Acid-Base Concepts & ABG Interpretation (Dall)

Question 1

What is the main enzyme involved in acid base balance?

What reactions does it catalyze?

Answer 1

Carbonic Anhydrase

CO2 + H2OH2CO3H + HCO3

Question 2

What equation can you to calculate hydrogen ion concentration?

Answer 2

Henderson Equation

[H]=24(pCO2/[HCO3])

Question 3

How much acid is produced daily? From what processes?

Answer 3

20,000 mmol

All cellular respiration

Question 4

What is the physiological pH range? What determines this range?

Answer 4

6.8-7.6 pH

This is the range at which enzymes are viable.

Question 5

What organs are responsible for acid base buffering? Which organ does most of the buffering?

Answer 5

Lung and Kidney

Lung buffers far more

Question 6

Where does buffering occur in the kidney?

Answer 6

Proximal tubule (HCO3 resorption) 
Collecting duct (H+ excretion)

Question 7

What tests are done when an acid/base disorder is suspected?

Answer 7

Arterial Blood Gases - pCO2, pH

Basic Chemistry- HCO3, Na, Cl, Urea,

Question 8

What is normal pH value? HCO3 values? pCO2 values?

Answer 8

pH- 7.40
HCO3- 24 mmol/L
pCO2- 40 mmHg

Question 9

What values denote acidosis or alkalosis?
pH
HCO3
pCO2

Answer 9

Acidosis
pH < 7.4
HCO3 < 24 mmol/L
pCO2 > 40 mmHg

Alkalosis
pH > 7.4
HCO3 > 24 mmol/L
pCO2 < 40 mmHg

Question 10

What is the condition where 2 or more acid/base values are abnormal?

Answer 10

Mixed acid-base disturbance

Question 11

What diseases are marked by an abnormal pCO2 value?

what diseases are marked by an abnormal HCO3 value?

Answer 11

Respiratory alkalosis or acidosis

Metabolic alkalosis or acidosis

Question 12

What formulas can you use to calculate the expected pCO2 compensation for metabolic acidosis?

Answer 12

pCO2= 1.5*[HCO3] +8
OR
pCO2=last two digits of pH (only works in narrow pH range)

Question 13

What formula can you use to calculate the expected pCO2 compensation for metabolic alkalosis?

Answer 13

pCO2= 0.9*[HCO3] +9

Question 14

What is the expected bicarbonate compensation in respiratory acidosis?

Answer 14

an increase of 1mmol/L HCO3/ 10 mmHg pCO2 acute

an increase of 4mmol/L HCO3/10 mmHg pCO2 chronic

Question 15

What is the expected bicarbonate compensation in respiratory alkalosis?

Answer 15

a decrease of 2mmol/L HCO3/ 10mmHg pCO2 acute

a decrease of 4mmol/L HCO3/ 10mmHg pCO2 chronic

Question 16

What is the anion gap? What is the accepted value for the anion gap?

Answer 16

A test that measures the difference between measured amounts of cations and anions in the blood.

Anion gap should be 10