(3) Physiology of Body Fluid (Walker) Flashcards
What is the main function of the kidney?
Regulate the volume and composition of the body fluids within narrow limits
How do you calculate total body water (TBW)?
0.6 x Body weight (kg)
How do you calculate extracellular fluid (ECF)?
0.2 x body weight (kg)
How do you calculate intracellular fluid (ICF)?
0.4 x body weight (kg)
What is the 60-40-20 rule?
60% of body weight is total body water
40% of body weight or 2/3 of total body water is intracellular fluid (ICF)
20% of body weight or 1/3 of total body water is extracellular fluid (ECF)
How is extracellular fluid (ECF) further divided?
Interstitial fluid (75%)
Plasma (25%)
______ is an intermediary b/w cells and the external enviornment
All exchanges of H2O and other constituents b/w ICF and the external world must occur through the ________
Water added to the body fluids always enters the _____ compartment first, and fluid always leaves the body via the ______
Extracellular fluid (ECF)
What is third spacing?
Too much fluid shifts from the blood vessels (intravascular) into the non-functional area of the cells
***Third spacing is problematic, fluid is being lost from the intravascular space
*See in burn victims
Describe osmosis
Water moves from an area of higher concentration of water (more dilute solution, lower solute concentration)
TO
Area of lower concentration of water (more concentrated solution, higher solute concentration)
What is the major(s) ion in the extracellular fluid?
What is the major(s) ion in the intracellular fluid?
Extracellular = Na+ and Cl-
Intracellular = K+
Define:
Nonelectrolytes
Contain covalent bonds that prevent them from dissociating in solution and therefore have no electrical charge
egs: glucose, lipids, and urea
Define:
Electrolytes
Dissociate into ions (ionize) in water
egs: Mg+, Na+, Cl-, K+
T/F
Electrolytes have a lower osmotic power than nonelectrolytes
FALSE!!!
Electrolytes have a higher osmotic power than nonelectrolytes because each electrolyte molecule dissociates into at least two ions
*Electrolytes have a greater ability to cause fluid shift
Write out the normal ranges for the following values
*PAY ATTENTION TO NA+, Cl-, Creatinine, BUN, Serum osmolality
Define:
Osmolality
Measure of the number of osmotically active particles per kilogram of H2O
Define
Osmolarity
The number of osmotically active particles per liter of total solution
Disturbances in plasma
ECF volume loss will result in…
INCREASED total plasma protein (concentration)
Disturbances in plasma
ECF volume gain will result in…
DECREASED total plasma protein (dilution)
Disturbances in Hematocrit
ICF volume loss will result in:
DECREASED hematocrit
(Shrinkage of RBCs)
Disturbances in Hematocrit
ICF volume gain will result in:
INCREASED hematocrit
(swelling of RBCs)
What are the indicators used for determining:
Volumes of |
Extracellular Fluid
Plasma
Extracellular Fluid = Inulin
Plasma = Radio labeled albumin
*** PRACTICE QUESTION ***
Intracellular volume = Increased
Intracellular osmolarity = Decreased
Extracellular volume = Decreased
Extracellular osmolarity=Decreased
Things to note:
Notice that the man is losing 3 L of SWEAT which contains electrolytes. That is different from the water!!!
What is the Gibbs-Donnan Effect?
The presence of a negatively charged protein on one side of a semipermeable membrane generates both osmotic and electrochemical gradients accross the membrane
What would happen if gibbs-donnan effects were not countered?
Intracellular proteins would result in an influx of water into the cell
CAUSING cell swelling and death
What counteracts the Gibbs-donnan effect?
Na/K+ ATPase pump
3 Na+ out, 2 K+ in
Maintains a high Na+ concentration outside the cell
Sodium is responsible for the ____ osmotic balance
Potassium maintais the ____ osmotic balance
Sodium is responsible for the ECF osmotic balance
Potassium maintais the ICF osmotic balance
What is the pressure called that refers to:
“the movement of fluids through capillaries as the result of blood pushing against the walls of the capillary”
Hydrostatisc pressure
When ______ pressure builds inside a capillary, it forces fluids and solutes out through the capillary walls into the interstitial fluid
When hydrostatic pressure pressure builds inside a capillary, it forces fluids and solutes out through the capillary walls into the interstitial fluid
“The pulling force of albumin in the intravascular space attracts water and holds it inside the blood vessel. This is referred to as __________”
Plasma colloid oncotic pressure
Describe with osmotic and hydrostatic pressures what is occuring with
Filtration
Capillary blood pressure > Plasma colloid osmotic pressure
Describe with osmotic and hydrostatic pressures what is occuring with
Absorption
Capillary blood pressure < Colloid osmotic pressure
What is edema?
Palpable swelling produced by expansion of interstitial fluid volume
What is edema caused by?
- Alteration in capillary hemodynamics
- Renal retention of dietary Na+ and water expansion of ECF volume
How would you calculate net filtration?
4 forces contribute (Starling forces)
- Capillary hydrostatic pressure (blood pressure)
- Capillary (plasma) oncotic pressure
- Interstitial hydrostatic pressure
- Interstitial oncotic pressure
What is the tonicity of a solution?
The effect the solution has on cell volume
(Whether the cell remains the same size, swells or shrinks)
Cells have a normal NaCl concentration equal to?
0.85%
Describe what an isotonic solution is
Isotonic-cell enviornment has a NaCl concentration equal to 0.85%
*If cells are placed in isotonic solution, there will be equal movement of water in and out of the cell
Describe what a hypertonic solution is
Hypertonic cells enviornment has a NaCl concentration greater than 0.85%
*If cells are placed in hypertonic solution, there will be a net movement of water out of the cell which will cause the cell to shrink
Describe what an hypotonic solution is
Hypotonic: cells’ enviornment has a NaCl concentration less than 0.85%
*If cells are placed in a hypotonic solution, there will be a net movement of water into the cell which will cause the cell to swell
What are replacement therapies used for?
What are the two categories?
It’s a method for treating fluid and electrolyte alterations by infusion of I.V. solutions
- Crystalloids
- Colloids
What are crystalloids?
What are colloids?
Crystalloids: contains organic or inorganic salts dissolved in sterile water (egs, glucose, sodium chloride, normal saline (0.9% sodium choloride), DOES NOT CROSS PM -> remains in ECF
Colloids: contains large molecules that don’t pass through semipermeable membranes (eg. albumin)
What is the equation for plasma (serum) osmolarity?
3 main solutes in the ECF are:
Sodium, Glucose, Urea
*normal range = 275 -295 mOsm/kg
What are the two ways dehydration can be divided?
ACCORDING TO SERUM SODIUM CONCENTRATION
Hypernatremic
Hyponatremic
Describe the state of hypotonic (hyponatremic) dehydration
Loss of sodium > loss of water in ECF
Serum [Na+] in ICF > ECF
Water shifts from ECF to ICF to establish osmotic equilibrium
*Serum Na+ and Serum osmolality will be less than the normal range
Describe the hypertonic (hypernatremic) dehydration state
Loss of water > Loss of Na+ in ECF
Serum osmolality will exceed 300mOsm/kg
Serum Na+ will be more than 150 mEq/L
Serum sodium = 150mEq/L
What state are we in?
Hypernatremia
Serum sodium above 147-150 mEq/L
Serum sodium = 125 mEq/L
What state are we in?
Hyponatremia
Serum sodium level below 130-135 mEq/L
What is a Darrow-Yannet diagram measuring?
Used to study the effect of various clinical conditions
Such as (dehydration, shock, vomiting, diarrhea)
On osmolality and volume of extracellular and intracellular fluid
Solid line=normal values
Dashed line=change in the volume and osmolality
What is occuring in this darrow-yannet diagram?
[Iso-osmotic volume contraction]
ACUTE FLUID LOSS (hemorrhage, diarrhea, vomiting)
Decrease in ECF volume
No change in body osmolality and ICF volume
What is occuring in this Darrow-yannet diagram?
[Hyperosmotic volume contraction]
HYPOTONIC FLUID LOSS (dehydration, DM, alcoholism)
Decrease in ECF and ICF volume
Increase in body osmolality
What is occuring in this Darrow-Yannet diagram?
[Isoosmotic volume expansion]
Isotonic saline
Increase in ECF volume
No change in osmolality and ICF volume
What is occuring in this Darrow-Yannet diagram?
[Hypo-smotic volume expansion]
Gain o hypotonic fluid
(conditions like excess water-drinking and SIADH)
Increase in ECF and ICF
Decrease in Body osmolality
*** Practice Problem ***
See last few slides in lecture for long explanation lol
*** Practice Problem ***
C. 0.9% NaCl IV
