Na and Water

Question 0

normal compartment osmolarity

Answer 0

280-290 mosm/L

Question 1

Osmotic pressure equation

Answer 1

=nCRT
n=dissociable parts
C=[ ]
R= 0.082
T=temp

Question 2

Calculate the Osmolarity from ECF

Answer 2

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

OR
2x[Na]+[glucose]/20

*this excludes hidden osmoles, so actual is higher

Question 3

idiogenic osmoles

Answer 3

brain produces these (ionositol or AA) to help maintain brain volume in states of Na flux

Question 4

ADH is primarily driven by…but…

Answer 4

osmolarity!

at low volumes, will ignore omolarity to preserve volume

Question 5

3 jobs of A2

Answer 5

1) efferent vasoconstriction–>GFR increases
2) reabs Na/Hco3 (isotonic fluid)
3) increase aldo

Question 6

ANP

Answer 6

direct vasodilation of afferent arteriole–>increase GFR–>decrease BP

increase Na excretrion

Question 7

FENa

Answer 7

=Una(Scr)/Sna(Ucr)

Question 8

venous congestion leads to

Answer 8

edematous tates

Question 9

four most common edematous states

Answer 9

cirrhosis
CHF
nephrotic syndrome
SIRS

Question 10

acute vs chronic hypernatremia timeline

Answer 10

chronic is 24-48 hrs already

Question 11

drugs that cause nephrogenic DI

Answer 11

lithium

demelcocyline

Question 12

how to estimate water deficit

Answer 12

0.6 x wt x [(Na/140)-1]

use 0.5 for girls

Question 13

how to correct water deficit

Answer 13

no more than 0.5 mEq/L/hr

Question 14

tx hypernatremia

Answer 14

Normal saline for hypovolemic patients, otherwise 1/2 normal saline

Question 15

Pseudohyponatremia

Answer 15

hidden effective osmoles are trapped in the ECF–>increase water–>decrease [Na] w/o decreasing total Na

Question 16

water excess formula

Answer 16

0.6 x wt x ([Na]0140/140)

Question 17

ADH independent hyponatremia

Answer 17

renal failure
primary polydipsia
beer potomania- alcohol/carbs provides calories but not osmoles; limits water excretion

Question 18

ADH independent hyponatremia

Answer 18

thiazide-induced hypoNa
hypoadrenalism: (decrease aldo–>decrease EcV–>+adh)
hypothyroidism (dec T4–>dec CO–>dec ECV–>+ADH)
reset osmostat
SIADH