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Year 2 Urinary (JK) > Acid base balance 1+2 > Flashcards

Acid base balance 1+2 Flashcards

1
Q

Why are metabolic reactions sensitive to the pH in which they occur?

A

hydrogen react with proteins (especially enzymes)to change configuration and function

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2
Q

Normal arterial blood pH

A

7.4

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3
Q

Source of respiratory acid

A

CO2+H2O -> H2CO3 -> H+ + HCO3-

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4
Q

When does problems with respiratory acid arise?

A

lung function impaired

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5
Q

2 sources of metabolic acid

A

organic eg sulphur containing amino acids, sulphuric and phosphoric acid
inorganic eg FA, lactic acid

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6
Q

How much H+ do we gain from our diet every day?

A

50-100mmoles

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7
Q

Where is our major source of alkali?

A

oxidation of anions eg citrate

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8
Q

Role of buffers

A

minimise changes in pH when H+ is added or removed

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9
Q

Main extracellular buffer

A

bicarbonate

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10
Q

How much more bicarbonate do you need than carbonic acid?

A

20 times

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11
Q

What does bicarbonate quantity depend on?

A

CO2 dissolved in plasma which depends on solubility and PCO2

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12
Q

Normal values for
a - pH
b - PCO2
3 - HCO3

A

7.4
40mmHg
24 mmoles

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13
Q

What is the unique importance of bicarbonate buffer?

A

does not reach new equilibrium

will increase or decrease ventilation to increase or decrease H+

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14
Q

Does bicarbonate buffering remove H+ from body?

A

no - just prevent free H+ contributing to pH

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15
Q

Aim of acid/base balance

A

arterial pH protected

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16
Q

What organ excretes H+ from the body?

A

kidneys

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17
Q

What is HCO3 and PCO2 under regulation of?

A

HCO3 - renal regulation

PCO2 - respiratory regulation

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18
Q

List 2 other types of buffers in ECF

A

plasma proteins

dibasic phosphate

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19
Q

List some intracellular buffers

A

Haemoglobin in RBC, proteins, organic and inorganic phosphates

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20
Q

What do ICF buffers do and what is the consequence of this?

A

change electrolyte balance

H+ movement accompanied by Cl- (RBC) or exchanged for K+

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21
Q

In acidosis what happens to potassium?

A

moved out of cells - hyperkalaemia

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22
Q

Why is there bone wasting in chronic renal failure?

A

bone carbonate is an extra source of buffer

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23
Q

For metabolic acid where is most of it buffered?

A

in cells

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24
Q

For respiratory acid where is most of it buffered?

A

in cells - 97% - Hb

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25
Q

Name 2 ways kidney regulates HCO3-

A

reabsorbing filtered HCO3-

Generating new HCO3-

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26
Q

What does kidney regulation of HCO3- depend on?

A

Active H+ secretion from tubule cells into lumen

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27
Q

What enzyme helps convert carbonic acid to CO2+H2O?

A

carbonic anhydrase

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28
Q

Where does the bulk of HCO3- reabsorption occur?

A

proximal tubule

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29
Q

Is there H+ excretion in HCO3- reabsorption?

A

no

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30
Q

Why is the HCO3- reabsorbed not the same as the HCO3- filtered?

A

large charged molecule changed to CO2 to save the buffer

net effect is still the same

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31
Q

Why must HCO3- be reabsorbed?

A

4320mmoles/l filtered per day

reabsorbed to prevent adding H+ into the ECF

32
Q

What is hydrogen buffered by in urine?

A

several weak acids and bases

dibasic phosphate, uric acid, creatinine

33
Q

What is titratable acidity?

A

buffering H+ in urine

extent measured by how much NaOH taken to titrate urine back to pH of 7.4 for 24 hour urine sample

34
Q

Importance of titratable acidity and what is it only used for?

A

generate new HCO3- and excrete H+

acid loads

35
Q

Where is the source of new HCO3- in titratable acidity?

A

PCO2 from the blood - indirect

36
Q

Where does the titratable acidity mostly occur? Why?

A

distal tubule - in-reabsorbed dibasic phosphate becomes highly concentrated due to removal of volume of filtrate

37
Q

When does ammonium excretion occur?

A

acid load

38
Q

What happens due to ammonium excretion?

A

H+ excreted

New HCO3- produced

39
Q

Is NH3 or NH4+ lipid soluble?

A

NH3

40
Q

How is NH3 produced?

A

deamination of amino acids - usually glutamine

41
Q

What enzyme deaminates glutamine?

A

renal glutaminase

42
Q

Difference between proximal and distal tubule mechanism in ammonium excretion

A

proximal tubule has a NH4+/Na+ exchanger so NH4+ ions formed within cells passed into lumen. Net effect is the same

43
Q

What is the activity of renal glutaminase dependent on?Significance of this

A

pH

Main adaptive response of kidney to acid load

44
Q

Why does it take 4-5 days for renal glutaminase to reach max effect?

A

requirements of protein synthesis

45
Q

Why may acid/base disorders occur?

A

respiratory/renal problems

extreme acid/base load

46
Q

Define acidosis and alkalosis on pH

A

decrease pH = acidosis

increase pH = alkalosis

47
Q

Do resp disorders affect PCO2 or HCO3-?

A

PCO2

48
Q

Do renal disorders affect PCO2 or HCO3-?

A

HCO3-

49
Q

Why does respiratory acidosis occur in terms of blood constituents

A

pH has increased - PCO2 has increased

CO2 retention and reduced ventilation

50
Q

Acute causes of respiratory acidosis

A

drugs - depress medullary resp centres eg barbiturates or opiates
obstruction of major airways

51
Q

Chronic causes of respiratory acidosis

A

Lung disease eg bronchitis, emphysema, asthma

52
Q

Response in respiratory acidosis to protect the pH

A

Increase the HCO3- to buffer the hydrogen ions

53
Q

When do problems arise in respiratory acidosis?

A

renal dysfunction

54
Q

Cause of respiratory alkalosis - blood constituents

A

fall in PCO2 - increased ventilation and CO2 blow off

55
Q

Acute causes of respiratory alkalosis

A

voluntary hyperventilation, aspirin, first ascent to altitude

56
Q

Chronic causes of respiratory alkalosis

A

Long term residence at altitude

57
Q

What happens in respiratory alkalosis to protect the pH?

A

HCO3- decrease

58
Q

Cause of metabolic acidosis - blood constituents

A

Decrease in HCO3-

59
Q

What must happen to protect the pH in metabolic acidosis?

A

PCO2 must decrease

60
Q

3 causes of metabolic acidosis

A

increase H+ produced eg DKA, lactic acidosis
increased HCO3- loss eg diarrhoea
fail to excrete H+ eg renal failure

61
Q

In metabolic acidosis what happens to breathing?

A

increase in depth - Kussmaul breathing - DKA/renal failure - serious

62
Q

Why does renal compensation take longer than respiratory compensation?

A

renal glutaminase

63
Q

Cause of metabolic alkalosis - blood constituents

A

HCO3- increased and PCO2 will increase to protect pH

64
Q

4 causes of metabolic alkalosis

A

H+ loss eg vomit
Renal H+ loss eg excess aldosterone, liquorice
excess HCO3- unlikely in renal function
massive blood transfusions due to citrate

65
Q

Treatment of hyperkalaemia

A

insulin (glucose in non diabetics)
calcium resonium
Ca gluconate

66
Q

Is restoring volume or correcting metabolic alkalosis more important?

A

volume

67
Q

Treatment of hypovalaemia and metabolic acidosis

A

give NaCl

restore volume and alkalosis corrected

68
Q

Why do you become alkalotic after sickness and diarrhoea?

A

lose ECF volume

aldosterone - contraction alkalosis

69
Q

Why can liquorice cause metabolic alkalosis?

A

contains glycrrhizic acid - similar to aldosterone

70
Q

Anion gap calculation

A

cations (Na+, K)- anions (Cl-, HCO3-)

71
Q

Normal anion gap

A

14-18mmoles/l

72
Q

What condition is it useful to measure anion gap?

A

metabolic acidosis

73
Q

2 outcomes of anion gap in metabolic acidosis

A

unchanged

increased

74
Q

Why would there be no change in anion gap in metabolic acidosis?

A

lose HCO3- from gut for example

Compensate by increase in Cl-

75
Q

Why would there be an increase in anion gap in metabolic acidosis?

A

Lactic or DKA

HCO3- reduction made up by other anions eg lactate

Year 2 Urinary (JK) (26 decks)

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