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Year 2 EMS MoD > Acid-Base Homeostasis > Flashcards

Acid-Base Homeostasis Flashcards

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)

A
  • Lactate metabolism

- Urea synthesis

22
Q

What are proteins and AAs converted to in the liver?

A
  • Carbon skeleton

- NH4+

23
Q

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

A

H+ and urea.

-inhibited by acidosis

24
Q

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

A

NH3.

  • stimulated by alkalosis
  • excreted in urine
25
Q

What is excess NH4+ produced by proteins used for?

A

Urea cycle.

-NH4+ and CO2 are combined to neutralise HCO3-

26
Q

Is CO2 acidic or alkali when dissolved?

A

Acidic.

27
Q

What pathways are blocked in severe liver failure? (2)

A

NH4+ + oxoglutarate&raquo_space; glutamine.

NH4+ + CO2&raquo_space; urea + H+.

28
Q

What are the main acid-base consequences of severe liver failure? (2)

A
  • Metabolic alkalosis

- NH4+ toxicity

29
Q

What are the 2 types of acidosis/alkalosis?

A
  • Metabolic

- Respiratory

30
Q

What are the main compensatory methods for acidosis/alkalosis? (3)

A
  • Respiratory
  • Renal bicarbonate regeneration
  • Hepatic shift (urea synthesis / ammonia excretion)
31
Q

Is bicarbonate (HCO3-) acidic or alkaline?

A

Alkaline.

32
Q

What is the normal [H+] value?

A

40 nmol/L.

range : 36-44

33
Q

What is the main equation involved with alkalosis/acidosis?

A

H+ + HCO3- &raquo_space; H2CO3 &raquo_space; CO2 + H2O.

34
Q

What are the causes of metabolic alkalosis? (3)

A
  • Generation of bicarbonate by gastric mucosa
  • Renal generation of HCO3- in hypokalaemia
  • Administration of bicarbonate
35
Q

What are the main consequences of metabolic alkalosis? (3)

A
  • K+&raquo_space; cells and urine
  • PO4&raquo_space; cells
  • Respiratory suppression
36
Q

What are the main signs / symptoms of metabolic alkalosis?

A
  • Vomiting/diarrhoea
  • Renal failure
  • Drug use
  • GI surgery
37
Q

What causes respiratory alkalosis?

A

Increased CO2 excretion due to hyperventilation.

-CO2 excretion > CO2 production

38
Q

How does respiratory alkalosis typically present?

A
  • Paresthesia
  • Chest pain
  • Dyspnoea
  • Dizziness
39
Q

What electrolyte imbalances does respiratory alkalosis cause?

A
  • Decreased H+
  • Increased pO2
  • Decreased pCO2
40
Q

What are the main causes of respiratory acidosis? (3)

A

CO2 retention due to:

  • inadequate ventilation
  • parenchymal lung disease
  • inadequate perfusion
41
Q

How does respiratory acidosis typically present?

A
  • Anxiety
  • Confusion
  • Dyspnoea
  • Disturbed sleep
42
Q

What electrolyte imbalances does respiratory acidosis cause? (3)

A
  • Increased H+
  • Decreased pO2
  • Increased pCO2
43
Q

What are the main causes of metabolic acidosis? (4)

A
  • Increased H+ formation
  • Acid ingestion
  • Reduced renal H+ excretion
  • Loss of bicarbonate
44
Q

What are the main causes of increased H+ formation? (4)

A
  • Ketoacidosis (alcoholic/diabetes)
  • Lactic acidosis
  • Poisoning
  • Inherited organic acidoses
45
Q

What are the main symptoms of metabolic acidosis?

A
  • Collapse
  • Hyperventilation
  • Tiredness
  • Weight loss
  • Jaundice
46
Q

What is diabetic keto-acidosis?

A

Lack of insulin&raquo_space;

  • hyperglycaemia
  • hyperketonaemia
  • increased FFA

which all&raquo_space; ACIDOSIS.

47
Q

What are the 2 types of lactic acidosis?

A
  • Type A - shock (decreased O2)

- Type B - metabolic / toxic causes

48
Q

Does high lactate always lead to lactic acidosis?

A

No, not in alkalosis.

|&raquo_space; increased glycolysis and vasoconstriction

49
Q

What causes reduced H+ excretion? (2)

A
  • Renal tubular acidosis

- Generalised renal failure

50
Q

How does renal failure cause reduced H+ excretion?

A

REDUCED VOLUME OF NEPHRONS;

  • increased HCO3- loss
  • reduced NH4+ secretion
  • NH4+ is needed by liver for urea and H+ synthesis
51
Q

What else is H+ derived from apart from NH4+?

A

Glutamine.

-only a very small fraction

52
Q

How do can chronic alcoholism lead to acidosis?

A 
NAD+ depletion
>> thiamine deficiency
>> enhanced glycolysis
>> keto-acids
>> vomiting

Year 2 EMS MoD (20 decks)

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