Fluid Physiology Part 2: Regulation of Body Fluids and the Distribution of Infusion Fluids

The regulation of body fluids and infusion fluid distribution is a critical aspect of intensive care management. In this chapter, we explore the various control systems that maintain fluid balance in the body, including the kidneys, nervous system, and hormones. We also discuss the impact of disease and medical treatments on these control systems and the resulting fluid derangements, such as hypovolemia, volume depletion, and dehydration. The use of infusion fluids to distribute into the different body fluid spaces is analyzed, including the plasma, extracellular fluid, and total body water. Hemodynamic responses and signs of organ dysfunction are the main clinical guides for fluid management, while electrolyte disturbances induced by disease and medication are also discussed. Volume kinetic analysis is utilized to compare the efficacy of crystalloid and colloid solutions, and the limitations of body fluid volume measurements are also examined. This chapter provides essential insights for intensivists and other medical professionals involved in the management of critically ill patients.