Simultaneous assessment of brain tissue oxygenation and cerebral perfusionduring orthostatic stress

Simultaneous registration of cerebral tissue oxygenation parameters obtaine d by near infrared spectroscopy (NIRS), intracranial blood flow velocity (C BFV) measured by transcranial Doppler sonography (TCD) and basic cardiovasc ular parameters was carried out during a passive 80 degrees head-up tilt ta ble test in 15 patients with a history of orthostatic syncope and 20 contro l subjects, In normals, the cardiovascular parameters showed a specific cou rse after changing to a vertical position: the heart rate increased, the me an arterial blood pressure remained unchanged, and the CBFV decreased. The NIRS mea surements showed an increase in deoxyhemoglobin (HHb) and a declin e in oxyhemoglobin (O(2)Hb) and the regional oxygen saturation (RSAT). Pati ents had a significantly more prominent decline in arterial blood pressure (p < 0.001), CBFV (p < 0.001) and RSAT (p = 0.04), Five patients experience d symptoms of (pre)syncope during the experiment, which were associated wit h a further sudden and marked (>10%) drop of O(2)Hb. The results indicate t hat the combination of TCD and NIPS increases the understanding of hemodyna mic and metabolic changes during orthostatic stress, which may lead to indi vidually suited therapeutic procedures. Copyright (C) 2000 S. Karger AG, Ba sel.