Fluid Distribution and Movement

Question 1

total body water

Answer 1

60% of total body weight in kg

Question 2

what is fluid

Answer 2

water + solute

Question 3

intracellular fluid

Answer 3

water inside of cells
- 2/3 of total body water
- separated by cell membrane from ECF
- regulated exchange

Question 4

extracellular fluid

Answer 4

water outside of cells
- 1/3 of total body water
- interstitial, intravascular, and transcellular fluid

Question 5

interstitial fluid

Answer 5

fluid within tissues
- 3/4 of ECFV
- separated by capillary endothelium from IVF

Question 6

intravascular fluid

Answer 6

fluid within vessels
- 1/4 of ECFV

Question 7

transcellular fluid

Answer 7

fluid within specialized compartments

Question 8

does the ratio of fluid distribution in each compartment change at homeostasis

Answer 8

NO - constant ratios

does NOT depend on fluid volume

Question 9

milliequivalence

Answer 9

content of a solute

mEq = millimoles x valence

1 mM CaCl2 =
- 1 mM Ca x 1 valence = 1 mM Ca
- 1 mM Cl2 x 2 valence = 2 mM Cl

Question 10

does solute concentration OR ionic strength differ in each fluid compartment

Answer 10

solute concentration

compartments have the SAME ionic strength
different solute concentration allows for fluid flow

Question 10

osmolarity

Answer 10

number of moles of solute per liter of solvent (mol/L)
- considers VOLUME

Question 11

osmolality

Answer 11

number of moles of solute per kg of solvent (mol/kg)
- considers MASS

Question 12

are osmolarity and osmolality equal in biology

Answer 12

YES - can be considered the same because 1 L of water = 1 kg of water

Question 13

what is the osmolarity of plasma in healthy animals

Answer 13

300 mOsm/L

Question 14

iso-osmotic

Answer 14

within 10% of 300 mOsm/L
(270-330 mOsm/L)

Question 15

hyperosmotic

Answer 15

> 330 mOsm/L

Question 16

hypo-osmotic

Answer 16

<270 mOsm/L

Question 17

osmotic pressure

Answer 17

the pressure needed to STOP osmosis (flow of water from high to low concentration)

Question 18

what does osmotic pressure depend on

Answer 18

NUMBER of molecules

Question 19

osmole

Answer 19

osmosis caused by a mole of a substance

1 mOsm = 1 mEq

Question 20

tonicity

Answer 20

effective osmolarity; creates osmotic gradients

ONLY measures effective osmoles

Question 21

effective osmoles

Answer 21

can NOT freely move across membranes
- exerts osmotic effects (causes water to move)
- excluded from ICFV

Na, Cl, proteins, glucose

Question 22

ineffective osmoles

Answer 22

can freely move across membranes
- does NOT exert osmotic effects (doesn’t cause water to move)

Urea, ethanol, lipid-soluble

Question 23

what type of solutes does osmolarity measure

Answer 23

effective AND ineffective solutes

Question 24

what type of solutes does tonicity measure

Answer 24

effective osmoles ONLY

Question 25

oncotic pressure

Answer 25

pressure exerted by proteins in plasma or interstitial fluid - pulls water INTO blood vessels

mostly due to albumin

Question 26

osmosis

Answer 26

water movement from area of high concentration to low
- causes a change in volume in each compartment
- equilibrates in 4 hrs

regulated by Starling forces - hydrostatic and oncotic

Question 27

blood volume

Answer 27

90 mL/kg in DOGS = IV fluid volume + red cell fluid volume

Question 28

if PCV = 50% in a 20 kg dog, how can you solve for blood volume?

Answer 28

20 kg dog = 60% TBW = 12 kg water = 12 L water

ECFV = 1/3 TBW = 4 L
intravascular fluid = 1/4 ECFV = 1 L

if PCV = 50%, then:
50% blood volume = IV fluid = 1 L
50% blood volume = red cells = 1 L

blood volume = IV fluid + RBC = 2 L

Question 29

how to assess IV fluid volume on exam

Answer 29

perfusion parameters:
- mentation
- MM color
- CRT
- pulse rate/quality
- extremity temp.

Question 30

hypovolemia

Answer 30

low IV fluid volume (hemorrhage or ECF lost through interstitial space)

• pale MM
• slow CRT
• inc. pulse rate
• dec. pulse quality
• cold extremities

Question 31

how to assess interstitial fluid volume

Answer 31

hydration parameters:
- skin turgor
- MM moist/dry
- tear film production

Question 32

dehydration

Answer 32

clinically detectable at 5% dehydrated (25% ECF loss)

• dec. skin turgor
• tacky MM
• dec. tear film

Question 33

where does fluid loss come from

Answer 33

interstitial fluid

NOT hemorrhage

Question 34

isotonic water loss

Answer 34

equal proportion of solute and water loss
- no net water movement
- intracellular water does NOT change
- extracellular water loses water proportionally in IS/IV fluid compartments (3/4 water loss from IS, 1/4 water loss from IV)

ex. diarrhea

Question 34

hypertonic water loss

Answer 34

more solute loss than water loss
- DECREASE osmolarity of interstitial fluid
- water moves IS –> IV + IC
- starling forces move water back from IV –> IS

Question 35

hypotonic water loss

Answer 35

more water loss than solute loss
- INCREASE osmolarity of interstitial fluid
- water moves IV + IC –> IS

hypernatremia - sign of hypotonic fluid loss

ex. vomiting

Question 36

pure water loss

Answer 36

caused by diabetes insipidus (excessive, unconcentrated urination)
- INCREASE osmolarity of interstitial fluid

hypernatremia

Question 37

effects of hyperglycemia on water movement

Answer 37

high IV glucose causes water to move from ICFV –> ECFV

causes hypervolemia + hyponatremia

Question 38

effects of azotemia on water movement

Answer 38

high BUN does NOT cause water to move

increases osmolarity w/o increasing volume in any compartment

Question 39

effects of isotonic (0.9% NaCl) IV infusion

Answer 39

increases ECFV proportionally
does NOT change ICF volume or osmolarity

Question 40

effects of 5% dextrose IV infusion

Answer 40

mechanism of giving pure water IV without causing local area of hypo-osmolality

increases all compartment volumes proportionally
- small osmolarity decrease in all compartments