Summary

Question 1

Normal pH lab value:

Answer 1

7.38 - 7.44

Question 2

Condition with pH < 7.38:

Answer 2

acidemia

Question 3

Condition with pH > 7.44:

Answer 3

alkalemia

Question 4

Normal PCO2 lab value:

Answer 4

35-45 (magic #40)

Question 5

Normal HCO3- lab value:

Answer 5

21-30 (magic #24)

Question 6

Normal anion gap value:

Answer 6

7-16 (magic #12)

Question 7

Normal ∆-∆ value:

Answer 7

-5 to +5

Question 8

Anion gap formula and when to use:

Answer 8

AG = [Na+] - ([Cl-] + [HCO3-])

Use: metabolic acidosis only.

Question 9

∆-∆ formula and when to use:

Answer 9

∆-∆ = ∆AG - ∆[HCO3-]

Use: AG elevated metabolic acidosis only.

Question 10

∆AG =

Answer 10

∆AG = measured AG - 12

use in ∆-∆ calculation

Question 11

∆[HCO3-] =

Answer 11

∆[HCO3-] = 24 - measured [HCO3-]

use in ∆-∆ calculation

Question 12

Winter’s formula and use:

Answer 12

PCO2 = 1.5[HCO3-] + 8 ± 2

• Use: metabolic acidosis only to determine whether or not PCO2 compensation has occurred. Should decrease in metabolic acidosis.

Question 13

Formula that should be used to determine compensation status in the setting of metabolic acidosis:

Answer 13

Winter’s formula
PCO2 = 1.5[HCO3-] + 8 ± 2

Question 14

Formula that should be used to determine compensation status in the setting of metabolic alkalosis:

Answer 14

PCO2 = 0.7[HCO3-] + 20 ± 2

• Use: calculate predicted PCO2. Should rise in metabolic alkalosis.

Question 15

Compensation rules for respiratory acidosis (acute versus chronic):

Answer 15

• acute: up 1 [HCO3-] for every up 10 PCO2.
• chronic: up 4 [HCO3-] for every up 10 PCO2.

Question 16

Compensation rules for respiratory alkalosis (acute versus chronic):

Answer 16

• acute: down 2 [HCO3-] for every down 10 PCO2.
• chronic: down 5 [HCO3-] for every down 10 PCO2.

Question 17

Compensation rule for metabolic acidosis:

Answer 17

Winter’s formula
PCO2 = 1.5[HCO3-] + 8 ± 2

Question 18

Compensation rule for metabolic alkalosis:

Answer 18

PCO2 = 0.7[HCO3-] + 20 ± 2

Question 19

Urine AG formula and when to use:

Answer 19

UAG = U_Na+ + U_K+ - U_Cl- ≈ 0

Use: metabolic acidosis with normal AG only.

Question 20

Metabolic acidosis + normal AG + UAG < 0:

Answer 20

• intact renal function
• (kidney is buffering H+ producing NH4Cl)

Question 21

Metabolic acidosis + normal AG + UAG > 0:

Answer 21

• impaired renal function
• (kidney can’t buffer H+; no NH4Cl produced)

Question 22

Metabolic acidosis + abnormal AG + ∆-∆ between -5 and +5:

Answer 22

AG metabolic acidosis only

Question 23

Metabolic acidosis + abnormal AG + ∆-∆ < -5:

Answer 23

• AG metabolic acidosis + non-AG metabolic acidosis
• ∆-∆ = ∆AG - ∆[HCO3-]

Question 24

Metabolic acidosis + abnormal AG + ∆-∆ > +5:

Answer 24

• AG metabolic acidosis + metabolic alkalosis
• ∆-∆ = ∆AG - ∆[HCO3-]