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Year 2 EMS MoD > Acid-Base Homeostasis > Flashcards

Acid-Base Homeostasis Flashcards

(52 cards)

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1
Q

What are the main organs that provide outputs to maintain acid-base homeostasis? (2)

A
  • Lungs

- Kidneys

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2
Q

How much CO2 do you produce a day?

A

25mol/day.

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3
Q

How much unmetabolised acids do you produce a day?

A

50mmol/day.

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4
Q

How much plasma [H+] do you produce a day?

A

40nmol/day.

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5
Q

What are the main buffering systems in the body? (6)

A
  • Haemoglobin
  • Bicarbonate
  • Phosphate
  • Proteins
  • Ammonia
  • Organic acids
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6
Q

What is the reference range for pH?

A

7.35 - 7.45

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7
Q

What is the reference range for [H+]?

A

35-45 nmol/L.

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8
Q

How are [H+] and pH related?

A

As [H+] increases, pH decreases.

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9
Q

What is the Henderson-Hasselbalch equation used for?

A
  • pH as a measure of acidity
  • Estimates the pH of a buffer
  • Finding equilibrium pH in acid-base reactions
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10
Q

What are the Henderson-Hasselbalch equation?

A

H+ + HCO3- H2CO3 CO2 + H2O

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11
Q

What does [H+] homeostasis require a balance between?

A

Balance between H+ production and regeneration of HCO3-.

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12
Q

What are the main sites of acid-base metabolism in the body? (4)

A
  • Lungs
  • Kidneys
  • GI tract
  • Liver
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13
Q

How long does it take for the kidneys to alter the acid-base balance?

A

A couple of days.

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14
Q

What do RBCs take up and release when acidified?

A

Take up CO2, release O2.

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15
Q

When does a right shift occur on an O2-Hb dissociation curve?

A 
*RIGHT*
Right shift with 
Increased 2,3 dipG
H+ acidosis
Temperature
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16
Q

What does a right shift on an O2-Hb dissociation curve mean?

A

RBCs cannot hold O2 as well.

-decreased SO2 at same PO2

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17
Q

What role does the kidney have in maintaining bicarbonate haemostasis?

A

Filtered by the kidneys;

  • renal reclaiming (absorption by NA/H pump)
  • renal regeneration
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18
Q

What happens at the distal tubule of the kidneys?

A

Endocrine control (aldosterone)&raquo_space; regulates salt/water through K+/H+ exchange.

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19
Q

What happens during acidosis to K+ and H+ at the distal tubule of the kidney?

A

H+ is lost, K+ is retained.

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20
Q

How is acid-base homeostasis maintained in the GI tract?

A
  • H+ excreted in stomach

- HCO3- excreted in pancreas to neutralise

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21
Q

How is the liver involved in acid-base metabolism? (2)

Study These Flashcards
A
  • Lactate metabolism

- Urea synthesis

22
Q

What are proteins and AAs converted to in the liver?

Study These Flashcards
A
  • Carbon skeleton

- NH4+

23
Q

What does the carbon skeleton go on the form in the liver?

Study These Flashcards
A

H+ and urea.

-inhibited by acidosis

24
Q

What does NH4+ go on too form in the liver?

Study These Flashcards
A

NH3.

  • stimulated by alkalosis
  • excreted in urine
25
What is excess NH4+ produced by proteins used for?
Urea cycle. | -NH4+ and CO2 are combined to neutralise HCO3-
26
Is CO2 acidic or alkali when dissolved?
Acidic.
27
What pathways are blocked in severe liver failure? (2)
NH4+ + oxoglutarate >> glutamine. | NH4+ + CO2 >> urea + H+.
28
What are the main acid-base consequences of severe liver failure? (2)
- Metabolic alkalosis | - NH4+ toxicity
29
What are the 2 types of acidosis/alkalosis?
- Metabolic | - Respiratory
30
What are the main compensatory methods for acidosis/alkalosis? (3)
- Respiratory - Renal bicarbonate regeneration - Hepatic shift (urea synthesis / ammonia excretion)
31
Is bicarbonate (HCO3-) acidic or alkaline?
Alkaline.
32
What is the normal [H+] value?
40 nmol/L. | range : 36-44
33
What is the main equation involved with alkalosis/acidosis?
H+ + HCO3- >> H2CO3 >> CO2 + H2O.
34
What are the causes of metabolic alkalosis? (3)
- Generation of bicarbonate by gastric mucosa - Renal generation of HCO3- in hypokalaemia - Administration of bicarbonate
35
What are the main consequences of metabolic alkalosis? (3)
- K+ >> cells and urine - PO4 >> cells - Respiratory suppression
36
What are the main signs / symptoms of metabolic alkalosis?
- Vomiting/diarrhoea - Renal failure - Drug use - GI surgery
37
What causes respiratory alkalosis?
Increased CO2 excretion due to hyperventilation. | -CO2 excretion > CO2 production
38
How does respiratory alkalosis typically present?
- Paresthesia - Chest pain - Dyspnoea - Dizziness
39
What electrolyte imbalances does respiratory alkalosis cause?
- Decreased H+ - Increased pO2 - Decreased pCO2
40
What are the main causes of respiratory acidosis? (3)
CO2 retention due to: - inadequate ventilation - parenchymal lung disease - inadequate perfusion
41
How does respiratory acidosis typically present?
- Anxiety - Confusion - Dyspnoea - Disturbed sleep
42
What electrolyte imbalances does respiratory acidosis cause? (3)
- Increased H+ - Decreased pO2 - Increased pCO2
43
What are the main causes of metabolic acidosis? (4)
- Increased H+ formation - Acid ingestion - Reduced renal H+ excretion - Loss of bicarbonate
44
What are the main causes of increased H+ formation? (4)
- Ketoacidosis (alcoholic/diabetes) - Lactic acidosis - Poisoning - Inherited organic acidoses
45
What are the main symptoms of metabolic acidosis?
- Collapse - Hyperventilation - Tiredness - Weight loss - Jaundice
46
What is diabetic keto-acidosis?
Lack of insulin >> - hyperglycaemia - hyperketonaemia - increased FFA which all >> ACIDOSIS.
47
What are the 2 types of lactic acidosis?
- Type A - shock (decreased O2) | - Type B - metabolic / toxic causes
48
Does high lactate always lead to lactic acidosis?
No, not in alkalosis. | >> increased glycolysis and vasoconstriction
49
What causes reduced H+ excretion? (2)
- Renal tubular acidosis | - Generalised renal failure
50
How does renal failure cause reduced H+ excretion?
REDUCED VOLUME OF NEPHRONS; - increased HCO3- loss - reduced NH4+ secretion - NH4+ is needed by liver for urea and H+ synthesis
51
What else is H+ derived from apart from NH4+?
Glutamine. | -only a very small fraction
52
How do can chronic alcoholism lead to acidosis?
``` NAD+ depletion >> thiamine deficiency >> enhanced glycolysis >> keto-acids >> vomiting ```

Year 2 EMS MoD (20 decks)

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