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CRAAB 7 > Katz: Acid Base > Flashcards

Katz: Acid Base Flashcards

1
Q

What is pH?

A

-log [H] = pH

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2
Q

What is a normal pH

A

7.4 (40 nm)

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3
Q

What is the isohydric principle?

A

Multiple acid/base pairs in solution will be in equilibrium with one another, tied together by their common reagent: the hydrogen ion and hence, the pH of solution.

CHANGE IN H LEADS TO A CHANGE IN IONIZATION

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4
Q

What is Le Chatelier’s Principle?

A
  1. increase in right side of the eqtn
  2. left shift
  3. increase in H
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5
Q

What is the most important extracellular buffer system? How does the buffer work when there’s acidosis?

A

C02 + H20 > H2C03 > H + HC03

  1. Increase in H
  2. Left shift
  3. Decrease in H (attenuated the rise in H)
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6
Q

Where does compensation occur? What does it do?

A

It occurs SLOWLY and return pH to NORMAL.

Lungs, kidney (liver)

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7
Q

How long does it take the lungs and kidneys to compensate?

A

lungs- minutes

kidneys- days

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8
Q

How does renal compensation respond to acidosis?

A

Acidosis stimulates the Na/H antiporter in the proximal tubule and increases proximal ammonium production.

H is added to the proximal lumen (much of it riding on NH3 as NH4), so the acid is TRAPPED in the lumen and excreted in the urine.

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9
Q

What is urine pH usually during acidosis?

A

It can be as low as 4-4.5 with 100mM NH4

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10
Q

How is plasma H reduced?

A

Plasma H is reduced by adding bicarbonate to the blood.

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11
Q

Why are renal ammonia production and renal H secretion often increased to compensate for an acidosis?

A

As acid builds up the cell becomes better at getting rid of acid and actually becomes MORE efficient.

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12
Q

What are the three cells involved in renal compensation to acid base disturbance?

A
  1. Proximal tubule cell (Secretes H/NH4, reabsorbs HCO3)
  2. Alpha intercalated cell (secretes H, reabsorbs K)
  3. Type B intercalated cell
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13
Q

Where are alpha intercalated cells located?

A

Distal tubule

Collecting ducts

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14
Q

What does an alpha intercalated cell do?

A

Reabsorbs K and secretes H

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15
Q

What is the primary urinary buffer in alpha intercalated cells? How much H rides on H2PO4 and how much on NH4+?

A

HPO4-/H2PO4 (1/2 of urinary H)

NH4 (2/3 of urinary H)

*you can excrete maybe 100 mM total H on these carriers per day, but urine pH range is from 4-8 (only a tiny amt of H is freely dissolved)

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16
Q

Why is alpha intercalated cell H secretion often increased as a compensation for acidosis?

A

Plasma H is reduced by adding bicarbonate to the blood. This creates more free H which leads to an increase in the H that is secreted.

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17
Q

Why is acidosis often accompanied by hyperkalemia?

A

As you stimulate the K/H ATPase to get rid of H, you simultaneously reabsorb more K. K can’t leave the cell via the luminal side, but there are many transporters on the basolateral side so MORE K is reabsorbed.

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18
Q

How does a beta intercalated cell compare do an alpha intercalated cell?

A

It has REVERSE polarity

Beta cells increase HCO3 secretion during alkalosis.

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19
Q

Why is alkalosis often accompanied by hypOkalemia?

A

As H is reabsorbed to counteract alkalosis, more K is secreted into the lumen along with bicarb. This leads to hyp0kalemia

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20
Q

What compensates for respiratory acidosis and alkalosis?

A

Respiratory acidosis/alkalosis are due to RESPIRATORY PROBLEMS so the KIDNEY must compensate. (slowly hours to days)

21
Q

What compensates for metabolic acidosis/alkalosis?

A

Both are caused by non-respiratory metabolic problems so are dealt with by the LUNGS with some help from renal mechanisms if possible. Alveolar ventilation is a means to keep plasma pH near 7.4 during a metabolic disturbance.

22
Q

What compensates faster, lungs or kidneys?

A

Lungs- w/in minutes, very fast!

23
Q

What happens when H increases in plasma? (acidosis)

A

Peripheral chemoreceptors (carotid bodies) directly sense this change and mediate a rapid increase in alveolar ventilation (increased breathing) thereby lowering H.

Increased breathing:

  1. Lowers pCO2
  2. Increases pO2
24
Q

How does a decrease in C02 (caused by rapid breathing) combat acidosis (decrease H)?

A

C02 + H20 < > H2CO3 < > H + HCO3

Breath more>
Decrease in C02>
left shift>
Decrease H

25
Q

What causes respiratory acidosis? Examples?

A

Decreased breathing!

Dope (depresses respiratory centers)
pulmonary edema (can't exchange O2)
airway obstruction
26
Q

What happens to both H and HCO3 initially in respiratory acidosis?

A

C02 + H20 < > H2CO3 < > H + HCO3

Decreased breathing>
Increased C02>
RIGHT shift>
Increased H and increased HCO3

(upper left corner)

27
Q

What is the renal response to respiratory acidosis?

A

Glutaminase: Glutamine> NH3 > NH4
CA: C02 + H20 < > H2CO3 < > H + HCO3

  1. Increase H excretion> increase key enzymes (glutaminase) and CA> increased HCO3 reabsorption (prox tubule and alpha cells)
  2. Na/H antiporter is stimulated by increased H
28
Q

How does the renal response compensate for respiratory acidosis?

A

C02 + H20 < > H2CO3 < > H + HCO3

Increased HCO3 in blood>
left shift>
decreased H

Renal addition of HCO3 to blood causes further increased HCO3 and decreased H (pH rises toward normal)

29
Q

What is a blood gas report for respiratory acidosis?

A

HCO3 (27): 36
pH (7.4): 7.3
pC02 (40): 80
P02 (90): 70

30
Q

What happens in metabolic acidosis?

A

Fixed acid H production is increasing

31
Q

What are the two major routes that cause metabolic acidosis?

A
  1. Lactic acidosis/Ketoacidosis:
    Increase H>
    right shift>
    decrease in HC03
  2. Diarrhea (loss of bicarb)
    Decreased bicarb (toilet)>
    left shift>
    increase H

C02 + H20 < > H2CO3 < > H + HCO3

pH DOWN, HC03 DOWN

32
Q

What is the primary compensatory force for metabolic acidosis?

A

Lungs!

Chemoreceptors sense increased H>
stimulates alveolar ventilation>
blow off C02

33
Q

What are kussmaul respirations?

A

A pattern of slow deep breathing often observed in metabolic acidosis

34
Q

How does decreased C02 help to coutneract metabolic acidosis?

A

C02 + H20 < > H2CO3 < > H + HCO3

Decreased C02>
left shift>
decreases H and HCO3

Compensatory hyperventilation REDUCES H (pH rises toward normal) and HC03 is further reduced.

35
Q

What is the normal renal response to metabolic acidosis? Is renal HCO3 reabsorption large enough to raise plasma HCO3?

A

Reabsorb all HCO3 and make an acidic urine with NH4 addition to urine.

NO

36
Q

What is the blood gas report for metabolic acidosis?

A

HCO3 (27): 15
pH (7.4): 7.3
pC02 (40): 32
P02 (90): 100

37
Q

What is the anion gap in metabolic acidosis?

A

Normally 10-14

Lactic acid and ketone bodies cause it to be higher (add acid and titrate away bicarb)

38
Q

What causes respiratory alkalosis?

A

Increased breathing–> causes C02 to fall b/c it’s blown off (Hypocapnia)

Drugs
panic attack
high altitude

39
Q

What happens to H and HCO3 initially in respiratory alkalosis?

A

C02 + H20 < > H2CO3 < > H + HCO3

Rapid breathing>
decreased CO2>
left shift>
decrease in H and HCO3

40
Q

How does the renal response to respiratory alkalosis differ from respiratory acidosis?

A

It is the OPPOSITE

Decrease in H:

  1. decrease in key enzymes (glutaminase, CA)
  2. Inhibits Na/H antiporter
  3. Appearance of beta interacalated cells
41
Q

What is the end result of renal compensation to respiratory alkalosis?

A

C02 + H20 < > H2CO3 < > H + HCO3

Decreased (renal H/NH4 secretion)>
HCO3 secreted in urine>
right shift>
increase H

42
Q

What is the blood gas report for respiratory alkalosis?

A

HCO3 (27): 16
pH (7.4): 7.5
pC02 (40): 27
P02 (90): 102

43
Q

What causes metabolic alkalosis?

A

The net loss of H from the extracellular space

Vomiting
hypokalemia

LOW H (high pH) with increased HCO3

44
Q

How does low acid production cause metabolic alkalosis?

A

C02 + H20 < > H2CO3 < > H + HCO3

Decreased H>
right shift>
increased HCO3

45
Q

How does vomiting cause a rise in plasma pH and increased HCO3?

A

C02 + H20 < > H2CO3 < > H + HCO3

Vomiting>
expel H>
right shift>
increase bicarb

46
Q

What is the compensatory respiratory response to metabolic alkalosis?

A

Less beathing
hypoventilation
hypercapnia (increased CO2)

47
Q

What is the end result of the respiratory response to metabolic alkalosis?

A

C02 + H20 < > H2CO3 < > H + HCO3
Increased CO2>
right shift>
increased H and HCO3

Hypoventilation INCREASES H (pH lowered toward normal) and HCO is further increased

48
Q

What is the normal renal response to metabolic alkalosis?

A

Excrete some of the huge filtered load of HCO3 and make an alkaline urine w/ little NH4 addition to the urine.

Renal HCO3 3xcretion attenuates the large rise in plasma HCO3. BUT the LUNGS PREDOMINATE and plasma HCO3 is high d/t compensatory hypoventilation

49
Q

What is the blood gas report for metabolic acidosis?

A

HCO3 (27): 36
pH (7.4): 7.48
pC02 (40): 50
P02 (90): 80

CRAAB 7 (4 decks)

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