Acid base balance - C Flashcards
1
Q
normal range for blood pH
A
7.35 - 7.45
2
Q
normal blood pH
A
7.4
3
Q
intracellular hydrogen ion concentration
A
50-100 mM
4
Q
extracellular hydrogen ion concentration
A
40 mM
5
Q
Stewart model: what three variables does the [H+] depend on?
A
- partial pressure of carbon dioxide (PCO2)
- strong ion difference (SID)
- total concentration of weak acids (Atot)
6
Q
why does the pH in the body have to be maintained at a particular value?
A
pH must be kept within a very narrow range because the structure and function of large organic molecules is very sensitive to [H+]
7
Q
what happens at 6.9 pH?
A
death
8
Q
what happens at 7.0 pH?
A
cerebral palsy in the newborn, asphyxia
9
Q
what happens at 7.1 pH?
A
blood vessels become calcified, bone is resorbed as hydrogen ions replace calcium ions
10
Q
what happens at 7.2 pH?
A
reduced cardiac contractility
11
Q
what happens at 7.3 pH?
A
hyperkalaemia - potassium ions move out of the cells and hydrogen ions move in
12
Q
what happens at 7.4 pH?
A
normal pH
13
Q
what happens at 7.5 pH?
A
tetany from low [Ca2+], fainting from low cerebral blood flow
14
Q
what happens at 7.6 pH?
A
hypokalaemia, cardiac dysrhythmias
15
Q
what happens at 7.7 pH?
A
haemolysis in dogs, death
16
Q
what happens when pH moves from 7.4 to 7.35? (4points)
A
- hyperventilation (under 7.4)
- systemic vasodilation
- pulmonary vasoconstriction
- renal ammoniagenesis (7.35)
17
Q
what happens when pH moves from 7.4 to 7.45? (4points)
A
- hypoventilation (over 7.4)
- systemic vasoconstriction
- pulmonary vasodilation
- renal bicarbonate secretion (7.45)
18
Q
traditional approach emphasises
A
the intake and output of ‘acids’ that can ‘donate’ hydrogen ions, and buffers react with the hydrogen ions to take it out of the solution, especially bicarb and protein
19
Q
what is the newer approach to acid base balance
A
it is controversial. it tries to account for the input and output for all substances that can affect hydrogen ions
20
Q
PCO2
A
partial pressure of CO2, 40mmHg
21
Q
SID
A
strong ion difference, 40mM
22
Q
[HCO3-]
A
concentration of bicarbonate ions
23
Q
[H+]
A
concentration of hydrogen ions
24
Q
[protein]
A
19mM
25
diagram for shift in acid base balance
(diagram)
26
what does a bigger SID mean?
bigger SID means more A- and HCO3-and so less hydrogen ions to keep in equilibrium
27
what does a bigger Atot mean?
it means that there is more AH and A- and so more hydrogen ions and less bicarbonate ions to keep in equilibrium
28
what is normal pH
7.4
29
normal pK
6.1
30
normal bicarb concentration
24mM
31
normal 'alpha' - meaning and value
solubility of CO2 in water/blood, 0.23mM per kPa
32
normal pCO2
5.3 kPa
33
what does an increase in PCO2 do to the acid base balance
an increase in PCO2 causes an increase in acidity i.e. drop in pH and also an increase in bicarb concentration
34
what does a decrease in PCO2 do to the acid base balance
a decrease in PCO2 causes a decrease in acidity i.e. a rise in pH and also a decrease in bicarb concentration
35
what is the chain reaction set off by an increase in PCO2
an increase in PCO2 causes an increase in bicarbonate ions which leads to a decrease in A- and therefore an increase in H+ (draw a diagram with the equations)
36
what is a davenport diagram?
draw or sketch one!
37
what is an example of respiratory acidosis?
retention of CO2
- heroin overdose
- anaesthesia - reduced drive to breathe
- kyphosis - lung restriction
- severe asthma or COPD - airway obstruction
- CO2 breathing
38
what is an example of metabolic acidosis?
- exercise - lactic acid
- diabetic ketoacidosis - insulin deficiency
- diarrhoea - loss of sodium and bicarbonate
- renal failure
- acetazolamide - altitude sickness, carbonic anhydrase inhibitor
39
what is an example of metabolic alkalosis?
- vomiting - loss of stomach acid
- antacid excess
- aldosteronism - tumour?
- diuretic therapy - furosemide leader to hydrogen and potassium ion loss
40
what is an example of respiratory alkalosis?
hyperventilation and therefore excessive clearing of CO2
- altitude
- anxiety
- during hypoxia
41
how to achieve compensation in respiratory acidosis or alkalosis?
renal compensation:
- respiratory acidosis = renal bicarbonate retention
- respiratory alkalosis = renal acid
42
how to achieve compensation in metabolic acidosis or alkalosis?
respiratory compensation:
| - breathing more or less than normal to bring the carbon dioxide levels back to normal
43
non volatile acids are produced from the metabolism of which amino acids?
sulphur containing like cysteine
| cationic like lysine
44
how much of the NVA are produced per day?
70 mmol
45
titration of NVA consumes how much bicarbonate?
70mEq
46
how does the kidney regenerate consumed bicarbonate?
by excreting hydrogen ions
47
what is the most abundant buffer in the body
bicarbonate ions
48
how do the kidneys regenerate the bicarbonate?
they must first reabsorb the filtered out bicarbonate ions and then regenerate plasma bicarbonate ions use to buffer the non volatile acids - both processes need hydrogen ions
49
how much HCO3- needs to be recovered daily?
4320 mEq/day
50
how much NVA needs to be excreted?
70 mEq/day
51
what is the total amount of hydrogen ions need to be secreted to balance out the amount of bicarbonate ions that need to be regenerated and NVA that needs to be excreted
4390 mEq/day
52
what is the simple model of acid secretion?
carbondioxide and water in the cell recombine and become hydrogen and bicarbonate ions catalysed by carbonic anhydrase. the hydrogen ions are removed into the lumen while the bicarbonate ions are reabsorbed back into the blood
53
what happens to the excreted hydrogen ions that move into the lumen?
it reacts with a buffer for safe removal from the system
54
what is the difference between type A and type B intercalated cells?
type A cells are proton secreting while type B are bicarbonate secreting. they are switched on for different regional environments - change in number of cells?
55
urinary buffers
ammonia
| phosphate
56
how are type A cells regulated?
they are regulated by pH
57
where do type A cells operated?
they operated in the MCD - collecting duct
58
what is renal tubular acidosis?
it is type 3 acidosis when a mutation in the carbonic anhydrase 2 generates reduced substrate for NBC and NHE and causes less sodium an hydrogen ion exchange activity, thus lowering SID causing acidosis (cablegram Na+ height goes down)
59
what is the reciprocity between [K+] and [H+]
hyperkalaemia leads to acidosis and acidosis leads to hyperkalaemia
60
acute metabolic acidosis is caused by:
- acute haemorrhage o 500ml
- strenuous muscular exercise
- hyperventilation
- renal failure
- vomiting
- strenuous muscular exercise
61
chronic metabolic acidosis is caused by
- committing
- renal failure
- COPD
- gastric ulceration
- hyperventilation
- renal failure
62
metabolic alkalosis is caused by
- vomiting
- diarrhoea
- renal failure
- strenuous muscular exercise
- acute haemorrhage
- vomiting
63
resp acidosis is caused by
- COPD
- hyperventilation
- renal failure
- acute haemorrhage
- use of carbonic anhydrase inhibitors
- COPD
64
resp alkalosis is caused by
- COPD
- hyperventilation
- renal failure
- acute haemorrhage
- use of carbonic anhydrase inhibitors
- hyperventilation
65
what happens to the normal point in a davenport diagram when there is:
- uncompensated rest depression by barbiturate poisoning
- uncompensated exposure to high altitude
- uncompensated diabetes mellitus
- partially compensated metabolic acidosis
- partially compensated respiratory alkalosis
- respiratory acidosis - so the point moves along the line to the top left of the graph
- respiratory alkalosis - so the point moves along the line to the bottom right of the graph
- metabolic acidosis - so the point moves along the curve to the bottom left of the graph
- the point moves along the curve to the top right of the graph but then again to the left towards the normal as it is partially compensated
- the point moves along the line to the bottom right of the graph but then again to the left towards the normal as it is partially compensated
