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Flashcards in Sodium and Water Deck (25):
1

draw diagram of body fluid distribution

see notes

2

formula to calculate osmolarity

2[Na+] + glucose/18 + [BUN]/2.8

3

increase in osmolarity triggers....

ADH release and thirst

4

JGA senses what? what happens?

change in Na+ flow rates --> stim RAAS

5

Baroreceptors sense what? what happens?

decreased arterial pressure --> stim adrenergic pressure, stim ADH release

6

Atrial stretch receptors sense what? what happens?

volume expansion --> ANP release

7

Action of angiotensin II (3)

1. direct vasoconstrictor (efferent arteriole)
2. increases Na+ and HCO3- reabsorption in proximal tubule
3. stim aldosterone release

8

Action of aldosterone

1. stimulates Na+ channels in the principal cells (CD)
2. stim H+ secretion in intercalated cells

9

ANP

1. direct vasodilator: lowers BP, afferent arteriolar dilation --> increased GFR
2. stim Na+ excretion

10

what is the response to increased ECV?

Na+ diuresis: increased renal blood flow --> less renin
ANP

11

equation to estimate free water deficit

0.6*wt*[(Na+/140))-1]

12

rate of correction for a given free water deficit

Estimated water deficit/[(desired change in Na+)x2] = cc/hr

13

correction for hyperosmolar hyponatremia

in hyperglycemia: Na+ falls 1.6-4 mEq/L for every 100mg/dL rise in glucose

14

pseudohyponatremia

when lots of lipids are in the serum, get an artificially inflated total sample volume --> hyponatremia

15

how to calculate water excess

0.6*weight*(([Na+]-140)/140)

16

when is ADH released? name an exception

when osmolarity increases
except, decreased ECV overrides osmolar control --> sim ADH to maintain BP

17

when do you get low ADH hyponatremia?

1. renal failure - water intake exceeds excretion as GFR falls
2. primary polydipsia - excessive intake exceeds excretion
3. beer potomania/"tea and toast" - take in lots of fluid but not enough osmoles to excrete large volumes of water

18

types of high ADH hyponatremia

1. decreased ECV: volume depletion, diuretics, CHF, etc.
2. reset osmostat
3. SIADH

19

reset osmostat

some pts have a lower ADH set point than normal
no other abnormalities other than low [Na+]
no tx needed

20

causes of euvolemic hyponatremia

1. SIADH
2. hypothyroidism
3. hypoadrenalism

21

osmotic demyelination

stroke-like syndrome of neurological deficits associated with overly rapid correction of hyponatremia

22

V2 antagonists - what do they do, when to use

block ADH action
useful for elevated ADH (SIADH, CHF, cirrhosis)

23

tx for SIADH

fluid restrict asymptomatic pts
hyperosmotic saline for symptomatic or severe
DO NOT GIVE NS

24

how to calculate FENa

FENa= (Una*Scr)/(Sna*Ucr)

25

draw a diagram of the whole nephron!

see notes