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My 2016 RUSVM Anesthesia > Blood Gase Dr. Ambrisko > Flashcards

Blood Gase Dr. Ambrisko Flashcards

1
Q

What are the buffering systems of the body

A

Chemical

Respiration

Renal

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2
Q

How fast do chemical buffers work

A

extracellular: in seconds (HCO3-)
intracellular: within hours (phosphate & proteins)

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3
Q

How fast does respiration buffer work

A

adjusting CO2 within minutes

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4
Q

How fast does the renal buffering system work

A

within hours to days by excreting H+ & retaining HCO3-

metabolic compensation

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5
Q

What is the simple way to understand how changes in HCO3 influence pH

A

pH = HCO3-/PaCO2

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6
Q

What are the measured blood gas variables

A

pH

PaCO2

PaO2

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7
Q

What are the calculated blood gas variables

A

HCO3

BE

Oxygen content (CaO2)

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8
Q

define -emia

A

applies to changes in blood

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9
Q

define -osis

A

applies to physiological processes (conditions)

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10
Q

What is assessed for respiratory component of pH

A

PaCO2

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11
Q

What is assessed for metabolic component

A

BE or HCO3

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12
Q

is there any metabolic compensation during anesthesia for pH changes

A

No! No time

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13
Q

Normal blood pH

A

7.35-7.45

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14
Q

define acidosis

A

a physiological process, that occuring alone, tends to cause acidemia

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15
Q

define alkalosis

A

a physiological process, that occurring alone, tends to cause alkalemia

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16
Q

what are mixed acid-base disorders

A

different kinds of acidosis a/o alkalosis occurring together

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17
Q

what is a primary acid-base disorder

A

defined by the initial change in HCO3 or PaCO2

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18
Q

What is compensation

A

secondary change in HCO3 or PaCO2 in order to attenuate the effect of the primary disorder on blood pH

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19
Q

in respiratory acidosis would PaCO2 elevated?

what would the compensation be?

A

yes

HCO3 would elevate to compensate (metabolic compensation)

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20
Q

in respiratory alkalosis would PaCO2 elevated?

what would the compensation be?

A

No!

Metabolic compensation would mean a decrease in HCO3

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21
Q

in metabolic acidosis would HCO3 be elevated?

what would the compensation be?

A

No

Respiratory compensation would be a decr in PaCO2

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22
Q

in metabolic alkalosis would HCO3 be elevated?

what would the compensation be?

A

Yes

the respiratory compensation should be an incr PaCO2

23
Q

How to tell if an acid-base disorder is mixed

A

pH value is unexpected from a change in HCO3 or PaCO2

normal pH w/ abnormal HCO3 or PaCO2

24
Q

normal HCO3

A

24 +/- 4 mEg/L

cats tend to be lower - think about diet, higher acid

herbivores tend to be higher - think about diet, higher base

25
Q

normal PaCO2

A

35-45 mmHg

cats tend to be lower (just weird animals)

26
Q

What is Base excess (BE)

A

refers to an excess or deficit in the amount of base present in blood

defines the metabolic component of acid-base disturbances

27
Q

What does a positive BE signify

A

metabolic ALKALOSIS

(positive for excessive base in blood)

28
Q

What does a negative BE signify

A

metabolic acidosis

29
Q

Normal BE

A

0 +/- 4 mEq/L

30
Q

How does CO2 exist in blood

A

as HCO3 & dissolved CO2

31
Q

What is TCO2

A

Total CO2

almost the same as HCO3

can use interchangeably if HCO3 not available

32
Q

What is PaCO2 equation

A

partial pressure (mmHG) of CO2 in the arterial blood

33
Q

What is important about PaCO2

A

it defines alveolar ventilation

34
Q

What are the factors that can reflect (make up) any PaCO2 value

A

Any combo of RR, TV or breathing effort

35
Q

A PaCO2 (mmHg) of >45 would indicate which blood condition

which state of ventilation

A

hypercapnia

hypoventilation

36
Q

A PaCO2 (mmHg) of 35-45 would indicate which blood condition

which state of ventilation

A

eucapnia

normal ventilation

37
Q

A PaCO2 (mmHg) of < 35 would indicate which blood condition

which state of ventilation

A

hypocapnia

hyperventilation

38
Q

What will an incr PaCO2 cause

(hypoventilation)

A

lower PAO2

lower pH

reflect respiratory acidosis

reflect respiratory compensation for metabolic alkalosis

*PAO2 = partial pressure (mmHg) of O2 in Alveolar space

39
Q

what do you need to remember when interpreting PaO2

A

does not reflect O2 content

interpreted in light of

  • FiO2
  • ambient pressure
  • PaCO2
40
Q

what is FiO2

A

inspired O2 fraction

  • at 100% O2 ⇒ FiO2 = 1*
  • at air ⇒ FiO2 = .21*
41
Q

what is PiO2

A

inspired O2 pressure (FiO2 x Pambient)

  • at 100% O2 ⇒ PiO2 = 760 mmHg*
  • at air ⇒ PiO2 = 160 mmHg*
42
Q

What should the PaO2 be when breathing 100% O2

and if not what expected?

A

expect PaO2 > 500 mmHg

Lower than expected PaO2 values may indicate V/Q mismatch resulting from atelectasis

43
Q

What is A-a difference

A

aka A-a gradient ⇒ is the real life difference between the Pressure of O2 in the Alveolar space vs the Pressure of O2 in arterial blood

44
Q

What is most likely cause for a high A-a difference (or gradient)

A

V/Q mismatch ⇒ #1 cause under anesthesia

45
Q

reasons for V/Q mismatch

A

Atelectasis (common under anesthesia)

46
Q

What can A-a difference be used for

A

to distinguish lung diseases (V/A mismatch) from hypoventilation as a cause of hypoxemia

with hypoventilation: A-a difference normal

with V/Q mismatch: A-a difference abnormal

47
Q

What is normal PaO2/FiO2 ratio

A

> 500 mmHg

48
Q

Name 5 causes for hypoxemia (low PaO2)

A

Low FiO2

Hypoventilation

Diffusion impairment

V/Q mismatch

R-L shunt

49
Q

define hypoxia

causes

A

insufficient oxygenation of the tissues

hypoxemia

insufficient perfusion

insufficient O2 uptake

50
Q

where is most O2 carried in arterial blood

A

carried by Hb

small portion dissolved in plasma

51
Q

in a clinical situation if lactate is >2 mmolL what is the significance

A

lactate >2mmol/L is high & may indicate incr anaerobic metabolism

52
Q

what is abnormally high lactate called

most common causes

A

lactic acidosis

Systemic: shock, sepsis (e.g. GDV, colic)

Local: tournequet, under-perfusion of dependent muscles, intestinal torsion, etc.

53
Q

what is the parameter that is a prognostic indicator when managing sick patients

A

lactate level

54
Q
A

My 2016 RUSVM Anesthesia (22 decks)

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