Acid Base Nonsense

Question 1

What is the normal pH of arterial blood?

Answer 1

7.4

Question 2

What are the two sources of H+?

Answer 2

Respiratory Acid

Metabolic Acid

• inorganic acids such as H2SO4 and phosphoric acids
• organic acids such as lactic acid and fatty acid

Question 3

What are the sources of alkali in the body?

Answer 3

Oxidation of organic anions such as citrate

Question 4

What is the role of buffers?

Answer 4

To minimise changes in pH when H+ ions are added or removed

Question 5

What is the ratio of HCO3- to H2CO3 in blood?

Answer 5

20:1

Question 6

What is the concentration of HCO3 in blood?

Answer 6

24mmol/l

Question 7

What is the normal level of pCO2 within the body?

Answer 7

40mmHg/5.3pKa

Question 8

What occurs if there is an increase in H+ (Acidosis)?

Answer 8

There is an increase in ventilation and a decrease in CO2

Question 9

What occurs if there is a decrease in H+ (alkalosis)?

Answer 9

There is a decrease in ventilation and an increase in CO2

Question 10

In the henderson-hasselbalch equation, what is each varient controlled by?

Answer 10

HCO3 - renal regulation

Pco2 - respiratory regulation

Question 11

What occurs if you decrease the concentration of HCO3?

Answer 11

pH then decreases and so does pCO2

Question 12

What can act as intracellular buffers?

Answer 12

Proteins, Organic/Inorganic phosphates, Erythrocytes, Haemoglobin

Question 13

What must occur if H+ ions are buffered by intracellular buffers?

Answer 13

They must be accompanies by Cl- or exchanged for K+

Question 14

What happens to potassium levels in acidosis?

Answer 14

Hyperkalaemia

Question 15

How much of metabolic acid is buffered by plasma?

Answer 15

43%

Question 16

How much of metabolic acid is buffered in cells?

Answer 16

57%

Question 17

How much respiratory acid is buffered within cells ?

Answer 17

97%

Question 18

What affects pCO2 ?

Answer 18

Respiratory Disorders

Question 19

What affects HCO3?

Answer 19

Renal disorders

Question 20

What occurs in respiratory acidosis?

Answer 20

There is a decrease in pH bc of an increase in pCO2

Question 21

What causes respiratory acidosis?

Answer 21

Acute - barbituates, opiates

Chronic - Bronchitis, Emphysema, Asthma

Question 22

What occurs in respiratory alkalosis?

Answer 22

Increase in pH bc of a decrease in CO2

Question 23

What are the causes of respiratory alkalosis?

Answer 23

Acute - hyperventilation, aspirin, altitude

Chronic - longterm residence at high altitude

Question 24

What is metabolic acidosis?

Answer 24

An decrease in pH due to a decrease in HCO3

pCO2 then decreases to compensate for acidic conditions

Question 25

What causes metabolic acidosis?

Answer 25

Increase in H+ production - ketoacidosis, lactic acidosis, failure to excrete normal dietary load of H+, Loss of HCO3 (diarrhoea)

Question 26

What is metabolic alkalosis?

Answer 26

Increased pH due to increased HCO3 pCO2 then also increases to compensate for alkalotic conditions

Question 27

What are the causes of metabolic alkalosis?

Answer 27

Increase in H+ ion loss - vomiting, Increase in H+ renal loss, Excess administration of HCO3- in those who are renally impaired, massive blood transfusions

Question 28

Describe HCO3- reabsorption

Answer 28

1. Sodium ions are reabsorbed from filtrate in exchange for H+ via an antiport mechanism in the apical membrane 2. Filtered HCO3- reacts with H+ to form H2CO3 which will combine with carbonic anhydrase to form H2O and CO2 3. Carbon dioxide enters cell and enters a reaction with H2O (aided by carbonic anhydrase) to form carbonic acid 4. Carbonic acid dissociates to form a bicarbonate ion and hydrogen ion 5. H+ ions are secreted and HCO3- pass into peritubular capillaries with Na+

Question 29

What is the min urine pH?

Answer 29

4.5-5

Question 30

What is the max urine pH?

Answer 30

8

Question 31

What upregulates the Na/H ion antiporter?

Answer 31

Angiotensin II - promotes Na+ reabsorption and H+ secretion.

Question 32

What is the basis of titratable acidity?

Answer 32

1. NaHPO4 lies within the lumen. One Na+ is exchanged for an H+ ion 2. Carbon dioxide indirectly forms bicarbonate which enters tubule cells and combines with water to form carbonic acid (aided by carbonic anhydrase) 3. Carbonic Acid then dissociates to yield H+ and HCO3-

Question 33

What is the function of titratable acidity?

Answer 33

To make new Bicarbonate and excrete H+

Question 34

What is the purpose of ammonium excretion?

Answer 34

Response to increased acid loads and forms new bicarbonate AND excretes H+

Question 35

What occurs in ammonium excretion?

Answer 35

1. Deamination of amino acids by glutaminase within renal tubule results in NH3 production 2. NH3 leaves tubule lumen and combines with H+ ions to produce NH4+. NH4+ then combines with CL- to produce NH3Cl- and this is excreted 3. New H+ions are generated from CO2 in blood 4. HCO3- passes with Na+ into peritubular capillaries

Question 36

What affect does pH have on renal glutaminase?

Answer 36

When intracellular pH decreases (becomes more acidic), renal glutaminase activity increases which increases NH4+ production and excretion

Question 37

What is the relationship between Hydrogen and SOdium in titratable excretion?

Answer 37

For every H+ excreted, one Na+ is absorbed

Question 38

What is the relationship between hydrogen, sodium and bicarbonate during HCO3 reabsorption?

Answer 38

For every H+ excreted, Na+ conserved, one bicarbonate is reabsorbed

Question 39

if pH = 7.25, [HCO3] = 12mmoles/l, Pco2= 25mmHg, why does this indicate impaired renal function?

Answer 39

Damage to nephron means that kidneys are not removing enough acid from the blood stream Evident that values show metabolic acidosis

Question 40

if pH = 7.45, [HCO3] = 12mmol/l, Pco2 = 20mmHg, why does this indicate that the patient has been living at high altitude?

Answer 40

pH is only slightly raised yet HCO3 and CO2 are lower than usual. Lower bicarb and carbon dioxide would suggest metabolic acidosis to compensate for the initial respiratory alkalosis

Question 41

if pH= 7.28, [HCO3]= 36mmol/l, Pco2= 60mmHg, why would the patient be excreting ammonium ions?

Answer 41

acute and chronic acid loads enhance ammonia production in the proximal tubule and secretion into the urine

Question 42

if pH=7.5, [HCO3]= 45mmol/l. Pco2= 60mmHg. why would the subject be secreting bicarbonate ions?

Answer 42

increased excretion of HCO3− as the filtered load of HCO3− exceeds the ability of the renal tubule to reabsorb it.