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My2 renal > Physiology 7+8: Acid Base Balance > Flashcards

Physiology 7+8: Acid Base Balance Flashcards

1
Q

what is the pH of arterial blood

A

7.45

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2
Q

what is the pH of venous blood

A

7.35 (more acidic from CO2)

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3
Q

what affect does acidosis and alkalosis have on the CNS

A

acidosis = depression, alkalosis = over-excitability

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4
Q

what are sources of H+ from metabolic pathways

A

carbonic acid formation/ breakdown of nutrients to inorganic products/ organic acids from metabolism eg lactic acid

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5
Q

what endocrine condition can cause build up of H+

A

diabetes mellitus

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6
Q

how do strong and weak acids act in solution

A

weak acids partly dissociate and strong acids fully dissociate

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7
Q

what does a buffer system do

A

manages equilibrium of solution ie yields free H+ when [H] decreases and binds to H+ when [H] increases

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8
Q

what is the general buffer equation

A

HA H+ + A- (HA = acid, A = base).

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9
Q

what effect does adding acid to a solution have on a buffer

A

the A- base will mop up the H+ to form HA

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10
Q

what effect does decreasing H+ in a solution have on the buffer

A

more HA will dissociate to form H+

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11
Q

what is the buffer dissociation constant equation

A

K = ([H+] x [A-]) / [HA]

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12
Q

what is the buffer equation

A

pH = pKa + log([A-]/[HA])

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13
Q

what catalyses CO2 + H2O to H2CO3 (carbonic acid)

A

carbonic anhydrase

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14
Q

how does carbonic acid (H2CO3) work as a buffer in the body

A

dissociates to hydrogen ions and bicarbonate: H2CO3 H+ + HCO3-

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15
Q

which organ controls bicarbonate levels in the body

A

kidneys

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16
Q

which organ controls CO2 levels in the body

A

lungs

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17
Q

how is bicarbonate (HCO3-) reabsorbed from the filtrate (what does it bind too and what is it reabsorbed as)

A

binds to H+ to become H2CO3 then is reabsorbed as CO2 and H2O

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18
Q

what drives HCO3- reabsorption

A

H+ secretion (increased secretion = increased reabsorption)

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19
Q

why is reabsorption of HCO3- needed

A

prevent acidosis

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20
Q

what available buffers are also in filtrate if HCO3- not available

A

phosphate –> TA

ammonia –> ammonium

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21
Q

what is the normal concentration of HCO3

A

25 mmol/l

22
Q

what is the normal arterial PCO2

A

40 mmHg

23
Q

what is compensation of acid-base (AB) vs correction of AB

A

compensation = restore pH to 7.4 irrespective of what happens to HCO3 and PCO2 // correction = pH, HCO3, CO2 all restored

24
Q

what are the 4 causes of AB disruptions

A

resp acidosis, resp alkalosis, metabolic acidosis, metabolic alkalosis

25
Q

what is pH proportional to in terms of HCO3- and CO2

A

[HCO3-] / [CO2)

26
Q

what is respiratory acidosis

A

retention of CO2 by body

27
Q

what causes resp acidosis

A

HYPOVENTILATION, COPD, airway restriction (asthma, tumour), chest injury, resp depression

28
Q

how does increased CO2 cause acidosis

A

CO2 + H20 H2CO3 H+ + HCO3- //// increased CO2 drives equilibrium to the right which increases H+ and HCO3-

29
Q

what pH and PCO2 levels would indicate uncompensated acidosis

A

pH < 7.35 and PCO2 > 45 mmHg

30
Q

how do the kidneys compensate for resp acidosis (3)

A

1) increased PCO2 drives H+ secretion 2) all HCO3 is reabsorbed to mop up H+ 3) TA and ammonium buffers are created

31
Q

in compensated resp acidosis, what levels of pH, PCO2 and HCO3 would you expect

A

normal pH // PCO2 raised // HCO3 raised

32
Q

how would correction of resp acidosis be achieved

A

normal ventilation to lower PCO2

33
Q

what is respiratory alkalosis

A

excessive removal of CO2 by the body

34
Q

what causes resp alkalosis

A

low inspired PO2 at altitude (hypoxia), hyperventilation (over breathing, fever)

35
Q

how does decreased PCO2 cause alkalosis

A

CO2 + H20 H2CO3 H+ + HCO3- //// decreased CO2 drives equilibrium to the left which also decreased H+ and HCO3-

36
Q

what levels of pH and PCO2 would be seen in uncompensated resp alkalosis

A

pH > 7.45 and PCO2 < 35 mmHg

37
Q

how do the kidneys compensate resp alkalosis (3)

A

1) reduces H+ secretion 2) HCO3- is excreted into the urine 3) no ammonium or TA formed

38
Q

what levels of pH, PCO2 and HCO3 are seen in compensated resp alkalosis

A

normal pH (increased H), decreased PCO2 and decreased HCO3

39
Q

what does correction of resp alkalosis require

A

normal ventilation and increased PCO2

40
Q

what is metabolic acidosis

A

increased H+ in the body (not from increased CO2)

41
Q

what can cause metabolic acidosis

A

ingestion of acids, excessive metabolic production of H+ (exercise, DKA), excessive base loss (diarrhoea)

42
Q

what happens to pH and HCO3- in metabolic acidosis

A

CO2 + H20 H2CO3 H+ + HCO3- /// increased pH and decreased HCO3- as not enough to mop up excess CO2

43
Q

how do the lungs compensate metabolic acidosis

A

increased ventilation and more CO2 blown off

44
Q

what levels of PCO2, pH and HCO3- are seen in compensated met acidosis

A

normal pH (H decrease) and low HCO3 and PCO2

45
Q

how is metabolic acidosis correction achieved by kidneys (4)

A

HCO3- reabsorbed, H+ secreted and TA and ammonium can create new HCO3-, acid excreted, normal ventilation

46
Q

what is metabolic alkalosis

A

excessive loss of H+ (nor as common as acidosis)

47
Q

what can cause metabolic alkalosis

A

vomiting HCL from stomach, ingestion of alkali, aldosterone hyper-secretion (Na/H exchange)

48
Q

what happens to pH, PCO2 and HCO3- in metabolic alkalosis

A

pH increased (decreased H+), increased HCO3-, normal PCO2

49
Q

how do lungs compensate metabolic alkalosis

A

slow ventilation to increase CO2 –> H+

50
Q

what happens to pH, PCO2 and HCO3- in compensated metabolic alkalosis

A

normal pH (increased H+), increased PCO2 and HCO3-

51
Q

how do the kidneys correct metabolic alkalosis

A

no HCO3- reabsorbed, no TA or ammonium generated

My2 renal (27 decks)

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