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CRRAB 2 > 1: Sodium > Flashcards

1: Sodium Flashcards

1
Q

Sodium normal range

A

135-145 meq/L

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2
Q

Equation for calculating plasma/serum osmolality

A

Na x2 + BUN/2.8 + Glc/18 (note that Na is main contributor)

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3
Q

Major cause of sodium imbalance

A

Almost always a water issue, not a salt issue.

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4
Q

Hyponatremia symptoms and their overall etiology

A

Extracellular hypoosm –> brain swelling. <115: obtundation, seizures, coma

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5
Q

Why might a patient have a sodium of 110 and be asymptomatic?

A

Chronic issue, developed gradually –> time to adjust

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6
Q

Symptoms of hypernatremia and cause

A

Hyperosm –> brain cell shrinkage –> possible rupture of cerebral vessels, lethargy, weakness, irritability, twitching, seizures, coma, death

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7
Q

ADH produced where? Stored where? How does secretion work?

A

Prod in hypothalamus in supraoptic and paraventricular nuclei, stored in sec granules which move down supraopticohypophyseal tract to post lobe of pituitary

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8
Q

Osmotic stimuli for ADH release

A

Increased plasma osmolarity

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9
Q

Non-osmotic stimuli for ADH

A

Baroreceptors signaling hypovolemia or dec ECV (effect. circ vol), pain (alters Na level), esophageal (tumors, intubation), meds

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10
Q

What type of vasopressin do humans have?

A

Arginine

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11
Q

ADH cascade

A

ADH binds V2 receptor (collecting tubules) -> act protein kinase -> AQP2 to luminal membrane

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12
Q

What can you evaluate to determine the kidney’s thoughts on body volume status?

A

Urine sodium: high = kidney behaving as though body is volume expanded. Low is vice versa

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13
Q

Normal urine osm range?

A

50-1400 in normal functioning kidney

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14
Q

What Uosm indicate ADH vs no ADH present?

A

100 = varying degrees of ADH activity

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15
Q

What determines max and min daily urine output? What is the usual mOsm load?

A

Daily osmolar load and urine osmolarity. Usual daily = 500-750 mOsm

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16
Q

Minimum vol water excreted daily (calculate)

A

Daily osm load/max Uosm = 500/1000 = 0.5 L daily

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17
Q

Max vol water excreted daily (calculate)

A

Daily osm load/ min Uosm = 750 mOsm/50 = 15 L/d

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18
Q

Which components respond to neurohumoral regulation?

A

Prox (Angiotensin II, dopamine, NE) and Collecting tubule (aldosterone, atrial natriuretic peptide)

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19
Q

How is reabsorption of sodium determined in the LoH and distal tubule?

A

Flow-dependent

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20
Q

What amount of urinary sodium is indicative of low vs high?

A

Low: < 10 meq/L
High: > 10 meq/L

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21
Q

Causes of hyponatremia with normal Posm

A

Hyperlipidemia, hyperproteinemia: these items take up more plasma space reducing plasma water space

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22
Q

Causes of hyponatremia with elevated Posm

A

Hyperglycemia, hypertonic mannitol: water shifts out of cells to reestablish equilibrium making Na more dilute

23
Q

Osmotic stimuli to ADH -> plasma reg within 1%. How does hypoNa develop then?

A

Non-osmotic stim (baroreceptors) maintain ECF (effec circ vol) at expense of plasma osm

24
Q

How much water would you have to drink/day to cause hypoNa?

A

10-15 L

25
Q

How can you run into hyponatremia without excessive fluid intake?

A

Low osmolar load e.g. usually big beer drinkers not eating much else or “toast and tea” elderly

26
Q

What might be some causes of hypoNa when volume depleted?

A

GI (n/v/d), skin losses (burns), diuretics, pure cortisol deficiency

27
Q

When might you have hypoNa with UNa <10 and be volume expanded?

A

Kidney/baroreceptors perceive reduced ECV e.g. CHF, cirrhosis/liver failure, nephrotic syndrome

28
Q

HypoNa with UNa >10 and volume depleted: what is this called? Causes?

A

Salt wasting. Adrenal insufficiency, renal disease, diuretics, hypothyroid, hypoK w met alkalosis after vomiting (Na loss with bicarb)

29
Q

HypoNa with UNa >10 and vol approp or expanded: causes?

A

Excess ADH production e.g. SIADH, reset osmostat, CKD

30
Q

Causes of SIADH

A

Tumors (oat cell), pulmonary (TB, pneumonia, asthma), drugs, esophageal, pain, neuropsych

31
Q

What happens in SIADH

A

Fixed ADH excretion w/o regard to osm or vol stimuli, fixed Uosm at high level

32
Q

SIADH treatment

A

Fluid restriction, inc osm load diet via sodium or protein.

33
Q

Hyponatremia treatment

A

Give NS to replenish volume and turn off ADH

34
Q

Severe hyponatremia treatment

A

hypertonic saline (3% = 513 meq Na/L) to get out of danger zone

35
Q

Volume expanded hyponatremia treatment

A

ADH antagonist “-vaptans” e.g. Tolvaptan or Conivaptan

36
Q

What is the “danger range” of hyponatremia? Over what time period should someone be corrected out of this?

A

115-120, correct over several hours (more slowly for the more chronic)

37
Q

Once out of danger range, how quickly should you correct hyponatremia?

A

12meq/L over 24 hours (0.5 meq/L/hour). This is the same rate at which you correct hypernatremia.

38
Q

What is the risk of rapid hyponatremia correction?

A

Demyelination of pons/ osmotic demyelination syndrome

39
Q

Treatment for hyponatremic seizures

A

100 cc 3% NaCl over 10 min

40
Q

Treatment for hyponatremic neurologic non-seizure symptoms

A

30-50 cc 3% NaCl/hour for several hours

41
Q

V1a and V1b ADH receptors involved in ___ (2)

A

vasoconstriction and ACTH release

42
Q

V2 ADH receptors involved in

A

Water channels moving into the luminal membrane

43
Q

Which ADH antagonist has a limit on duration of treatment? Why?

A

Tolvaptan <30 days due to risk of liver failure

44
Q

What is max UOsm in humans?

A

800-1400, corresponds to urine SG of 1.025 to 1.030

45
Q

What UOsm constitutes severe CDI or NDI during hypernatremia?

A

<300 UOsm

46
Q

What is central diabetes insipidus?

A

hypothalamus or pituitary not releasing ADH -> can’t reabsorb free water

47
Q

What is nephrogenic DI?

A

Collecting tubules don’t respond to ADH

48
Q

What is the action of renal prostaglandins on ADH response?

A

PG impairs ADH response -> inc water loss. NSAIDs decrease this.

49
Q

In what situation would dDAVP be given for DI treatment?

A

Central DI. dDAVP is ADH, giving extra won’t make a difference in nephrogenic DI.

50
Q

How do you determine treatment of hypernatremia?

A

Replace calculated water deficit over 60 hours

51
Q

Equation for calculating free water deficit

A

(%body water) x (mass) x {([Na]/140) -1}

52
Q

Standard % body water for males and females

A

males: 60%, females: 50%

53
Q

Fluid used for hypernatremia treatment

A

Water PO or D5W IV

54
Q

When would you use NS with hypernatremia?

A

Concomitant fluid loss and hypotension. Use NS until tissue perfusion improves

CRRAB 2 (12 decks)

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