Acid-Base Homeostasis Flashcards Preview

Year 2 EMS MoD > Acid-Base Homeostasis > Flashcards

Flashcards in Acid-Base Homeostasis Deck (52):
1

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

-Lungs
-Kidneys

2

How much CO2 do you produce a day?

25mol/day.

3

How much unmetabolised acids do you produce a day?

50mmol/day.

4

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

40nmol/day.

5

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

-Haemoglobin
-Bicarbonate
-Phosphate
-Proteins
-Ammonia
-Organic acids

6

What is the reference range for pH?

7.35 - 7.45

7

What is the reference range for [H+]?

35-45 nmol/L.

8

How are [H+] and pH related?

As [H+] increases, pH decreases.

9

What is the Henderson-Hasselbalch equation used for?

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

10

What are the Henderson-Hasselbalch equation?

H+ + HCO3- H2CO3 CO2 + H2O

11

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

Balance between H+ production and regeneration of HCO3-.

12

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

-Lungs
-Kidneys
-GI tract
-Liver

13

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

A couple of days.

14

What do RBCs take up and release when acidified?

Take up CO2, release O2.

15

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

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

16

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

RBCs cannot hold O2 as well.
-decreased SO2 at same PO2

17

What role does the kidney have in maintaining bicarbonate haemostasis?

Filtered by the kidneys;
-renal reclaiming (absorption by NA/H pump)
-renal regeneration

18

What happens at the distal tubule of the kidneys?

Endocrine control (aldosterone) >> regulates salt/water through K+/H+ exchange.

19

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

H+ is lost, K+ is retained.

20

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

-H+ excreted in stomach
-HCO3- excreted in pancreas to neutralise

21

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

-Lactate metabolism
-Urea synthesis

22

What are proteins and AAs converted to in the liver?

-Carbon skeleton
-NH4+

23

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

H+ and urea.
-inhibited by acidosis

24

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

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