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GIR Test 3 > B5.057 Electrolyte Abnormalities > Flashcards

B5.057 Electrolyte Abnormalities Flashcards

1
Q

distribution of body water

A

total body water (TBW) = 60% of body weight
extracellular fluid = 20 % BW (5% plasma, 15% interstitial)
intracellular fluid = 40% BW

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2
Q

2 methods to calculate total body water

A

BW * 0.6
OR
0.72 * BW * (1- %fat)

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3
Q

why is there a different method depending on fat content

A

fat cells contain less water

more accurate to say TBW is 72% of lean body mass

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4
Q

average TBW in a person weighing 70 kg with 17% body fat

A

41.83 L

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5
Q

how to calculate distribution of TBW

A

2/3 intracellular
1/3 extracellular
-1/4 plasma
-3/4 interstitial

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6
Q

variations of body fluid with age

A

preterm infants 85% TBW (less in cells)
neonates 80% TBW
adults 60% TBW
elderly 50% TBW

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7
Q

significance of body fluid variation with age

A

problems with dehydration more common in neonates and elderly

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8
Q

body fluid variation with gender

A

women higher % of body fat so lower % TBW

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9
Q

forces involved in movement of water between body compartments

A 
hydrostatic pressure (MAP)
osmotic/oncotic pressure (protein content)
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10
Q

water movement between ECF and ICF

A

driven by osmotically active solutes

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11
Q

water movement within ECF (vascular > interstitium)

A

depends on hydrostatic and oncotic pressure (Starling forces)

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12
Q

what compartment does water enter the circulation in

A

plasma

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13
Q

what is osmotic pressure

A

minimum pressure that needs to be applied to a solution to prevent inward flow of its pure solvent across a semipermeable membrane

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14
Q

oncotic pressure

A

osmotic pressure exerted by proteins

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15
Q

summary fluid movement across capillaries

A

fluid leaves arteriolar end of capillaries by outward hydrostatic pressure
fluid returns to plasma at venous side of capillaries due to inward force of oncotic pressure

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16
Q

what is the significance of the Starling forces at work in capillaries

A

constant recycling of fluid between plasma and interstitium

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17
Q

describe transcellular water movement

A

oncotic pressure draws water into the cell
water flows out of the cell following Na+ via Na/K ATPase (prevents cell from bursting)
ions distribute according to their electrochemical equilibrium (concentration and charge both taken into account)

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18
Q

discuss the role of sodium in body fluids

A

key role in water movement
main extracellular cation and value is double from an osmotic perspective due to sodium attending anions (bicarb and Cl-)

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19
Q

what % of ATP is used for Na/K ATPase function

A

60%!!!!
hella important y’all
hi leesy

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20
Q

tonicity

A

defines the effect a solution has on the steady state volume of a cell

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21
Q

hypotonic

A

final cell volume greater than initial

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22
Q

isotonic

A

final cell volume same as initial

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23
Q

hypertonic

A

final cell volume smaller than initial

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24
Q

osmolality

A

number of solute molecules in solution

does not predict how a cell will respond to solution

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25
Q

iso-osmotic but hypotonic solution

A

EX: permeant solute
cell in 290 mOsm urea
urea enters cell by diffusion, increasing intracellular solute concentration
water enters cell causing it to swell and eventually rupture

26
Q

hyperosmotic but hypotonic solution

A

EX: permeant solute
cell in 580 mOsm urea
cell initially shrinks as water rapidly leaves cell, intracellular osmolality increases to 580 mOsm
urea enters cell by diffusion, increasing intracellular solute concentration
water enters cell causing it to swell and eventually rupture

27
Q

hyperosmotic but isotonic solution

A

cell in 290 mOsm NaCl + 290 mOsm urea
cell shrinks initially as water leaves and intracellular osmolality increases to match extracellular
urea enters cell and water follows until cell returns to normal volume and intracellular urea concentration is 290 mOsm

28
Q

examples of hypotonic solutions

A

all solution with less than the osmolality of normal plasma (290 mOsm)
all solution that contain only permeant solutes
solution containing both impermeant and permeant solute when osmolality due to the impermeant solute is less than 290

29
Q

examples of isotonic solutions

A

all solutions containing only impearmeant solutes with osmolality equal to the osmolality of normal plasma
solutions containing both impermeant and permeant solute when osmolality due to impermeant solute equals the osmolality of normal plasma

30
Q

examples of hypertonic solutions

A

all solutions containing only impermeant solutes with osmolality greater than that of normal plasma
solutions containing both impermeant and permeant solute when osmolality due to impermeant solute is greater than the osmolality of normal plasma

31
Q

hypotonic expansion

A 
excessive H2O intake
ECF osmolality - decrease
ECF volume - increase
ICF osmolality - decrease
ICF volume - increase
32
Q

hypotonic contraction

A 
kidneys excreting too much salt (removal of salt in excess of water)
ECF osmolality - decrease
ECF volume - decrease
ICF osmolality - decrease
ICF volume -increase
33
Q

isotonic expansion

A 
IV normal saline infusion
ECF osmolality - no change
ECF volume - increase
ICF osmolality - no change
ICF volume - no change
34
Q

isotonic contraction

A 
hemorrhage
ECF osmolality - no change
ECF volume - decrease
ICF osmolality - no change
ICF volume -no change
35
Q

hypertonic expansion

A 
drinking sea water
ECF osmolality - increase 
ECF volume - increase
ICF osmolality - increase
ICF volume - decrease
36
Q

hypertonic contraction

A 
severe sweating (removal of water in excess of salt)
ECF osmolality - increase
ECF volume - decrease
ICF osmolality - increase
ICF volume - decrease
37
Q

compensation for hypotonic expansion(hyponatremia)

A

decreased H2O intake
increased H2O output
decreased Na+ output
ECF to ICF fluid shift

38
Q

what is water intoxication

A

acute dilutional hyponatremia

movement of water into brain cells causes neurological symptoms

39
Q

compensation for hypotonic contraction

A 
decreased H2O intake
increased Na+ intake
increased H2O output (decreased ADH)
decreased Na+ output (via R-A-A)
ECF to ICF fluid shift
40
Q

compensation for hypertonic expansion (hypernatremia)

A

increased H2O intake
decreased H2O output
increased Na+ output
ICF to ECF fluid shift

41
Q

discuss hypertonic expansion in the context of hyponatremia

A

pseudohyponatremia due to increased concentration of another solute (glucose, ureas, etc.)
normal total body sodium but increased osmolality

42
Q

compensation for hypertonic contraction

A

increased H2O intake
decreased H2O output
increased Na+ output
ICF to ECF shift

43
Q

Na+ deficit

A

amount of NaCl necessary to raise plasma Na+ to the desired value

44
Q

Na+ deficit formula

A

Na+ deficit = TBW * (desired Na+ - present Na+)

45
Q

calculation of H2O deficit

A

normal TBW * normal Na+ = current TBW * current Na+

water deficit = present TBW * [(current Na+/normal Na+) - 1]

46
Q

when can hyponatremia occur

A

hypotonic expansion - increased H2O
hypotonic contraction- increased Na+ loss
water in excess of solute

47
Q

hyponatremia with plasma hypertonicity

A

severe hyperglycemia
hypertonic mannitol
hyperproteinemia (myeloma)

48
Q

hyponatremia with plasma hypotonicity

A 
renal failure
edematous states
thiazides
SIADH
endocrine
genetic (Bartter, Gitelmans)
49
Q

signs and symptoms of hyponatremia

A

frequently asymptomatic
symptomatic < 120
usually CNS symptoms: lethargy, weakness, confusion, delirium, seizures

50
Q

diagnosis of hyponatremia

A
  1. severe w seizures or less severe, water restriction if less severe
  2. exclude pseudohyponatremia
  3. investigate hyponatremia with hypotonicity (renal water excretion, excess free water sources)
  4. identify signs of ECFV depletion or overload
51
Q

treatment of hyponatremia with increased tonicity

A

usually due to hyperglycemia

0.9% saline until stable, then 0.45%

52
Q

treatment of renal failure hyponatremia

A

water restriction

53
Q

treatment of ECFV depletion hyponatremia

A

0.9% saline

54
Q

treatment of edematous hyponatremia

A

water restriction
sodium restriction
diuretics to remove edema

55
Q

treatment of increased ADH hyponatremia

A

water restriction

treat cause

56
Q

treatment of endocrine hyponatremia

A

treat hypothyroidism

correct adrenal failure

57
Q

when can hypernatremia occur

A

hypertonic expansion- increased Na+ intake
hypertonic contraction- decreased H2O
solute in excess of water

58
Q

reasons for hypernatremia

A

extra renal water loss (sweat, burns, GI)
renal water loss (osmotic diuresis, DI)
excess sodium (iatrogenic, Liddles)

59
Q

signs and symptoms of hypernatremia

A

w dehydration: orthostatic hypotension and oliguria
altered mental status
w severe hyperosmolality: hyperthermia, delirium, coma

60
Q

diagnosis of hypernatremia

A
  1. find reason for water loss or Na+ gain
  2. find why patient is unable to replace water loss
  3. identify if polyuria is present
61
Q

treatment of hypernatremia

A
  1. correct severe ECFV depletion with 0.9% saline, continue with hypotonic fluid 0.45%
  2. calculate water deficit and administer water replacement at a rate sufficient to correct hyponatremia but slowly enough to avoid cerebral edema

GIR Test 3 (19 decks)

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