ABSTRACT
In this chapter, we review the physiology of fluid balance in the body. Electrolyte physiology, relevant investigations and management of electrolyte abnormalities are reviewed at the end of this chapter. To understand the fluid therapy we prescribe, it is necessary to know where the fluid goes, how it is distributed and what effects it has. To appreciate this, we need a good understanding of the different fluid compartments, how they are connected and what affects their composition (resulting in the clinical signs outlined in Chapter 1). To begin, we review the fluid composition of the human body. As this is a book about intravenous fluids (IVF), we also review currently used IVF, including their composition and most common uses. Water in the human body is intricately related to electrolytes and we cover the main electrolyte abnormalities, and their assessment, investigation and management. The end of this chapter contains a list of definitions of some essential concepts.
