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ICU > Systemic Oxygenation > Flashcards

Systemic Oxygenation Flashcards

0
Q

What is the equation for Hb bound oxygen?

A

1.34 (O2 binding capacity of hemoglobin in ml) X Hb X SO2 (ml/DL)

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1
Q

What is oxygen content?

A

The amount of oxygen that is Hb bound and dissolved in plasma

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2
Q

What happens to oxygen solubility in plasma as the body temperature rises?

A

The oxygen solubility will decrease

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3
Q

What is the equation for dissolved O2 in plasma?

A

0.003 X PO2

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4
Q

What is the arterial O2 content (CaO2)?

A

CaO2 = (1.34 X Hb x SaO2) + 0.003 X PaO2

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5
Q

What is normal arterial O2 content?

A

20 ml/DL

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6
Q

What is normal venous o2 content?

A

15 ml/DL

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7
Q

What is the O2 extracted for a normal person?

A

5 ml/DL or 50 ml/L

250 ml/min with a cardiac output of 5L/min

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8
Q

What is DO2?

A

The rate of oxygen delivery

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9
Q

What is the equation for DO2?

A

CO x CaO2 X 10

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10
Q

What is normal DO2?

A

900-1100 ml/min

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11
Q

What’s VO2?

A

The rate of O2 transport from the systemic capillaries to the tissues

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12
Q

What is the equation for VO2?

A

VO2 = CO X (CaO2-CvO2) X 10

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13
Q

What is the VO2 in healthy patients?

A

200-300 ml/ min

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14
Q

What does DO2 depend on?

A

Cardiac output

Oxygen content of the blood (Hb concentration and O2 sat)

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15
Q

What does VO2 depend on?

A

Cardiac output
o2 sat
SvO2
Hb concentration

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16
Q

What is whole body VO2?

A

Accounts for O2 uptake in the lungs

VO2 = VE X (FiO2-FeO2)

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17
Q

What is the normal O2 consumption of the lungs?

A

Less than 5%

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18
Q

What are the two conditions associated with low VO2?

A
  1. Decreased metabolism

2. Inadequate tissue oxygenation

19
Q

What is oxygen debt?

A

The cumulative deficit in tissue oxygenation

20
Q

What lab value correlates with a low VO2?

A

Lactate levels (begin to rise after 6 hours lag time)

21
Q

What is the oxygen extraction ratio?

A

O2ER = VO2/DO2
Or
O2ER = (SaO2 - SvO2)/SaO2

22
Q

What is normal O2ER?

A

.25

23
Q

What is the equation for the control of VO2?

A

VO2 = DO2 X O2ER

24
Q

What is the point at which VO2 begins to decrease?

A

When O2 extraction is maximal at 50%

25
Q

How is SaO2 monitored?

A

By pulse oximetry

26
Q

How is SvO2 monitored?

A

By the pulmonary artery catheter

27
Q

What is normal SaO2-SvO2 or oxygen extraction?

A

20-30%

28
Q

What does an increase in the oxygen extraction above 30% indicate?

A

A decrease in O2 delivery

29
Q

What does an increase in O2 extraction that approaches 50% indicate?

A

Inadequate tissue oxygenation

30
Q

What does a decrease in oxygen saturation below 20% mean?

A

A defect in O2 utilization (usually sepsis)

31
Q

What is the simplified equation for O2 extraction?

A

1 - SvO2

32
Q

What is the equation for SvO2 (mixed venous oxygen saturation?

A

SvO2 = SaO2 -(VO2/ CO X 1.34 X Hb)

33
Q

What is the simplified equation of SvO2 is the arterial blood is fully saturated?

A

SvO2 = 1 - VO2/DO2

34
Q

What is the normal range for SvO2?

A

65-75%

35
Q

A change in SvO2 is only significant when….

A

It changes by more than 5% and lasts longer than 10 minutes

36
Q

What does a decrease in SVO2 mean?

A

There is a decrease in oxygen delivery (cardiac output or anemia)

37
Q

What does an increase in SvO2 mean?

A

A defect in O2 utilization

38
Q

What is the normal range for central venous oxygen saturation?

A

70-89%

39
Q

How is central venous oxygen saturation monitored?

A

By a central line in the SVC

40
Q

What are the oxygen markers for impaired tissue oxygenation?

A

VO2 less than 200 ml/min or 110 ml/m2/min
SaO2 - SvO2 approaching 50%
SvO2 less than 50%

41
Q

What are the chemical markers of impaired tissue oxygenation?

A

Lactate over 2 mM/l

Base deficit over 2

42
Q

How is lactate used for prognosis?

A
  1. The initial value of lactate

2. The amount of time is takes to return to normal

43
Q

What is the mechanism of lactate accumulation in sepsis?

A

Inhibition of pyruvate dehydrogenase which inhibits the movement from glycolysis to the Krebs cycle in mitochondria and therefore o2 utilization

44
Q

What is arterial base deficit?

A

The amount of base that must be added to one liter of blood to raise the ph to 7.4

45
Q

What is a normal arterial base deficit?

A

Less than 2

ICU (17 decks)

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