pH Disorders

Question 1

What is the difference between Acidemia vs. Acidosis?

Answer 1

acidemia is the pH’s change away from the reference range (so just a description of the lab)

acidosis refers to the abnormal condition or process that contributes to the pH’s change

(same difference for alkalemia and alkalois)

Question 2

What is the normal pH range?

Answer 2

7.36-7.44

Question 3

What is the normal pCO2 range?

Answer 3

38-42 mm hg

Question 4

What is the normal HCO3 range?

Answer 4

22-28 mEq/L

Question 5

What are the implications of the henderson-Hasselbach equation?

Answer 5

it’s the HCO3/H2CO3 buffer system

Basically, if pCO2 goes up, then pH goes down

If HCO3 goes up, then pH goes up

CO2 is the acid and HCO3 is the base

Question 6

What are Dr. Li’s steps for working through acid base problems?

Answer 6

identify all the abnormalities (pH/CO2/bicarb)

acidosis vs alkalosis

metabolic or respiratory

acute or chronic

calculate anion gap

calculate the expected pCO2 range

Question 7

How do you calculate the anion gap?

Answer 7

Na - (Cl + HCO3)

Question 8

What’s the normal range for anion gap?

Answer 8

7-16 (12 typically used)

Question 9

WHat are the normal “unmeasured” anions in the gap?

Answer 9

phosphates
sulfates
albumin

Question 10

If the anion gap is over 20, but the pH and bicarb is normal, does the patient have an acidosis?

Answer 10

YES - anion gap over 20 defines metabolic acidosis regardless of what the pH or bicarb are doing, which is why you always need to calculate it

just means there is a mixed process going on

Question 11

Why do you need to calculate the expected pCO2 range?

Answer 11

it determines whether respiratory compensation is adequate or under or over-compensated

Question 12

How do you calculate the expected pCO2 range?

Answer 12

1.5 x (measured HCO3) + 8 +/- 3

Question 13

If the pCO2 is above the expected range, what is the secondary process?

Answer 13

respiratory acidosis even if the pCO2 is below 40

Question 14

If the pCO2 is less than the expected range, what’s oging on?

Answer 14

they’re not compensating appropriately, so there is a concomitant respiratory alkalosis

Question 15

If there is an anion gap, what do you need to calcualate next? Why?

Answer 15

the excess anion gap (or delta gap)

It allows you to determine the “corrected” bicarbonate to see whether there are any other metabolic disturbances

Question 16

How do you calculate the excess anion gap?

Answer 16

Calculated AG - 12

Question 17

How do you calculate the corrected bicarbonate?

Answer 17

Corrected bicarb = measured bicarb + excess anion gap

Question 18

A corrected bicarb over what will reveal an underlying primary metabolic alkalosis?

Answer 18

over 30

Question 19

A corrected bicarb under what will reveal an underlying primary metabolic acidosis?

Answer 19

23