OnlineMedEd: Nephrology - "Acid Base II"

Question 1

Review how much pH should change in acute and chronic CO2 distrubances.

Answer 1

For every change of 10 in CO2 levels, the pH should change by 0.08 acutely and 0.04 chronically.

Question 2

Review how much bicarb should change in acute and chronic CO2 disturbances.

Answer 2

• Respiratory acidosis: for every increase of 10 in CO2, bicarb should change 1 acutely and 3 chronically.
• Respiratory alkalosis: for every decrease of 10 in CO2, bicarb should change 2 acutely and 4 chronically.

Question 3

How do you calculate appropriateness of the pCO2 response in metabolic acidosis?

Answer 3

Winter’s formula:

pCO2 should equal 1.5 x bicarb + 8 +/- 2

If pCO2 is greater than this range, then you have a coexisting respiratory acidosis. If pCO2 is less, then a coexisting respiratory alkalosis.

Question 4

Review the mnemonics you made for calculating compensation.

Answer 4

• For respiratory alkalosis, the bicarb should change by 2 acutely and 4 chronically.
-> Think of someone hyperventilating (respiratory alkalosis) because the show 24 is so intense. (2… 4…)

• For respiratory acidosis, imagine someone holding their breath (respiratory acidosis) as they pass the 13th floor in an elevator. (1… 3…)
• For Winter’s formula, imagine someone riding a BIke with an extra wheel (1.5 bicarbs) with a velvet 8 ball dangling from the handlebars over a pool of acid.

Question 5

The only additional test you need to do in metabolic alkalosis is _____________.

Answer 5

check the anion gap for possible superimposed metabolic acidosis