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Renal > 2.3: Physiology 8 > Flashcards

2.3: Physiology 8 Flashcards

1
Q

Normal pH of the body?

A

7.4

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2
Q

Normal range for [HCO3-]

A

25mmol/l

Range is 23-27

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3
Q

Normal range for arterial PCO2?

A

40mmHg

Range is 35-45

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4
Q

What is compensation?

A

If acid base balance is disturbed, the first priority is to return pH to 7.4 as soon as possible

Compensation restores pH to 7.4 irrespective of what happens to pCO2 and [HCO3-]

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5
Q

What is correction?

A

Correction of an acid base balance is restoration of:

  • pH
  • pCO2
  • [HCO3-]

back to normal

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6
Q

What occurs first - compensation or correction?

A

Compensation occurs first - fix pH

Then correction - fix pCo2 and [HCO3-]

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7
Q

Describe:

  • Respiratory acidosis?
  • Respiratory alkalosis?
  • Metabolic acidosis?
  • Metabolic alkalosis?

BRIEFLY

A

Respiratory Acidosis: There is a disturbance of respiratory origin that causes decreased plasma pH

Respiratory Alkalosis: Disturbance of respiratory origin that causes increased plasma pH

Metabolic Acidosis: Disturbance of metabolic origin that causes decreased plasma pH

Metabolic Alkalosis: Disturbance of metabolic origin that causes increased plasma pH

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8
Q

Describe the immediate buffering of a pH change?

  • How is this done?
  • What is the most important buffer?
  • Speed?
  • How long do the buffers last?
A
  • Immediate dilution of acid or base in ECF
  • Blood buffers (Eg: Haemaglobin, Bicarbonate)
  • Buffers in the ECF (Particularly bicarbonate)

Most important buffer is the co2-bicarbonate ion buffer

Very rapid buffering

Buffer stores deplete quickly (needs rectified by kidney)

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9
Q

Use the Henderson Hasselbach equation to link pH, [HCO3-] and [Co2]?

A
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10
Q

Describe what blood gas analyser measures?

What can be worked out?

A

Measures pH and PCO2

You can use this to work out [HCO3-]

Use the Henderson Hasselbach equation

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11
Q

Label the points on this Davenport Diagram?

A

A = Respiratory Acidosis

B = Metabolic Acidosis

C = Respiratory Alkalosis

D = Metabolic Alkalosis

E = Normal

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12
Q

What is respiratory acidosis?

Name some conditions it is seen in?

A

Retention of Co2 by the body

Eg: Chronic Bronchitis

Chronic Emphysema

Airway restriction (Asthma, tumour)

Chest Injuries

Respiratory Decompression

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13
Q

Describe the physiology behind respiratory acidosis?

A

Co2 is retained

This drives equilibrium of Co2/Bicarbonate to the right

[H+] and [HCO3-] rise

This causes ACIDOSIS

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14
Q

Uncompensated respiratory acidosis is indicated if..?

(Give the expected ranges for pH and Pco2)

A

pH = <7.35

pCo2 = >45mmHg

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15
Q

Describe compensation for respiratory acidosis?

A

There is no extracellular buffering

Renal system must compensate as respiratory system is cause

Retained Co2 causes increased H+ secretion

All filtered HCO3- is reabsorbed (none excreted)

H+ forms titratable acid and NH4+ (acid phosphate and ammonium ions)

The HCO3- rises

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16
Q

Describe correction for respiratory acidosis?

A

Requires lowering pCo2 by restoration of normal ventilation by removing blockage or obstruction

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17
Q

Give the expected values in compensated respiratory acidosis?

A

High PCO2 (>45mmHg)

High Bicarbonate (>25mmol/l)

Normal pH

18
Q

Very simply, how do you get rid of the acid in compensated respiratory acidosis?

A

It is excreted as NH4+ and titratable acid (phosphate acid)

19
Q

What is respiratory alkalosis?

Name some conditions that could cause this?

A

Excessive removal of Co2 by the body

  • Low inspired pO2 (eg: High altitude)
  • Hyperventilation
  • Hystertical over breathing
20
Q

Describe the physiological changes in respiratory alkalosis?

A

Decrease in Co2

Causes equilibrium to shift to left

Both [H+] and [HCO3-] fall

Decreased H+ causes alkalosis

21
Q

Give the expected values in uncompensated respiratory alkalosis?

A

pH > 7.45

PcO2 < 7.35mmHg

22
Q

Describe compensation in respiratory alkalosis?

A

The respiratory system is the cause so the renal system must compensate

Reduced pCo2 reduces H+ secretion

There is not enough H+ to reabsorb HCO3-

HCO3- ions are excreted in urine

No new HCO3- is formed

Bicarbonate falls

pH returns to 7.4

23
Q

Describe correction for respiratory alkalosis?

A

Restoration of normal ventilation

24
Q

Give the expected values in compensated respiratory alkalosis?

A

Normal pH

Low Bicarbonate

Low PCo2

25
Q

Very simply, how do you compensate for respiratory alkalosis?

A

Urination out bicarbonate

26
Q

What is metabolic acidosis?

Give some causes?

A

This is excess Co2 from any source other than respiratory

Eg:

  • Ingestion of acid or acid producing food-stuff
  • Excessive metabolic production of H+ (Lactic acid during exercise, ketoacidosis)
  • Excess loss of base from body (Eg: Diarrhoea)
27
Q

Describe the physiology behind metabolic acidosis?

A

[HCo3-] is depleted

Can be the result of buffering excess H+ or due to loss of HCO3- from the body

Causes acidosis

28
Q

Give the expected values for uncompensated metabolic acidosis?

A

pH = Low (<7.3)

[HCo3-] = Low (<35mmol/l)

pCo2 = Normal

29
Q

Describe compensation in metabolic acidosis?

A

Renal system is cause so respiratory system compensates

  • Ventilation increases
  • More Co2 is blown off

This lowers [H+]

30
Q

Describe the expected values in compensated metabolic acidosis?

A

pH = 7.4 (Normal)

pCo2 = Low, ,35mmHg (has been blown off)

[HCo3-] = Low (<23mmol/l)

31
Q

Describe correction in metabolic acidosis?

A

This is slow

More HCO3- is produced and acid is excreted (as titratable acid and NH4+)

This process is slow

Acid load cannot be excreted immediately therefore respiratory compensation is essential

32
Q

Which is faster?

Respiratory compensation or renal?

A

Respiratory compensation is very fast

Renal compensation can take days

33
Q

Describe metabolic alkalosis?

A

This is excessive loss of H+ from the body

Eg:

  • Vomiting (loss of H+)
  • Ingestion of alkali producing foods
  • Adolsterone Hypersecretion
34
Q

Describe the physiology behind metabolic alkalosis?

A

HCo3- rises

May be due to H+ loss or addition of base

Causes alkalosis

35
Q

Give the expected values for uncompensated metabolic alkalosis?

A

pH = High (>7.45)

PCo2 = Normal (40mmHg)

HCO3- = High (>27mmol/l)

36
Q

Describe compensation for metabolic alkalosis?

A

Increasing pH slows ventilation

This causes Co2 retention

This causes increased H+ and increased HCo3-

Increased H+ returns pH to normal

37
Q

Describe correction for metabolic alkalosis?

A

The filtered load of HCO3- is much larger than usual

Excreted in urine

HCo3- returns to normal

38
Q

Describe the expected values in compensated metabolic alkalosis?

A

pH = 7.4 (Normal)

PCo2 = High (>45mmHg)

HCo3- = High (>27mmol/l)

39
Q

What is the pattern for compensated

  • Respiratory acidosis
  • Respiratory alkalosis
  • Metabolic acidosis
  • Metabolic alkalosis?
A

High

Low

Low

High

(Normal pH for all - high refers to both PCo2 and HCo3-)

40
Q

Briefly describe each on:

  • Respiratory acidosis
  • Respiratory Alkalosis
  • Metabolic Acidosis
  • Metabolic alkalosis
A

Respiratory Acidosis: Retention of CO2 by the body

Respiratory Alkalosis: Excessive Co2 emoval by the body

Metabolic Acidosis: Excess H+ (from any source except respiratory)

Metabolic Alkalosis: Excess loss of H+ from the body

41
Q
A

Renal (34 decks)

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