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P&T Block 5 Renal > L49 > Flashcards

Flashcards in L49 Deck (31)
1

What transporter maintains the proper Na and K concentrations in cells?

2K in // 3 Na out transporter

2

What happens ↑[K] extracell?

Higher resting membrane potential - dangerous b/c shrinks gap between threshold = ↑automaticity

3

What happens with short term ↑extracell K?

Shift excess into cells w/o dramatically changing fxn
1ary storage = muscle
2ary = liver and blood

4

What substances enhance and inhibit the 2K/3Na transporter?

Enhance via ↑rate pump:
1. B ad agonists
2. Insulin
Inhibit = a-ad agonists

5

What is mechanism that maintains long-term K homeostasis?

Renal excretion of K

6

Explain the movement of K in the prox convoluted tubule?

> 50% K filtered in Bowman's reabsorbed in PCT

7

What happen to K in the thick ascending loop?

Comes in via urine
Uptake via 2Cl/Na/K transporter
Regenerate K into urine to maintain charge
Also reabsorbed K from blood to ↑Na reabsorption via 2K/3Na ATPase transporter

8

What is the drug that targets the Na/2Cl/K transporter?

Loop diuretics

9

Which cell is responsible for K excretion in the collecting duct? Mechanism?

Principle cell
To reabsorb Na via ENAC, you must excrete K into negative urine lumen
[K enters this cell from the blood via 2K/3Na ATPase transporter]

10

What are the 3 factors that determine K excretion rate?

1. Na+ getting absorbed = lumen negative voltage that pulls K out
2. Faster flow rate, keeps urine [K] right outside low aka follow [ ] gradient
3. Aldosterone = ↑rate ATPase + ↑ENAC + ↑K channels

11

2 populations that would have low dietary K and therefore are at risk for hypoK?

Alcoholics
Anorexic

12

2 main systems that can cause hypoK

Renal
1. Excess aldosterone
2. Diuretic use
3. Renal tubular acidosis
4. Chornic interstital nephritis
5. Mannitol or hyperglycemia = osmotic diuresis
GI
1. NG tube suction
2. Diarrhea or vomiting

13

Which 3 diuretics are most likely to cause hypoK?

Furosemide
Hydrochlorothiazide
Why: force more Na to go downstream in nephron, ↑flow, ↑K excretion

14

Why is hypoK on diuretics limited?

↓intravasc volume = ↓flow
Stabalizes amt K excreted

15

What happens if you eat salty foods on a loop diuretic?

↑Na = more at distal nephron
You must save more Na there
You have to waste K

16

Which 2 drugs ↓K secretion but making the urine lumen less negative @ collecting duct?

Amiloride
SMX TMP

17

What drug ↑K secretion by ↑distal delivery of Na -> ↑flow?

Furosemide

18

What 3 drugs ↓K secretion by ↓effects of aldosterone?

ACE inhibitors
ARBs
Spironolactone

19

If pt is hypoK w/ U K

GI b/c kidney is holding onto K appropriately

20

If pt is hypoK w/ U K > 20, what is the source of the loss?

Renal - shouldn't be losing K if hypoK!

21

EKG changes for hypoK

T wave flattens
Develop U wave right in front of T

22

Causes of pseudo-hyperK

Trauma when drawing blood
↑WBC or PLT (leukocytosis or thrombosis)

23

3 causes of hyperK

1. Redistribution
2. ↓excretion
3. ↑input

24

Give the example of redistribution cause hyperK

Acidemia = excess H is buffered in cells, K moves out as consequence

25

Give the examples of ↓excretion causing hyperK - TESTQUESTION

Acute or chronic kidney disease
K sparing diuretics
**↓Aldosterone
- Addison's
- ↓renin -> ↓aldo = type 4 rental tubular acidosis**

26

Give the examples of ↑input causing hyperK

1. Intravasc hemolysis - releasing intracell contents (Sickle, TTP, HUS)
2. Rhabdo - pigment from these cells injures kidney, can't properly secrete K
3. K salt substitutes
4. K penicillin

27

EKG changes with hyper K

EMERGENCY
1. Peaked T waves
2. Prolonged QRS
3. Lose P wave

28

What do you give to treat hyperK to antagonize membrane effects?

Ca // hypertonic saline - ↓membrane effects
Aka increase threshold to re-est distance between elevated resting membrane potential

29

What do you give to treat hyperK via moving K back into cells?

Insulin (w/ glucose) - stim Na/K pump
B2 agonists - stim Na/K pump
NaHCO3 not shown to work in people

30

What do you give to remove excess K in hyperK?

Loop diuretics
K exchange resin - osmotically pulls K in gut
Dialysis

31

Why do subjects with chronic kidney disease tolerate higher K levels?

Better short term sequestration mechanism
High K diet in these pts is protective against K shifts