Fouty- Arterial Blood Gas Flashcards by Madeline Wing

resp. alkalosis?

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resp. acidosis?

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3 main things arterial blood gases provide info on:

pH
adequacy of ventilation (PCO2)
adequacy of oxygenation (PaO2)

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how to calculate P(A-a)O2 gradient

alveolar gas equation (PAO2)-PaO2 measured

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_____ is directly related to alveolar ventilation

arterial CO2

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Henderson-Hasselbach equation

pH=pKa + log (HCO3-)/s x PCO2

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s in HH equation is what

solubility of CO2

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normal pH in people (range)

7.36-7.44

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normal solubility of CO2

0.03

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PCO2 (lung or kidney)

lung

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HCO3- (lung or kidney)

kidney

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decrease in HCO3- and PCO2 stays the same

uncompensated metabolic acidosis

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HCO3- increased and PCO2 remains the same

uncompensated metabolic alkalosis

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increase in PCO2 and HCO3- the same

uncompensated respiratory acidosis

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what decreases when PCO2 is increased

alveolar ventilation

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decrease in PCO2 and HCO3- hasn’t changed

uncompensated respiratory alkalosis

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2 things that make pH alkalinic

less PCO2
more HCO3-

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2 things that make pH acidotic

decrease in HCO3-
increase in PCO2

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____ and ____ are pathologic processes in which the values for acid and base are out of the normal range

acidosis and alkalosis

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____compensation is fast

respiratory compensation

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___ compensation is slow

metabolic

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decreased HCO3-, and then decrease PCO2

compensated metabolic acidosis

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causes of metabolic acidosis

seizure
DKA
severe diarrhea

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in compensated metabolic acidosis, does the pH go back to normal due to increased alveolar ventilation

no, it gets it back into normal range but not all the way normal

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cause of increase PCO2

hypoventilation too much morphine

increase in PCO2 (respiratory acidosis), in 3-5 days, kidneys will compensate by what

increasing HCO3- (kidneys get pH back to normal)

Acidemia and alkalemia denote that the process has resulted in an abnormal pH. This frequently indicates that the initial acid-base abnormality is _________

uncompensated or inadequately compensated

blood pH>/= 7.45

alkalemia

denotes a blood pH

acidemia

body handles acidemia better than what

alkalemia

acute change of PaCO2 of 10 mmHg leads to pH change of ____

0.08

if PaCO2 is down, what is increased

alveolar ventilation

if PaCO2 is increased, what is decreased

alveolar ventilation

main way CO2 is carried from tissues to lungs

HCO3-

PCO2 correlates linearly w/ _____ content over human range

CO2

normal range of PaCO2

38-42 mmHg

normal range of HCO3

22-26 meq/L

PaCO2

primary respiratory alkalosis

PaCO2>/= 45 mmHg

primary respiratory acidosis

HCO3- >/=28 meq/L

primary metabolic alkalosis

HCO3-

primary metabolic acidosis

uncompensated respiratory acidosis

if PaCO2 changes by 10, HCO3- changes by ____

change in pH is directly a result of change in ____

PaCO2

uncompensated respiratory alkalosis

primary respiratory alkalosis and primary metabolic alkalosis

primary metabolic acidosis

hyperventilation is PaCO2 < ____

36 mmHg

compensation for metabolic acidosis

hyperventilation

Winter's formula used for what

to check is there is adequate compensation for metabolic acidosis

Winter's formula:

PaCO2= 1.5HCO3 + 8 +/- 2

for normal respiratory compensation, pH does not return to _____

normal range

point of compensation

to keep us from dying acutely from metabolic acidosis while physician tries to correct it

- lactic acidosis - ketoacidosis - toxic ingestions - loss of HCO3 - severe diarrhea

causes of metabolic acidosis

primary respiratory alkalosis w/ metabolic compensation

primary metabolic acidosis with some respiratory compensation (went from 40 to 30)

reasons for metabolic acidosis with inadequate respiratory compensation (can't blow out CO2 like they should)

neuromuscular weakness w/ severe diarrhea ILD narcotics

if this person was well yesterday and this is their ABG

metabolic acidosis

this ABG has occurred over weeks

metabolic compensation

aspirin toxicity

respiratory alkalosis w/ metabolic acidosis

long standing asbestos exposure

induced lung disease w/ respiratory alkalosis w/ metabolic compensation

if it's an acute event, what doesn't have time to kick in

metabolic compensation

If they can’t blow down CO2 enough, means they have underlying reason/weakness and cant generate _____to blow CO2 down

alveolar ventilation

lactic acidosis ketoacidosis renal failure diarrhea aspirin

common causes of primary metabolic acidosis

vomiting diuretics hypokalemia excessive tums hyperaldosteronism

causes of primary metabolic alkalosis

retain arterial CO2

hypoventilation

ILD neurologic injuries aspirin intoxication hypoxia

causes of primary respiratory alkalosis

Takes time (48-72 hours minimum) for compensation

excretion of HCO3 by kidney

ILD chest wall disease neuromuscular disease opiate use

causes of primary respiratory acidosis

how to compensate for respiratory acidosis

retain HCO3-

respiratory compensation for metabolic acidosis--- fast, but ____

incomplete

metabolic compensation for respiratory acidosis-----slow, but ______

more complete

inadequate tissue oxygen

hypoxia

low arterial oxygen tension (PaO2) less than 80 mmHg

hypoxemia

low arterial oxygen saturation (SaO2) less than 90%

desaturation

will widen A-a gradient and lead to hypoxemia

low V/Q and shunt

alveolar gas equation

PAO2= (Pb - PH2O) x FiO2 - PaCO2/R

best estimate to low V/Q mismatch

P(A-a) gradient

normal A-a gradient

10-12

5 main causes of hypoxemia (PaO2<80 mmHg)

altitude hypoventilation diffusion low V/Q mismatch shunt

extreme exercise or extreme altitude (doesn’t occur very often in clinical medicine) as the blood passes through the capillary in the alveolar interface, there is not complete equilibration b/t alveoli and the blood going past it

diffusion as cause of hypoxemia

normal A-a O2 gradient w/ hypoxemia

altitude hypoventilation

increased A-a gradient w/ hypoxemia

diffusion low V/Q mismatch shunt

___ and ___ contribute to arterial hypoxemia

shunt and low V/Q

shunt

low V/Q

responds to 100% oxygen

low V/Q (not shunt)

How you get carboxyHb and methemoglobin

co-oximeter

failure to excrete CO2

hypercapneic (ventilatory) respiratory failure

inability to oxygenate

hypoxic respiratory failure

minute ventilation decreased or dead space increased

respiratory failure