Anesthesia and Renal Physiology

Question 1

What is normal ECF H+ concentration?

Answer 1

40nEq/L

Question 2

T/F: Acid is a proton acceptor and base acts as proton donor?

Answer 2

False; Acid=proton donor

Base = proton acceptor

Question 3

What equations describes the relationship between pH, PaCO2, and serum HCO3?

Answer 3

Henderson- Hasselbalch Equation

Question 4

T/F: Buffers are least efficient when pH=pKa?

Answer 4

False. They are most efficient if pH=pKa

Question 5

What are 5 examples of the body’s buffers?

Answer 5

1. HCO3
2. Hgb
3. Intracellular proteins
4. Phosphate
5. Ammonia

Question 6

What is the pKa of HCO3?

Answer 6

6.1

Question 7

Is bicarbonate buffer effective against metabolic or respiratory acid-base disturbances?

Answer 7

Metabolic

Question 8

What is main reason bicarbonate acts as a good buffer?

Answer 8

Because it is present in high concentrations in the ECF

Question 9

Where is HCO3 reabsorbed into the blood?

Answer 9

Proximal tubule

Question 10

What molecule hyrdolyzes carbonic acid into water and CO2?

Answer 10

Carbonic anhydrase

Question 11

In the proximal tubule, what is exchanged with H+ ions?

Answer 11

Na+

Question 12

What percent of filtered bicarbonate is reabsorbed in the proximal tubule?

Answer 12

80-90%

Question 13

What percent of filtered bicarbonate is reabsorbed in the distal tubule?

Answer 13

10-20%

Question 14

Does reabsorption of HCO3 create acidic or alkalotic urine?

Answer 14

Acidic

Question 15

What does H+ combine with to become trapped in renal tubule?

Answer 15

Hydrogen Phosphate to form H2PO4

Question 16

Since Phosphate has a pKa of 6.8, does it work better as a buffer in acidic or alkalinic urine?

Answer 16

Acidic

Question 17

What is H2CO3 called?

Answer 17

Carbonic acid

Question 18

What is ammonium synthesized from?

Answer 18

Glutamine

Question 19

Where does NH4 (Ammonium) act as a fluid buffer?

Answer 19

Proximal tubule, thick loop, and distal tubule

Question 20

Metabolic aklalosis is mainly possible in what two situations?

Answer 20

1. Na+ Depletion

2. Increased aldosterone

Question 21

What is an example of contraction alkalosis?

Answer 21

When sodium is reabsorbed in the proximal tubule and this causes Chloride to move with it. As chloride decreases in tubule, HCO3 must be reabsorbed.

Question 22

What can cause a contraction alkalosis?

Answer 22

Long term diuretic use

Question 23

What is base excess?

Answer 23

Defined as the amount of acid or base that must be added to return the blood pH to 7.4 with PaCO2 to 40mmHg

Question 24

A positive base excess indicates what?

Answer 24

Metabolic alkalosis

Question 25

A Negative or base deficit indicates what?

Answer 25

Metabolic acidosis

Question 26

What 3 main concepts cause metabolic alkalosis?

Answer 26

1. Loss of acid from extracellular space 2. Excessive HCO3 loads 3. Posthypercapnic states

Question 27

What are examples of things that cause a loss of acid from extracellular space?

Answer 27

1. Loss of gastric fluid 2. Acid loss in the urine\ 3. Acid shifts into the cells 4. Loss of acid into stool

Question 28

What 6 factors maintain metabolic alkalosis?

Answer 28

1. Decreased GFR 2. Volume contraction 3. Hypokalemia 4. Hypochloremia 5. Passive backflux of HCO3 6. Aldosterone

Question 29

Severe combined resp/metabolic alkalosis will create what 3 major issues surrounding anesthesia time?

Answer 29

1. Cardiac suppression 2. Arrhythmias 3. Further hypokalemia

Question 30

Treatment of metabolic alkalosis:

Answer 30

1. Give Potassium | 2. Give NS

Question 31

How much does Potassium increase for each 0.1 unit decrease in pH?

Answer 31

0.6mEq/L

Question 32

What are four physiologic effects of acidosis?

Answer 32

1. K+ increase 0.6mEq/L for each 0.1 unit decrease in pH 2. Rightward shift 3. Cardiac contractility is decreased 4. Decreased responsiveness to catecholamines

Question 33

Which patient population should NaHCO3 not be given for treatment of metabolic acidosis?

Answer 33

Patients with respiratory failure because CO2 will go up as compensatory mechanism

Question 34

Excessive infusions of NS and LR create what acid/base disturbances?

Answer 34

NS= creates acidosis | LR=creates alkalosis

Question 35

What is the main treatment concept for treating metabolic acidosis?

Answer 35

Treat underlying cause (ex: hypovolemia, anemia, cardiogenic shock

Question 36

What is treatment of alkalosis?

Answer 36

1. IV HCl in rare cases 2. Spironolactone 3. Stop diuretics 4. Correct gastric fluid loss 5. Give NS instead of LR

Question 37

What is the most common cause of chloride sensitive metabolic alkalosis?

Answer 37

Diuretics

Question 38

By doubling alveolar ventilation, what happens to PaCO2 and cerebral blood flow?

Answer 38

Reduces PaCO2 to 20mmHg and halves cerebral blood flow.

Question 39

T/F: PaCO2 is proportionally related to cerebral blood flow?

Answer 39

False; they are inversely related

Question 40

How do you calculate anion gap?

Answer 40

(Na+)- [(Cl-)+(HCO3)]

Question 41

What is normal anion gap?

Answer 41

7-14mEq/L

Question 42

What is the most common reason we will see a normal anion gap metabolic acidosis?

Answer 42

Hyperchloremia (Cl- takes the place of the HCO3 anion)

Question 43

What are 9 causes of normal anion gap metabolic acidosis?

Answer 43

1. Hyperchloremia 2. Renal tubular acidosis 3. Diarrhea 4. Carbonic anhydrase inhibition 5. Ureteral diversions 6. Early renal failure 7. Hydronephrosis 8. HCl Administration 9. Saline administration

Question 44

What are 7 causes of elevated anion gap metabolic acidosis?

Answer 44

1. Uremia 2. Ketoacidosis 3. Lactic acidosis 4. Methanol 5. Ethylene glycol 6. Salicylates 7. Paraldehyde

Question 45

In chronic respiratory acidosis, how would HCO3 compensate?

Answer 45

Expect a 4mEq/L increase in HCO3 for every 10mmHg increase in CO2

Question 46

In acute respiratory acidosis, how would HCO3 compensate?

Answer 46

Expect a 1mEq/L increase in HCO3 for every 10mmHg increase in CO2