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ECMO > Physiology of ECMO > Flashcards

Physiology of ECMO Flashcards

1
Q

Our bodies depend on…

A

Delivering the appropriate amount of oxygen to each cell

The ability of each cell to take-up and consume the proper amount of oxygen

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2
Q

What ECMO will do to help

A

Drain venous blod
provide a pump for cardiac output
oxygenate and remove CO2 via an artificial lung
maintain temperature via a heat exchanger
returning blood to the patient via a:
vein (VV) or an artery (VA)

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3
Q

ECMO Physiological Goals

A

Improve blood O2 delivery
Remove CO2
allow normal aerobic metabolism to take place while “resting” the lungs
provide cardiac and/or respiratory support as necessary

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4
Q

What are the two places of gas exchange we look at ?

A

Pulmonary respiration

Tissue respiration

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5
Q

Pulmonary respiration

A

refers to the gas exchange between blood and inspired gas

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6
Q

Tissue respiration

A

refers to the exchange of oxygen and carbon dioxide at cellular level

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7
Q

Aerobic Tissue Oxygenation

A

In order for tissues to engage in aerobic metabolism they need oxygen
allows conversion of glucose to ATP
Get 36 moles ATP per mole glucose

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8
Q

Anaerbic Tissue Oxygenation (Hypoxia)

A

If not enough oxygen is available, we have anaerobic metabolism
Get 2 moles ATP per mole glucose and production of lactate

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9
Q

4 principle hemodynamic processes

A
  1. O2 content
  2. O2 delivery
  3. o2 consumption
  4. o2 reserve/return
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10
Q

Oxygen Content Equation (CaO2)

A

CaO2 = 1.34* HGb* SaO2 +(0.003 *paO2100)

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11
Q

What is 1.34 in the oxygen content equation?

A

the amount of oxygen (ml at 1 atm) bound per gram of hemoglobin

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12
Q

What is the 0.003 in the oxygen content equation?

A

represents the amount of oxygen dissolved in plasma

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13
Q

WHat is the primary way to increase oxygen content?

A

Hemoglobin

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14
Q

O2 Delivery Equation (DO2)

A

Available Oxygen x Delivery Rate

Arterial Content x Cardiac Output

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15
Q

What is normal DO2?

A

600 cc/min/m2

(900-1000) cc/min

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16
Q

How do we assess the effectiveness of oxygen transport?

A

Arterial and mixed venous blood gas determination (central lab)
Noninvasive pulse oximetry
Invasive mixed venous saturation monitoring
Continuous indwelling arterial blood gas monitoring
Point of care blood gas monitoring
Transcutaneous po2 monitoring
transcutaneous meausre of local tissue oxygen saturation

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17
Q

Continuous indwelling arterial blood gas monitoring

A

20 gauge fiberoptic probe that measures pH, pCO2 and PO2

conflicting results on accuracy/very expensive/ no commerical units

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18
Q

Transcutaneous PO2 monitirng

A

meausres oxygen tension of heated skin (43C) more problems than worth so not commonly used clinically

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19
Q

How Does the Body Compensate

A

Increased cardiac output
Extract more oxygen from hemoglobin at the systemic capillaries
increase amount of hemoglobin and red cell mass

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20
Q

Increased cardiac output

A

primary phsyiology response

healthy heart: 15-25 L/min

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21
Q

Extract more oxygen from the hemoglobin at the systemic capillaries

A

decrease venous saturation to 32%

below 32% anaerobic metabolism and metabolic acidosis start

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22
Q

Increase amount of hemoglobin and red cell mass

A

takes weeks to develop

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23
Q

Oxygen Consumption

A

the difference between the deliveyr and what is returned

AVO2 difference = Ca-Cv

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24
Q

Ca

A

the oxygen concentration of arterial blood (oxygenated blood)

25
Q

Cv

A

the oxygen concentration of venous blood (deoxygenated blood)

26
Q

Oxygen Consumption is a function of….

A

Cardiac output
difference in oxygen content b/w arterial and venous blood
VO2 = CO x 1.34 x Hb (SaO2 - SvO2) 10

27
Q

Oxygen Consumption (O2 Demand)

A

150 cc/min/m2

200-240 cc/min

28
Q

Oxygen Extraction Ratio

A

VO2/Do2 x 100
Ratio of oxygen uptake to delivery
Usually 20-30%
uptake is kept constant by increasing extraction when delivery drops

29
Q

Conditions that may affect tissue extraction

A

Excessive tissue requirements
Demand > Supply
Inability of body to use oxygen
Impaired oxygen unloading at the capillary level

30
Q

Demand > Supply

A

oxygen demand higher than system can provide
hypermetabolism/systemic inflammatory response syndrome (post CPB)
sepsis/ malignant hyperthermia

31
Q

Why would the body not be able to use oxygen?

A

Toxic hypoxia

sepsis/cyanide or ethanol toxicity

32
Q

Why would the body have impaired oxygen unloading at the capillary level?

A

Alkalemia/Hypocarbia

Administration of large amounts of banked blood

33
Q

Conditions that may affect tissue oxygenation

A

Inadquate blood flow
decresaed oxygen saturation of arterial hemoglobin
severe anemia

34
Q

Inadequate blood flow

A

ischemic hypoxia

-obstruction lesions of blood vessels/peripheral vascular disease

35
Q

Decreased oxygen saturation of arterial hemoglobin

A

hypoxemic hypoxia
inadequate oxygen transfer from lungs to blood
-hypoxemia most common cause (PaO2 less than 60 mmHg) / carbon monoxide poisoning / methemoglobinemia

36
Q

Severe anemia

A

anemic hypoxia
deificiency ofh emoglobin molecules
hemorrhage / nutritional deficiencies/dilution

37
Q

Oxygen Reserve (RO2)

A

oxygen reserve can be described as what’s left after consumption has taken place
venous gases returning ot the heart
it is essentially a build in phsyiological buffer

38
Q

Normal Oxygen Reserve

A

450 cc/min/m2

700-800 cc/min

39
Q

Carbon Dioxide

A

produced as part of the metabolic process and has an emission rate that is dependent on the level of activity

while co2 is not normally harmful, the concentration of CO2 can act as a marker for the adequacy of ventilation

40
Q

CO2 is produced where

A

at the tissue

41
Q

CO2 is picked up by what

A

the capillary

42
Q

ECMO will provide

A

oxygenation
carbon dioxide removal
maintenace of PH

43
Q

ECMO will have the ability to _______ and ______ both oxygenation and carbon dioxide removal.

A

Assist and control

44
Q

V-V ECMO

A

Oxygenated blood returned to the right side of hte heart (preoxygenated)

45
Q

V-A ECMO

A

oxygenated blood returned to the left side of the heart (as normal)

46
Q

Oxygenation is controlled on ECMO via ….

A

an O2 blender
Control of FIO2
Monitor PaO2

47
Q

If you increase FiO2 % = ______ PaO2 (mmHg)

A

increase

48
Q

Carbon Dioxide Removal

A

controlld by gas flowing across a membrane (LPM)
Blows off CO2 from the membrane
Monitor pCO2 (mmHg)

49
Q

Increase gas flow = ____ pCO2 (mmHg)

A

decrease

50
Q

Gas to BF ratio of ____ when intiating ECMO

A

1

51
Q

An increase in GBFR (more sweep) results in _____ pCO2

A

lower

52
Q

A decrease in GBFR (less sweep) results in _____ pco2

A

higher

53
Q

Cool stuff to know about gases

A

The body attempts to control PH
Respiratory centers control pCO2
metabolic processes control carbonic acid cycle
Hence ABG problems are referred to as metabolic or respitaory

54
Q

Modified Henderson Hasselbach Equation

A

pH = 6.1 + log ([HCO3-]/0.03 x pCO2)

55
Q

pH is proportional to …..

A

HCO3-

56
Q

pH inversely proportion to….

A

CO2

57
Q

Carbonic Acid Cycle

A

Carbonic acid is an intermediate step in the transport of CO2 out of the body via respiratory gas exchange
H20 + Co2(g) H2CO3 (carbonic acid) H+ + HCO3-

58
Q

The goal of ECMO is to….

A

rest the body

ECMO (7 decks)

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