Chapter 18 - Fluid, Electrolyte, and Acid-Base Balance

Abstract

The body fluids are arranged in dynamic but orderly functional compartments. Maintenance of these compartments in terms of volume and composition is essential for maintenance of normal physiologic and biochemical events. The electrolytes dissolved in the body fluids fulfill vital roles in virtually all of life's processes. Transmembrane movements of electrolytes are responsible for the electrical events that result in nerve conduction and muscular contraction and also serve as essential cofactors in many enzymatically mediated metabolic reactions. The pH of body fluids is maintained within narrow limits. This is necessary for the maintenance of protein structure and function, which is an essential condition for normal progression of metabolic events. Virtually every organ system participates in the maintenance of fluid balance and/or is adversely affected by imbalances. In many disease states, impaired fluid intake, excessive fluid losses, or organ damage and dysfunction results in a state of altered fluid and electrolyte balance. Regardless of whether fluid and electrolyte alterations are the primary problems or represent secondary manifestations of some other disease process, successful patient management depends on correct evaluation and appropriate therapy. To do this, one must have a clear understanding of the anatomy and physiology of the body fluids, the pathologic mechanisms by which normal processes become deranged, the means by which these disturbances can be identified accurately, and finally the procedures that can be used to correct such disturbances in a prompt, safe, and effective manner.