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CRRAB Week 7 > Acid Base > Flashcards

Acid Base Flashcards

1
Q

What is pH technically?

A

the -log[H+]

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2
Q

So the higher the H+ concentration, the ____ the pH and the _____ acidic the fluid is

A

lower the pH

more acidic

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3
Q

What is the isohydric principle in a nut shell?

A

Even a small change in H+ concentration will completely alter the isonization state of proteins in the body - particularly bad for enzymes (but also carbs, DNA, RNA, weak acids, etc)

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4
Q

What is Le Chatelier’s Principle in a nut shell?

A

In an equipibrium equation, if concentration of one of the solutes goes up, the equation will shift away from that solute.

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5
Q

What is the main buffer in the body?

A

the carbonic acid system:

CO2 + H+ H2CO3 H+ HCO3-

it attenuates any rise in H+

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6
Q

What is normal body pH?

A

7.4

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7
Q

What is pH typically with respiratory or metabolic acidosis? alkalosis

A
  1. 3

7. 5

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8
Q

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

A

proximal tubule epithelial cell
Type A or alpha intercalated cell
Type B or beta intercalated cell

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9
Q

What is the GOAL of the proximal tubule eptihelial cell in acidosis?

A

add H+ to the lumen so it gets excreted

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10
Q

What are the two ways the proximal tubule epithelial cell gets H+ into the lumen? Which is mroe prevalent and why?

A
  1. stimulates the Na/H antiporter
  2. stimulates glutaminase, so you get increased proximal ammonium production - ammonium is then exchanged for sodium as well

ammonium is the more important method because you can’t put all that much free H+ in the lumen, toherwise the urine gets acidic and painful (2/3 of the urinary H+ rides out this way)

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11
Q

Do the proximal tubule eptihelial cell can spit H into the urine, blah blah….
What ACTUALLY causes a decrease in H+ in the PLASMA?

A

If you spit out the hydrogen, something has to happen with the bicarb

turns out the bicarb gets pumped via a Na/bicarb symporter on the basal membrane. thus, bicarb enters the plasma. As bicarb increases in the plasma, lechateleier’s principle kicks in and you get a decrease in H+

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12
Q

How does the alpha intercalated cell respond to acidosis?

A

It will ramp up activity of the K/H ATPase antiporter and the vacuolar ATPase (which just kicks out H+) so that more H+ gets put in the lumen for excretion

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13
Q

What is the “side effect” of this increased activity to get H in the urine?

A

K gets reabsorbed, so you get hyperkalemia

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14
Q

Since all the ammonium gets used up in the proximal tubule, whtat is the main urinary buffer once the H+ gets pumped out of the alpha intercalated cell?

A

phosphate - the HPO4–/H2PO4- system

1/3 of the urinary H+ rides out on H2PO4-

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15
Q

How is the beta intercalated cell related to the alpha intercalated cell?

A

the beta cell is just the reversed polarity of the alpha cell. It secretes HCO3- and reabsorbs H+ in alkalosis

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16
Q

What is the effect on K+ balance during alkalosis?

A

remember, the beta cell is active during alkalosis and it’s the opposite polarity from the alpha cell

this means the K+ can only leave the cell on the lUMINAL side now, instead of the basement side. Thus, you excrete more K+ along with the bicarb and you get a hypokalemia

17
Q

What organ has to compensate for a RESPIRATORY acidosis or alkalosis?

A

the lungs normally would, but the lungs are what’s malfunctining in a respiratory acidosis or alkalosis.

this means the kidneys have to do the compensation, which takes longer

18
Q

If the carotid bodies sense an increase in H+ in the plasma, what will they trigger in the respiratory centers? WHy?

A

They will trigger an increase in respiratory rate

This was lower pCO2 and raise pO2

If you lower pCO2, you shift the buffer reaction to the left. This means the H+ gets used up, and H+ in the plasma decreases = compensation

19
Q

While the carotid bodies chemoreceptors sense the high H+, what chemoreceptors sense an increase in CO2?

A

the central chemoreceptors - CO2 easily crosses the BBB, so you get an increase in H+ near the medullary central chemoreceptors

20
Q

What is the primary disturbance in a respiratory acidosis?

A

the lungs aren’t working, so you don’t breath out CO2 and it increases

21
Q

What happens because of the rise in CO2?

A

the buffer reaction shifts to the right and you get an increase in both H+ and bicarb

results in an acidosis and decrease in pH

22
Q

What will the renal response be to a respiratory acidosis?

A
  1. increase glutaminase and carbonic anhydrase
  2. stimualte the Na+/H+ antiporter

This means you get more H+ leaving in the urein either freely or on ammonium

this also means you have increased bicarb that gets reabsorbed back into the plasma. The increased bicarb pushes the buffer equation back to the left, causing a dro pin H+ = compensation

23
Q

Aside - what are normal values on a blood gas report?

A 
bicarb = 27 mM
pH = 7.4
pCO2 = 40 mmHg
pO2 = 90 mmHg
24
Q

What will the blood gas results be in a respiratory acidosis?

A 
bicarb HIGH (renal compensation)
pH LOW (acidosis)
pCO2 HIGH (primary disturbance)
pO2 LOW (primary disturbance)
25
Q

What are the two major routes of the primary disturbance in a metabolic acidosis?

A

increase production of an acid = lactic acidosis or ketosis

low bicarb - diarrhea

(either way - you have high H+ - low pH and low bicarb)

26
Q

How do the lungs compensate for a metabolic acidosis?

A

by breathing off CO2 with increased ventilation - Kussmaul’s repsirations

27
Q

Describe what happens to the buffer equation as you blow off CO2 in compensation?

A

CO2 decreases, so you shift the buffer reaction to the right

this decreases H+ and bicarb, raising the pH in compensation

28
Q

What would blood gas results be in a metabolic acidosis?

A

Bicarb would be low
pH would be low (acidosis)
pCO2 would be low (respiratory compensation)
pO2 would be high (respiratory compensation)

29
Q

What will happen to the anion gap in acidosis?

A

bicarb falls, so based on the equation [Na+] - ([HCO2- + Cl-]), you get a high anion gap
(normal is 10-14 and it might be 20)

30
Q

What is the primary disturbance in a respiratory alkalosis?

A

hyperventilation (relative to the CO2 concentration - so not in compensation)

you blow off CO2, so you decrease [CO2}, which pushes the buffer reaction to the left. This decreases [H+] and [bicarb], increasing pH

31
Q

What is the kidney’s response to respiratory alkalosis?

A

You decrease the H+ secretion (both free and as ammonium - inhibit carbonic anhdyrase and glutaminase) from the proximal tubule epithelial cells and you upregulate the beta cells to pump bicarb into the urine and reabsorb H+

This means you get a decrease in HCO3- (pee it out), shifts the buffer reaction to the right, increasing H+ concentration and lowering pH back to normal

32
Q

What will blood gas results be in a respiratory alkalosis?

A

bicarb = low (you pee the bicarb out)
pH = high (alkalosis - H+ low)
pCO2 - low (you’re hyperventilating it out)
pO2 = high (you’re hyperventilating it in)

33
Q

What is the primary disturbance in metabolic alkalosis?

A

net loss of H+ from the extracellular space either thorugh vomiting or hypokalemia (since the alpha intercalated cells cause excetion of H+ in order to reabsorb K+)

34
Q

What are the two reasons you have a decrease in H+ from vomiting?

A
  1. there’s lots of H+ in the vomit that’s now on the side walk
  2. hepatic an dpancreatic cells will pump bicarb into the stomach lumen (and stop H+ in the blood) to counteract the acidity under normal conditions, but if you vomit, there’s nor more acid for them to counteract, so they stop doing their hting. THis means you have a decrease in the H+ in the blood = alkalosis
35
Q

Describe what happens to the buffer equation in a metabolic alkalosis?

A
  1. you get a decrease in H+ (high pH)
  2. shifts the reaction to the left
  3. increases bicarb concentration
36
Q

What is the respiratory response to metabolic alkalosis?

A

hypoventilation

37
Q

What happens to the buffer equation with the hypoventilation response?

A

CO2 builds up
shifts the equation to the left
H+ goes up (pH goes down) and bicarb goes up

38
Q

What will blood gas results be in a metabolic alkalosis?

A 
bicarb = high
pH = high
pCO2 = high
pO2 = low

CRRAB Week 7 (4 decks)

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