Section 11 (Acid-Base Regulation)

Question 1

What are the normal resting levels of pH, [HCO3], and PACO2?

Answer 1

pH = 7.35-7.45
[HCO3] = 22-26 mM (24 mM)
PCO2 = 35-45 mm Hg (40 mm Hg)

Question 2

What is the addition of [H+] buffered by within a few minutes?

Answer 2

Hb**, albumin, and HCO3

Question 3

How does the body compensate for increased [H+] in minutes to hours?

Answer 3

Increased Ve to remove CO2 (compensation for metabolic acidosis?

Question 4

How does the body compensate for increased [H+] in hours and days?

Answer 4

CO3 (bone carbonate) is released from bone; patients with chronic acid compensation have weak bones

Question 5

What does “compensated” acidosis mean?

Answer 5

“compensated” means that the added [H+] to the blood is buffered to an extent or amount that the blood pH is within the normal limits or ~ 7.4 (7.36)

Question 6

What does the Base Excess (BE) of the kidney mean?

Answer 6

A BE > +2 means that the kidneys are retaining base[HCO3-].
A BE < -2 means that the kidneys are excreting base [HCO3-].
Normal laboratory values for BE are between -2 and +2.

Question 7

How does a person with respiratory acidosis compensate?

Answer 7

Person will have a BE of >2+, indicating kidneys are reabsorbing base in order to buffer the adde [H+]

Question 8

What should a PT keep in mind when working with a person who has chronic (after several months) compensated respiratory acidosis?

Answer 8

Their bones will be very weak and only a gentle passive force should be applied (if needed) to reduce the probability of a pathological fracture of the stressed bone.

Question 9

What are the non bicarbonate buffer systems in the blood and kidneys?

Answer 9

Blood = Hb and other plasma proteins (albumin)
Kidneys = phosphates (HPO4) and ammonia (NH3)

Question 10

What is the source of NH3 in the body?

Answer 10

Tubular cells of the kidney

Question 11

What increases the concentration gradient of NH3 from the tubular cells of the kidney into the tubular fluid (urine)?

Answer 11

Decreasing the urine pH from 9.0 to 4.0 (as [H+] is in urine, combines with NH3 to produce NH4); NH3 is a base and it flows towards its concentration gradient. Once combined with H+, it becomes an acid and further decreases the pH of the urine, resulting in more of a concentration gradient for other NH3 molecules to flow down

Question 12

Where does HPO4- - buffer or bind H+?

Answer 12

Within the urine or tubular fluid.

Question 13

Increased PCO2 in the blood [increases/decreases] the pH of the blood, while decreased PCO2 in the blood [increases/decreases] the prof the blood.

Answer 13

decreases; increases

Question 14

What compensations does the body make after several months of chronic fully compensated respiratory acidosis?

Answer 14

1. pt will have BE>2+
2. [H+] will be buffered by HCO2. Hb, and bone CaCO3
3. There will be increased H+ excretion as NH4 and H2PO4 by the kidneys

Question 15

The ______ system compensates for metabolic disturbances and the _____ system compensates for respiratory disturbances.

Answer 15

Respiratory; Metabolic

Question 16

What substances are reabsorbed from tubular fluid into interstitial fluid?

Answer 16

1. HCO3
2. CO2
3. H+
4. Na+

Question 17

What substances are secreted into the tubular fluid from tubular cells?

Answer 17

1. NH3
2. H+
3. CO2
4. HCO3

Question 18

What causes respiratory acidosis and alkalosis?

Answer 18

Acidosis = decrease in ventilation (can't get rid of CO2)
Alkalosis = increase in ventilation

Question 19

In a patient with respiratory acidosis, their PCO2 levels would be [high/low/normal] and their HCO3 would be [high/low/normal].

Answer 19

high; normal

Question 20

In a patient with metabolic acidosis, their PCO2 levels would be [high/low/normal] and their HCO3 would be [high/low/normal].

Answer 20

normal; low

Question 21

In a patient with respiratory alkalosis, their PCO2 levels would be [high/low/normal] and their HCO3 would be [high/low/normal].

Answer 21

low; normal

Question 22

In a patient with metabolic alkalosis, their PCO2 levels would be [high/low/normal] and their HCO3 would be [high/low/normal].

Answer 22

normal; high

Question 23

What would the compensation be for acute respiratory acidosis?

Answer 23

Kidneys would compensate and BE would be >2+ (urine would be more acidic)

Question 24

What would the compensation be for acute metabolic acidosis?

Answer 24

The lungs would compensate by hyperventilation

Question 25

What would the compensation be for acute respiratory alkalosis?

Answer 25

Kidneys would compensate and BE would be <2- (urine would be more alkaline)

Question 26

What would the compensation be for acute metabolic alkalosis?

Answer 26

Lungs would compensate by hypoventilation

Question 27

What is the Alkali Reserve of the blood?

Answer 27

Blood is slightly alkaline because HCO3 concentration is higher to readily buffer to free H+ ions so we don’t go into acidosis