Acid Base Disorders - Finding disturbances.

Question 1

First step of working up an acid base d/o?

Answer 1

pH > 7.4 = alkalemia

pH

Question 2

Second step of working up an acid base d/o?

Answer 2

CO2.
If acidemia, CO2 > 40 = respiratory acidosis
If alkalemia, CO2

Question 3

Third step of working up an acid base d/o?

Answer 3

3a. Anion gap (always, no matter what the primary disturbance).

Question 4

If the primary process is respiratory, what are the next steps in working up additional disturbances?

Answer 4

3b. Acute or chronic?

Question 5

In respiratory disturbances, how do you determine if it’s acute/chronic?

Answer 5

1. Find change in pH from 7.4
2. Find change in CO2 from 40.
3. For each 10 change in CO2, expect 0.08 change in pH for acute process, and 0.04 change in pH for chronic process. Do the math to figure out which is closer.

Question 6

After determining acute/chronic in a respiratory disturbance, what is the next step?

Answer 6

Is the bicarb response appropriate?

Question 7

How does bicarb change in response to respiratory acidosis? How does this happen at the cellular level for acute v. chronic?

Answer 7

As CO2 increases, bicarb should increase.
Acute: intracellular buffering
Chronic: Generation of new bicarb via ammonium excretion.

Question 8

How does bicarb change in response to respiratory alkalosis? How does this happen at the cellular level for acute v. chronic?

Answer 8

As CO2 decreases, bicarb should decrease.
Acute: intracellular buffering
Chronic: decrease excretion of bicarb, decreased ammonium excretion.

Question 9

How do you determine the appropriate bicarb compensation for respiratory acidosis?

Answer 9

For every 10 change in CO2, the bicarb changes by 1 in acute, 3 in chronic. If too much bicarbs, coexisting metabolic alkalosis. If too little bicarb, coexisting metabolic acidosis.

Question 10

How do you determine the appropriate bicarb compensation for respiratory alkalosis?

Answer 10

For every 10 change in CO2, the bicarb changes by 2 in acute, 4 in chronic. If too much bicarbs, coexisting metabolic alkalosis. If too little bicarb, coexisting metabolic acidosis.

Question 11

After determining that the primary process is a metabolic alkalosis, what is the next step?

Answer 11

Check the anion gap, for another process.

For etiology, check the urine chloride (greater or less than 10 is the decision point).

Question 12

After determining that the primary process is a metabolic acidosis, what is the next step?

Answer 12

Check the anion gap.

Question 13

What is the formula for checking the anion gap?

Answer 13

Sodium - (Cl + Bicarb)

Normal gap= 3xalbumin (usually 12).

Question 14

If the gap is

Answer 14

Non-gap acidosis. Check the urine anion gap.

Question 15

What is the formula for the urine anion gap?

Answer 15

Sodium + Potassium - Chloride (positive or negative is the decision point).

Question 16

If the gap>12, then what do you have?

Answer 16

Anion Gap acidosis!

Question 17

How do you find further disturbances after finding an anion gap metabolic acidosis?

Answer 17

Winter’s formula - is the pCO2 appropriate?

Question 18

How should pCO2 change in metabolic acidosis?

Answer 18

As bicarb decreases, PCO2 should decrease.

Question 19

What is winter’s formula? Then what?

Answer 19

1.5(bicarb) + 8 (+/-2).
If given pCO2 is more than expected, coexisting respiratory acidosis.
If given pCO2 is less than expected, coexisting respiratory alkalosis.

Question 20

After determining results of Winter’s formula, what is the last step in working up anion gap metabolic acidosis?

Answer 20

Add back method to determine if there is another bicarb problem.
“Anion gap” - “Bicarb” = Diff
Diff + Bicarb should equal 24.
If Diff + bicarb > 24, coexisting metabolic alkalosis.
If Diff + bicarb