Acid/Base Balance

Question 1

What is the value of the Bunson Coefficient?

Answer 1

Alpha=.03

Question 2

What is the apparent pK of blood?

Answer 2

pK=6.10

Question 3

What is the Henderson-Hasselbach equation?

Answer 3

pH=pK + log (HCO3 / alpha*pCO2)

Question 4

What is the ratio of salt/acid at pH of 7.40? (what is the ratio of bicarb:CO2)

Answer 4

20:1

Question 5

What does the Total CO2 (TCO2) =?

Answer 5

TCO2= HCO3 + alpha*pCO2

Question 6

What is the physiologic pH range?

Answer 6

7.35-7.45

Question 7

What are the three buffering systems in the body?

Answer 7

1) Serum Proteins-> 1st to pull up H, these are weak acids with high affinity for H, H binds to Histidine residues on proteins
2) Phosphates
3) Hgb-> contains many histidines

Question 8

<p>

| Tell the story of HCO3 buffering system.</p>

Answer 8

<p>
As H increases in the blood bicarb picks it up and turns into CO2 and H2O. CO2 is a nonpolar gas which diffuses across the cell membranes of RBC's. When inside the cell CO2 is acted upon by carbonic anhydrase which turns it back into bicarb and H. H binds to Hgb and bicarb moves down a concentration gradient outside the RBC while taking Cl in. (Bicarb out, Cl in) Once Hgb is saturated with H it starts to build up in the cell which acidifies the cytoplasm. This shuts down carbonic anhydrase. If more CO2 gets in, it can bind directly to Hgb making it carbaminoHemoglobin. When in the alveoli of the lungs, CO2 is removed from Hgb first due to weak bond and partial pressure (moving down its' concentration gradient). As CO2 is removed and expired, O2 Moves down its' concentration gradient (from the lungs to the RBC) and binds to Hgb. As O2 binds, H is released from Hgb. Hgb that is released protonates intracellular bicarb and turns into CO2 and H2O. CO2 diffuses out of the cell down its' concentration gradient and is expired. More bicarb is brought in as Cl is pumped out. (HCO3 in, Cl out)</p>

Question 9

What is O2 Sat?

Answer 9

Oxyhemoglobin / Total Functional Hgb x 100

Question 10

Which way does a decrease in pH shift the O2 Saturation Curve?

Answer 10

To the right

Question 11

Which way does an increase in pH shift the O2 Saturation Curve?

Answer 11

To the Left

Question 12

What is the Hill Plot?

Answer 12

A transformation of the O2 Saturation Curve into a linear form. Good for finding right/left shifts

Question 13

What methods does the Renal system utilize to regulate acid/base balance?

Answer 13

1) Weak acid pump in glomerulus
2) Na/K ATPase will select for H instead of K
3) Renal production of ammonia from glutamine
4) Reclamation of HCO3

Question 14

What concentration gradient regulations are in place so that the Na/K ATPase does not keep selecting H instead of K?

Answer 14

1) There is a maximum urine to blood pH difference of 3
2) There is a maximum urine acidity of ~4.4
If either of these is reached first, Na/K ATPase will select K instead of H.

Question 15

How does Renal production of ammonia compensate for acidosis?

Answer 15

Glutamine is released from skeletal muscle and is acted on by glutaminase producing one mol of NH3 and forming glutamate. Glutamate is acted on by glutamate dehydrogenase releasing one mol of NH3 and forming alpha ketoglutarate. NH3 is pumped into urine and is protonated by the extra H in the urine and forms ammonium which is eliminated.

Question 16

How does the reclamation of HCO3 compensate for acidosis?

Answer 16

HCO3 is small MW so it is filtered in the kidney. When in the urine, it combines with extra H to form CO2. CO2 is a nonpolar gas that diffuses freely into renal tubular cells and is acted upon by carbonic anhydrase, turning it back into HCO3 and H. Bicarb is pumped into plasma and H is pumped back into urine.

Question 17

How many days does it take to see complete renal compensation for acid/base abnormalities?

Answer 17

2-4 days

Question 18

What is there a deficit of in metabolic acidosis?

Answer 18

HCO3

Question 19

What causes metabolic acidosis?

Answer 19

1) Excess production of organic acids
2) Reduced renal excretion of fixed acids
3) Excessive loss of HCO3-> Diarrhea

Question 20

What causes an increased anion gap in metabolic acidosis?

Answer 20

1) Lactic Acidosis due to hypoxia
2) Ketoacidosis-> Type II diabetic
3) Renal Failure
4) Toxins-> salicylates
methanol-> Metabolized to formic
acid

Question 21

What causes a normal anion gap in metabolic acidosis?

Answer 21

1) Diarrhea
2) Renal Tubular Acidosis
3) Hypoaldosteronism

Question 22

How does the body compensate for metabolic acidosis?

Answer 22

1) Hyperventilation
2) Increased excretion of H and NH4
3) Increased reclamation of HCO3

Question 23

What is in excess during metabolic alkalosis?

Answer 23

HCO3

Question 24

What causes metabolic alkalosis?

Answer 24

1) Over administration of bicarbonate
2) Citrate-> Na2Citrate is used as anticoagulant in blood bags. Get a transfusion and citrate acts as a base, sucking up protons.
3) Prolonged vomiting
4) Hyperaldosteronism

Question 25

How does the body compensate for metabolic alkalosis?

Answer 25

1) Hypoventilation
2) Low excretion of H and NH4
3) Increased excretion of HCO3

Question 26

Explain how vomiting causes a metabolic alkalosis.

Answer 26

After purging the stomach acid, the stomach needs to replace the acid. The way it does this is by taking up CO2 from circulation. When CO2 enters the cell, it is acted upon by carbonic anhydrase turning it into H and HCO3. The H is pumped into the stomach lumen and the HCO3 is pumped back into the circulation, causing a metabolic alkalosis.

Question 27

What is in excess during respiratory acidosis?

Answer 27

CO2

Question 28

What causes respiratory acidosis?

Answer 28

1) Anything that causes a depression of CNS respiratory centers
2) Mechanical obstruction such as pneumonia or asthma

Question 29

How does the body compensate for respiratory acidosis?

Answer 29

Probably not respiratory
Renal Compensation
1) Low urinary pH
2) High Urinary Ammonium
3) High bicarbonate reclamation

Question 30

What is deficient in respiratory alkalosis?

Answer 30

CO2

Question 31

During the early stage of pneumonia, is there a respiratory alkalosis or acidosis? Why?

Answer 31

During the early stages of pneumonia there is a respiratory alkalosis because O2 cannot pass through the alveolar membrane due to a buildup of mucus. CO2 can pass through however. Since O2 cannot pass through, the PO2 drops and the body compensates by hyperventilating. This gets rid of more CO2 causing a respiratory alkalosis.

Question 32

During the late stage of pneumonia, is there a respiratory alkalosis or acidosis? Why?

Answer 32

During the late stage of pneumonia there is a respiratory acidosis. In late stage pneumonia there is heavy mucus buildup in the alveoli. This impedes gas exchange for both O2 and CO2. Now, CO2 builds up in the circulation and causes a respiratory acidosis.

Question 33

What causes respiratory alkalosis?

Answer 33

1) Hyperventilation
a) Anxiety
b) Stimulatory Drugs-> Ecstacy, Cocaine
c) Hypoxia
1) Pneumonia
2) Cardiac Insufficiency-> BP falls, early organs use O2, later organs are hypoxic, PO2 falls and body compensates by hyperventilating. This leads to respiratory alkalosis.

Question 34

How does the body compensate for respiratory alkalosis?

Answer 34

High pH
Increased HCO3 in urine
Decreased NH4 in urine