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

Acid base balance 1+2 Flashcards

(75 cards)

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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
Name 2 ways kidney regulates HCO3-
reabsorbing filtered HCO3- | Generating new HCO3-
26
What does kidney regulation of HCO3- depend on?
Active H+ secretion from tubule cells into lumen
27
What enzyme helps convert carbonic acid to CO2+H2O?
carbonic anhydrase
28
Where does the bulk of HCO3- reabsorption occur?
proximal tubule
29
Is there H+ excretion in HCO3- reabsorption?
no
30
Why is the HCO3- reabsorbed not the same as the HCO3- filtered?
large charged molecule changed to CO2 to save the buffer | net effect is still the same
31
Why must HCO3- be reabsorbed?
4320mmoles/l filtered per day | reabsorbed to prevent adding H+ into the ECF
32
What is hydrogen buffered by in urine?
several weak acids and bases | dibasic phosphate, uric acid, creatinine
33
What is titratable acidity?
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
Importance of titratable acidity and what is it only used for?
generate new HCO3- and excrete H+ | acid loads
35
Where is the source of new HCO3- in titratable acidity?
PCO2 from the blood - indirect
36
Where does the titratable acidity mostly occur? Why?
distal tubule - in-reabsorbed dibasic phosphate becomes highly concentrated due to removal of volume of filtrate
37
When does ammonium excretion occur?
acid load
38
What happens due to ammonium excretion?
H+ excreted | New HCO3- produced
39
Is NH3 or NH4+ lipid soluble?
NH3
40
How is NH3 produced?
deamination of amino acids - usually glutamine
41
What enzyme deaminates glutamine?
renal glutaminase
42
Difference between proximal and distal tubule mechanism in ammonium excretion
proximal tubule has a NH4+/Na+ exchanger so NH4+ ions formed within cells passed into lumen. Net effect is the same
43
What is the activity of renal glutaminase dependent on?Significance of this
pH | Main adaptive response of kidney to acid load
44
Why does it take 4-5 days for renal glutaminase to reach max effect?
requirements of protein synthesis
45
Why may acid/base disorders occur?
respiratory/renal problems | extreme acid/base load
46
Define acidosis and alkalosis on pH
decrease pH = acidosis | increase pH = alkalosis
47
Do resp disorders affect PCO2 or HCO3-?
PCO2
48
Do renal disorders affect PCO2 or HCO3-?
HCO3-
49
Why does respiratory acidosis occur in terms of blood constituents
pH has increased - PCO2 has increased | CO2 retention and reduced ventilation
50
Acute causes of respiratory acidosis
drugs - depress medullary resp centres eg barbiturates or opiates obstruction of major airways
51
Chronic causes of respiratory acidosis
Lung disease eg bronchitis, emphysema, asthma
52
Response in respiratory acidosis to protect the pH
Increase the HCO3- to buffer the hydrogen ions
53
When do problems arise in respiratory acidosis?
renal dysfunction
54
Cause of respiratory alkalosis - blood constituents
fall in PCO2 - increased ventilation and CO2 blow off
55
Acute causes of respiratory alkalosis
voluntary hyperventilation, aspirin, first ascent to altitude
56
Chronic causes of respiratory alkalosis
Long term residence at altitude
57
What happens in respiratory alkalosis to protect the pH?
HCO3- decrease
58
Cause of metabolic acidosis - blood constituents
Decrease in HCO3-
59
What must happen to protect the pH in metabolic acidosis?
PCO2 must decrease
60
3 causes of metabolic acidosis
increase H+ produced eg DKA, lactic acidosis increased HCO3- loss eg diarrhoea fail to excrete H+ eg renal failure
61
In metabolic acidosis what happens to breathing?
increase in depth - Kussmaul breathing - DKA/renal failure - serious
62
Why does renal compensation take longer than respiratory compensation?
renal glutaminase
63
Cause of metabolic alkalosis - blood constituents
HCO3- increased and PCO2 will increase to protect pH
64
4 causes of metabolic alkalosis
H+ loss eg vomit Renal H+ loss eg excess aldosterone, liquorice excess HCO3- unlikely in renal function massive blood transfusions due to citrate
65
Treatment of hyperkalaemia
insulin (glucose in non diabetics) calcium resonium Ca gluconate
66
Is restoring volume or correcting metabolic alkalosis more important?
volume
67
Treatment of hypovalaemia and metabolic acidosis
give NaCl | restore volume and alkalosis corrected
68
Why do you become alkalotic after sickness and diarrhoea?
lose ECF volume | aldosterone - contraction alkalosis
69
Why can liquorice cause metabolic alkalosis?
contains glycrrhizic acid - similar to aldosterone
70
Anion gap calculation
cations (Na+, K)- anions (Cl-, HCO3-)
71
Normal anion gap
14-18mmoles/l
72
What condition is it useful to measure anion gap?
metabolic acidosis
73
2 outcomes of anion gap in metabolic acidosis
unchanged | increased
74
Why would there be no change in anion gap in metabolic acidosis?
lose HCO3- from gut for example | Compensate by increase in Cl-
75
Why would there be an increase in anion gap in metabolic acidosis?
Lactic or DKA | HCO3- reduction made up by other anions eg lactate

Year 2 Urinary (JK) (26 decks)

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