ABSTRACT
Fluid Compartments The water of the body is divided into intracellular, intravascular, and extravascular compartments (Figure 2-1).
Of these compartments, 40% of all water is intracellular whereas the remaining 20% (assuming the percentage of water as total body weight for an average male) is located outside cells.1 The extracellular compartment has two subdivisions: interstitial and intravascular (plasma). The interstitial compartment, the compartment containing fluid outside of cells and blood vessels, is also known as the third space. Fifteen percent of total body water is located in the interstitium. The intravascular compartment is essentially plasma and comprises the remaining 5% of the extracellular fluid.
