ABSTRACT
The human body is composed mostly of water, which accounts for up to 80% of the body weight of a preterm infant and 60% of the weight of an adult.1
The remaining fraction of weight comprises the structural components: protein, mineral, and fat.2 Body water, with its dissolved minerals and gases, is what Claude Bernard referred to in 1879 as a ‘bit of primeval sea within us all’.1 The precise maintenance of body fluids and their constitutions are critical to the normal function of the body.
