Fluid and Electrolytes Lecture

Instructor: Ms. Ashley Flack
Date: Summer 2026
Core Objectives: * Summarize the physiology of the various body systems involved in the maintenance of fluid and electrolyte balance. * Identify common occurring alterations in fluid and electrolyte balance and their related therapies. * Differentiate common assessment procedures used to examine fluid and electrolytes across the lifespan. * Describe diagnostic and laboratory tests to determine the individual’s fluid and electrolyte balance. * Explain management of fluid and electrolyte balance and prevention of imbalances. * Demonstrate the nursing process in providing culturally competent and caring interventions across the lifespan for individuals with common alterations in fluid and electrolyte imbalances. * Compare and contrast collaborative care for clients with alterations in fluid and electrolyte balance.

Composition and Vitality: * The human body is composed of fluid in many different forms. * Every type of body fluid contains electrolytes. * In the average adult, approximately $60\%$ of weight is water. * Water is considered vital to the maintenance of health and is essential for normal cellular functioning.

Extracellular Fluids (ECF): * Defined as fluid located outside of the cell. * Represents approximately $1/3$ of the total body fluid. * The ECF is further divided into two sub-compartments: * Intravascular Fluid: Often referred to as plasma. * Interstitial Fluid: The fluid surrounding the cells.
Intracellular Fluids (ICF): * Defined as fluid located inside the cell. * Represents approximately $2/3$ of the total body fluid.

Diffusion: * The process by which molecules move through a semipermeable membrane from an area of higher concentration to an area of lower concentration. * The rate at which diffusion occurs varies based on three primary factors: * The size of the molecules involved. * The concentration of the solution. * The temperature of the solution.
Osmosis: * The movement of water across cell membranes from areas of less concentration (of solutes) to areas of higher concentration. * Solutes naturally seek to equalize their concentration on both sides of the membrane. * Osmolality: This term refers to the specific concentration of solutes within body fluids.
Filtration: * The movement of fluid through a cell or blood vessel membrane resulting from hydrostatic pressure differences on either side of the membrane. * Hydrostatic Pressure: Defined as the force exerted by fluid in a specific compartment as it pushes against a cell membrane or a vessel wall.
Active Transport: * The movement of substances across cell membranes from areas of less concentration to areas of higher concentration. * Unlike passive processes, active transport requires an outside energy source to move substances against their concentration gradient.

Fluid Regulation: * Regulation is critical for maintaining homeostasis within the body. * Body fluids are primarily regulated through two mechanisms: * Fluid intake. * Fluid output.
Electrolyte Regulation: * Electrolytes are present in all body fluids and all fluid compartments. * Electrolytes are essential for the following physiological functions: * The maintenance of overall fluid balance. * Acid-base regulation ( $pH$ balance). * Facilitating the movement of nutrients into the cells. * Facilitating the movement of wastes out of the cells. * The transmission of neuromuscular reactions.

Nursing History and Observation: * Review of Past Medical History (PMH). * Review of current medications and treatments. * Monitoring of intake and output ( $I+O$ ). * Observation for signs and symptoms ( $s/s$ ) of electrolyte imbalances.
Physical Examination: * Assessment of specific body systems: Skin, oral mucosa, cardiovascular system, respiratory system, neurologic system, and muscular system. * Monitoring of daily weights. * Monitoring of vital signs. * Ongoing monitoring of $I+O$ .
Diagnostic and Laboratory Tests: * Serum electrolyte levels. * Complete Blood Count (CBC), with a specific focus on Hematocrit ( $hct$ ). * Osmolality tests for both serum and urine. * Urine specific gravity.

All fluids within the human body contain electrolytes.
Fluids and electrolytes are dynamic, shifting from the Extracellular Fluid (ECF) to the Intracellular Fluid (ICF) and vice versa.
The body possesses sensory mechanisms to detect when fluids or electrolytes are imbalanced.
The body will perpetually work to maintain homeostasis and correct any existing imbalances.