When Blood Pressure Increases with Standing: Consensus Definition for Diagnosing Orthostatic Hypertension

Abstract

When changing from the supine to the standing position approximately 500–1000 ml blood is pooled below the diaphragm and hydrostatic pressure forces fluids from the intravascular to the interstitial compartment. These changes impose a major hemodynamic burden on the cardiovascular system. Baroreflex-mediated withdrawal of cardiac parasympathetic activity and sympathetic activation maintain standing blood pressure in healthy persons. Orthostatic hypotension occurs when these counterregulatory mechanisms fail. Conversely, some patients have a paradoxical increase in upright blood pressure to hypertensive levels, presumably due to sympathetic activation overshoot. This orthostatic hypertension is not a benign condition because it is associated with increased cardiovascular morbidity and mortality independently of traditional risk factors.Citation1,Citation2 Yet, there has not been a uniform definition of orthostatic hypertension and the entity is not covered in current hypertension guidelines. Because diagnostic criteria vary profoundly between studies, data on epidemiology, associated health risks, and management of orthostatic hypertension in the existing literature is difficult to interpret.