Acid Base Balance Flashcards

1
Q

What is the Henderson-Hasselbach equation?

A

describes relationship between pH, bicarbonate (HCO3-), and partial pressure of CO2 (PCO2)

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2
Q

What does the bicarbonate (HCO3-) buffering system do?

A

maintain pH of extracellular fluid

unique – has the capacity for independent regulation of HCO3- (by kidneys) and PCO2 (by lungs)

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3
Q

What are two other buffering systems involved in maintaining ECF pH?

A

phosphate (HPO42- )

hemoglobin (Hb-)

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4
Q

How do kidneys contribute to maintaining pH?

A

by maintaining plasma [HCO3-]

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5
Q

What are some typical sources of acids?

A

dietary intake
- meat acids > vegetable acids

metabolic byproducts

  • volatile acids (ie. H2CO3) – acids that can dissociate easily
  • non-volatile acids (ie. H2SO4, H3PO4)
  • organic acids (lactic, β-butyric, & acetoacetic acid)
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6
Q

Under normal conditions, how do kidneys accomplish pH maintenance? (2)

A

reabsorbing any filtered HCO3- (primarily in PT)

pairing generation of NEW HCO3- with secretion of H+ as:

  • H2PO4- (titratable acid)
  • NH4+
  • protons are secreted and ultimately excreted in urinary output
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7
Q

Reabsorption of Filtered HCO3- – Mechanism

A

see notes

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8
Q

What are the two ways that new HCO3- can be generated?

A
  • through formation of titratable acid

- through excretion of ammonium (NH4+)

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9
Q

Generation of New HCO3-

Formation of Titratable Acid – Mechanism

A

see notes

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10
Q

Generation of New HCO3-

Excretion of Ammonium – Mechanism

A

see notes

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11
Q

What does the liver do when the body has a higher acid load?

A

liver will favour use of glutamine to package nitrogenous waste

  • liver will produce more glutamine
  • glutamine is then delivered to kidney
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12
Q

What can acid production in body can be influenced by? (3)

A
  • diet: meats produce more acids, vegetables produce fewer acids
  • starvation: increased lipid metabolism results in increased production of both β-OH butyric and acetoacetic acid
  • trauma, surgery, strenuous exercise, & fever: increased catabolism results in increased acid formation
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13
Q

How much renal acid excretion occurs through titratable acids vs. ammonium under normal conditions?

A

1/3 to 1/2 as titratable acid (mainly H2PO4-)
- for one titratable acid excreted, we get one new bicarbonate formed

1/2 to 2/3 as ammonium (NH4+)
- for one glutamine, we get two ammonia excreted and two new bicarbonates formed

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14
Q

How does excretion of both titratable acids and ammonium change under acid-loaded conditions?

A

increased

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15
Q

What is the most effective mechanism for management of increased acid load? Why?

A

excretion of ammonium

  • in response to prolonged acid load, amount of NH3 will be increased further because it’s our most effective way of clearing that acid
  • getting rid of more acid through NH3, but also helping replenish bicarbonate buffer system by producing more HCO3-

there’s a ceiling to how much increase we can have in titratable acid
- ie. starvation – for a longer period of time, titratable acid increase plateaus

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16
Q

What are we trying to do when doing acid-base compensation?

A

fix pH

17
Q

How do we maintain pH if bicarbonate goes down?

A

decrease PCO2 to restore 20:1 ratio

18
Q

How do we maintain pH if bicarbonate goes up?

A

increase PCO2 to restore 20:1 ratio

19
Q

What are the variables on a Davenport diagram? (3)

A

bicarbonate
arterial blood pH
PCO2 – represented by red lines

20
Q

Compare PCO2 in metabolic acidosis and metabolic alkalosis.

A

metabolic acidosis and metabolic alkalosis fall relatively similar in terms of where PCO2 is

21
Q

What are acid-base nomograms used for?

A

to clinically to assess acid-base disturbances

diagnosis can be made using only blood pH and PCO2

22
Q

What are metabolic disturbances?

A

changes in [HCO3-]

23
Q

How are metabolic disturbances compensated for?

A

compensation is respiratory – change in PCO2

24
Q

What is metabolic acidosis? How is it compensated for?

A

loss of bicarbonate – ie. due to diarrhea

respiratory compensation: decrease PCO2 by hyperventilating (breathe out more CO2)

25
Q

What is metabolic alkalosis? How is it compensated for?

A

gain in bicarbonate – ie. due to vomiting

respiratory compensation: increase PCO2 by hypoventilating (breathe out less CO2)

26
Q

What are respiratory disturbances?

A

changes in PCO2

27
Q

How are respiratory disturbances compensated for?

A

compensation is metabolic – renal change in [HCO3-]

28
Q

What is respiratory acidosis? How is it compensated for?

A

higher PCO2 – ie. caused by hypoventilation, obstructive lung disease

metabolic compensation: increase [HCO3-]

29
Q

What is respiratory alkalosis? How is it compensated for?

A

lower PCO2 – ie. due to hyperventilation, high altitude

metabolic compensation: decrease [HCO3-]

30
Q

Compensation of Acid-Base Disturbances

Response to Respiratory Acidosis – Mechanism

A

see notes

31
Q

Compensation of Acid-Base Disturbances

Response to Respiratory Alkalosis – Mechanism

A

see notes

32
Q

What is acid-base handling conducted by in collecting duct?

A

intercalated cells

  • alpha intercalated cells deal with acid issues
  • beta intercalated cells deal with base issues