Acid-Base Physiology

Question 1

Explain the difficulty with carbonic acids

Answer 1

• metabolism of carbohydrates and fats generates CO2
• when CO2 combines with water, makes carbonic acid
• must be continuously eliminated by breathing

Question 2

What happens when you decrease respiration?

Answer 2

• CO2 increases
• increased formation of bicarbonate
• increased H+

Question 3

What happens when hydrogen ions from metabolic processes increases?

Answer 3

• H+ increases
• increased formation of bicarbonate
• increased CO2

Question 4

Acidosis

Answer 4

any process promoting a decrease in blood pH

Question 5

Metabolic acidosis

Answer 5

characterized by decreased plasma bicarbonate

Question 6

Respiratory acidosis

Answer 6

characterized by increased partial pressure of CO2

Question 7

Alkalosis

Answer 7

any process promoting an increase in blood pH

Question 8

Metabolic alkalosis

Answer 8

characterized by increased plasma bicarbonate

Question 9

Respiratory alkalosis

Answer 9

characterized by decreased partial pressure of CO2

Question 10

Can a patient have acidosis and alkalosis?

Answer 10

yes

Question 11

Acidemia

Answer 11

blood pH below normal

Question 12

Alkalemia

Answer 12

blood pH above normal

Question 13

Can a patient have acidemia and alkalemia?

Answer 13

no

Question 14

What are the 3 primary defense mechanisms against acid-base changes?

Answer 14

• chemical buffers (immediate effects)
• respiratory regulation of CO2 (rapid effect)
• renal excretion of acid or base (occurs over days)

Question 15

The respiratory system regulates what type of acid excretion?

Answer 15

volatile acid excretion

Question 16

How does a buffer work?

Answer 16

a buffered solution resists changes in pH by reversibly binding H+

(buffers do not eliminate H+, just hold it for later excretion)

Question 17

What is the optimum buffer effect of the bicarbonate buffer system?

Answer 17

pK of BBS is 6.1, so optimum effect is between 5.1 and 7.1

Question 18

Name some components of the bicarbonate buffer system

Answer 18

• H2CO3 (weak acid)

- NaHCO3 (bicarbonate salt)

Question 19

Name some other extracellular buffers

Answer 19

• inorganic phosphates

- plasma proteins

Question 20

Titratable acidity

Answer 20

excretion of H+ with inorganic anionic buffers, predominately phosphates

Question 21

Characteristics of ammonia/ammonium

Answer 21

• provides a controllable additional method of H+ excretion
• generated by the kidneys
• can adjust production as needed
• produced in proximal tubule, formed in distal nephron

Question 22

What is the fate of ammonium from the proximal tubule?

Answer 22

• excreted in final urine

- excreted indirectly

Question 23

Where is bicarbonate reabsorbed

Answer 23

• proximal tubules
• thick ascending limb (2nd largest fraction)
• distal tubule and collecting duct

Question 24

Renal acid-base metabolism involves what?

Answer 24

• recovery of bicarbonate
• excretion of fixed acid as titratable acid
• excretion of fixed acid as ammonium

Question 25

How does the kidney regulate acid-base?

Answer 25

- PCO2 is regulated by the rate of alveolar ventilation - blood pH affects respiratory chemoreceptors - rapid response

Question 26

Respiratory acidosis and respiratory alkalosis cause what?

Answer 26

respiratory acidosis - intracellular acidosis respiratory alkalosis - intracellular alkalosis

Question 27

Enhanced loss of bicarbonate in the urine results in what?

Answer 27

alkalosis

Question 28

Explain changes in bicarbonate concentration

Answer 28

1. decreased [bicarbonate] = metabolic acidosis and respiratory alkalosis 2. increased [bicarbonate] = metabolic alkalosis and respiratory acidosis

Question 29

Explain changes in PCO2

Answer 29

1. increased PCO2 = respiratory acidosis and metabolic alkalosis 2. decreased PCO2 = respiratory alkalosis and metabolic acidosis

Question 30

``` What is the acid-base disorder? A 6-year old dog with chronic kidney disease: pH = 7.23 PCO2 = 30 mmHg HCO3 = 12.1 mmol/L ```

Answer 30

metabolic acidosis

Question 31

``` What is the acid-base disorder? A 2-year old dog that has been vomiting for several days: pH = 7.47 PCO2 = 41.5 mmHg HCO3 = 29.0 mmol/L ```

Answer 31

metabolic alkalosis