  • improved satisfaction
  • ONE part of the big picture to help monitor hemodynamics
56
Q

BIS disadvantages

A
  • trending device
  • can’t treat level of sedation
  • often monitor only faces anesthesia
57
Q

INVOS system

A
  • most primitive NIRS

- most widely used

58
Q

NIRS benefits

A
  • non-invasive
  • continuos
  • real time
  • site specific
  • EARLY warnings of ischemia
  • not pulse / pressure / temp dependent
59
Q

NIRS facts

A
  • must baseline patient first
  • gives us rSO2
  • can aid in decision making
  • drops MOM from 13 to 3%
60
Q

NIRS applications

A
  • OR
  • Neuro
  • ER
  • any surgery
  • Peds (ECMO / surgery / neuro)
61
Q

Adequacy of cerebral perfusion

A
  • head position
  • O2 delivery
  • cerebral vascular resistance
  • cerebral O2 demand
  • venous drainage
62
Q

Cerebral inflow issues

A
  • head position
  • heart position
  • arterial obstruction
  • cannula malposition
  • NIRS can help detect inflow supply issues and prescriptive perfusion
63
Q

RSO2 target and thresholds

A
  • Normal: 47-83
  • Intervention threshold: <50 or 20% drop from baseline
  • Critical: <40 or 25% drop from baseline
64
Q

What can we do to protect brain

A
  • medical history
  • monitor
  • filters on machines
  • controlled temp
  • maintain correct pressures and flow
  • drugs
  • brain hypothermia

553 - Monitoring & CV Patient (10 decks)

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