Acid-Base Disorders

Question 1

emia vs osis

Answer 1

emia: pH change aWAY from the reference range
osis: abnormal condition or process that CONTRIBUTES to pH change

Question 2

Normal pH, pCO2, HCO3

Answer 2

7.4
40
24

Question 3

What are implications of the Henderson Hasselbach equation?

Answer 3

If pCO2 increases then pH decreases

If HCO3 increases then pH increases

Question 4

What are the steps to identify acid base disorders?

Answer 4

1. Henderson‐Hasselbalch equation
   • to determine whether metabolic or respiratory process is the primary
   process driving acidosis or alkalosis
2. Anion gap
   • AG ≥ 20, metabolic acidosis is present
3. Expected pCO2 range
   • Determines whether respiratory compensation is adequate, under‐,
   or over‐compensation
4. Excess anion gap (ΔΔ)
   • Used only if there is an anion gap
   • Determines “corrected” bicarbonate to see whether there are any other metabolic disturbances

Question 5

7.5
29
22

Answer 5

Alkalosis
CO2 LOW —> Hyperventilation
HCO2 low normal

Primary respiratory alkalosis (acute)

Question 6

7.34
60
31

Answer 6

Acidosis
CO2 HIGH –> Hypoventilation
HCO3 HIGH –> compensated/chronic?

Primary respiratory acidosis, chronic

Question 7

7.20
21
8

Answer 7

Acidosis
CO2 LOW –> hyperventilation
HCO3 LOW –> Metabolic

Primary metabolic acidosis

Question 8

How do you calculate the AG?

Answer 8

Na - Cl + HCO3

Question 9

What does hte gap represent?

Answer 9

unmeasured anions (Phosphates, sulfates, albumin)

Question 10

What is the normal range for the AG?

Answer 10

7-16 (12)

Question 11

What is an AG acidosis?

Answer 11

pH decreases and acidosis

Question 12

If AG is >20?

Answer 12

metabolic acidosis is present regardless of pH or HCO3

Question 13

Why do we calculate the expected pCO2 range?

Answer 13

Determines whether respiratory compensation is adequate, under‐, or over‐compensation

Question 14

How do you calculate hte expected pCO2 range?

Answer 14

Expected Range = 1.5 ×(measured HCO3‐) + 8 ±2

Question 15

If pCO2 = 28

Answer 15

> the expected range, then respiratory acidosis even though pCO2 is below 40.

Question 16

If pCO2 20

Answer 16

within the expected range, then normal respiratory compensation.

Question 17

Why do we calculate the excess AG?

Answer 17

ONLY if there is an AG

determines “corrected” bicarb to see whether there are other metabolic disturbances

Question 18

excess AG formula?

Answer 18

calculated AG - 12

Question 19

Corrected HCO3

Answer 19

measured HCO3 + exccessAG

Question 20

If corrected HCO3 > 30

Answer 20

underlying primary metabolic alkalosis

Question 21

If corrected HCO3 <23

Answer 21

underlying primary metabolic acidosis

Question 22

pH 7.5
pCO2 20

Na 140
Cl 103
HCO3 15

Answer 22

ONE:
Alkalosis
pCO2 LOW –> hyperventilation
**PRIMARY respiratory alkalosis

AG?:
AG = 140 - (103 + 15) = 22 (greater than 12!)
**Underlying primary metabolic acidosis

pCO2 range?:
1.5 x 15 + 8 = 30.5 (Greater than 18-22!)… Since a pCO2 of 20 is BELOW the expected range then respiratory alkalosis

Excess AG?
22-12 = 10
Corrected = 15 + 10 = 25 No hidden acid/alkalosis

Question 23

7.20
25
Po2 130
O2 sat 94%

Answer 23

1. Primary:
Acidosis
CO2 LOW
HCO3 10
* Primary metabolic acidosis

2. AG
   AG = 130 - (80+10) = 40
   > 20 *metabolic acidosis is present
3. PCO2 range
   Expected pCO2 = 1.5 x 10) + 8 +/-2= 21 -25
   * PCO2 falls w/in the range so there is normal resp compensation
4. Expected AG
   40-12 =28
   Corrected HCO3 = 10 +28 = 38
   * Primary metabolic alkalosis

Question 24

Which of the following best represents the acid base disorder in this patient?
A. Primary metabolic acidosis with concomitant non‐ anion gap metabolic alkalosis
B. Mixed metabolic and respiratory acidosis with concomitant metabolic alkalosis
C. Anion‐gap metabolic acidosis with respiratory compensation and concomitant metabolic alkalosis
D. Anion‐gap metabolic alkalosis, respiratory alkalosis, and metabolic alkalosis
E. More information is required to determine the acid base disorder

Answer 24

Anion‐gap metabolic acidosis with respiratory compensation and concomitant metabolic alkalosis