CIS - Mechanisms to Adjust Urine Concentration/Na, Water Balance/Disorders of Osmoregulation

Question 1

hyponatremia

Answer 1

Na to low

fluid movement into cells

Question 2

hypernatremia

Answer 2

Na to high

fluid movement out of cells

Question 3

Hypovolemia

Answer 3

not enough ECF volume

ECF volume contraction

Question 4

Hypervolemia

Answer 4

too much ECF volume

ECF volume expansion

Question 5

Pseudohyponatermia

Answer 5

hyperproteinemia
hyperlipidemia
hyperchoelsterolemia
hyperlycemia
umeasured osmol

Question 6

True Hyponatremia

Answer 6

Dilute urine, low ADH
- reset osmostat (pregnancy)
- psychogenic polydipsia
Concentrated urine, high ADH
- dec ECF volume (CHF, cirrhosis)
- SIADH

Question 7

Uosm/Posm < 1.0

Answer 7

urine osmolarity is low
pt excreting water
high Ch2o

Question 8

Uosm/Posm > 1.0

Answer 8

urine osmolarity is high
pt holding onto water
low Ch2o

Question 9

Osmolar Gap

Answer 9

difference between measured plasma osmolality and estimated (calculated) plasma osmolality
important: tells us if an unmeasured solute is present
normal <10mOsm/kg H2O

Question 10

Ethylene glycol poisoning

Answer 10

increased osmotically activated substance in blood
pulls water from vasculature causing hyponatremia by diluting blood
high osmolar gap
pseudohyponatremia
high serum osmolality

Question 11

DKA

Answer 11

hyponatremia
polydipsia, polyuria
glucose in urine
high serum osmolality
normal osmolar gap

Question 12

True hyponatremia

Answer 12

plasma Na concentration and osmolality are below normal

Question 13

Reset osmostat

Answer 13

Pregnancy

- pts are volume expanded causing hyponatremia

Question 14

Psychogenic Polydipsia

Answer 14

• hx of schizophrenia
• Na and osmolarity both low
• urine specific gravity low

Question 15

SIADH

Answer 15

pt with lung mass
- small cell carcinoma
-pulmonary TB
ectopic foci for ADH production
hyponatremia
normal osmolar gap
concentrated urine

Question 16

Tests to distinguish between Nephrogenic and Central DI

Answer 16

• water deprivation test should inc urine osmolarity
• measure ADH
• give Desmopressin and see reaction

Question 17

Hypernatremia

Answer 17

due to unreplaced water (NOT Na gain)

cell shrink due to hypertonicity

Question 18

Common causes for Nephrogenic DI

Answer 18

lithium use over long time
Hypercalcemia
Hyperkalemia

Question 19

Common causes for Central DI

Answer 19

head trauma
postpartum hypophysitis (autoimmune)
hypothalmus or pituitary tumor

Question 20

Common causes for SIADH

Answer 20

pulmonary TB
CHF
CNS issue (SVA, sx, trauma)
Intubation with mechanical vent
Drugs (cyclophosphamide, SSRIs, carbamazepine)