Diagnosis of Central Hypovolemia in a Spontaneously Breathing Patient

Volemia is the total blood volume of the body (plasma and cells) and is normally situated in the range of 65 to 75 ml/kg. Hypovolemia is a very frequent clinical situation in intensive care. Two types of hypovolemia are distinguished: Absolute and relative hypovolemia. Absolute hypovolemia is defined as a reduction in total circulating blood volume [1, 2], which may be related to blood loss (hemorrhage) or plasma loss (gastrointestinal, renal, cutaneous, extravasation into interstitial tissues). Relative hypovolemia is defined as an inadequate distribution of blood volume between the central and peripheral compartments (venodilatation or during positive pressure ventilation).