N5315 Advanced Pathophysiology
Fluid and Electrolytes
Core Concept and Objectives with Advanced Organizers
Fluid and Electrolytes
1. Analyze the pathologic consequences of fluid volume disorders on the mechanisms of
fluid homeostasis.
a. Explain the three main fluid compartments and describe how fluid shifts between
the compartments and the implications for clinical practice.
Total body water is approximately 60% of the body weight and is spread between
the three main fluid compartments.
Fluid Compartments Definition Pattern of Fluid Shifts Clinical Implications
Intravascular The intravascular Both in and out of the Volume overload
space contains 20% interstitial and Venous retention
Main ECF compartment of the total body intracellular spaces Increased venous
water. pressure
Hypertonic IV solution, edema
when administered, will
increase the solute
concentration in the
intravascular space
Interstitial The interstitial Due to the increase in Fluid will shift from
space contains 20% solute concentration in intracellular into the
Main ECF compartment of the total body the intravascular extracellular space.
water. space, water will flow
via osmosis from the Edema
total volume of ECF extracellular space to
outside of the blood the intravascular
vessels and is space. This will leave
separated from the extravascular
plasma by walls of space with a higher
body’s vasculature concentration of
solutes than the
intracellular space.
Hydrostatic
(movement by force)
and osmotic
(concentration of
solutes movement
of fluid) pressures
cause movement of
fluid
*capillary hydrostatic
pressure
*capillary oncotic
, pressure
*interstitial
hydrostatic pressure
*interstitial oncotic
pressure
Intracellular The intracellular Fluid flows via osmosis The cell will continue
space contains the from the intracellular to shrink.
(ICF) 40% of total body largest portion of space into the
water the total body water extracellular space to Possible cellular
2/3 of body’s fluid (40%). equalize the injury r/t oncosis
concentration of
-fluid present inside solutes. This will cause
of the cells and the cell to shrink. Water
considered sum will continue to flow
total of the fluid into the intravascular
volume in all of the space from the
body’s cells extracellular space if the
-separated from intravascular space still
ECF by plasma remains more
membrane concentrated than the
extracellular space.
Controlled by osmotic
pressure with Na/K
concentrations
b. Analyze the principles of fluid balance and describe the implications for clinical
practice.
Mechanisms of Fluid Definition Clinical Implications
Balance
Osmolality Measure of solute concentration May be altered by IVF
in a solution concentrations fluid shifts
Plasma osmolality normal
Is 280-295mmOskg Is preferred measure of osmotic
Low potentially 275 activity in clinical assessments.
Even though urea is a solute in the
Controls distribution and plasma it freely diffuses through
movement of water between the cell membranes and has no
body compartments. effect on osmolality, whereas
sodium and glucose are limited to
the extracellular space and greatly
contribute to the effective
osmolality.
Osmosis Movement of water between Hypertonic solutions can pull
compartments from an area of fluid into the intravascular
low concentration of solutes to space, while hypotonic
Fluid and Electrolytes
Core Concept and Objectives with Advanced Organizers
Fluid and Electrolytes
1. Analyze the pathologic consequences of fluid volume disorders on the mechanisms of
fluid homeostasis.
a. Explain the three main fluid compartments and describe how fluid shifts between
the compartments and the implications for clinical practice.
Total body water is approximately 60% of the body weight and is spread between
the three main fluid compartments.
Fluid Compartments Definition Pattern of Fluid Shifts Clinical Implications
Intravascular The intravascular Both in and out of the Volume overload
space contains 20% interstitial and Venous retention
Main ECF compartment of the total body intracellular spaces Increased venous
water. pressure
Hypertonic IV solution, edema
when administered, will
increase the solute
concentration in the
intravascular space
Interstitial The interstitial Due to the increase in Fluid will shift from
space contains 20% solute concentration in intracellular into the
Main ECF compartment of the total body the intravascular extracellular space.
water. space, water will flow
via osmosis from the Edema
total volume of ECF extracellular space to
outside of the blood the intravascular
vessels and is space. This will leave
separated from the extravascular
plasma by walls of space with a higher
body’s vasculature concentration of
solutes than the
intracellular space.
Hydrostatic
(movement by force)
and osmotic
(concentration of
solutes movement
of fluid) pressures
cause movement of
fluid
*capillary hydrostatic
pressure
*capillary oncotic
, pressure
*interstitial
hydrostatic pressure
*interstitial oncotic
pressure
Intracellular The intracellular Fluid flows via osmosis The cell will continue
space contains the from the intracellular to shrink.
(ICF) 40% of total body largest portion of space into the
water the total body water extracellular space to Possible cellular
2/3 of body’s fluid (40%). equalize the injury r/t oncosis
concentration of
-fluid present inside solutes. This will cause
of the cells and the cell to shrink. Water
considered sum will continue to flow
total of the fluid into the intravascular
volume in all of the space from the
body’s cells extracellular space if the
-separated from intravascular space still
ECF by plasma remains more
membrane concentrated than the
extracellular space.
Controlled by osmotic
pressure with Na/K
concentrations
b. Analyze the principles of fluid balance and describe the implications for clinical
practice.
Mechanisms of Fluid Definition Clinical Implications
Balance
Osmolality Measure of solute concentration May be altered by IVF
in a solution concentrations fluid shifts
Plasma osmolality normal
Is 280-295mmOskg Is preferred measure of osmotic
Low potentially 275 activity in clinical assessments.
Even though urea is a solute in the
Controls distribution and plasma it freely diffuses through
movement of water between the cell membranes and has no
body compartments. effect on osmolality, whereas
sodium and glucose are limited to
the extracellular space and greatly
contribute to the effective
osmolality.
Osmosis Movement of water between Hypertonic solutions can pull
compartments from an area of fluid into the intravascular
low concentration of solutes to space, while hypotonic
