Chapter 30: Fluids & Electrolytes – Balance & Replacement Therapy

Fluids & Electrolytes – Balance & Replacement Therapy on fluid and electrolyte management outlines the vital physiological principles governing total body water (TBW) distribution into intracellular fluid (ICF) and extracellular fluid (ECF), which includes intravascular fluid (IVF or plasma) and interstitial fluid (ISF). Key concepts such as osmolality, tonicity (isotonic, hypotonic, hypertonic), hydrostatic pressure (HP), and colloid oncotic pressure (COP) are explained as they regulate water movement across compartments. Pharmacological interventions are categorized into three main groups used to treat deficits and excesses: Crystalloids (like normal saline), which replace water and sodium and are preferred for dehydration; Colloids (such as albumin and dextran), which are protein substances that increase COP to draw fluid into the blood vessels, acting as plasma expanders; and Blood Products (like packed red blood cells and fresh frozen plasma), used for substantial blood volume loss, offering both plasma expansion and oxygen-carrying capacity. The text details major electrolyte roles, focusing on sodium (the principal ECF cation) and potassium (the principal ICF cation), and discusses the clinical presentations and treatments for imbalances like hypernatremia, hyponatremia (sometimes treated with agents like tolvaptan), hyperkalemia, and hypokalemia (often managed with potassium supplementation or sodium polystyrene sulfonate). Finally, the nursing process is applied, emphasizing critical assessments of fluid status, laboratory values, vital signs, and safety protocols for administering high-alert medications like IV potassium (which must always be diluted and given via a controlled infusion pump) and blood products.