Body fluids Flashcards
What are the functions of body fluids?
Dissolve chemical substance
Transport insoluble fat after emulsification
Dissociation of substances to form ions
Act as medium for chemical reactions
Thermoregulation
Digestion and prevent constipation
What is the average daily water intake and output? How are they related?
Fluids ingested - 2100 mL
From metabolism - 200 mL
Total - 2300 mL
Insensible: Skin - 350 mL
Insensible: Lungs - 350 mL
Sweat - 100 mL
Feces - 100 mL
Urine - 1400 mL
Total - 2300 mL
Input = output
What is total body water and what causes it to vary?
60% of total body weight - average male has 42 L
Age, sex, percent body fat
How are body fluids distributed?
20% body weight in ECF (about 14L) split into 10.5 L in interstitial fluid and 3.5 L in plasma
40% of body weight in ICF about 28 L
What is the equation used in indicator dilution technique?
Vol B = (Vol A x Conc A) / Conc B
V = (Amount administered - excreted) / concentration in plasma
or V = i/c
What does the indicator dilution technique assume?
Indicator disperses evenly, only in the compartment measured
Indicator is not metabolized or excreted - corrections can be made for loss
What indicators can be used for total body water?
Tritium
Deuterium
Antipytine
What indicators can be used for ECF?
22Na
125I-iothalamate
Thiosulfate
Inulin
Mannitol
How do you calculate volume of ICF?
No indicators
Total body water - ECF
What indicators can be used for plasma?
125I-albumin
Evans blue dye
What indicator and equation can be used for blood volume?
51Cr-labeled RBCs
Blood volume=plasma volume/(1-hct)
How do you calculate interstitial fluid?
ECF volume - plasma volume
In what direction will osmosis take place?
From low solute concentration to high solute concentration
What is an osmole?
Concentration of a solution in terms of number of particles
1 osmole = 1 gm molecular weight of non-dissociated solute
What is osmotic pressure and its equation?
Pressure necessary to prevent solvent migration
Vant Hoff’s equation
P = nRT/V
P = osmotic pressure
n = number of particles
R = gas constant
T = absolute temp
V = volume of solution
What is osmolarity and its equation?
Osmolarity = g x C
g = number of particles in solution (Osm/mol)
C = concentration in mol/L
What is osmolality?
Concentration of osmotically active particles per Kg of solvent
When is the body at osmotic equilibrium?
When plasma, ISF, and ICF all equal 300 mOsm
What does isosmotic mean?
Two solutions with the same osmolarity
What do we call two solutions with different osmolarities?
Hyperosmotic - for solution with higher osmolarity
Hyposmotic - for solution with lower osmolarity
What is tonicity and how does it relate to osmolarity?
How a solution would affect cell volume if the cell was placed in that solution
compares osmolarity of a solution with plasma
What is the definition of isotonic?
The same as plasma - no net water movement
What is the definition of hypotonic and what occurs?
Less water in cell than plasma or higher conc of solutes in cell than in plasma
Cells swell leading to lysis
What is the definition of hypertonic and what occurs?
Greater fluid in cell than plasma, or greater conc of solutes in plasma than in cell
Shrinkage/crenation of cell occurs
What are factors that cause fluid movement between ICF and ECF?
Ingestion or renal retention of water
Dehydration
IV infusion of different types of solutions
Loss of large amounts of fluid from GI tract
Loss of abnormal amount of fluids from sweating or through the kidneys
What are two basic principles of fluid movement?
Water moves rapidly across cell membranes
Cell membranes are almost completely impermeable to many solutes
What is the method for analyzing fluid shift problems?
-Determine what is gained and/or lost
-Assume any loss or gain affects ECF first
-Predict change, if any, in ECF osmolarity
-Determine which way water must shift to each equal ICF and ECF osmolarities
-Predict directional changes for osmolarities, ICF volume, ECF volume, and total body water
