1. ICF – Intracellular Fluid
About 2/3 by volume. This is the fluid within the cells. It provides nutrients for metabolism because it is high in Potassium, Phosphate, and protein; and moderate levels of Magnesium and Sulfate. It also assists in cellular metabolism.
2. ECF – Extracellular fluid
ECF is comprised by three major components:
a. Intravascular – Plasma (the fluid portion of blood)
b. Interstitial – Fluid in and around the tissues
c. Transcellular – Over and across the cells found in cerebrospinal fluid, eye humors, synovial fluid, serous fluid, and gastrointestinal secretions.
Regulations of Fluid in Compartments:
1. Osmosis – Movement of water through a selectively permeable membrane from an area of low solute concentration to a higher concentration until equilibrium occurs.
2. Diffusion – Movement of solutes from an area of a higher concentration to an area of lower concentration in a solution and/or across a permeable membrane.
3. Active Transport – Allows molecules to move against concentration and osmotic pressure to areas of higher concentration
Osmolality – the concentration of body fluids which reflects hydration status. It is measured by urine and serum.
Normal serum value: 280- 300 mOsm/kg *<240 and >320 is critically abnormal
Serum Osml/L =(serum Na x 2) + BUN/3 + Glucose/18