Assessment of Acid-Base Status

Question 1

What is the isohydric principle?

Answer 1

It is the phenomenon where multiple A/B pairs in solution are in equilibrium tied to each other via H+

Question 2

How is the isohydric principle important in the overall A/B balance?

Answer 2

Any change in H+ will change the balance of a single buffer system that will also change the balance of all the other buffer systems as the H+ ions shift back and forth from each system.

Question 3

Why does only one buffer system need to be examined in order to understand the [H+] in the buffer space?

Answer 3

Due to the isohydric principle all the buffer systems are linked via a common H+

Question 4

For medical purposes what are the 1st, 2nd and 3rd most important buffer systems?

Answer 4

1st: Bicarbonate
2nd: Hb
3rd: Phosphate

Question 5

What is used to examine the acid-base status of the body?

Answer 5

Arterial blood - NOT venous blood because the arterial blood is highly buffered and pH controlled but venous blood is not.

Question 6

What buffer system is an open system?

Answer 6

Bicarbonate

Question 7

What buffer systems are closed systems?

Answer 7

Phosphate and protein (Hb)

Question 8

What is the bicarbonate system?

Answer 8

•Open Buffer: CO2 + H2O HCO3– + H+ (pK = 6.1)

Question 9

What is the Hb system?

Answer 9

•Closed Buffer: Hb-H+ Hb + H+ (pK = 7.0)

Question 10

What happens with insufficient CO2 removal?

Answer 10

Respiratory acidosis -> acidemia

Question 11

What happens with excessive CO2 removal?

Answer 11

Respiratory alkalosis -> alkalemia

Question 12

What can happen as an A/B renal disturbance?

Answer 12

Improper H+ and HCO3- secretion or reabsorption

Question 13

what happens with extra-renal disturbances that can lead to A/B imbalance?

Answer 13

Excessive CO2 or H+ formation

Question 14

How rapid is kidney compensation for lung dysfunction?

Answer 14

Slow

Question 15

How rapid is lung compensation for kidney dysfunction?

Answer 15

Rapid

Question 16

What occurs in respiratory acidosis?

Answer 16

Increased PaCO2

Question 17

What happens with respiratory alkalosis?

Answer 17

Decreased PaCO2

Question 18

What happens with metabolic acidosis?

Answer 18

Low [HCO3-]

Question 19

What happens with metabolic alkalosis?

Answer 19

High [HCO3-]

Question 20

What is the anion gap?

Answer 20

Accounts for unmeasured anions that must be present to neutralize the charge of the measured cation, Na+

Question 21

What is the anion gap used for?

Answer 21

It allows you to differentiate between acid-base disorders that are due to renal/GI problems or other metabolic disorders.

Question 22

What does a normal anion gap indicate?

Answer 22

It indicates a renal/GI problem

Question 23

What does a high anion gap indicate?

Answer 23

It indicates other metabolic disorders (diabetes)

Question 24

What is the normal range for pH?

Answer 24

7.35-7.45

Question 25

What is the normal range for PaCO2?

Answer 25

35-45 mmHg

Question 26

What is a double A/B disturbance?

Answer 26

It occurs if the plasma pH is abnormal and both the HCO3- and PaCO2 levels are abnormal and causes severe alkalosis or acidosis.

Question 27

What is a mixed A/D disturbance?

Answer 27

When the plasma pH is normal and both the HCO3- and CO2 are not normal. Low CO2 with low HCO3 or vice versa

Question 28

Can secondary compensations make up for primary disturbances?

Answer 28

Yes but they can never be complete.

Question 29

What is the compensation for metabolic acidosis?

Answer 29

Decrease CO2

Question 30

What is the more common acid base disorder?

Answer 30

Acidosis

Question 31

What A/B is more easily regulated?

Answer 31

Acidotic distrubances. Respiratory ones in particular are much less complicated.

Question 32

What is the cause of primary respiratory acidosis?

Answer 32

Hypoventilation (COPD/barbituate posioning)

Question 33

What is the result of primary respiratory acidosis?

Answer 33

Increased PaCO2 and decreased pH

Question 34

What is the compensation for primary respiratory acidosis?

Answer 34

Increased HCO3- retention via CO2's effect on the PT

Question 35

What is the cause of primary respiratory alkalosis?

Answer 35

Hyperventilation

Question 36

What is the result of primary respiratory alkalosis?

Answer 36

Decreased PaCO2 and increased pH

Question 37

What is the compensation for primary respiratory alkalosis?

Answer 37

Decreased HCO3- retention via reverse CO2 effect on PT

Question 38

What is the cause of primary metabolic acidosis?

Answer 38

Renal and extrarenal causes: - Diabetes (larger anion gap) - Renal Increased H+ Retention (normal anion gap)

Question 39

What is the result of primary metabolic acidosis?

Answer 39

Increased H+ and/or decreased HCO3- leading to decreased pH

Question 40

What is the compensation for primary metabolic acidosis?

Answer 40

Increased CO2 elimination via ventilation

Question 41

What is the cause of primary metabolic alkalosis?

Answer 41

Renal and extrarenal causes: - Chronic Potassium Depletion - Dehydration

Question 42

What is the result of primary metabolic alkalosis?

Answer 42

Decreased H+ and/or increased HCO3- leading to increased pH

Question 43

What is the compensation for primary metabolic alkalosis

Answer 43

Increased CO2 retention and a decrease in ventilation

Question 44

If there is chronic depletion of K+ ions, what happens to the urine?

Answer 44

It will be very acidic