Chapter 9 Flashcards

1
Q

What is PAO2?

A

Alveolar partial pressure

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2
Q

How is PAO2 calculated?

A

PAO2 = FiO2 (barometric pressure - saturated pressure of water) - PaCo2/0.8

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3
Q

What is the normal alveolar-arterial oxygen gradient?

A

Room air - <25
100% oxygen - <120

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4
Q

How is BE calculated? What is it’s advantage over HCO3?

A

The amount of acid needed to to return pH to 7.4 at PaCO2 of 40
Takes into consideration all buffering systems, not just H2CO3-HCO3 buffer

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5
Q

What is normal BE?

A

+/-4

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6
Q

Ddx metabolic acidosis

A

Loss of HCO3 - d+
Failure to excrete H+ - RTA
Acid accumulation - lactic (shock), DKA

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7
Q

How is anion gap calculated?

A

AG = (Na + K) - (Cl + HCO3)

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8
Q

What is normal anion gap?

A

Dogs - 12-25
Cats - 13-27

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9
Q

What is the physiological cause of a normal anion gap acidosis?

A

Decrease in HCO3 balanced by increase in chloride or unmeasured anions

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10
Q

What causes high anion gap acidosis?

A

D - hyperosmolar non-ketotic DM, DKA
U - uraemia/azotaemia
E - ethylene glycol (also aspirin, methanol, paraldehyde)
L - lactic acidosis

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11
Q

What causes normal anion gap acidosis?

A

D+
Early renal failure
RTA
Carbonic anhydrase inhibitor
Acidifying agents
Hyperalimentation
Rapid IV rehydration (dilution of HCO3)
Ketoacidosis with renal ketone loss

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12
Q

What causes a low anion gap?

A

Retained non-sodium cations (hyperproteinaemia, ^^Ca++, ^^Mg, lithium toxicity) => extracellular fluid Na reduced to maintain electroneutrality
Hypoalbuminaemia, dilution - dilutes unmeasured anions, compensatory increase in anions to maintain electroneutrality

Not normally associated with acidosis

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13
Q

Ddx metabolic alkalosis

A

HCO3 overload
Severe gastric vomiting
Loop/thiazide diuretics

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14
Q

Acute respiratory acidosis - what is the expected compensation for each 10mmHg increase in PaCO2?

A

^HCO3 by 1.5

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15
Q

Chronic respiratory acidosis - what is the expected compensation for each 10mmHg increase in PaCO2?

A

^HCO3 by 3.5

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16
Q

Acute respiratory alkalosis - what is the expected compensation for each 10mmHg decrease in PaCO2?

A

vHCO3 by 2.5

17
Q

Chronic respiratory alkalosis - what is the expected compensation for each 10mmHg decrease in PaCO2?

A

vHCO3 by 5.5

18
Q

Metabolic acidosis - what is the expected compensation for each 1mmol/l decrease in HCO3?

A

vPaCO2 by 0.7

18
Q

Metabolic alkalosis - what is the expected compensation for each 1mmol/l increase in HCO3?

A

^PaCO2 by 0.7