Normvolumen

Normvolumen (also called normovolemia) is a medical term describing a physiologic state in which the circulating blood volume and the extracellular fluid volume are within normal reference ranges, supporting adequate tissue perfusion and stable blood pressure. In clinical practice, the term is often used to differentiate a fluid status that is neither hypovolemic nor hypervolemic from states of dehydration or edema. The normal volumes are commonly expressed relative to body weight; in healthy adults, blood volume is about 70 mL/kg, while total extracellular fluid accounts for roughly 14 L in a 70 kg person. These values vary with age, sex, body size, and health status.

Maintenance of normovolemia is achieved by integrated regulation of fluid intake, renal function, capillary dynamics, and neurohumoral systems, including the renin–angiotensin–aldosterone system, antidiuretic hormone, and natriuretic peptides. Clinically, assessment of normovolemia relies on a combination of signs, laboratory data, and functional tests. Indicators include stable blood pressure and heart rate, normal capillary refill, balanced hematocrit and serum electrolytes, and in critical care, dynamic measures such as response to fluid challenges or ultrasound–based estimates of venous return and venous capacitance. Direct methods such as indicator-dilution techniques can quantify blood volume, but are used selectively.

Normovolemia is the reference state against which hypovolemia (low volume) and hypervolemia (high volume) are diagnosed and treated, particularly in anesthesia, surgery, critical care, and fluid management. Related concepts include euvolemia, hypovolemia, and hypervolemia.