L49

Question 1

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

Answer 1

2K in // 3 Na out transporter

Question 2

What happens ↑[K] extracell?

Answer 2

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

Question 3

What happens with short term ↑extracell K?

Answer 3

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

Question 4

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

Answer 4

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

Question 5

What is mechanism that maintains long-term K homeostasis?

Answer 5

Renal excretion of K

Question 6

Explain the movement of K in the prox convoluted tubule?

Answer 6

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

Question 7

What happen to K in the thick ascending loop?

Answer 7

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

Question 8

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

Answer 8

Loop diuretics

Question 9

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

Answer 9

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]

Question 10

What are the 3 factors that determine K excretion rate?

Answer 10

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

Question 11

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

Answer 11

Alcoholics

Anorexic

Question 12

2 main systems that can cause hypoK

Answer 12

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

Question 13

Which 3 diuretics are most likely to cause hypoK?

Answer 13

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

Question 14

Why is hypoK on diuretics limited?

Answer 14

↓intravasc volume = ↓flow

Stabalizes amt K excreted

Question 15

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

Answer 15

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

Question 16

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

Answer 16

Amiloride

SMX TMP

Question 17

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

Answer 17

Furosemide

Question 18

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

Answer 18

ACE inhibitors
ARBs
Spironolactone

Question 19

If pt is hypoK w/ U K

Answer 19

GI b/c kidney is holding onto K appropriately

Question 20

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

Answer 20

Renal - shouldn’t be losing K if hypoK!

Question 21

EKG changes for hypoK

Answer 21

T wave flattens

Develop U wave right in front of T

Question 22

Causes of pseudo-hyperK

Answer 22

Trauma when drawing blood

↑WBC or PLT (leukocytosis or thrombosis)

Question 23

3 causes of hyperK

Answer 23

1. Redistribution
2. ↓excretion
3. ↑input

Question 24

Give the example of redistribution cause hyperK

Answer 24

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

Question 25

Give the examples of ↓excretion causing hyperK - TESTQUESTION

Answer 25

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

Question 26

Give the examples of ↑input causing hyperK

Answer 26

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

Question 27

EKG changes with hyper K

Answer 27

EMERGENCY

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

Question 28

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

Answer 28

Ca // hypertonic saline - ↓membrane effects

Aka increase threshold to re-est distance between elevated resting membrane potential

Question 29

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

Answer 29

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

Question 30

What do you give to remove excess K in hyperK?

Answer 30

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

Question 31

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

Answer 31

Better short term sequestration mechanism

High K diet in these pts is protective against K shifts