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Year 2 Renal > Sodium and water balance > Flashcards

Sodium and water balance Flashcards

1
Q

sodium disorders are almost always caused by disorders of ____________

A

water (im)balance

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2
Q

lab value: hyponatremia

A

[Na} under 135 mmol / L

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3
Q

what are the CNS symptoms of hyponatremia?

A
  • N/V
  • headache
  • fatigue
  • WEAKNESS
  • seizure
  • coma
  • death
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4
Q

the severity of the hyponatremia symptoms is related to what factors?

A
  • rapidity

- severity

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5
Q

lab value: severe hyponatremia

A

[Na} under 120 mmol/L

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6
Q

what level of [Na] indicates an absolute requirement to treat?

A

[Na} under 120 mmol/L (severe hyponatremia)

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7
Q

what is the concept of osmotic adaptation?

A
  • brain cells can produce or excrete osmols in order to protect against cellular dehydration or over hydration
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8
Q

how does the concept of osmotic adaptation relate to hypo-osmotic states? hyperosmotic?

A
  • hypo-osmotic states: brain cells adapt initially by excreting intracellular osmols; thereby reducing the risk of cellular overhydration
  • hyperosmotic states: brain cells adapt by producing intracellular osmols in an effort to prevent cellular dehydration
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9
Q

what is osmotic demyelination syndrome?

A

process of demyelination of the central nervous system

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10
Q

what are the characteristics of central pontine myelinolysis? how does it occur?

A
  • paraparesis
  • dysarthria
  • dysphagia
  • seizure
  • coma
  • death
  • occurs by overly rapid correction of hyponatremia
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11
Q

what is the relationship of primary polydipsia and hyponatremia?

A

disorder with normal water excretion (uncommon) - primary polydipsia (excessive water intake that overwhelms kidney ability to excrete water load)

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12
Q

what is pseudohyponatremia?

A
  • in states of severe hyperlipidemia or hyperproteinemia, the fraction of plasma water may be reduced
  • lab measured serum sodium may be artifactually lower as this is measured as a liter of total plasma - not just plasma water
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13
Q

what are the HYPOvolemic causes of hyponatremia / hypo-osmolality (renal and extra-renal)?

A
  • renal losses: diuretics, osmotic diuresis

- extra-renal losses: blood loss, diarrhea / vomiting

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14
Q

what are the HYPERvolemic causes of hyponatremia / hypo-osmolality?

A
  • renal failure: increased urinary sodium
  • CHF, cirrhosis, nephrotic syndrome: increased ECF by decreased effective circulating volume (decreased urinary sodium, higher urinary osmolarity)
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15
Q

what are the EUvolemic causes of hyponatremia / hypo-osmolality?

A
  • hypoadrenalism / hypothyroidism: increased ADH

- SIADH: elevated ADH

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16
Q

how does hypoadrenalism cause hyponatremia / hypo-osmolarity?

A
  • cortisol directly inhibits ADH secretion
  • low BP in hypoadrenalism stimulates ADH secretion
  • CRH mimics ADH function
17
Q

how does hypothyroidism cause hyponatremia / hypo-osmolarity?

A

thyroid hormone inhibits ADH

18
Q

what is the mechanism for why SIADH causes hyponatremia / hypo-osmolarity?

A
  • urine osmolarity is inappropriately elevated [concentrated] for the hyponatremic state
  • urine is NOT maximally dilute as it should be
19
Q

what is the 1) edema state and 2) volume expansion status in SIADH / hyponatremia?

A
  • no edema

- very modest volume expansion

20
Q

what are the serum uric acid and BUN levels for SIADH / hyponatremia?

A

commonly low serum uric acid and BUN

21
Q

what are the diagnostic characteristics for SIADH?

A
  • hyponatremia and hypoosmolarity
  • inappropriately elevated urine osmolarity
  • normovolemic on clinical exam (no edema)
  • normal renal / adrenal / thyroid function
22
Q

what is the treatment for pseudohyponatremia?

A

underlying causes:

  • hyperlipidemia or
  • myeloma
23
Q

what is the treatment for true hyponatremia?

A
  • raise serum sodium by a safe rate
  • 0.9 NS for volume depletion
  • restrict free water intake for euvolemia or hypervolemia
  • demeclocycline
  • vasopressin antagonists
24
Q

what is the treatment for severe hyponatremia?

A

consider hypertonic 3% saline

25
Q

what is the role of demeclocycline for true hyponatremia?

A

increases urinary water loss

26
Q

what is the role of vasopressin antagonists for true hyponatremia?

A

increases urinary water loss

27
Q

hypernatremia results from what 3 factors?

A
  • water loss
  • sodium retention (rare)
  • water loss in excess of sodium loss
28
Q

how do you combat hypernatremia?

A

stimulate ADH production

29
Q

how does hypernatremia persist?

A

inability to access water and/or inability of the kidne to appropriately reabsorb water

30
Q

what are the causes of diabetes insipidus? what is the result?

A
  • ADH production or secretion (central)
  • renal response to ADH (nephrogenic)
  • RESULT: reduction in water reabsorption by the kidney and a diuresis of dilute urine leading to hypernatremia
31
Q

what is the hypothalamic function and ADH release status in nephrogenic DI?

A

normal

32
Q

what are the etiologies of NDI?

A
  • congenital
  • hypercalcemia
  • hypokalemia
  • drugs (lithium, demeclocycline)
  • renal parenchymal disease
33
Q

what drugs cause NDI?

A
  • lithium

- demeclocycline

34
Q

does primary polydipsia cause hypernatremia or hyponatremia?

A

hyponatremia

35
Q

how do you differentiate between NDI/CDI and primary polydipsia?

A

water deprivation test

36
Q

following a water deprivation test, in what condition will you see a change of urine osmolarity after administering ADH? what is this change?

A

CDI (increase)

37
Q

when is treatment indicated for hypernatremia?

A
  • symptomatic
  • volume depleted
  • hypernatremia is severe

Year 2 Renal (38 decks)

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