link rel="shortcut icon" type="image/x-icon" href="medrx-education.com/files/theme/favicon.ico"
Third spacing is the physiological phenomenon in which body fluids accumulate in the third space. In medicine, the term is most commonly used with regard to burns, but also can refer to ascites and pleural effusions.
With regard to severe burns, fluids may pool on the burn site (i.e. fluid lying outside of the interstitial tissue, exposed to evaporation) and cause depletion of the fluids in the first and second compartments. With pancreatitis or ileus, fluids may "leak out" into the peritoneal cavity, also causing depletion of the first and second compartments.
Patients who undergo long, difficult operations in large surgical fields can collect third-space fluids and become intravascularly depleted despite large volumes of intravenous fluid and blood replacement. Extensive tissue swelling occurs when the third space fills with excess fluid, known as edema. Third spacing conditions may include peritonitis, pyometritis, and pleural effusion.