Renal Acid/Base

Question 1

How does pH affect free plasma concentrations of other cations (Ca++)?

Answer 1

Lower pH = more H+ = kick Ca off of protein = MORE free Ca++

Higher pH = LESS free Ca++

Question 2

Phosphate buffer system (pKa = 6.8)

H2PO4 –> H + HPO4

What will happen if excess acid is added to the system?

Answer 2

pH

Question 3

Volatile vs. fixed acids

Answer 3

Volatile - produced by CO2 and excreted by lungs (H2CO3 only)

Fixed - produced by something other than CO2 (metabolically) and excreted normally

Question 4

Ways of generating fixed acids via metabolism (+ acids generated)

Answer 4

Glycolysis (lactic acid)

FA beta-ox (keto acids)

Protein/NA/PL metabolism (sulfuric, phosphoric, HCl)

Question 5

Chemical buffer systems w/in the ECF

Answer 5

Bicarb/CO2

Phosphate

Plasma proteins (grab protons)

Question 6

Chemical buffers w/in the ICF

Risk?

Answer 6

Organic phosphates
Bicarb/CO2
Cell proteins (Hb)

K+ comes out in exchange –> hypokalemia

Question 7

Renal regulation for excess acid

Answer 7

Reabsorb HCO3

Secrete H+ and excrete as ammonium

Question 8

Renal regulation for excess base

Answer 8

Decrease HCO3 reabsorption

Decrease H+ secretion

HCO3 secretion in CD (beta-IC cells)

Question 9

The body creates H+ during many metabolic processes. Is it all excreted as free H+ in the urine?

Why or why not?

Answer 9

NO - a lot combines w/ renal buffers and is excreted

Otherwise, WAY TOO MUCH water would need to be excreted to get rid of all the free H+

Question 10

Buffers used in the urine to lower free H+

Answer 10

Titratable acids (phosphate, creatinine, urate)

Ammonia

Question 11

How to measure the amount of H+ excreted in urine? (Broad concept)

Answer 11

(Titratable acids excreted) + (ammonium excreted) - (HCO3 excreted)

Question 12

Where is the biggest change in luminal pH throughout the nephron?

Why?

Answer 12

DCT/CD

Lots of H+/HCO3 secretion and reabsorption here

Question 13

Explain H+ secretion in the CD

Answer 13

H+ ATPase (alpha-IC cells)

Question 14

Explain HCO3 balance in CD

Answer 14

Basolateral - Reabsorbed in exchange for Cl- (alpha-IC cells)

Apical - Secreted in exchange for Cl- (beta-IC cells)

Question 15

C.A. Inhibitors make the body acidic or alkalotic?

Why?

Answer 15

Acidic

Block HCO3 reabsorption (PCT) = retaining H+

Question 16

What main buffer system is used w/ C.A. inhibitors to maintain pH in PCT and help decrease acidosis?

Answer 16

Phosphate secreted, binds w/ H+ for excretion

Question 17

Screwing with the Na/K ATPase in the PCT will cause what change in body pH?

Why?

Answer 17

Acidosis

No drive to secrete H+ for HCO3 reabsorption

Question 18

In acidic conditions, what AA can help buffer in the PCT?

How?

Answer 18

Glutamine oxidation

Converted to 2 ammonium + 2 HCO3

The HCO3 is reabsorbed, but 2 H+ are excreted as ammonium

Question 19

Metabolic acidosis and alkalosis are about balances between __ and __

Answer 19

HCO3

PCO2

Question 20

Metabolic acidosis has a ___ HCO3:PCO2 ratio

Why? (2)

Answer 20

Decreased

Increased fixed acid eats up HCO3
OR
Loss of HCO3 (diarrhea)

Question 21

Metabolic alkalosis has a ___ HCO3:PCO2 ratio

Why? (2)

Answer 21

Increased

Strong base/HCO3 gain
OR
Loss of fixed acid (vomiting)

Question 22

Compensations for metabolic acidosis

Answer 22

Hyperventilation

H+ secretion (alpha-IC)

Question 23

Compensations for metabolic alkalosis

Answer 23

Hypoventilation

Incomplete HCO3 reabsorption + HCO3 secretion (beta-IC)

Question 24

Anion gap measurement

What is the “gap”?

Answer 24

Na - Cl - HCO3

Unmeasured anions (albumin, phosphate, sulfate, citrate, lactate, keto acids)

Question 25

Normal anion gap range

Answer 25

8-16 mEq/L

Question 26

2 types of metabolic acidoses Other name for them?

Answer 26

High anion gap acidosis Normal anion gap acidosis ``` High = Normochloreic acidosis Normal = Hyperchloremic acidosis ```

Question 27

Explain hyperchloremic acidosis Show the equation

Answer 27

Anion gap is unchanged because HCO3 is being lost, but Cl- is being gained in the metabolic process of getting rid of the H+ HCl + HCO3 --> Cl- + H2O + CO2

Question 28

Explain normochloremic acidosis Equation?

Answer 28

High anion gap because HCO3 is being eaten up by unmeasured acid HA + HCO3 --> A- + H2O + CO2

Question 29

Acronym for causes of high anion gap acidoses

Answer 29

``` Methanol Uremia (urea) DKA Propylene glycol Iron Lactic acidosis Ethylene glycol Salicylates ```

Question 30

Explain the MUD in mudpiles

Answer 30

Methanol - converted to unknown conjugate base when using HCO3 to get rid of H+ Urea - see above DKA - high glucose converted to keto acids, then see above

Question 31

What is the Henderson Hasselbalch equation for the H2CO3 buffer system?

Answer 31

pH = 6.1 + ([HCO3] / (.03 • PCO2))