Initial orthostatic hypotension
Initial orthostatic complaints originate from a transient rapid fall in arterial pressure occurring upon active standing. This fall in blood pressure is a physiological response (Sprangers et al., 1991). However, normally blood pressure does not drop for more than 40 mm Hg systolic and 20 mm Hg diastolic (See chapter Wieling & Karemaker). The onset of symptoms between 5-10 s and disappearance within 20 seconds after the onset of standing up is typical for this condition. The diagnosis can only be confirmed by a stand test with continuous beat-to-beat blood pressure monitoring (figs. 5 and 6)(Wieling et al., 2007). Because initial orthostatic hypotension is associated with ‘active’ arising (fig. 5), tilt testing (i.e. head up tilting) wil not reveal a diagnosis.
Epidemiology
Most teenagers and adolescents are familiar with a brief feeling of light-headedness and some visual blurring within a few seconds of standing up quickly (de Marées, 1976). Symptoms typically resolve spontaneously within 20 s. Such complaints are most common upon arising suddenly after prolonged supine rest or after arising from the squatted position (figs. 5 and 6) (Krediet, 2002;Wieling et al., 2007). In some the symptoms are severe and syncope may occur upon standing in otherwise healthy subjects (Wieling et al., 2007). In a study, performed in 2003, in 394 young adults (i.e. medical students) standing up was reported as the trigger for transient loss of consciousness in 8% (Ganzeboom et al., 2003).
Triggers
Rising from squatting encompasses a heavier orthostatic stress than rising from supine (SHARPEY-SCHAFER, 1956;Rossberg & Penaz, 1988). On average blood pressure in healthy young adults falls transiently by 60 mm Hg systolic and 40 mm Hg diastolic with a nadir about 7 s after rising (Rossberg & Penaz, 1988). Mild symptoms of transient light-headedness are often present. Rising from squatting is a recognized trigger for syncope in daily life (fig. 6). Arising after prolonged squatting during gardening and other house-hold activities is a common scenario (SHARPEY-SCHAFER, 1956).
Treatment
Treatment of initial orthostatic hypotension is symptomatic. The goal is to diminish the drop in blood pressure after standing up. A clear explanation of the underlying mechanism and avoidance of the main triggers (rapid rise) are the main treatment-options. A novel approach is training in blood pressure rising manoeuvres. Tensing of leg, abdominal and buttock muscles for 20-40 s at maximal voluntary force immediately after standing up may be an effective manoeuvre to decrease the fall in pressure (Krediet & Wieling, 2004). In addition volume-expansion can be applied by raising water- and salt-intake (Shichiri et al., 2002;Wieling et al., 2004a).