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Bloc D - Renal > Jan8 M1-Disorders of Water Balance > Flashcards

Jan8 M1-Disorders of Water Balance Flashcards

1
Q

cause and consequence of water imbalance ultimately

A

ADH is cause. Hypo and hyperNa is consequence

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2
Q

what controls plasma Na conc

A

water balance

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3
Q

consequence of too much Na and too little Na (not related to water balance)

A

too much = edema

not enough = volume depletion

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4
Q

main worry in Na imbalances

A

neuron swelling in the brain (cerebral edema)

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5
Q

what can cause cerebral edema (swelling of neurons)

A

HYPOTONIC hyponatremia

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6
Q

cause of central pontine myelinolysis

A

too rapid correction of hypoNa or hyperNa

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7
Q

4 types of water excretion impairment hyponatremias and volume state in each

A
  • circulating volume depletion (low IV volume. can have high ECF volume though bc high ISF volume)
  • SIADH (euvolemic)
  • advanced renal failure (hypervolemia)
  • hormonal changes (euvolemia)
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8
Q

conditions where appropriate ADH release with high ECF volume but low IV volume and ones with low ECF

A

CHF, cirrhosis, nephrotic syndrome
diarrhea, vomiting: high ECF low IV volumes
low ECF: diarrhea, vomiting, volume depletion with thiazides

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9
Q

causes of SIADH and mechanisms

A
  • neuropsychiatric disorder (any CNS disorder) or severe pain or nausea (signaling to hypothalamus)
  • lung tumor (making ADH)
  • pulmonary diseases (unknown)
  • drugs
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10
Q

volume state, Na and osms in SIADH

A

euvolemic, hypoosmolar, hypoNa

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11
Q

hormonal changes that can cause water excretion impairment hypoNa and mechansims

A
  • hypothyroidism (thyroid contributes to water excretion)
  • cortisol deficiency (adrenal problem and low BP, perceived as low volume)
  • pregnancy
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12
Q

4 questions in hypoNa history

A
  • why hospitalized?
  • concurrent illnesses (renal disease, thyroid, low cortisol=Addison’s)
  • medications (diuretics**)
  • pain and nausea
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13
Q

how to assess volume status in general

A

intravascular: BP, HR, urine output, JVP, postural hypotension BP
extravascular: edema and where

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14
Q

what’s a postural hypotension BP

A

check BP diff when seat after lying down and if ­­>10, hypovolemia

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15
Q

how to approach hypoNa and determine the cause

A

depending on volumee status

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16
Q

hypoNa causes in hypovolemia

A

water loss (dehydration, diarrhea, vomiting), meds like diuretics

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17
Q

hypoNa causes in euvolemia

A

SIADH, thyroid, adrenal insufficiency

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18
Q

hypoNa causes in hypervolemia

A

CHF, liver disease, nephrotic syndrome, advanced renal failure

19
Q

most common causes of severe hypoNa

A
  • SIADH,
  • thiazide diuretics
  • postoperative state (pain and nausea)
  • GI fluid loss
  • polydipsia in psychiatric patients (rare)
20
Q

formula for plasma osmolality

A

2 x Na + glucose + urea + (alcohol)

21
Q

4 criteria to diagnose SIADH

A

U Na>40
U osms>100
Na<125
serum osms<275

22
Q

why do you not retain volume or develop edema in SIADH (and stay euvolemic)

A

when sense excess volume, aldo and AT2 turned off so Na excreted

23
Q

hypoNa that is not a water excretion impairment

A

reset osmostat (hypothalamus is reset to be thirsty at a lower osmolality during pregnancy)

24
Q

ADH turned on or off in reset osmostat

A

turned off

25
Q

fluid treatment in hypoNa with peripheral edema + ADH before and after

A

fluid restrict to limit water reabso and return Na back up

ADH turned on initially and still turned on after

26
Q

fluid treatment in hypovolemia due to GI loss + ADH before and after

A

isotonic saline. ADH on before and turned off after

27
Q

fluid treatment in SIADH + ADH before and after

A

hypertonic saline (ADH on before and after, it’s constitutively active..)

28
Q

D5W composition + what are we giving

A

water with 300 mosms of dextrose (is like giving pure water)

29
Q

normal saline composition

A

0.9% (0.9g per 100 mL NaCl): 154 mEq Na and 154 mEq Cl

30
Q

half NS composition and used when

A

77 mmol of Na. maintenance when not drinking or eating before surgery

31
Q

d5w + 3 ampules of NaHCO3 composition + used when

A

145 meq or Na and 145 meq of HCO3 per L (used in acid base disorder when need bicarb)

32
Q

3% saline composition and used when

A

513 mmol Na per L. SIADH

33
Q

Adrogue formula for Na correction

A

change = (infusate Na - serum Na)/(TBW + 1)

34
Q

long term treatment in SIADH

A

water restriction, dietary Na, loop diuretic to wipe out medullary interstitium osmotic gradient

35
Q

goal for speed of Na correction

A

5 mM per 12 hours

36
Q

why NS doesn’t work in SIADH hypoNa

A

patient is euvolemic so extra Na seen is secreted

37
Q

2 categories of causes of hyperNa

A
  1. increased water losses unreplaced due to impairment of thirst
  2. administration of hypertonic NaCl or NaHCO3
38
Q

hyperNa due to increased water losses unreplaced due to impairment of thirst: 4 types

A
  • insensible and sweat losses (fever, resp infections) (hypotonic)
  • urinary losses (central or nephrogenic DI: ADH not working, or osmotic diuresis with glucose or mannitol)
  • GI loss (hypotonic)
  • lesion to hypothalamic thirst center
39
Q

hyperNa is usually caused by what 2 things

A

fluid deficit (volume contraction) and inability/failure to drink

40
Q

first formula to estimate water deficit

A

TBW x (Na/140 - 1) = water deficit in L

41
Q

2nd formula to estimate water deficit

A

C1V1 = C2V2

V1 and V2 being TBW

42
Q

treatment to hyperNa

A

give water (d5w)

43
Q

why NS doesn’t work for hyperNa

A

NS outplaced by the ongoing hypotonic losses of water (sweat, GI, etc.)
would have to give too much saline to retrieve normal Na

44
Q

ADH turned on or off in hypernatremia

A

on (osmotic receptors in the hypothalamus)

Bloc D - Renal (32 decks)

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