volumedeficit

Volumedeficit, also referred to as volume deficit or hypovolemia, is a clinical condition characterized by a loss of circulating blood volume and extracellular fluid. It results from disproportionate losses of water and electrolytes or from shifts of fluid into third spaces, reducing preload and tissue perfusion.

Causes include gastrointestinal losses (vomiting, diarrhea, drainage), renal losses (diuretics, osmotic diuresis), cutaneous losses (sweating, burns), third-spacing from conditions such as pancreatitis or sepsis, and acute hemorrhage. Inadequate intake can worsen volume deficit, especially in the elderly or ill patients.

Pathophysiology centers on reduced venous return to the heart, leading to decreased stroke volume and cardiac output. Compensatory mechanisms include tachycardia, vasoconstriction, and activation of the renin-angiotensin-aldosterone system and antidiuretic hormone. Severe volume deficit can cause hypoperfusion, organ dysfunction, and shock.

Clinical features often include tachycardia, hypotension or orthostatic intolerance, cool clammy skin, dry mucous membranes, decreased skin turgor, decreased urine output, and altered mental status. Laboratory findings may show hemoconcentration (elevated hematocrit), an elevated BUN relative to creatinine, and electrolyte abnormalities depending on the losses.

Management relies on prompt assessment and fluid replacement. In adults, isotonic crystalloids (0.9% saline or lactated Ringer’s) are typically given as boluses (for example, 500–1000 mL) with reassessment after each dose. Severe or ongoing losses from trauma or bleeding may require blood products and hemodynamic support. Addressing the underlying cause and close monitoring of vitals and urine output are essential.

Volumedeficit differs from pure dehydration, which is predominantly a water deficit; many patients have overlapping features. See also hypovolemia, dehydration.