FLUIDS AND ELECTROLYTES
Composition of Body Fluids
● Electrolyte - an element or compound that when melted or dissolved dissociates into
ions and is able to carry an electric current.
○ Vital Function - neuromuscular function and acid-base balance.
● Minerals - ingested as compounds; important in maintaining physiological processes,
inorganic compounds that yield no energy. Also acts as catalysts in nerve response,
muscle contraction, and metabolism of nutrients in food.
● WBC/RBC
Movement of Body Fluids
● Purpose:
○ Tissue Oxygenation
○ Acid-Base Disturbances
○ Response to Illness
○ Response to Drug Therapies
● Solute - solid particle.
● Solvent - universal solvent is water.
● Diffusion - a process in which solid, particulate matter in a fluid moves from an area
of higher concentration to area of decreased concentration.
● Osmosis - movement of pure solvent from a solution that has solute decreased
concentration to increased concentration.
○ Osmotic Pressure - the pressure exerted on the semi-permeable membrane.
○ Osmolality - osmols or mOsm/kg of water.
○ Osmolarity - osmols or mOsm/kg of solution. Base is water or solution.
■ Normal Osmolality - 280 to 295 mOsm/kg
● Isotonic - equal pressure, no movement of water. Used for maintenance purposes.
○ PNSS
○ D5W
○ LR
○ Normosol - R
● Hypotonic - water moves inside cell due to lower concentration, cell swells.
○ .45% NaCl
○ .3% NaCl
● Hypertonic - water moves outside cell, cell shrinks.
○ D5 Saline Solution
○ D10 Saline Solution
● Oncotic Pressure - pressure exerted by plasma proteins.
● Filtration - process by which water and diffusible substance move together in
response to fluid pressure.
● Hydrostatic Pressure - pressure exerted by a liquid.
● Active Transport - movement of materials across the cell membrane by chemical
activity or energy expenditure.
Regulation of Body Fluids
● Fluid Intake - regulated primarily through thirst mechanism.
○ Thirst Control Center
Carl G. Villarant
