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19 Cards in this Set

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What is the relationship between hydrogen ion concentration [H+] and partial pressure of carbon dioxide (PCO2) and concentration of bicarbonate [HCO3]?
[H+] in nEq/L = 24 x (PCO2/[HCO3])
What is normal arterial PCO2?
40 mm Hg
What is normal HCO3 concentration?
24 mEq/L
What is the primary change for a respiratory acidosis?
decreased ventilation and ↑PCO2
What is the primary change for a respiratory alkalosis?
increased ventilation and ↓PCO2
What is the primary change for a metabolic acidosis?
↓HCO3
What is the primary change for a metabolic alkalosis?
↑HCO3
For a primary metabolic acid-base disorder, pH and PCO2 change in the same direction. True or False.
True.
When do suspect a superimposed respiratory acid-base disorder on a primary metabolic acid-base disorder?
1. When measured PCO2 is nl.
2. When measured PCO2 is higher or lower than the expected PCO2
What is the expected change in PCO2 for a metabolic acidosis?
PCO2 = 1.5 x HCO3 + (8 ± 2)
what is the expected change in PCO2 for a metabolic alkalosis?
PCO2 = 0.7 x HCO3 + (21 ± 2)
For a primary respiratory acid-base disorder, pH and pCO2 change in the same direction. True or False.
False.
What is the expected pH change for an acute respiratory acidosis? a chronic respiratory acidosis?
ΔpH = 0.008 x (PCO2 - 40)
ΔpH = 0.003 x (PCO2 - 40)
What is the expected pH change for an acute respiratory alkalosis? chronic respiratory alkalosis?
ΔpH = 0.008 x (40 - PCO2)
ΔpH = 0.017 x (40 - PCO2)
Are compensatory responses to primary acid-base disorders able to comletely correct the primary abnormality?
No
What does the anion gap help distinguish?
Whether a metabolic acidosis is due to an accumulation of hydrogen ions vs. a loss of bicarbonate.
In the setting of metabolic acidosis, what does a high anion gap suggest?
organic acid accumulation (ie lactic acid or ketoacids or renal failure with impaired hydrgoen ion excretion

Excess hydrogen ions combine with bicarbonate to form carbonic acid. This decreases bicarb concentration and increases the anion gap.
What is suggested by a metabolic acidosis with a normal anion gap?
Sign of bicarbonate-wasting process such as diarrhea or increased bicarbonate losses in the urine in early renal failure.
What is the AG excess/ HCO3 deficit ratio and what is its utility?
(AG - 12)/(24 - HCO3)
Useful for differentiating mixed metabolic acidosis. In high AG metabolic acidosis, ratio is one. In nl AG metabolic acidosis, ratio appraches zero. In mixed acidosis, ratio suggests the equivalent contribution from high AG and nl AG acidoses.