9 Acid-Base Balance Flashcards

1
Q

Why is alkalaemia more dangerous than acidaemia?

A

Alkalaemia causes calcium ions to come out of solution and bind to other molecules

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2
Q

Why does alkalaemia increase neuronal excitability?

A

Lowers free calcium by causing Ca2+ ions to come out of solution

Also causes hypokalemia- more excitable state for neurons

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3
Q

What symptoms might someone get if their blood pH reach >7.45?

A

Parasthesia and tetany (intermittent muscular spasms)

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4
Q

Explain how acidaemia can cause arrhythmia. What other consequences can acidaemia have systemically?

A
  • Increase K+ concentration in plasma
    • Effects excitability of muscle (esp cardiac)
  • Denatures proteins
    • Affects glycolysis
    • Hepatic function
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5
Q

What is the normal concentration of hydrogen carbonate in the blood? Where is it made and where is it controlled?

A
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6
Q

Why is hydrogen carbonate concentration in plasma not depleted when we produce acid due to metabolism?

A
  1. Kidney’s recover all filtered HCO3-
  2. HCO3- made:
    1. PCT: from amino acids- put NH4+ into urine
    2. DCT: from CO2 and H2O
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7
Q

How is hydrogen carbonate reabsorbed in the proximal convulted tubule?

A
  1. HCO3- in lumen of PCT
  2. Sodium- hydrogen exchanger- pumps hydrogen ions into lumen and sodium in
  3. H+ and HCO3-​ react to from H2O and CO2
  4. H2O and CO2 move into tubular cell
  5. Converted back into HCO3-​ - moves into ECF
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8
Q

How is HCO3- created from glutamine in the PCT?

(glutamine= an amino acid)

A
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9
Q

What happens to hydrogen ions and the hydrogen carbonate ions that are produced from the reaction of water and carbon dioxide in the distal tubules and collecting ducts?

A

Phosphate therefore used to create buffering system

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10
Q

Outline the role of ammonia in the control of pH.

A

pH drop- increase excretion of ammonia

ammonia buffers more hydrogen ions to form amonium- ammonium trapped

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11
Q

What is the minimum pH of urine? Why does the pH not go below this?

A

minimum pH: 4.5

doesn’t fall below: Due to buffering system (ie phosphate and ammonia if no HCO3-)

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12
Q

Why does acidosis result in hyperkalaemia?

A

Reciprocal ion shift

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13
Q

What effect will hypokalaemia have on acid base balance?

A

Will cause metabolic alkalosis- H+ ions move into cells

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14
Q

What causes these blood levels:

A

Hypoventilation

Hypercapnia

Respiratory acidosis

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15
Q

What causes these blood levels:

A

Hyperventilation

Hypocapnia

Respiratory alkalosis

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16
Q

What happens to [HCO3-] to compensate for:

Repiratory acidosis?

Respiratory alkalosis?

How long does this take (to return to normal)

A
17
Q

What do these levels indicate?

A

Compensated respiratory acidosis

18
Q

What do these levels indicate?

A

Compensated respiratory alkalosis

19
Q

If there is a fall in [HCO3-] in the blood, this can lead to metabolic acidosis. Why will there not be an increase in arterial pCO2?

A
20
Q

Which anions and cations are used to measure the anion gap?

A
21
Q

What would cause the anion gap to increase?

A

If HCO3- is replaced by anions from other acids (eg lactic acid)

22
Q

What condition is initially characterised by these values?

A

Metabolic acidosis

23
Q

How is metabolic acidosis compensated for?

A
24
Q

What condition is charaterised by these values?

A

Compensated metabolic acidosis

25
Q

What condition is characterised by these values?

A

Metabolic alkalosis

26
Q

Why can’t metabolic alkalosis be completely compensated for by reducing breathing?

A

Need to maintain pO2 so can only reduce breathing by so much

27
Q

What effect will type 2 respiratory failure have on pH? Give examples of what can cause type 2 respiratory failure.

A

Effect on pH: Low O2 and High CO2- RESPIRATORY ACIDOSIS

(compensated for by incrase HCO3-)- so pH near normal

Conditions causing:

  • Severe COPD
  • Severe asthma
  • Drug overdose (supressed ventilation)
  • Neuromuscular disease
28
Q

What is type 1 respiratory failure?

A

hypoxia without hypercapnia

Low pO2 and normal to low pCO2

eg. Hypervenitlation in response to long-term hypoxia

29
Q

What is an ion gap increase indicative of? What can cause this?

A

Metabolic production of an acid

30
Q

Give examples of conditions which can cause metabolic acidosis without affecting the anion gap (ie renal related and hydrogen carbonate replaced by chloride ions)

A
31
Q

Acidosis can result in hyperkalaemia within the body. Why might diabetic ketoacidosis cause an overall depletion of potassium ion concentration?

A

Because of polyuria as a result of the diabetes- K+ lost in urine anyway

32
Q

Identify some causes of metabolic alkalosis:

A
33
Q

Theoretically metabolic alkalosis should be quite easy to correct ( HCO3-excreted) . However why might this be more difficult when there is volume depletion?

A
34
Q

Useful: thinking about metabolic acidosis

A