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Flashcards in Sodium disorders Deck (65):
1

Normal serum Na+?

135-145 Meq/L

2

Normal plasma/serum osmolality?

285-300 Meq/L

3

Eqn to estimate plama/serum osmolality?

Na x 2 + BUN/2.8 + Gluc/18

4

Main contributor to serum osmolality?

Na

5

Symptoms of hypo/hypernatremia are due to effects on which orhan?

Brain

6

Sodium abnormalities are usually caused by ____________ NOT ___________.

Water problems

NOT

Salt problems

7

Extracellular hyp-O-osmolality have what effent on neurons?

swelling

8

Sx if Na+

nausea

malaise

9

Sx if Na+ = 115-120:

headache

lethargy

10

Sx if Na+

obtundation

seizures

coma

11

More severe sx in fast or slow hyp-O-natremia?

Fast

brain has less time to adapt

12

Effect of hyp-ER-natremia on neurons?

cells shrink

13

Sx of hyp-ER-natremia?

lethargy

weakness

irritability

twitching

seizures

coma

death

14

Decreased brain volume due to hyp-ER-natremia can have what effect on vasculature?

rupture cerebral vessels

15

Clinically significant water shift occurs with 30-35 mosm/kg osmolar gradient between plasma and brain; what is the corresponding rise in serum Na+?

17 meq/L

16

Hormone responsible for maintenance of plasma osmolality:

ADH

(arginine vasopressin)

17

Where is ADH produced?

supraoptic and paraventricular nuclei of hypothalamus

18

Where is ADH stored and released?

secretory granules

posterior pituitary

19

Osmotic stumuli of ADH release:

INCREASED plasma osmolality

20

Non-osmotic stimuli of ADH release:

hypovolemia --> baroreceptors

pain

esophageal stimuli

medications

21

What receptor binds ADH to release aquaporin 2 to luminal membrane?

Where does this occur?

V2 (activates protein kinase)

collecting tubule

22

With high presence of ADH:

Urine osmolality = ?

Plasma osmolality = ?

urine- increased

serum- decreased

**water flows out of tubule back into blood

23

In low/absent ADH state:

Urine osmolality= ?

Blood osmolality= ?

urine- increased

blood- decreased

**water excreted in urine

24

Physiologic responses to HIGH plasma osmolality:

thirst

ADH release

water reabsorption

concentration of urine --> high urine osmolality

25

Physiologic response to LOW plasma osmolality:

No thirst

No ADH release

Loss of free water -- collecting tubules impermeable

Low urine osmolality -- dilute urine

26

Plasma osmolality maintained within __%.

1%

27

Indicator of the presence of ADH?

Urine osmolality

28

What generally tells you what the kidney THINKS about the body's volume status?

urine sodium

29

Range of urine osmolality in a normal kidney?

50-1400 mosm/L

30

Normal daily osmolar load from dietary protein/salt?

500-750 mosm

excreted in urine

31

If you have 500 mosm/day to get rid of and your maximum urine osmolarity is 1000 mosm/L, how much urine will be excreted?

0.5 L

32

If you have 500 mosm/day to get rid of and your minimum urine osmolarity is 50 mosm/L, how much urine will you excrete?

10 L

33

Hormones responsible for retention of sodium in volume depleted state?

Ang II

Aldosterone

34

What is the kidney doing of urine sodium is

senses low effective circulating volume, so it's holding on to sodium

35

What's going on in the kidney if urine sodium is > 10 meq/L?

-sensing expanded ECV

OR

-not able to properly retain Na+

OR

-excreting Na as an obligate cation with something else

36

What is pseudohyp-O-natremia?

What causes this?

low Na with normal or elevated Plasma osmolality.

Caused by:

Hyperlipidemia (normal Posm)

Hyperproteinemia (normal Posm)

Hyperglycemia (elevated Posm)

Hypertonic mannitol (elevated Posm)

37

How does hyponatremia develop if mechanisms are in place to maintain plasma osmolality within 1%?

Non-osmotic stimuli override osmotic stimuli (or lack of) to secrete ADH at the expense of plasma osmolarity

**perfusion to brain is more important than perfect osmolality in plasma

38

Four steps in clinical eval of hyponatremia:

1. Check Posm: confirm true hypoosmolar hyponatremia

2. Check Uosm: is ADH acting?
- 100 -- yes, despite hypoosmolar state, either appropriate for volume status or inappropriate

3. Check UNa+: what is the kidney's perception of ECV?

4. Check the patient: volume status/clinical picture?

39

Hyponatremia with Uosm

excess water intake (primary polydipsia)

**need to drink 10-15 L/day to overwhelm kidney's ability to clear free water

40

Two exceptional causes of hyponatremia with Uosm

beer potomania

tea and toast syndrome

**not ingesting enough(or any) protein/solutes for an extended period (low daily osmolar load)

41

Treatment for primary polydypsia?

water restriction

42

UNa+

Reabsorbing Na+ in an effort to reexpand vascular space

43

UNa+

Recieving the wrong signal.

Edematous states: think CHF/cirrhosis/nephrosis

44

UNa+ > 10, patient is volume depleted and hyponatremic. What is the kidney doing?

Salt wasting. Receiving the wrong signals. This is rare.

45

UNa+ > 10, patient is volume expanded and hyponatremic. What is the kidney doing?

Volume is appropriate or expanded

Brain or kidney is confused

46

Causes of volume depleted hyponatremia with UNa+ of

GI-- N/V, diarrhea

Skin-- burns

Diuretics-- late

Pure cortisol deficiency (Addison's???)

47

Causes of hyponatremia with UNa+

Edematous states/poor perfusion--reduced ECV

-CHF

-Cirrhosis/liver failure (low albumin?)

-nephrotic syndrome (proteinuria?)

48

Causes of salt wasting (hyponatremia with volume depletion and UNa+ > 10):

adrenal insufficiency

salt wasting renal disease

Early diuretics

Hypokalemia with metabolic alkalosis after vomiting (lose sodium and bicarb)

hypothyroid

49

Causes of hyponatremia with UNa+ > 10 and appropriate or expanded volume:

SIADH-- Syndrome of Inappropriate ADH secretion
-oat cell carcinoma (paraneoplastic)
-pulmonary process (TB, PNA, asthma)
-Drugs (chlorpropamide, oxytocin, tegretol, cytoxan)
-esophageal process
-pain
-neuropsychiatric

Reset osmostat

CKD

50

Fixed ADH secretion without regard to osmotic or volume status:

SIADH

51

Tx for SIADH:

fluid restriction

increase osmolar load (high protein/Na diet)

52

Treatment for volume depleted hyponatremia?

NS

**replenish volume, turn off ADH

53

Tx for volume neutral or expanded hyponatremia:

restrict free water intake

treat state of poor perfusion

54

Tx for severe hyponatremia not related to pure volume depletion OR with neurologic sx:

hypertonic saline

55

Pharm tx for volume expanded hyponatremia:

ADH antagonists

Tolvaptan, Conivaptan

56

Rapid correction of hyponatremia risks?

Central Pontine Myelinolysis (BAD)

57

Brain's own mechanism of compensation for slowly developing hyponatremia:

idiogenic osmoles

**more risk in rapid correction

58

V1a and V1b receptors response to ADH?

vasoconstriction and ACTH release

59

Hypothalamus/pituitary not releasing ADH?

Central diabetes insipidus

60

Collecting tublues don't respond to ADH:

nephrogenic diabetes insipidus

61

How could you differentiate central vs nephrogenic DI?

give exogenous ADH

if UOsm increases --> central etiology

62

Dx of diabetes insipidus usually made by patient complaint of?

polyuria (usually not hypernatremia)

63

Drug to know that causes nephrogenic DI?

lithium

64

Safe rate for correcting hypernatremia?

slowly

0.5 meq/hour --> 12 meq/24 hr

65

What to give to replace free water deficit?

Free water ORALLY (NOT IV)

D5W IV

**can give 1/4 NaCl if volume depleted