2025 Volume 62 Issue 1 Pages 26-31
Instantaneous orthostatic hypotension (INOH), a subtype of orthostatic dysregulation, is defined as recovery time of blood pressure of more than 25 seconds, or that for more than 20 seconds with a 60% or greater decrease in mean arterial pressure after standing during an orthostatic standing test. To better understand the pathophysiology of INOH, the recovery time of the total peripheral vascular resistance (TPR) while standing was measured. The study included 121 patients aged 7–17 years who were diagnosed with INOH based on active orthostatic standing test from 2019 to 2023. Blood pressure, heart rate, and TPR were measured using a continuous sphygmomanometer (Finapress). Recovery time was defined as the time taken for the mean arterial pressure (MAP) and TPR values to return to the values recorded before standing. The TPR recovery time was longer than the MAP recovery time in 34 patients (28%), shorter in 60 patients (50%), and same in 27 patients (22%). When the TPR recovery time is longer than the MAP recovery time, peripheral blood flow increases; when it is shorter than the MAP recovery time, peripheral blood flow decreases. It is suggested that INOH exhibits distinct pathophysiological conditions in terms of blood flow and vascular resistance.
