Session 6 - Acidosis and Alkalosis Flashcards Preview

Semester 3 - Urinary > Session 6 - Acidosis and Alkalosis > Flashcards

Flashcards in Session 6 - Acidosis and Alkalosis Deck (79)
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1

How do the kidneys control plasma volume?

• Filtering and variably recovering salts

2

How do the kidneys control plasma osmolarity?

• Filtering and variably recovering water

3

How do the kidneys variably control plasma pH?

• Filtering and variably recovering hydrogen carbonate and active secretion of hydrogen ions

4

What is normal pH range?

• 7.38 - 7.42

5

When does alkalaemia occur?

>7.42

6

When does acidaemia occur?

• <7.38

7

What is normal conc of H+?

37-43 nmol/l

8

Outline what occurs in alkalaemia

• Lowers solubility of Ca2+ salts, free Ca2+ binds to proteins. Results in hypocalcaemia
○ Increases excitability of nerves
• Paraesthesia
• Tetany

9

What is % mortality at pH 7.55?

45%

10

What is % mortality at pH 7.65?

80%

11

Outline what occurs in acidaemia

• Hyperkalaemia (heart arrythmias and arrest)
• Affects many enzymes
○ Reduces cardiac and skeletal muscle contractility
○ Reduced glycolysis in many tissues
○ Reduced hepatic function
• Effects severe under 7.1
• Life threatening below pH 7.0

12

How much HCO3- is required for accurate pH maintenance?

• 20x as much HCO3- as there is CO2
• pH = pK + log (HCO3-/pCO2 x 0.23)
• Log 20 (20x higher) = 1.3
• pK - 6.1 + 1.3 = 7.4

13

What is CO2 determined by?

• Controlled by chemoreceptors
• Disturbed by respiratory disease

14

What is HCO3- conc determined by?

• Controlled by kidney

Disturbed by metabolic and renal disease

15

What is HCO3- largely created by?

• Red blood cells

16

What is respiratory acidaemia (acidosis)?

• Hypoventilation leads to hypercapnia
• Hypercapnia causes plasma pH to fall
• Less than 20x amount of HCO3-
• pH <7.35

17

What is respiratory alkalaemia (alkalosis)?

• Hyperventilation leads to hypocapnia
• Fall in pCO2 causes pH to rise
• More than 20x amount of HCO3- than CO2

18

What is normal pH?

7.38 - 7.42

19

What is normal HCO3-

• 22 - 29 mmol/l

20

What is normal pO2?

• 9.8 - 14.2 kPa

21

What is normal pCO2?

• 4.2 - 6.0 kPa

22

How is pH corrected in respiratory alkalosis/acidosis?

• Central chemoreceptors normally control pCO2 within tight limits
• Peripheral chemoreceptors enable changes in respiration driven by changes in plasma pH
• This is CORRECTION - Changing the factor at hand

23

How is pH compensated in respiratory acidosis/alkalosis

• changes in pCO2 compensated by changes in HCO3-
• Kidney control HCO3-
• Respiratory acidosis is compensated by kidneys increasing HCO3-
• Respiratory alkalosis is compensated by kidneys decreasing HCO3-

24

What is metabolic acidosis?

• Tissues produce acid (or acid in blood - amino acids)
• H+ reacts with HCO3-, leading to fall in pH

Metabolic acidosis

25

How is metabolic acidosis compensated (acidosis means alteration in buffer base!)?

• Compensated by changes in ventilation
○ Peripheral chemoreceptors increase ventilation
○ This lowers pCO2

Restores pH towards normal

26

What is metabolic alkalosis caused by?

• Plasma HCO3- rises (after vomiting for instance)
• Plasma pH rises
• Metabolic alkalosis

27

How is metabolic alkalosis compensated?

• Partially compensated by decreased ventilation

28

How are respiratory changes in pH changed? (use correct terminology)

• Compensated by kidney
• Corrected by breathing

29

How are metabolic changes in pH modified? (use correct terminology)

• Compensated by breathing (changing factor than other directly changes)
• Corrected by kidney

30

What is produced in metabolic acidosis?

• H+ ions which react with HCO3- to produce CO2 in venous blood
• CO2 breathed out, proportionally reducing HCO3-