Pathophysiology
Clinical meaning
Intravenous (IV) fluid therapy is one of the most common interventions in clinical practice, used to restore and maintain fluid volume, correct electrolyte imbalances, deliver medications, and provide nutritional support. Understanding fluid physiology is essential for the practical nurse to administer IV fluids safely and monitor for complications. Total body water comprises approximately 60 percent of body weight in adult males and 50 percent in adult females, distributed between two major compartments: the intracellular fluid (ICF, approximately two-thirds of total body water) and the extracellular fluid (ECF, approximately one-third). The ECF is further divided into the intravascular compartment (plasma, approximately 25 percent of ECF) and the interstitial compartment (fluid between cells, approximately 75 percent of ECF). Fluid movement between compartments is governed by osmosis -- the movement of water across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration. Osmolarity measures the total concentration of solutes per liter of solution and determines how a fluid will affect cell size and fluid distribution when infused intravenously. Normal serum osmolarity ranges from 275 to...