Urinary 5 - Acid-base balance Flashcards Preview

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Flashcards in Urinary 5 - Acid-base balance Deck (27):
1

What is the normal plasma pH range?

7.35 - 7.45

2

Define acidosis:

Plasma pH < 7.35

3

Define alkalosis:

Plasma pH > 7.45

4

Why is the acid-base balance of the body dependent on the kidneys and the lungs?

Kidneys = responsible for HCO3- (base) regulation
Lungs = responsible for CO2 (acid) regulation

5

Why does Alkalosis lead to paraesthesia and/or tetany?

Alkalosis leads to lowered free Ca2+ (increased binding to plasma proteins), which increases neuronal excitability

6

Why does alkalosis has a high mortality (if pH > 7.65)?

Alkalosis lowers free Ca2+ which increases neuronal excitation leading to tetany. If tetany of respiratory muscles --> lead to death

7

Describe the pathophysiology of respiratory alkalosis:

Hyperventilation leads to hypocapnia = increased pH

8

How does the body compensate for alkalosis?

Central chemoreceptors detect hypocapnia and reduce ventilation rate (limited by tissue O2 demand)
Kidney tubular cells decrease H+ excretion, and decrease HCO3- recovery

9

What are the main causes of Metabolic alkalosis?

Loss of H+ - vomiting, diarrhoea, increased secretion (Aldosterone)
Shift of H+ into ICF - hypokalaemia
Increased [HCO3-] - renal failure

10

Metabolic alkalosis can lead to what kind of K+ disorder?

HYPOkalaemia

11

Define acidosis:

pH < 7.35

12

At what point is acidosis life threatening?

If pH < 7.0

13

Describe the pathophysiology of respiratory acidosis:

Hypoventilation = hypercapnia = decreased pH

14

How does the body compensate for acidosis?

Central chemoreceptors detect decreased pH, and increase respiratory rate
Kidneys increase HCO3- recovery and production

15

Where does the majority of HCO3 reabsorption occur?

PCT (80%)

16

What enzyme catalyses the conversion of H+ + HCO3- to H2O + CO2?

Carbonic Anhydrase

17

List the 3 ways in which the kidneys increase production of HCO3-:

1 - increased conversion of CO2 + H2O into H+ and HCO3- (due to increased metabolic rate = increased CO2)
2 - From amino acids in the PCT
3 - Buffering of H+ via HPO4(2-) increases conversion of CO2 + H2O into H+ and HCO3- in DCT

18

What in the tubular lumen buffers H+ allowing the increased production of HCO3-?

HPO4(2-)
NH3

19

What are the main causes of metabolic acidosis?

Increased metabolic production of acid - lactic acidosis, ketoacidosis, damaged muscle cells (trauma/tumour)
Ingestion of acid
Increased HCO3- loss - renal failure, diarrhoea
Decreased H+ excretion - renal failure

20

What is the Anion Gap?

Difference between [Na+] + [K+] and [Cl-] + [HCO3-]

21

What is the normal Anion Gap?

10-15 mM (usually less anions than cations)

22

What type of acid-base disorder can cause an increased anion gap?

Metabolic acidosis

23

A decreased anion gap is rare, but what can cause it?

Hypermagnesia
Paraprotein anaemia - Multiple myeloma

24

Why is metabolic acidosis associated with an increased anion gap?

Metabolically produced acids have an associated anion (ie Lactate) which replaces HCO3- in plasma = decreased pH

25

What kind of acid-base disorder is associated with HYPOkalaemia?

Metabolic alkalosis

26

What kind of acid-base disorder is associated with HYPERkalaemia?

Metabolic acidosis

27

Metabolic acidosis is associated with what kind of K+ disorder?

HYPERkalaemia