Body Water

Question 1

Total body water (TBW)

Answer 1

. Most abundant component of the body
. The % of your body weight that is water will depend on how much adipose tissue you have
. Estimation: 0.6(body weight)
. Equation: BW = ICF + ECF
. 2/3 water is inside cells and 1/3 is outside cells

Question 2

Extracellular fluid

Answer 2

. Interstitial fluid: 3/4 of ECF, located outside the blood vessels (interstitial space)
. Plasma volume: 1/4 of ECF, located inside blood vessels
. ECFV = interstitial fluid + plasma volume

Question 3

Composition of ECF and ICF

Answer 3

. ISF and plasma have essentially the same ionic compositions
. However ISF has essentially no proteins while plasma has lots of large proteins like albumin)
. ECF and ICF have different ionic compositions
. ECF major cation = Na (accompanied by Cl and HCO3)
. ICF major cation = K (accompanied by phosphates and anionic proteins

Question 4

Plasma Na reference range

Answer 4

135-145 mEq/L

Question 5

Plasma K reference range

Answer 5

3.5-5.0 mEq/L

Question 6

Osmosis

Answer 6

. Occurs due to conc. Difference (water moves into compartment w/ high conc. Of solute)
. Solute particles are restricted to their compartment
. Pure water is the highest conc. Of water you can have
. Asking solute to a volume of water dec. conc. Of water molecules

Question 7

Osmolality

Answer 7

. Number of particles per kg of water (mOsm/kg)
. Higher this is, lower the water concentration
. Difference in osmolality is called osmotic gradient

Question 8

Osmolarity

Answer 8

. Number of particles per liter of water (mOsm/L)

Question 9

Osmotic pressure

Answer 9

. Measure of the drive for water movement
. Amount of hydrostatic pressure needed in a compartment to stop the osmotic flow of water into that compartment
. A solution w/ high osmolality has high osmotic pressure
. Determined by number of molecules in the solution
. In dilute biological fluids, 1 molecules/L of solute exerts an osmotic pressure of 1 mOsm/kg water or 1 mOsm/L
. When net movement of water is 0, the 2 compartments have reached equilibrium

Question 10

How water in and out of cells reaches equilibrium

Answer 10

. Water moves until osmolality is the same in each compartment
. OR hydrostatic pressure in the receiving compartment equals the osmotic force driving water movement into that compartment
. Cells involved can burst or shrink to the point of nonviability but cell sure good at protecting themselves

Question 11

Effective osmoles

Answer 11

. Solute will only exert osmotic effect if the particles do not leave the compartment in which they are dissolved
. These solutes are nonpermant/effective osmoles

Question 12

Ineffective osmoles

Answer 12

. Solute is permanent
. Diffuses across the membrane and the osmotic gradient due to this molecule will eventually dissipate
. Considered ineffective
. Example: urea

Question 13

Main determinants of plasma osmolality

Answer 13

. Plasma Na

. Accompanying anions

Question 14

Effective osmolality

Answer 14

. Solute will only exert an osmotic effect if the particles do not leave the compartment in which they dissolved
. Effective osmolality of a solution takes into account only the conc. Of non permanent solutes in the solution
. It is possible for the solution’s effective osmolality to be less than the total osmolality of that solution

Question 15

Ideal osmolality

Answer 15

. 0.93 I’d the osmotic coefficient for NaCl

. 286 mOsm/kg is the ideal osmolality

Question 16

Cell response to acute cell shrinkage

Answer 16

Change in cell size in response to ECF hyperosmolality activates solute-uptake processes in the cell (uptake of ions)
. Addition of ions to the cell will be accompanied by the osmotic influx of water

Question 17

Response to acute cell swelling

Answer 17

. Change in cell size in response to ECF hypo-osmolality activates solute-efflux mechanisms
. Efflux of particles will be accompanied by osmotic flow of water

Question 18

Mechanisms of cells in response to inc. ECF osmolality

Answer 18

. Accumulate over hours to days additional organic osmotic particles (osmolytes)
. Done by transporting into the cell or making new osmoles
. Particles include alcohol sugar derivatives sorbitol and inositol, amines taurine, and betaine

Question 19

Hypo-osmolality

Answer 19

. Conditions of a slowly developing and chronic hypoatremia

. Cells will lose osmolytes to minimize cell swelling

Question 20

What occurs w/ rapid correction of an established hypernatremia

Answer 20

. If you correct too fast w/ IV hypotonic fluids, the brain cells can initiate swelling because they can’t rid themselves of the accumulated organic osmoles quickly enough
. Matters how long the hyperosmolar state has been present
. Same for hypoosmolar state

Question 21

Body fluid dynamics basic principles

Answer 21

. Capillary endothelium and most cells membranes are permeable to water
. Osmolar equilibrium, the plasma, interstitial fluid, and intracellular fluid have the same osmolality
. H2O distribution is determined by the number of osmotically active (effective) particles in each compartment
. Any loss or gain of H2O and/or electrolytes must initially occur in ECF
. If ECF osmolality changes, H2O shifts among compartments to maintain osmolar equilibrium

Question 22

What occurs in cells during gain in isotonic fluid

Answer 22

. Inc. in ECF volume
. Inc. in TBW
. No change in ICF volume
. No change in ECF or ICF osmolality

Question 23

What occurs in cells during loss of isotonic fluid

Answer 23

. Dec. in ECF volume
. Dec. in TBW
. No changed in ICF volume
. No change in ECF or ICF osmolality

Question 24

What occurs in cells during gain in hypotonic fluid (water)

Answer 24

. Inc. in TBW
. Inc. in ECF and ICF volume
. Dec. in ECF and ICF osmolality

Question 25

What occurs in cell during loss of hypotonic fluid (water/sweat/ having diabetes insipidus)

Answer 25

. Dec. TBW
. Dec. ECF and ICF volume
. Inc. ECF an ICF osmolality

Question 26

What solution do you use to replace pure water in body?

Answer 26

. Isotonic glucose
. Used to slowly add pure/free water to the body
. Glucose is transported into cells and then is metabolized into CO2 and H2O
. End result is expansion of ECF and ICF w/ dec. in osmolality

Question 27

What occurs when you add D5W to body

Answer 27

. Done via IV infusion 
. Transient inc. in ECF volume 
. Glucose transported into cell, metabolized to CO2 and H2O 
. ECF and ICF diluted by water
. Inc. in volume of ECF and ICF
. Dec. in osmolality of ECF and ICF

Question 28

What happens w/ Addition of NaCl to body

Answer 28

. No change in TBW
. Inc. in ECF
. Dec. in ICF (shift of water into ECF)
. Inc. in ICF osmolality

Question 29

What happens during loss of NaCl in body

Answer 29

. Dec. in ECF volume and osmolality
. Inc. in ICF volume (shift of water from ECF)
. Dec. in ICF osmolality

Question 30

What type of solution is 5% dextrose in water (DSW)?

Answer 30

Isotonic at infusion

Question 31

What type of solution is 0.9% NaCl (normal saline)

Answer 31

Isotonic

. Used to expand ECF

Question 32

What type of solution is 0.45% NaCl (1/2 normal saline)

Answer 32

. Hypotonic

. Used to treat hyperatremia

Question 33

What type of solution is 3% NaCl?

Answer 33

. Hyper tonic

. May be used to treat severe hypoatremia

Question 34

What type of solution is lactated ringers?

Answer 34

. Isotonic solution w/ Na, Cl, K, Ca, and lactate

. Used to treat hypovolemia, burns, diarrhea

Question 35

Hypoatremia is under how much Na?

Answer 35

Under 135 mEq/L

Question 36

Hyperatemia is over how much Na?

Answer 36

Over 145 mEq/L

Question 37

What does 1 osmolal solution of glucose mean?

Answer 37

. 1 mole dissolved into 1 kg of H2O