The use of postural vital signs in the assessment of fluid volume status.

Postural or orthostatic vital signs, although frequently used in many clinical settings to aid in the diagnosis of fluid volume disturbance, can be a source of confusion. Practitioners often have questions about how to perform the test and may be uncertain about what results mean in various clinical situations. Some of this confusion is reflected in the literature, where studies on normal orthostatic responses seem to contradict clinically used parameters of "normal," and where very few studies appear on evaluating unusual responses as indicators of patients' fluid volume status. A review of existing literature is presented, in which relevant data are reviewed in terms of their impact on the use of this clinical sign. Recommendations regarding the use of the orthostatic test are given.