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clin lab med exam 2 > sodium > Flashcards

sodium Flashcards

1
Q

how much body weight does water account for? How much is in ICF and ECF?

A
  • 60% of body weight
  • TBW = 40 L
    • 2/3 is in ICF = 25 L
    • 1/3 is in ECF = 15 L
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2
Q

is body water less or more in obese individuals

A
  • proportion of TBW per weight is less in obese adults
  • body fat is essentially free of water
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3
Q

of the body water that is in the extracellular fluid, how much is in interstitial fluid and plasma

A
  • 3/4 = interstitial fluid
  • 1/4 = plasma
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4
Q

normal range of osmolality? when so symptoms occur

A

280-295 mOsm/kg

  • symptoms occur if
    • > 320
    • < 265
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5
Q

What is the equation to calculate osmolality

A
  • osmolality = 2 Na + (glucose/18) + (BUN/2.8)
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6
Q

where does fluid tend to shift in hyponatremic conditions? Hypernatremic?

A
  • Hyponatremic: water movement from ECF -> ICF => cell swells
  • hypernatremic: water movement from ICF -> ECF => cell shrinks
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7
Q

isotonic changes in body fluids are largely confined to what

A

ECF

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8
Q

these clinical features are consistent with what volume status

  • increased thirst, decreased sweating
  • decreased skin turgor and dry mucus membranes
  • olifuria with increased urine concentration
  • CNS depression
  • weakness and muscle cramps
  • decreased BP
  • tachycardia
A

hypovolemia

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9
Q

list causes of sequestration causing hypovolemia

A
  • bowel obstruction
  • peritonitis
  • pancreatitis
  • sepsis
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10
Q

these clinical features are characteristics of what volume status

  • edema
  • SOB
  • orthopnea, PND
  • HTN, tachycardia
  • ? crackles
  • JVD
  • hepatojugular reflux
A

hypervolemia

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11
Q

what conditions can cause primary renal sodium retention

A
  • ARF
  • acute GN
  • chronic RF
  • nephrotic syndrome
  • cushing’s syndrome
  • liver disease
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12
Q

what conditions can cause secondary renal sodium retention

A
  • heart failure
  • liver disease
  • pregnancy
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13
Q

where is ADH produced and stored

A
  • produced in hypothalamus
  • transported to and stored in posterior pituitary
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14
Q

function of aldosterone

A
  1. increase renal sodium reabsorption
  2. increase renal potassium secretion
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15
Q

homeostatic mechanisms respond to what rather than the total extracellular fluid volume

A
  • effective circulating volume (intravascular volume)
    • therefore conditions in which there is total ECF excess but decreased ECV continue to stimulate volume sensors to promote further salt and water retention
      • ex: heart failure and liver failure
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16
Q

water rentention is influenced by what two things

A
  • thirst
  • ADH
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17
Q

salt retention is influenced by

A
  • renin-angiotensin system**
  • ANP and catecholamines
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18
Q

What are some treatment options for volume overload

A
  • dietary sodium restriction
  • fluid restriction (hyponatremic)
  • diuretics
  • avoid offending medications
    • promote sodium retention: NSAIDs, corticosteroids, estrogens/androgens
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19
Q

danger zone of hyponatremia (level)

A

< 125

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20
Q

symptoms of hyponatremia

A
  • weakness, lethargy
  • anorexia, N/V
  • muscle cramps, sz, coma
  • death
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21
Q

what is the most common electrolyte abnormality in hospitalized patients

A

hyponatremia

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22
Q

What are some causes of hypervolemic hyponatremia

A
  • CHF
  • cirrhosis
  • renal failure
  • nephrotic syndrome
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23
Q

What are some causes of euvolemic hyponatremia

A
  • SIADH ** (most common cause)
  • diuretic use
  • hypothyroidism
  • adrenal insufficiency
24
Q

What are some causes of hypovolemic hyponatremia with urine sodium < 10; FENa < 1%

A
  • urine Na < 10: extrarenal
    • vomiting
    • diarrhea
    • hemorrhage
    • excessive sweating
25
Q

What are some causes of hypovolemic hyponatremia with urine sodium >10; FENa > 1%

A
  • renal causes
    • adrenal insufficiency
    • diuretics
    • salt wasting nephropathy: interstitial nephritis, PCKD
    • partial urinary tract obstruction
26
Q

if patient presents with hyponatremia, need to r/o pseudohyponatremia. What is it

A
  • serum Na < 135 but normal osmolality
  • due to hyperlipidemia or hyperproteinemia, with decrease in aqueous portion of plasma
27
Q

if patient presents with hyponatremia, need to r/o hyponatremia due to hyperosmolar state. What can cause this

A
  • increased glucose in ECF causes shift of water from ICF to ECF thus lowering serum Na
28
Q

Na drops how much for every 100mg/dl rise of plasma glucose

A

1.5mmole/L

29
Q

if hyponatremia with hypovolemia is a chronic process, rapid correction may cause what

A
  • osmotic demylination
    • neurologic morbidity or mortality
    • no more than 10 mEq/L increase in 24 hours
30
Q

small cell carcinoma of lung can cause what condition that can result in hyponatremia

A

SIADH

31
Q

List the etiologies of SIADH

A
  • neuropsychiatric disorders
  • malignancies
  • pulmonary disorders (small cell CA lung)
  • drug induced:
    • carbamezepine, tricyclic antidepressants, antineoplastic agents, narcotics
32
Q

List the 4 characteristics of SIADH

A
  • serum osmolarity below normal
  • inappropriately concentrated urine
  • euvolemia
  • normal renal, adrenal, and thyroid function
33
Q

treatment of SIADH induced hyponatremia

A

fluid restriction

34
Q

treatment of hypervolemic hyponatremia

A
  1. manage underlying disease
  2. sodium and water restriction
  3. diuretics
35
Q

what sodium lab value should warrant hospitalization

A

Na < 125

36
Q

overall, if patient has hypervolemic or euvolemic hyponatremia, first line of tx is

A

restrict fluids

37
Q

overall, if patient has hypovolemic hyponatremia, first line of tx is

A

replace fluid, usually with isotonic saline

38
Q

what is the traditional treatment of chronic hyponatremia

A
  • demeclocycline
  • induces nephrogenic diabetes insipidus
39
Q

clinical presentation is consistent with

  • thirst
  • restlessness
  • irritability
  • AMS
  • sz
  • muscle twitching
  • hyperreflexia
  • ataxia
A

hypernatremia

  • clinical features due to brain shrinkage secondary to increased ECF osmolality
40
Q

what are the big picture causes of hypernatremia

A
  • too little dietary water
  • too much dietary salt
  • excessive water loss from body
41
Q

name some conditions or situations that will cause hypovolemic hypernatremia

A
  • loss of solute-free water
  1. renal: loop diuretics, osmotic diuresis
  2. extrarenal: osmotic diarrhea, sweat
42
Q

in response to hypernatremia, the body’s homeostatic mechanism would normally

A
  1. create thirst and increase fluid intake
  2. maximally concentrate the urine to prevent further water loss
43
Q

list the body’s homeostatic priorites in order

A
  • volume
  • pH
  • electrolytes
44
Q

what is central diabetes insipidus

A
  • impaired secretion of ADH
  • see nonosmotic urinary water loss in setting of elevated serum sodium (urine is dilute when it should be concentrated)
45
Q

what is nephrogenic diabetes insipidus

A
  • lack of kidney response to ADH causing continued water loss even though patient is low on water
  • adequate ADH is present
46
Q

list some causes of acquired nephrogenic diabetes insipidus

A
  • chronic renal insufficiency
  • tubulointerstitial renal disease
  • amyloidosis
  • lithium toxicity
  • hypercalcemia, hypokalemia
47
Q

in diabetes insipidus, a urine osmolarity of what indicated impaired release or action

A

<500 mOsm/kg

48
Q

Giving vasopressin will increase urine osmolality in which form of diabetes insipidus

A

central DI

49
Q

tx options for nephrogenic Diabetes insipidus

A
  • thiazide diuretics
  • amiloride (potassium sparing diuretic)
  • chlorpropamide
50
Q

Why should a patient with hypernatremia present for several days not be given water too rapidly

A
  • could result in rapid shift of water into brain cells causing seizures or brain damage
    • central pontine myelinolysis (osmotic demyelination)
51
Q

how do you calculate water deficit

A
  • water deficit = normal TBW - current TBW
  • normal TBW = 0.6 x body weight in Kg
  • current TBW = (normal serum Na x normal TBW / measured serum Na)
52
Q

name some conditions or situations that will cause hypervolemic hypernatremia

A
  • excess sodium and extracellular volume expansion
  1. excess saline or sodium bicarb
  2. exteral or parenteral feeding without free water
53
Q

name some conditions or situations that will cause euvolemic hypernatremia

A
  • loss of fluid low in sodium and potassium
  1. diabetes insipidus
    1. central:
      1. head trauma, inflammatory, neoplastic, infiltrative
    2. nephrogenic
      1. congential or acquired defect of vasopressin 2 receptors
54
Q

treatment of hypovolemic hypernatremia

A
  • rehydrate
  • isotonic solution initially then hypotonic
55
Q

treatment of euvolemic hypernatremia

A
  • rehydration
    • D5 or 1/2 normal saline
56
Q

treatment of hypervolemic hypernatremia

A

loop diuretics

clin lab med exam 2 (5 decks)

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