Electrolytes

Question 1

What determines resting membrane potential?

Answer 1

Ratio of ICF K: ECF K

Question 2

Which factors regulate cellular K?

Answer 2

1. Cell membrane patency
2. K+ channels (usually open)
3. Na+ channels (usually closed)
4. NHE1 (pumps Na in for Na K exchange)
5. Na K ATPase pump
6. Negative intracellular charges (want positive)

Question 3

When sodium is low what is the first thing to look at?

Answer 3

Plasma osmolarity
if high=fake, from shift of water, high osmoles
if low= real, procede

Question 4

What measure helps us differentiate between intact and impaired kidney water excretion in hyponatremia?

Answer 4

1. Urine osmolarity
2. If LOW then water excretion is normal, you just drink a lot
3. If HIGH then water excretion is not happening appropriately

Question 5

What shows us there is a low EABV in hyponatremia?

Answer 5

Urine sodium less than 20 (Watch out for diarrhea)

Question 6

When do we expect ADH to be activated?

Answer 6

1. When Plasma osmolarity is >280

2. OR when >270 and volume depleted

Question 7

What is the treatment for hyperkalemia with ECg changes?

Answer 7

First priority=protect heart with calcium gluconate

Shift potassium back into cells: insulin, beta 2 stimulation

Prevent further uptake: potassium binding resin

Waste what is there: furosemide

Question 8

What are the ECG changes in hyperkalemia?

Answer 8

Peaked t waves
Absent p waves
QRS prolongation
Sine waves

Question 9

ECG changes in hypokalemia?

Answer 9

QT prolongation
T waves flattening
U waves
St depression

Question 10

What shifts potassium out of cells?

Answer 10

Metabolic acidosis (affects nhe1)
Hyperosmolarity
Cell lysis

Decreased entry: 
Insulin deficiency(nhe1)
Beta blockade ( Na/k pump)