Acid-base balance Flashcards
What is normal pH?
7.35-7.45 (remember 7.4)
What is normal pCO2?
4.7-6kPa (remember 5.5ish)
What is normal pO2?
11-13kPa (remember 12)
What is normal bicarb?
22-26 (remember 24)
What is normal base excess?
-2 to plus 2
What does pCO2/pO2 actually mean?
Concentration of CO2 or oxygen dissolved in blood
Between base excess and bicarbonate, which is measured and which is calculated?
Base excess is CALCULATED
Bicarbonate is measured
How do you approach an ABG?
- Check whose ABG it is
- What are you expecting from this ABG?
- Is the pt on any oxygen? If so, how much and has this been adjusted for?
- Check pH
- Check respiratory component (pCO2)
- Check metabolic component (BE/bicarb)
How quickly does compensation happen?
Metabolic compensation is slow - takes days
Respiratory compensation is quicker
pH 7.2
pCO2 7kPA
Bicarb 24
Respiratory acidosis, no compensation
pH = low
pCO2 = high
BE/Bicarb = normal
pH 7.2
pCO2 - 4.5kPa
Bicarb - 20
Metabolic acidosis with respiratory compensation
pH = low
pCO2 = low (quick compensation)
BE/Bicarb = low (problem)
pH 7.5
pCO2 - 4.3 kPa
Bicarb - 22
Respiratory alkalosis, no metabolic compensation
pH = high
pCO2 = low
BE/Bicarb = normal (too slow to compensate)
pH 7.5
pCO2 - 6.5 kPa
Bicarb - 27
Metabolic alkalosis
pH = high
pCO2 = high (to compensate)
BE/Bicarb = high
pH 7.35
pCO2 6.5kPa
Bicarb - 27
Chronic respiratory failure
pH = normal (compensated)
pCO2 = high from COPD etc
Bicarb - compensated high
Causes of respiratory acidosis
Hyperventilation
CO2 retention -
