Chapter 42: Fluid, Electrolyte, and Acid-Base Balance

Fluid, Electrolyte, and Acid-Base Balance review for Fundamentals of Nursing students explores the critical physiological mechanisms of fluid, electrolyte, and acid-base balance essential for maintaining homeostasis and optimizing cellular function. It begins by examining the distribution of body fluids across intracellular and extracellular compartments, detailing the movement of water and solutes through active transport, diffusion, osmosis, and filtration to maintain osmotic pressure. The summary explains the hormonal regulation of fluid intake and output, focusing on the roles of the thirst mechanism, antidiuretic hormone (ADH), the renin-angiotensin-aldosterone system (RAAS), and atrial natriuretic peptides (ANPs). Significant attention is given to distinguishing between extracellular fluid volume (ECV) imbalances, such as hypovolemia and hypervolemia, and osmolality imbalances like hypernatremia and hyponatremia, often described as clinical dehydration when combined. The text delves into electrolyte dynamics, analyzing the etiology, assessment findings, and nursing interventions for imbalances in potassium, calcium, magnesium, and phosphate, with a specific focus on life-threatening cardiac and neuromuscular complications. Acid-base homeostasis is broken down into acid production, buffering systems, and excretion by the lungs and kidneys, leading to an in-depth discussion of respiratory and metabolic acidosis and alkalosis, along with the interpretation of arterial blood gases (ABGs) and the anion gap. The nursing process is applied to fluid management, emphasizing assessment strategies like daily weights, intake and output (I&O) measurement, and physical examination of skin turgor and mucous membranes. Finally, the chapter covers the implementation of acute care interventions, including enteral replacement, fluid restrictions, and parenteral replacement via intravenous (IV) therapy. It details the management of vascular access devices (VADs), the selection of isotonic, hypotonic, and hypertonic crystalloids, and the prevention of IV complications such as infiltration, extravasation, phlebitis, and air embolisms, concluding with safety protocols for blood component therapy and the management of transfusion reactions.