Water, Sodium, Potassium

Question 1

How is ICF estimated clinically?

Answer 1

plasma sodium

Question 2

How is ECF volume estimated clinically?

Answer 2

physical exam; edema, crackles, JVD

Question 3

Abnormal plasma sodium indicates a disorder with what?

Answer 3

water balance

Question 4

Abnormal ECF volume indicates a disorder with what?

Answer 4

Na+ balance

Question 5

Under what conditions is ECF not based on sodium?

Answer 5

SIADH, pure water loss

Question 6

What is the mechanism of hypertonic hyponatremia?

Answer 6

Solutes pulling ICF into the serum, diluting sodium

Question 7

What is the cause of hypotonic hyponatremia when Uosm<100?

Answer 7

polydypsia (too much water)

Question 8

What are the causes of hypotonic hyponatremia when Uosm>100 and UNa>40?

Answer 8

SIADH, hypothyroid, glucocorticoid deficiency

Question 9

What are the causes of hypotonic hyponatremia when Uosm>100 and UNa<20 with hypovolemia?

Answer 9

burns, diarrhea, vomiting

Question 10

What are the causes of hypotonic hyponatremia when Uosm>100 and UNa<20 with hypervolemia?

Answer 10

CHF, Cirrhosis, Nephrosis

Question 11

What is the cause of pseudohyponatremia?

Answer 11

high lipids or proteins reducing plasma volume

Question 12

How is pseudohyponatremia diagnosed?

Answer 12

Osmolal gap >10mOsm/Kg

Question 13

What are the causes of hypertonic hyponatremia?

Answer 13

hyperglycemia, mannitol, glycine, sorbitol, sucrose

Question 14

What is the treatment for symptomatic hyponatremia?

Answer 14

3% saline

Question 15

What is the effect of rapid correction of hyponatremia?

Answer 15

Osmotic Demyelination Syndrome

Question 16

In water diuresis polyuria, what separates diabetes insipidus form primary polydipsia?

Answer 16

DI: hypernatremic
polydipsia: hyponatremic

Question 17

What test separates central DI from nephrogenic DI?

Answer 17

NPO - desmopressin. If urine is still dilute, DI is nephrogenic

Question 18

What is the effect of rapid correction of hypernatremia?

Answer 18

cerebral edema

Question 19

How much fluid must accumulate in the interstitium before edema is apparent?

Answer 19

2.5-3.0 L

Question 20

What are the two pathways of fluid retention in nephrotic syndrome?

Answer 20

hypoalbuminemia reduces osmotic pressure; kidneys retain more sodium

Question 21

What is nephrotic syndrome?

Answer 21

> 3.5g/hr protein excretion with hypoalbuminemia, edema, lipiduria, and dyslipidemia

Question 22

Acidosis leads to what change in K+?

Answer 22

hyperkalemia

Question 23

Alkalosis leads to what change in K+?

Answer 23

hypokalemia

Question 24

What is the effect of aldosterone on K+?

Answer 24

secretion from the principal cells

Question 25

What are the five stimulants of K+ secretion?

Answer 25

high plasma K+, aldosterone, dietary K+, increased tubular flow rate, negative charge in the tubule

Question 26

What are the two inhibitors of K+ secretion?

Answer 26

ACEi/ARB, tubular damage

Question 27

What are the two mechanisms of hyperkalemia?

Answer 27

redistribution, decreased excretion

Question 28

What stimulates the movement of K+ from ECF to ICF?

Answer 28

insulin, beta2-agnosts, alkalosis, anabolism

Question 29

What stimulates the movement of K+ from ICF to ECF?

Answer 29

insulin deficiency, high tonicity, cell injury, beta-blockers, alpha-agonists, drugs, mineral acidosis

Question 30

Why does mineral acidosis cause hyperkalemia but not organic acidosis?

Answer 30

Cl- can't cross cell membranes freely, but organic anions can

Question 31

What factors impair K+ excretion?

Answer 31

positive charge in tubule, decreased flow/Na to the CCD, decreased aldosterone

Question 32

What causes pseudohyperkalemia?

Answer 32

hemolysis, tourniquet time, thrombocytosis

Question 33

What are the causes of hyperkalemic distal RTA?

Answer 33

anything that interferes with ENaC action (RAAS)

Question 34

What EKG changes are seen in hyperkalemia?

Answer 34

peak-T waves

Question 35

Why is Ca2+ given in hyperkalemia?

Answer 35

it raises the threshold potential in myocytes to counter the rise of membrane potential from K

Question 36

What is the treatment for hyperkalemia?

Answer 36

IV-Ca, insulin, albuterol, bicarb if acidotic, dialysis, cation exchange, K-trapping resin

Question 37

What are the causes of hypokalemia?

Answer 37

intracellular redistribution, inadequate intake/GI loss, urinary loss

Question 38

What does urine K/createnine ratio measure?

Answer 38

normalizes the amount of K+ lost in the urine

Question 39

What is a normal urine K/creatinine ratio?

Answer 39

13-15