Salt and Water disorders

Question 1

total body water equation?

Answer 1

TBW= .6L/Kg…so in a 60 Kg dude, it is 36L

.5 L/Kg in women

Question 2

Plasma osmolality equals what?

Answer 2

two times the Na concentration + glucose + BUN

Question 3

Explain the difference between extracellular fluid volume and effective circulating blood volume

Answer 3

ECFV is the total volume in the extracellular space. This can be independent of effective blood volume. Effetive circulating blood volume is determined by cardiac output and venous resistance. In diseases like cirrhosis or CHF, ECFV can be normal or high and ECBV is low.

Question 4

What intrarenal system senses reduced blood volume?

Answer 4

Macula Densa

Question 5

What cells is renin secreted by?

Answer 5

Juxtaglomerular cells

Question 6

RAAS?

Answer 6

Renin ANgiotensin Aldosterone System….controls SODIUM BALANCE> NOT WATER

Question 7

What does renin do directly>

Answer 7

cleaves angiotensin I to Angiotensin II

Question 8

What does ANgiotensin II do?

Answer 8

increases vasoconstriction (raises bp) and stimulates aldosterone which increases sodium reabsorption

Question 9

ANP is actually important

Answer 9

true

Question 10

What does ANP do?

Answer 10

the exact opposite of angiotensin II and aldosterone…it vasodilates and increases Na excretion

Question 11

What kind of tonicity does the body want?

Answer 11

ISOtonicity…if serum sodium is high or low (osmolarity is high or low) body responds to it.

Question 12

Where is the thirst center?

Answer 12

Third ventricle

Question 13

What stimulates the thirst center?

Answer 13

Increased extracellular fluid osmolarity

Question 14

What is the serum osmolarity threshhold for activation of the thirst center?

Answer 14

2mEq/L

Question 15

What is the only hormone that plays a role in water reabsorption?

Answer 15

AVP- vasopressin

Question 16

Is hyponatremia a water problem or a sodium problem?

Answer 16

Its tricky, although it sounds like a sodium problem, hyponatremia is really a water imbalance. There is low sodium CONCENTRATION…this is because there is excess water.

Question 17

Low extracellular fluid volume is related to what?

Answer 17

Low sodium content

Question 18

What is hypovolemic hyponatremia

Answer 18

Low sodium concentration associated with low ECFV.

Question 19

Clinical signs of sodium depletion

Answer 19

1) decrease in blood pressure (esp orthostatic bp)
2) Poor skin turgor
3) Disproportionate increase in BUN
4) reduced urine sodium

Question 20

What does SIADH mean>

Answer 20

this is euvolemic hyponatremia due to water autonomous or altered regulation of vasopressin release. Basically, SIADH means altered vasopressin realease …too much(Vasopressin is an antidiuretic)

Question 21

Clinical signs of SiADH>

Answer 21

Decreased serum osmolarity, inappropriate urine concentration (its not maximally dillute like it should be), clinical euvolemia,