Renal

Question 1

Is the kidney capable of metabolism?

Answer 1

Yes, it’s capable of phase I and phase II biotransformations

Question 2

Hormones made by the kidney

Answer 2

EPO
Calcitriol
Prostaglandins

Kidneys are also able to perform gluconeogenesis (from amino acids) about as well as the liver

Question 3

Prostaglandins and their effects on renal arteries

Answer 3

Dilators: PGE2 and PGI2

Constrictor: Thromboxane A2 (TXA2)

Question 4

This % of blood that reaches the kidney is actually filtered by the glomerulus

Answer 4

20%

Question 5

Part of the kidney most sensitive to drops in PaO2

Answer 5

Medulla, because it only receives 10% of RBF to begin with

Question 6

MAP range of kidney auto regulation

Answer 6

50-180

Question 7

UO is linearly related to what?

Answer 7

MAP > 50

Question 8

How is renal auto regulation performed?

Answer 8

• Myogenic mechanisms**
• JG apparatus and tuboglomerular feedback**
• RAAS
• Prostaglandins
• ANP
• SNS

Question 9

Where is the JG apparatus located?

Answer 9

Distal tubule as it passes through the afferent and efferent arterioles

Question 10

ANS influence in kidney

Answer 10

SNS (from T8-L1) innervates afferent and efferent arterioles. Very little PSNS present.

Internal autoregulatory mechanisms overrise SNS effects.

Question 11

Renin is released in response to these 3 things

Answer 11

Reduced renal perfusion
B1 stimulation
Decreased NaCl delivery to distal tubule (decreased delivery means flow is slow and perfusion is thus poor)

Question 12

What does the JG apparatus monitor?

Answer 12

2 things:

• Renal perfusion
• Solute concentration

Feedback about NaCl composition of tubular fluid affects arteriolar tone

Question 13

Angiotensin II affects which arteriole?

Answer 13

It constricts the efferent arteriole

Question 14

How does aldosterone exert it’s effects

Answer 14

Activates the Na/K/ATP pump in the principal cells of the distal tubules and collecting ducts

Question 15

RAAS stimulates aldosterone secretion from the adrenal gland, but what else does as well?

Answer 15

Hyponatremia and hyperkalemia

b/c aldosterone will fix both of these things

Question 16

2 mechanisms that control ADH release

Answer 16

1) Increased osmolarity of ECF
- Shrinks the osmoreceptors in hypothalamus (supraoptic an paraventricular nuclei), resulting in ADH release

2) Decreased blood volume
- Baroreceptors in carotid bodies, transverse aortic arch, great veins, and RA stimulate ADH release

Question 17

1/2 life of ADH

Answer 17

5-15 minutes

Question 18

What is fenoldopam?

Answer 18

DA1 agonist that increases RBF

Question 19

3 general things that promote renal vasodilation

Answer 19

1) Prostaglandins
2) ANP
3) DA agonism

Question 20

Where are prostaglandins made in the nephron?

Answer 20

Afferent arteriole

Question 21

RAAS has this effect on RBF

Answer 21

decreases

Question 22

The afferent arteriole makes prostaglandins in response to what?

Answer 22

Ischemia
NE
Angiotensin II

Helps promote a balance!

Question 23

Leukotrienes have this effect on renal vasculature

Answer 23

Constriction

Question 24

Only DA1 agonist that may reduce mortality and dialysis requirement and outcomes in aortic surgery and CPB

Answer 24

Fenoldopam

Question 25

Effects of efferent constriction

Answer 25

Small constriction = increased GFR

Excessive constriction = decreased GFR and RBF

Question 26

Normal BUN

Answer 26

10-20

Question 27

What IS BUN?

Answer 27

Primary metabolite of protein metabolism in the liver

amino acids –> ammonia –> urea

Question 28

What does a 100% increase in serum creatinine represent?

Answer 28

A 50% reduction in GFR

Question 29

BUN:Cr ratio

Answer 29

Should be 10:1

> 20:1 suggests preener azotemia

Question 30

Fractional excretion of sodium

Answer 30

Relates sodium clearance to Cr clearance

If Fe(Na+) 3%, then more sodium was excreted relative to the amount of Cr cleared, and it suggests impaired tubular function

Question 31

Spec grav analysis

Answer 31

1.010-1.015 = ATN (loss of concentrating ability)

> 1.015 = Pre-renal oliguria

> 1.024 = Physiologic oliguria

Question 32

Which is a better test of tubular function, spec grav or urine osmolality?

Answer 32

Urine osmolality

Question 33

How can the risk of preener azotemia be reduced?

Answer 33

Maintaining MAP > 65 and giving adequate hydration

Question 34

What is prerenal azotemia?

Answer 34

Basically, prerenal kidney injury that results in azotemia (buildup of BUN and other nitrogenous waste products)

Question 35

Effect of A1 agonists on RBF

Answer 35

Causes a decrease in RBF

Septic patients will benefit though because increasing the MAP will outweigh the renal vasoconstrictive effects

Question 36

This medication is better at increasing GFR and UO than phenylephrine or NE

Answer 36

Vasopressin

Preferentially constricts the efferent arteriole

Question 37

Top causes of CKD

Answer 37

1) DM

2) HTN

Question 38

1st line treatment for uremic coagulopathy

Answer 38

Desmopressin to increase vWF and Factor VIII

Cryo can be given for this reason too, but carries risk of viral transmission

Question 39

ADH mech of action

Answer 39

stimulates V2 receptors (increased cAMP) in the collecting ducts –> increased aquaporins –> increased water re-absorption –> decreases blood oSm and plasma volume

Stimulates V1 receptors in the vasculature (increased IP3, DAG, Ca+) –> vasoconstriction