Reg & Disorders of salt & water (Gyamlani)

Question 1

Total Body water (2 equations m & f)

Answer 1

TBW = 0.6 L / kg (males)
TBW = 0.5 L/ kg (females)

Question 2

Fractions of ICF & ECF

Answer 2

ICF 2/3 (20 L)

ECF 1/3 (10 L)

Question 3

ISF volume

Answer 3

7.5 L

Question 4

Plasma volume

Answer 4

2.5 L

Question 5

Effective blood volume

Answer 5

arterial blood & perfusing tissues

~0.5 L (remaining 2 L is in veinous system)

Question 6

Surrogate marker for serum osmolality

Answer 6

Na

Question 7

How is serum Osm regulated?

Answer 7

water balance

Question 8

TBNa is synonymous with?

Answer 8

ECFV and regulated by changes in EABV

Question 9

Posm =

Answer 9

Posm = 2[Na] + glc/18 + BUN/2.8 = 275-290 mosm/kg

Question 10

[Na] =

Answer 10

[Na] = TBNa/TBW = 137-143 mosm/kg

Question 11

How is plasma osmolality sensed & what are the effectors?

Answer 11

Hypothalamic osmoreceptors
ADH/thirst
urin osmolality & water intake affected

Question 12

How is volume sensed, what are the effectors, and what is affected?

Answer 12

Macula densa, afferent arterioles, atria, and carotid sinus
Renin-angiotensin-aldosterone, ANP, Noepinephrine, ADH
Urine Na excretion, thirst

Question 13

Does RAAS control Na or water?

Answer 13

RAAS controls Na, no control over water

Question 14

ANP has opposite effects as what?

Answer 14

angiotensin

Question 15

Atrial natriuretic peptide (ANP) source, action

Answer 15

Atria

vasodilation, Na excretion

Question 16

effect of increased sympathetic nervous system action on RAAS, vasopressin, sodium

Answer 16

RAAS activated
vasopressin released
sodium retained

Question 17

CHF effect on sodium

Answer 17

Reduced cardiac output, lowered effective blood volume, sympathetics, RAAS, and vasopressin
Sodium retention

Question 18

Thirst center location, stimuli, mechanism

Answer 18

third ventricle
osmolality, volume depletion, angiotensin II
increased Sr Osm -> inc thirst -> drinking -> reduced Sr Osm

Question 19

AVP (formation, release, stimuli)

Answer 19

Supraoptic & paraventricular pituitary areas
released post pituitary
Stim: fluid osm increase, vol depletion, angiotensin II, Pain, nausea/vomiting, meds

Question 20

AVP mechanism

Answer 20

opens AQP-2 in CD, more water reabsorption

Question 21

hypovolemic hyponatremia recognition

Answer 21

reduction in BP, poor skin turgor, absence of dependant edema, increase in BUN, reduced urine Na. Serum Na may be normal, low or increased.

Question 22

Euvolemic hyponatremia

Answer 22

water retention due to autonomous or altered reg of vasopressin (SIADH)

TBW up, TB Na stays the same

Pain, pulm disorders, think antipsychotics

Question 23

Hypervolemic hyponatremia

Answer 23

retention of both sodium and water

Clinical: Na excess, edema, elevated JVD, crackles

Causes: CHF, hep cirrhosis, nephrotic syndrome, renal disease

Question 24

Symptoms of acute hyponatremia

Answer 24

nausea, malaise (120/125 meq/L)
headache, lethargy, obtundation (115-120 meq/L)
seizures & coma (<115 meq/L)

Question 25

Brain volume equilibration time upon correction of hyponatremia

Answer 25

48 h

Question 26

Cerebral demyelination syndrome

Answer 26

central and extrapontine myelinosis
Caused by excessive correction of Na
Locked-in syndrome, can be permanent or fatal

Question 27

Rx for hyponaremia

Answer 27

volume correction w/isotonic normal saline

Question 28

Rx for hypernatremia

Answer 28

Na restriction
treat primary disorder
furosemide + HD if renal failure

Question 29

Hypernatremia - disorder of what?

Answer 29

water