Ap2 Abg Review

Front 1

What parts of an ABG are measured?

Back 1

PaO2, PaCo2, pH

Front 2

What parts of an ABG are calculated?

Back 2

HCO3 and Base status

Front 3

What is the electrode used to measure PaO2?

Back 3

Clark electrode

Front 4

What is the electrode used to measure pH?

Back 4

Senz electrode

Front 5

What is the electrode used to measure PaCO2?

Back 5

Servinghaus

Front 6

Name the normal values for the following components of an ABG?
PaO2/PaCo2/pH/HCO3/BE

Back 6

PaO2 80-100 torr
PaCO2 35-45 torr
pH 7.35-7.45
HCO3 22-26 meq/L
BE 0 +/-2

Front 7

What does base status tell us?

Back 7

The status of the buffering system within the body, and whether or not there is adequate supply
It may also be an indicator of intravascular status

Front 8

How is Bicarb units measured?

Back 8

meq/L

Front 9

Define:
1.Acid-
2.Base-
3.Buffer-
4.pH

Back 9

1.A molecule which dissociates and gives up a H+
2.A molecule which binds and associates (takes up) a H+
3.A substance that readily accepts or donates H+ ions
4.-puissance Hydrogen, the strength of hydrogen

Front 10

How is acid defined?

Back 10

Not by its charge but its ability to dissociate (give up) H+

Front 11

Which acid/base conjugate are we most concerned with in ABG/pH regulation?

Back 11

H2CO3 (carbonic acid) ----> HCO3 + H+

Front 12

What is the #1 extracellular buffering system in the body?

Back 12

Bicarbonate (50%)

Front 13

What are the other extracellular buffering systems?

Back 13

Hgb (35%)
PO4
Plasma proteins

Front 14

What is the main Intracellular buffering system in the body?

Back 14

Proteins

Front 15

Why is H+ excreted in the kidneys and HCO3 reabsorbed?

Back 15

So more does not have to be synthesized, it is just reused

Front 16

What is the main excretion route for modest H+ loads in the body?

Back 16

the lungs-handles most acute loads in about 5 minutes, however is not complete

Front 17

How are chronic loads of H+ handled?

Back 17

The kidneys

Front 18

How do the kidneys buffer H+?

Back 18

Active exchange of Na+ for H+
Presence of Carbonic Anhydrase-which carries CO2 and dissociates into water and CO2

Front 19

What is the range of life sustaining pH and why does life cease to exist beyond this range?

Back 19

6.8-7.8- because out of this range enzyme systems fail particularly membrane systems where ion transportation is a necessity
Should be concerned outside 7.25 and 7.55

Front 20

What is an indices that is followed to determine adequate tissue perfusion?

Back 20

The base status

Front 21

Neutral pH has an H+ ion concentration of how much?

Back 21

7.4 contains 40 nnmols/L
7.5=30
7.3=50

Front 22

The pH scale of H+ ion concentration is what type of scale and how much does it change with pH changes?

Back 22

It is a logrhythmic scale with a base of 10 that changes approximately 20% for each 0.1 change in pH.

Front 23

What does neutral pH mean?

Back 23

That there is equal amts of H+/OH- ions

Front 24

Define the following terms related to the Henderson-Hasselbach Equation?
pH-
pKa-
{A-}
{HA-}

Back 24

pH- The negative log of the H+ ion concentration
pKa- Dissociation constant for carbonic acid-H2CO3
{A-} HCO3
{HA-} Carbonic acid or 0.3*paCO2

Front 25

What is the Henderson-Hasselbach equation?

Back 25

pH=pka+log [A-]/[HA]
pH = relative amount of hydronium/bicarb
base/acid

Front 26

Neutral pH has an H+ ion concentration of how much?

Back 26

7.4 contains 40 nnmols/L
7.5=30
7.3=50

Front 27

The pH scale of H+ ion concentration is what type of scale and how much does it change with pH changes?

Back 27

It is a logrhythmic scale with a base of 10 that changes approximately 20% for each 0.1 change in pH.

Front 28

What does neutral pH mean?

Back 28

That there is equal amts of H+/OH- ions

Front 29

Define the following terms related to the Henderson-Hasselbach Equation?
pH-
pKa-
{A-}
{HA-}

Back 29

pH- The negative log of the H+ ion concentration
pKa- Dissociation constant for carbonic acid-H2CO3
{A-} HCO3
{HA-} Carbonic acid or 0.3*paCO2

Front 30

What is the Henderson-Hasselbach equation?

Back 30

pH=pka+log [A-]/[HA]
pH = relative amount of hydronium/bicarb
base/acid

Front 31

What is 0.3 in the bicarb replacement formula?

Back 31

The solubility coefficient of carbon dioxide in blood

Front 32

What equation is used to determine H+ ion concentration for a given pH?

Back 32

Henderson equation
H+= 24 x PaCO2/HCO3-

Front 33

Define the alveolar Air equation?

Back 33

Determines the best possible PAO2 that you can have based on the atmospheric pressure and FiO2 in a given environment
PAO2= FiO2 (PB – PH2O) – (PCO2/R)

Front 34

Which laws affect the alveolar gas equation?

Back 34

Henry’s/Daltons law

Front 35

What is normal A-a DO2?

Back 35

5-15mmHg-may be as high as 20mmHg

Front 36

Why is there a difference?

Back 36

Because there is a normal shunt

Front 37

What does this formula A-aDo2 determine?

Back 37

The amount of shunt of perfused but not ventilated airways
Qs/Qt

Front 38

An increase of 1% shunt will do what to the A-a DO2?

Back 38

Increase it by 20 mmHg

Front 39

How is shunt calculated when supraphysiologic O2 is admin (FiO2>50%) calculated?

Back 39

A-a O2D/20

Front 40

An increase of PCO2 of 10 torr will do what to pH normally?

Back 40

Decrease the pH by 0.05 units

Front 41

A decrease of PCO2 of 10 torr will do what to pH normally?

Back 41

Increase the pH by 0.1 units

Front 42

How much CO2 is produced each minute in the body?

Back 42

200 cc’s

Front 43

Ventilatory failure occurs when PaCO2 reaches what levels?

Back 43

> 50 torr

Front 44

How do you calculate base status?

Back 44

Use conversion formula to determine what pH should be.
Calculated pH- actual pH
Negative or positive # determines deficit or excess
Express that # as a whole # then multiply by 2/3’s

Front 45

How do you calculate HCO3 replacement?

Back 45

ECF% * kg * Base
0.3 * kg * Base
give ½ calculated dose to begin

Front 46

What problems are associated with NaHCO3 replacement?

Back 46

Na+ loads
Oxyhgb shifting

Front 47

In an acute PaCO2 setting what affects does PaCO2 have on plasma HCO3?

Back 47

IncreasePaCO2 of 10 torr= Increase HCO3 by 1mmol/liter
Decrease PaCO2 of 10 torr= DecreaseHCO3 by 2mmol/liter

Front 48

In a chronic PaCO2 setting what affects does PaCO2 have on plasma HCO3?

Back 48

IncreasePaCO2 of 10 torr= Increase HCO3 by 4mmol/liter
Decrease PaCO2 of 10 torr= Decrease HCO3 by 6 mmol/liter

Front 49

How much will the PaCO2 (Respiratory compensation) increase for metabolic alkalosis?

Back 49

PaCo2 will increase 0.5-0.6 torr for every 1.0 mEq increase in HCO3
The last two digits of the pH should = the HCO3 + 15

Front 50

Define:
Daltons Law:
Henry’s Law:
Graham’s Law:

Back 50

Daltons Law: All gasses in a closed container will exert a pressure that is cumulative
Henry’s Law: The amt of gas that can be dissolved in a liquid is proportional to the p of the gas to which the liquid is exposed.
Graham’s Law: The diffusibility of a gas in inversely proportional to the square root of its molecular weight.

Front 51

What is the critical saturation of a venous O2 sat?

Back 51

50%

Front 52

What is the formula for total arterial content?

Back 52

CaO2= (1.34 x Hgb) x (SaO2%) + (PaO2 x .003)

Front 53

What is the 1.34?

Back 53

The amount O2 that can be carried on 1 Hgb molecule

Front 54

What is the .003?

Back 54

The solubility of O2 in the blood

Front 55

What is the formula for arterial O2 transportation?

Back 55

CaO2 x CO

Front 56

What is the formula for venous O2 transportation?

Back 56

CvO2 x CO

Front 57

How do you calculate the O2 extraction?

Back 57

A-VO2d= CaO2-CvO2

Front 58

What is the P50?

Back 58

The PaO2 at which Hgb is 50% saturated
Adults= 27 Child= 19

Front 59

What things will cause a right shift of the Oxyhgb curve?

Back 59

Increase 2,3 DPG
Decrease pH
Increase Temp
Increase PaCO2

Front 60

Why do ABG’s need temp correction?

Back 60

Because gas is more soluble in blood when it is cold

Front 61

How do you calculate the Anion Gap?

Back 61

Na+ -((Cl-) +(HCO3))

Front 62

Anion gap is beneficial for what purposes?

Back 62

Determining causes of acidosis

Front 63

What do you look for when your patient is Acidotic and has an elevated anion gap?

Back 63

L-lactate
U-Uremia-renal failure-organic acids (SO4/PO4)
K-Ketoacidosis (DKA/Starvation/Ethanol/ETOH)
S-Salicylates
E-Ethylene glycol
M-Methynol
P-Paraldehyde

Front 64

What do you look for when you have acidosis with a normal anion gap?

Back 64

B-Bicarb loss (diarrhea/GI losses)
A-Acid loads
D-Dilutional HCO3 w/NSS
R-Renal defects-poor HCO3 reabsorption and acid secretion

Front 65

CO2 transportation is primarily dependent upon what factor?

Back 65

HCO3

Front 66

100 meq of bicarb makes how many L of CO2?

Back 66

over 2L
intracellular acidosis may worsen acutely

Front 67

What is the normal anion gap?

Back 67

12=/-2mmol/L

Front 68

The normal gap is attributed to the presence of what negatively charged substance?

Back 68

Albumin

Front 69

Does hypochloremia narrow or widen the gap?

Back 69

Widen - metabolic acidosis

Front 70

How is knowing the anion gap useful?

Back 70

Use value to focus diagnostic evaluation

Front 71

What is THAM?

Back 71

Tromethamine - proton acceptor- used as a buffer when Na+ load not desired. Crystalloid. 500 ml=3amp of bicarb

Front 72

What is the total dose of tromethamine solution for a 70 kg adult having a base deficit of 5meq/L?

Back 72

385 ml of 0.3 M solution
(ml of 0.3M solution = body wt (kg)x base deficit(meq/L)x1.1 (constant)