Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Respiratory > Lec 9 - Acid base balance > Flashcards

Lec 9 - Acid base balance Flashcards

1
Q

What is alkalaemia?

A

Plasma pH greater than 7.45

—> This leads to paraesthesia and tetany.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is acidaemia?

A

Plasma pH less than 7.35

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What happens in alkalaemia do?

A
  • Alkalaemia lowers free calcium by causing Ca2+ ions to come out of solution.
  • –> increases neuronal excitability.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the mortality rates of alkalaemia?

A
  • 45% mortality if pH rises to 7.55

- 80% mortality at pH 7.65.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What happens in acidaemia?

A
  • Acidaemia increases plasma potassium ion concentration.
  • –> This effects excitability and can lead to arrhythmia.
  • Increasing the concentration of H+ affects many enzymes, which can denature enzymes and effect muscle contractility, glycolysis and hepatic function.
  • effects are severe below pH 7.1
  • Life threatening below pH 7.0
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is pCo2 determined by?

A
  • It is determined by respiration.
    it is controlled by chemoreceptors.
  • It is disturbed by respiratory disease.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is [HCO3-] determined by?

A
  • determined by the kidneys.

- It is disturbed by metabolic and renal disease.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How do the kidneys work to control plasma pH?

A
  • The kidneys control pH.

- –> There is variable recovery of hydrogen carbonate and active secretion of hydrogen ions.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How do the lungs work to control plasma pH?

A
  • Alveolar ventilation allows diffusion of O2 into blood and CO2 out of blood.
  • –> control pO2 and pCO2.
  • The rate of ventilation is controlled by chemoreceptors.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the normal concentration of HCO3- in arterial blood?

A

The range is 22-26 mmol.I-1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Why does the acid we produce due to metabolism not deplete HCO3-?

A

This is because:

  1. The kidneys recover all filtered HCO3-.
  2. The Proximal tubule makes HCO3- from amino acids, putting NH4+ into urine.
  3. The distal tubule makes HCO3- from CO2 and H20.
    - –> H+ is also buffered by phosphate and ammonia in the urine.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Describe the renal control of HCO3- (recovery).

A
  1. HCO3- is filtered at the glomerulus.
  2. It is mostly recovered in the PCT.
  3. H+ excretion is linked to Na+ entry in the PCT.
  4. H+ reacts with HCO3- in the lumen to form CO2 which enters the cell.
  5. It is converted back to HCO3- which enters ECF.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How is HCO3- created?

A
  1. Glutamine —> glutamate —> alpha ketoglutarate.
    - –> It produces HCO3- and ammonium (NH4+)
    - ———-> This then dissociates into ammonia and H+.
    - –> HCO3- enters the ECF.
    - –> NH4+ enters the lumen (urine)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the major adaptive response to an increased load in healthy individuals?

A

Excretion of ammonium is the major adaptive response.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How is ammonium generation from glutamine in proximal tubule be increased?

A

It can be increased in response to low pH.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How is NH4+ converted to H+?

A

NH4+ —> NH3 + H+

  1. NH3 freely moves into the lumen and throughout the interstitium.
  2. H+ is actively pumped into the lumen in the DCT and CT.
  3. H+ combines with NH3 to form NH4+ which is trapped in the lumen.
  4. NH4+ can also be taken up in the TAL and transported to interstitium and dissociates to H+ and NH3 —> goes to lumen of collecting ducts.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the minimum pH of urine?

A

4.5

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What does acidosis?

A

Hyperkalaemia

  1. potassium ions move out of cells.
  2. Decreased potassium excretion in distal nephron.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What does alkalosis?

A

Hypokalaemia

  1. Potassium ions move into cells.
  2. Enhanced excretion of potassium in distal nephron.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What happens in hyperkalaemia?

A
  • Hyperkalaemia makes intracellular pH of tubular cells more alkaline.
  • –> H+ ions move out of the cells.
  • –> This favours HCO3- excretion. —> Metabolic acidosis.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What happens in hypokalaemia?

A
  • Hypokalaemia makes the intracellular pH of tubular cells more acidic.
  • –> H+ ions move into the cells.
  • –> This favours H+ excretion and HCO3- recovery. —> Metabolic alkalosis.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is respiratory acidosis (acidaemia)?

A
  • high pCO2
  • normal HCO3-
  • Low pH
23
Q

What is respiratory acidosis (acidaemia) characterised by?

A
  • high pCO2
  • normal HCO3-
  • Low pH
24
Q

What is respiratory alkalosis (alkalaemia) characterised by?

A
  • Low pCO2
  • normal HCO3-
  • Raised pH
25
Q

What does hypoventilation lead to?

A
  • hypoventilation leads to hypercapnia —> pCO2 rises
26
Q

What does hyperventilation lead to?

A
  • Hyperventilation leads to hypocapnia. —> pCo2 falls.
27
Q

What compenates for changes in pCO2?

A

Compensated by changes in [HCO3].

28
Q

How is respiratory acidosis compensated for?

A
  • The kidneys would increase [HCO3]
  • SO in the end there would be:
    1. high pCO2
    2. Raised [HCO3-]
    3. Relatively normal pH.
29
Q

How is respiratory alkalosis compensated for?

A
  • The kidneys would decrease [HCO3-] to compensate for respiratory alkalosis.
  • So in the end there would be:
    1. Low pCO2
    2. Lowered [HCO3-]
    3. Relatively normal pH
30
Q

What happens in metabolic acidosis?

A
  1. The tissues produce acid which reacts with and removes HCO3-.
  2. There is a fall in [HCO3-] leading to a fall in pH.

*The extra CO2 produced is breathed off at the lungs so there is no increase in arterial pCO2.

31
Q

What is the anion gap?

A

This is the difference between measured cations and anions.

  • ([Na+] + [K+]) - ([CL-]+[HCO3-]
  • –> It is normally 10-18 mmol.I -1
32
Q

When are there changes in the anion gap?

A
  • The gap is increased if HCO3- is replaced by other anions.

- –> If a metabolic acid such as lactic acid reacts with HCO3-, the anion of the acid replaces HCO3-.

33
Q

Where are there no changes in the in the anion gap?

A
  • In renal causes of acidosis the anion gap is unchanged because:
    1. not making enough HCO3- but this is replaced by Cl-.
34
Q

What is metabolic acidosis characterised by?

A
  • Normal pCO2
  • Low HCO3-
  • Low pH.
35
Q

What is compensated metabolic acidosis characterised by?

A
  • Low HCO3-
  • Lowered pCO2
  • Nearer normal pH
36
Q

What is pH drop detected by and what does it lead to?

A
  • Peripheral chemoreceptor ( carotid bodies) detect pH drop.
    1. They stimulate ventilation
    2. Leads to decrease pCO2.
37
Q

When does metabolic alkalosis occur?

A

It occurs if [HCO3-] increases.

38
Q

What is metabolic alkalosis characterised by?

A
  • Normal pCO2
  • Raised HCO3-
  • Increased pH
39
Q

What can not compensate metabolic alkalosis?

A
  • It cannot be compensated to a great extent by reducing breathing as need to maintain pO2.
40
Q

What conditions lead to respiratory acidosis?

A
  1. Type 2 respiratory failure
    - Low pO2 and high pCO2
    - The alveoli cannot be properly ventilated.
    - These include severe COPD, severe asthma, drug overdose and neuromuscular disease.
41
Q

What conditions lead to respiratory alkalosis?

A
  1. Hyperventilation
    - Anxiety/ panic attacks - acute setting.
    - Low pCO2 leads to a rise in pH.
  2. Hyperventilation in response to long-term hypoxia - Type 1 respiratory failure.
    - Low pCO2 with initial rise in pH
    - Chronic hyperventilation can be compensated for by fall in [HCO3-].
    - Can restore pH to near normal.
42
Q

What conditions lead to metabolic acidosis is the anion gap is increased?

A
  1. kets-acidosis
    - –> diabetes
  2. Lactic acidosis
    - –> Exercising to exhaustion
    - –> poor tissue perfusion
  3. Uraemic acidosis
    - –> Advanced renal failure
    - ———-> reduced acid secretion leads to build up of phosphate, sulphate and urate in blood.
43
Q

What does increased anion gap indicate?

A
  • Increased anion gap indicates a metabolic production of an acid.
44
Q

What conditions lead to metabolic acidosis with a normal anion gap?

A
  1. Renal tubular acidosis
    - This has problems with transport mechanisms in the tubules.
    - Type 1 (distal) RTA - inability to pump out H+.
    - Type 2 (proximal) RTA (very rare) - problems with HCO3- reabsorption.
  2. Severe persistent diarrhoea can also lead to metabolic acidosis due to loss of HCO3-.
    - –> HCO3- is replaced by CL- therefore the anion gap is unaltered.
45
Q

What indicates that the anion gap is normal?

A
  • If anion gap is normal HCO3- is replaced by Cl-.
46
Q

What do non-renal causes of metabolic acidosis cause?

A
  • They cause increased reabsorption of K+ by kidneys and movement of K+ out of cells.
  • –> This leads to hyperkalaemia.
  • In diabetic ketoacidosis, may be a total body depletion of K+.
  • –> K+ moves out of cells due to acidosis and lack of insulin, but osmotic diuresis means K+ is lost in urine.
47
Q

What conditions lead to metabolic alkalosis?

A
  1. HCO3- is retained in place of Cl-.
  2. The stomach is a major site of HCO3- production.
    - –> By-product of H+ secretion.
    - –> Severe prolonged vomiting leads to loss of H+.
    - –> Or mechanical drainage of stomach.
  3. Potassium depletion/ mineralocorticoid excess.
  4. Certain diuretics (loop and thiazide)
48
Q

What is metabolic alkalosis corrected by?

A
  1. Rise in pH of tubular cells which leads to fall in H+ secretion and reduction in HCO3- recovery.
    - But there is a problem if there is also volume depletion because:
    - –> The capacity to loose HCO3- is reduced because of the high rate of Na+ recovery.
    - –> Recovering Na+ favours H+ excretion and HCO3- recovery.
49
Q

How does metabolic alkalosis lead to hypokalaemia?

A
  1. Less H+ is excreted in the nephron which leads to more K+ being excreted.
  2. Alkalosis also causes movement of K+ ions into cells.
50
Q

How do the values indicate Respiratory acidosis/ alkalosis?

A

If pCO2 is not normal, [HCO3-] is normal and pH has changed in opposite direction to pCO2.

51
Q

How do the values indicate Metabolic acidosis/ alkalosis?

A

If [HCO3-] is not normal, pCO2 is normal and pH has changed In the same direction as [HCO3-]

52
Q

How do the values indicate compensated respiratory acidosis?

  • note that metabolic alkalosis can not be compensated for*
A

If pCO2 is high, [HCO3-] is raised and pH is relatively normal.

53
Q

How do the values indicate compensated respiratory alkalosis or compensated metabolic acidosis?

A

If [HCO3-] is low, pCO2 is low, pH is relatively normal.

Respiratory (9 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions