Table 3 Clinical terminology

Fluid bolus

The rapid administration of intravenous fluid with therapeutic intent, most often to rapidly replace intravascular volume in patients who are presumed to be fluid responsive.

Fluid challenge

The rapid administration of intravenous fluid with diagnostic intent, most often to determine whether a patient with hemodynamic compromise will benefit from further fluid administration.

Fluid overload (overhydration)

Increased total body fluid volume (intravascular, interstitial, and intracellular). Fluid overload may be defined by at least 10% increase in total body fluid volume. Sometimes referred to as “overhydration” or “hyperhydration.” Fluid overload is the opposite of dehydration.

Fluid underload (dehydrataion)

Decreased total body fluid volume. The percentage of fluid loss is defined by dividing the cumulative fluid balance in liters by the patient’s baseline body weight and multiplying by 100%. Dehydration is defined by a minimum value of 5% fluid loss. Dehydration is considered mild (5-7.5%), moderate (7.5-10%), while loss of over 10% is considered severe. Sometimes referred to as “fluid underload.” Dehydration is the opposite of fluid overload.

Fluid responsiveness

An increase in stroke volume in response to an increase in intravascular volume. Also referred to as “volume responsiveness.”

Hypovolemia

Reduced intravascular volume and marked by increases in stroke volume when intravenous fluid is given (i.e., the state of being fluid responsive). Clinical “hypovolemia” may exist, for example, from loss of intravascular volume (e.g., hemorrhage) or from reductions in intravascular volume due to increases in venous capacitance. Sometimes referred to as “fluid underload.”

Hypervolemia

Hypervolemia is above normal or increased intravascular volume. Hypervolemia is the opposite of hypovolemia.

Passive leg raise

A diagnostic postural maneuver raising the lower extremities up to 45 degrees from the recumbent position, to transiently increase venous return from the lower extremities in order to measure the hemodynamic effect and thus determine if a patient is fluid responsive.