Hyponatremia

Question 1

what is osmolarity?

Answer 1

measure of water balance

Question 2

calculation for serum osmolarity

Answer 2

2[Na+] + [glucose]/18 + [urea]/2.8 + [EtOH]/4.6 = calculated

osm

Question 3

what is the main determinant of serum osmolarity?

Answer 3

serum Na+

Question 4

what is serum [Na+] a surrogate of?

Answer 4

water

Question 5

what is serum [Na+] NOT a surrogate of?

Answer 5

Na+ content

Question 6

what is an osmole?

Answer 6

amound of a substance that dissociate in solution to form one mole of osmotically ACTIVE particles

Question 7

dysnatremias are a disorder of

Answer 7

WATER metabolism

Question 8

volume regulation clinically defined by

Answer 8

effective arterial blood volume

Question 9

water regulation clinically defined by

Answer 9

plasma osmolality

Question 10

volume regulation clinically measured by

Answer 10

physical exam

Question 11

water regulation clinically measured by

Answer 11

serum [Na+]

Question 12

volume regulation regulated by

Answer 12

baroreceptors

Question 13

water regulation regulated by

Answer 13

osmoreceptors

Question 14

volume regulation hormones activated

Answer 14

renin, angiotensin, aldosterone, catecholamines, atrial natriuretic peptide, ADH

Question 15

water regulation hormones activated

Answer 15

ADH

Question 16

volume regulation evaluated by

Answer 16

urine Na+

Question 17

water regulation evaluated by

Answer 17

urine osmolality

Question 18

volume regulation treated by

Answer 18

giving or restricting SALT or VOLUME

Question 19

water regulation treated by

Answer 19

giving or restricting WATER

Question 20

how much water, how much volume in 1 liter of: 0.9% saline

Answer 20

• water 0 L

- volume 1 L

Question 21

how much water, how much volume in 1 liter of: d5w

Answer 21

• water 1 L

- volume 0 L

Question 22

how much water, how much volume in 1 liter of: 0.45% saline

Answer 22

• water 500 ml

- volume 500 ml

Question 23

how much water, how much volume in 1 liter of: d5w w/ 3 amps NaHCO3

Answer 23

• water 0 L

- volume 1 L

Question 24

how much water, how much volume in 1 liter of: 1/4% saline (39 meq NaCl)

Answer 24

• water 750 ml

- volume 250 ml

Question 25

TBW equals?

Answer 25

60% weight

Question 26

ICF = how much of TBW?

Answer 26

2/3

Question 27

ECF = how much of TBW?

Answer 27

1/3

Question 28

ISF = how much of ECF?

Answer 28

3/4

Question 29

IVF = how much of ECF?

Answer 29

1/4

Question 30

movement of fluid between ECF and ICF is determined by

Answer 30

Starling forces (hydrostatic, oncotic)

Question 31

what % of plasma is protein and lipids?

Answer 31

7%

Question 32

why does pseudohyponatremia occur?

Answer 32

indirect ion-selective electrode measurements (sample is diluted prior)

Question 33

MCC of iso/hypertonic hyponatremia

Answer 33

hyperglycemia

Question 34

causes of hyponatremia w/ low urine osmolality

Answer 34

• primary polydipsia
• beer potomania
• tea and toast diet

Question 35

what drives urine output?

Answer 35

solute intake

Question 36

impaired renal dilution d/t

Answer 36

• diminished GFR
• older age
• thiazide diuretic
• ADH (SIADH, volume depletion, nausea, pain)
• abnormal ADH receptor in cortical collecting duct

Question 37

stimuli for ADH

Answer 37

• increased tonicity
• volume depletion (true OR ineffective arterial volume 2/2 CHF or cirrhosis)
• pain
• nausea
• medications (antidepressants, antieplieptics, antipsychotics, MDMA)
• cancer (paraneoplastic ADH release)

Question 38

uric acid level in SIADH

Answer 38

LOW

Question 39

main consequence of hyponatremia

Answer 39

ODS

Question 40

organic osmolytes released from brain cells as defense against water (takes several days)

Answer 40

• glutamate
• taurine
• myoinositol

Question 41

signs/symtpoms of cerebral edema from hyponatremia

Answer 41

• lethargy
• seizures
• fatal herniation
• noncardiogenic pulmonary edema

Question 42

treatment of hyponatremia

Answer 42

• fluid restriction for ALL pts
• correct ADH stimulus
• 3% saline, aquaporin antagonists, loop diuretics