Acid/Base Balance

Question 1

what does pH measure

Answer 1

free hydrogen ion concentration

Question 2

alkalosis

Answer 2

high blood pH

Question 3

acidosis

Answer 3

low blood pH

Question 4

HCO3/CO2 buffer system

Answer 4

pH = HCO3 / CO2

Question 5

what is pCO2 regulated by

Answer 5

lungs

Question 6

what is HCO3 regulated by

Answer 6

kidneys

Question 7

metabolic acidosis

Answer 7

low HCO3

loss of HCO3 or gain of acid

Question 8

metabolic alkalosis

Answer 8

high HCO3

gain of HCO3 or loss of acid

Question 9

respiratory acidosis

Answer 9

high pCO2

hypoventilation

Question 10

respiratory alkalosis

Answer 10

low pCO2

hyperventilation

Question 11

what does TCO2 measure

Answer 11

proxy for HCO3

measures metabolic a/b abnormalities

Question 12

standard base excess

Answer 12

estimates how much acid/base is missing/in excess

Question 13

what does SBE = 0 indicate

Answer 13

normal health

Question 14

what does SBE > range indicate

Answer 14

alkalosis

Question 15

what does SBE < range indicate

Answer 15

acidosis

Question 16

when does respiratory compensation occur

Answer 16

immediately

Question 17

when does metabolic compensation occur

Answer 17

starts in hours, finishes in days

Question 18

does compensation completely normalize pH

Answer 18

NO

Question 19

what is a mixed a/b abnormality

Answer 19

both respiratory and metabolic abnormalities

Question 20

can mixed abnormalities normalize pH

Answer 20

YES

Question 21

causes of respiratory acidosis/alkalosis

Answer 21

lung or brain/nervous system disease

Question 22

causes of metabolic alkalosis

Answer 22

loss of acid - renal or gastric
gain of bicarb - iatrogenic

Question 23

causes of metabolic acidosis (high AG)

Answer 23

D: diabetic ketoacidosis
U: uremic acidemia
E: ethylene glycol toxicity
L: lactic acidosis

Question 24

causes of metabolic acidosis (normal AG)

Answer 24

loss of bicarbonate - renal or intestinal

Question 25

anion gap

Answer 25

unmeasured anions AG = (Na + K) - (HCO3 + Cl)

Question 26

what is the function of the kidneys in acid/base balance

Answer 26

1. reabsorb filtered bicarbonate 2. excrete daily acid load (carnivores) 3. excrete excess bicarbonate (herbivores)

Question 27

is losing a bicarbonate the same as gaining a hydrogen ion

Answer 27

YES

Question 28

where does the majority of HCO3 reabsorption occur

Answer 28

PCT and loop of henle (constant amount)

Question 29

where does the regulation of HCO3 reabsorption occur

Answer 29

DCT

Question 30

is HCO3 directly reabsorbed

Answer 30

no - does not cross luminal membrane combines with H+ and undergoes carbonic anhydrase reaction to form CO2 + H2O which transports into tubule epithelial cell, then undergoes another CA reaction to reform HCO3 HCO3 gets reabsorbed and H+ gets pushed back out to the tubule lumen

Question 31

is HCO3 reabsorption acid/base neutral

Answer 31

YES for every 1 HCO3 filtered at glomerulus there is 1 HCO3 getting reabsorbed

Question 32

what drives HCO3 reabsorption

Answer 32

gradients established by Na/K ATPase

Question 33

how does the DCT regulate HCO3 reabsorption

Answer 33

two types of intercalated cells (type A and B)

Question 34

intercalated A cells

Answer 34

push acid (H+) out into lumen reabsorbs bicarb (HCO3) into blood

Question 35

intercalated B cells

Answer 35

push bicarb (HCO3) out into lumen reabsorbs acid (H+) into blood

Question 36

if H+ excretion = HCO3 filtration at glomerulus, what is the net HCO3 loss/gain

Answer 36

NO loss or gain for every 1 H+ excreted --> 1 HCO3 gets reabsorbed so if H+ excretion is equal to HCO3 filtration, then no net change in A/B balance

Question 37

how does H+ excretion change in ALKALOSIS

Answer 37

do not want to reabsorb all HCO3 because there is already excess in the blood decrease H+ excretion until H+ excretion < HCO3 filtration causes net loss of HCO3

Question 38

how does H+ excretion change in ACIDOSIS

Answer 38

need to generate new bicarbonate to raise pH increase H+ excretion until H+ excretion > HCO3 filtration excess H+ cannot be freely excreted --> must bind to buffers to avoid changing urine pH

Question 39

urinary buffers

Answer 39

1. phosphate 2. ammonium

Question 40

how does phosphate help during acidosis

Answer 40

combines with free H+ in tubule for excretion allows reabsorption of a new HCO3 ion --> net gain HCO3 --> increases pH

Question 41

how does ammonium help during acidosis

Answer 41

NH4 is produced by glutamine metabolism in PCT --> metabolism gets up-regulated during acidosis every 1 NH4+ excreted = 1 H+ excreted = 1 HCO3 generated --> increases pH

Question 42

how does the kidney respond to alkalemia

Answer 42

1. decrease H+ excretion by inhibiting intercalated A cells 2. increase HCO3 excretion by stimulating intercalated B cells 3. down regulate glutamine metabolism

Question 43

what is acute kidney injury

Answer 43

decrease in GFR --> kidney failure

Question 44

what acid/base changes are common in AKI in carnivores

Answer 44

metabolic acidosis w/ high anion gap protein metabolism --> increase acids --> unable to excrete daily load

Question 45

what acid/base changes are common in AKI in herbivores

Answer 45

metabolic alkalosis carbohydrate metabolism --> increase bicarb --> unable to excrete daily load OR metabolic acidosis w/ high AG due to uremic acid accumulation

Question 46

sign of renal tubular acidosis

Answer 46

metabolic acidosis w/ normal AG NOT in kidney failure - GFR is normal