Week 10: Fluid and Electrolyte Management
1. Fluid Balance Overview
Water
o The primary component of body fluids (60% of adult weight)
o A medium for metabolic reactions within cells
o Insulates and help to regulate and maintain body temperature
(evaporation and perspiration)
o Transports nutrients and oxygen to cells and waste products from cells
o Constitutes about 60% of the adult body weight.
o Amount varies based on gender, age and amount of body fat (why is
this?)
Body Fluid Compartments
o Intracellular (fluid within a cell)
o Extracellular (fluid outside the cell)
o Intravascular fluid (in blood vessels in the form of plasma or serum)
o Interstitial fluid (fluid surrounding the cells)
Electrolytes: Chemical substances that develop an electric charge and can
conduct an electric current when placed in water; ions.
Cations: ions that carry a positive charge: sodium, potassium, calcium,
magnesium.
Anions: Ions that carry a negative charge: chloride, bicarbonate, phosphate,
sulphate
Solute: Substances dissolved in a liquid.
Solvent: The liquid in which solutes are dissolved.
Osmolality: The concentration of solutes in a solution
Hypertonic solution: Solutions that have a higher osmolality than body fluids: 3%
sodium chloride.
Hypotonic solution: Solutions that have a lower osmolality than body fluids;
0.45% sodium chloride.
Osmotic pressure: Power of a solution to pull water across a semipermeable
membrane.
Water and solutes move in the body through:
o Diffusion, osmosis, filtration, and active transport.
Electrolytes
o Are substances that dissociate in solution to form ions.
o The cations are positively charged (sodium Na+ and potassium K+).
o Anions are negatively charged
o Plays a role in enzyme reaction
o Essential to neuromuscular activity
o Help to regulate water and acid-base balance
o Measured in mmol/L
o Vital to many bodily functions
, Body Fluid Regulation
o Thirst (hypothalamic osmoreceptors): stimulates thirst and ADH –
o which ↑ reabsorption of water in the distal and collecting tubules.
o Thirst mechanism decreases in the elderly.
o Renal (regulate fluid volume and electrolyte balance)
o Cardiac (ANF – Atrial natriuretic factor (hormone released by cells in atria
in response
o Response to fluid overload)
o Inhibits renin secretion, and block aldosterone.
o Promote Na+ and water loss and cause vasodilation.
o GI System
o Insensible Water Loss (from skin, vaporization,
Electrolytes
o Maintain a balance between positive and negative charges (homeostasis)
o Concentration measured in milliequivalents per liter (mEq/L)
o They can move from one fluid compartment to another
o Sodium Na+ (most abundant electrolyte, found mainly in the extracellular
fluid 90%).
o Major role in body fluid regulation, nerve impulse conduction, and acid-
base balance.
o Potassium K+ is the major cation in intracellular fluid (98%). Helps to
maintain fluid osmolarity and volume within the cell.
o Essential for normal membrane excitability (nerve impulses)
o Needed for protein synthesis breakdown of glycogen
o Helps to maintain plasma acid-base balance
Fluid Regulation
Fluid Balance in the Older Adults
1. Fluid Balance Overview
Water
o The primary component of body fluids (60% of adult weight)
o A medium for metabolic reactions within cells
o Insulates and help to regulate and maintain body temperature
(evaporation and perspiration)
o Transports nutrients and oxygen to cells and waste products from cells
o Constitutes about 60% of the adult body weight.
o Amount varies based on gender, age and amount of body fat (why is
this?)
Body Fluid Compartments
o Intracellular (fluid within a cell)
o Extracellular (fluid outside the cell)
o Intravascular fluid (in blood vessels in the form of plasma or serum)
o Interstitial fluid (fluid surrounding the cells)
Electrolytes: Chemical substances that develop an electric charge and can
conduct an electric current when placed in water; ions.
Cations: ions that carry a positive charge: sodium, potassium, calcium,
magnesium.
Anions: Ions that carry a negative charge: chloride, bicarbonate, phosphate,
sulphate
Solute: Substances dissolved in a liquid.
Solvent: The liquid in which solutes are dissolved.
Osmolality: The concentration of solutes in a solution
Hypertonic solution: Solutions that have a higher osmolality than body fluids: 3%
sodium chloride.
Hypotonic solution: Solutions that have a lower osmolality than body fluids;
0.45% sodium chloride.
Osmotic pressure: Power of a solution to pull water across a semipermeable
membrane.
Water and solutes move in the body through:
o Diffusion, osmosis, filtration, and active transport.
Electrolytes
o Are substances that dissociate in solution to form ions.
o The cations are positively charged (sodium Na+ and potassium K+).
o Anions are negatively charged
o Plays a role in enzyme reaction
o Essential to neuromuscular activity
o Help to regulate water and acid-base balance
o Measured in mmol/L
o Vital to many bodily functions
, Body Fluid Regulation
o Thirst (hypothalamic osmoreceptors): stimulates thirst and ADH –
o which ↑ reabsorption of water in the distal and collecting tubules.
o Thirst mechanism decreases in the elderly.
o Renal (regulate fluid volume and electrolyte balance)
o Cardiac (ANF – Atrial natriuretic factor (hormone released by cells in atria
in response
o Response to fluid overload)
o Inhibits renin secretion, and block aldosterone.
o Promote Na+ and water loss and cause vasodilation.
o GI System
o Insensible Water Loss (from skin, vaporization,
Electrolytes
o Maintain a balance between positive and negative charges (homeostasis)
o Concentration measured in milliequivalents per liter (mEq/L)
o They can move from one fluid compartment to another
o Sodium Na+ (most abundant electrolyte, found mainly in the extracellular
fluid 90%).
o Major role in body fluid regulation, nerve impulse conduction, and acid-
base balance.
o Potassium K+ is the major cation in intracellular fluid (98%). Helps to
maintain fluid osmolarity and volume within the cell.
o Essential for normal membrane excitability (nerve impulses)
o Needed for protein synthesis breakdown of glycogen
o Helps to maintain plasma acid-base balance
Fluid Regulation
Fluid Balance in the Older Adults
