Insight into the normal distribution of water and electrolytes in the unstressed state is
necessary for an understanding of disordered fluid and electrolyte balance in the critically
ill patient. The distribution of the extracellular fluid (ECF) and intracellular fluid (ICF)
spaces in the normal state is described by the Yannet-Darrow diagram, as is the
normal electrolyte distribution of the plasma and ICF (Fig. 1). Normal fluid homeostasis
Figure 1 Yannet-Darrow diagram of distribution of ECF and ICF volumes in the normal state. Values are for a 70 kg person with 60% water content.