April 29, 2016 - Approach to Acid-Base

Question 1

Approach to ABGs

Answer 1

1. What is the pH?
2. Look at the bicarb
3. Look at the pCO2 and look for patterns
4. Calculate AG

Question 2

Appropriate Respiratory Responses

Answer 2

To metabolic acidosis… a drop in pCO2 to HCO3 should be 10:10

To metabolic alkalosis… a drop in pCO2 to HCO3 should be 7:10

Question 3

Appropriate Metabolic Responses

Answer 3

The pCO2 to HCO3 ratio should be…

Acute Respiratory Acidosis - 10:1

Chronic Respiratory Acidosis - 10:3

Acute Respiratory Alkalosis - 10:2

Chronic Respiratory Alkalosis - 10:5

Question 4

dAnion Gap : dHCO3

Answer 4

If the dAnion Gap = dHCO3 that means that anion gap acidosis is the only problem that is occuring.

If the dAnion Gap < dHCO3 that means that there is mixed anion gap + normal anion gap acidosis.

If the dAnion Gap > dHCO3 that means there is mixed anion gap + metabolic alkalosis.

Question 5

Henderson Equation (Modified)

Answer 5

H = ( 24 / [HCO3] ) x pCO2

Question 6

Anion Gap

Answer 6

AG = Na⁺ - (HCO₃^- + Cl^-)

Should be 12 +/- 2

If the anion gap is higher, that indicates that there are acids that are unaccounted for in our equation. High AG indicates acid gain.

Normal AG implies buffer loss.

For every drop in serum albumin of 10, you need to add 2.5 to the AG.

Question 7

Normal Anion Gap

Answer 7

Implies buffer loss.

When we lose bicarbonate we are forced to gain chloride. When we lose chloride we are forced to gain bicarbonate. Buffer loss doesn’t change the anion gap.

Question 8

High Anion Gap

Answer 8

Implies the gain of an acid that is unaccounted for.

Question 9

Metabolic Acidosis and dAG : dHCO3

Answer 9

If the anion gap is not increased, this implies normal anion gap acidosis alone.

If the dAG = dHCO3 it implies anion gap acidosis alone.

If the dAG < dHCO3 this implies mixed anion gap AND normal anion gap acidosis

If the dAG > dHCO3 this implies mixed anion gap AND metabolic alkalosis

Question 10

Stepwise Approach to Problems

Answer 10

1. What is the pH
2. What is the HCO3 / pCO2 (to determine of respiratory)
3. Calculate AG
4. Determine dAG/dHCO3