endocrine and metabolic disorders
Volume Depletion
Introduction
Volume depletion, or extracellular fluid (ECF) volume contraction, occurs as a result of loss of total body sodium. Causes include vomiting, excessive sweating, diarrhea, burns, diuretic use, and kidney failure. Clinical features include diminished skin turgor, dry mucous membranes, tachycardia, and orthostatic hypotension. Diagnosis is clinical. Treatment involves administration of sodium and water. (See also Water and Sodium Balance and Because water crosses plasma membranes in the body via passive osmosis, loss of the major extracellular cation (sodium) quickly results in water loss from the extracellular fluid (ECF) as well as from intracellular (ICF) spaces. In this way, sodium loss always causes water loss. However, depending on many factors, serum sodium concentration can be high, low, or normal in volume-depleted patients (despite the decreased total body sodium content). Total body sodium content and ECF volume are related to effective circulating volume. A large enough decrease in ECF causes a decrease in effective circulating volume, which in turn causes decreased organ perfusion and leads to clinical sequelae. Common causes of volume depletion are listed in the table Common Causes of Volume Depletion . 