Key result
Sympathetic activation and involuntary muscle contraction significantly reduced the drop in systolic BP upon standing (-20 to -28 mm Hg) compared to no intervention (-34 mm Hg).
Why the study?
Initial orthostatic hypotension occurs during active standing rather than passive tilt, but how sympathetic activation affects it had not been explored.
Do pre-standing maneuvers that induce sympathetic activation or involuntary muscle contraction reduce the drop in systolic blood pressure in female patients with initial orthostatic hypotension?
Do pre-standing maneuvers that induce sympathetic activation or involuntary muscle contraction reduce the drop in systolic blood pressure in female patients with initial orthostatic hypotension?
Absolute Event Rate: -26% vs -34%
p-value: p=0.004
Both sympathetic activation and involuntary muscle contraction prior to standing significantly mitigate the initial drop in systolic blood pressure in patients with initial orthostatic hypotension.
Background: Initial orthostatic hypotension (IOH) is defined by a large drop in blood pressure (BP) within 15 s of standing. IOH often presents during an active stand, but not with a passive tilt, suggesting that a muscle activation reflex involving lower body muscles plays an important role. To our knowledge, there is no literature exploring how sympathetic activation affects IOH. We hypothesized involuntary muscle contractions before standing would significantly reduce the drop in BP seen in IOH while increasing sympathetic activity would not. Methods: Study participants performed 4 sit-to-stand maneuvers including a mental stress test (serial 7 mental arithmetic stress test), cold pressor test, electrical stimulation, and no intervention. Continuous heart rate and beat-to-beat BP were measured. Cardiac output and systemic vascular resistance were estimated from these waveforms. Data are presented as mean±SD. Results: A total of 23 female IOH participants (31±8 years) completed the study. The drops in systolic BP following the serial 7 mental arithmetic stress test (−26±12 mm Hg; P =0.004), cold pressor test (−20±15 mm Hg; P <0.001), and electrical stimulation (−28±12 mm Hg; P =0.01) were significantly reduced compared with no intervention (−34±11 mm Hg). The drops in systemic vascular resistance following the serial 7 mental arithmetic stress test (−391±206 dyne×s/cm 5 ; P =0.006) and cold pressor test (−386±179 dyne×s/cm 5 ; P =0.011) were significantly reduced compared with no intervention (−488±173 dyne×s/cm 5 ). Cardiac output was significantly increased upon standing (7±2 L/min) compared with during the sit (6±1 L/min; P <0.001) for electrical stimulation. Conclusion: Sympathetic activation mitigates the BP response in IOH, while involuntary muscle contraction mitigates the BP response and reduces symptoms. Active muscle contractions may induce both of these mechanisms of action in their pretreatment of IOH. Registration: URL: https://www.clinicaltrials.gov ; Unique identifier: NCT03970551.
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A 2022 study studied Initial orthostatic hypotension (n=23). Mental stress test, cold pressor test, and electrical stimulation vs. No intervention was evaluated on Drop in systolic blood pressure following sit-to-stand maneuver (p=0.004). Sympathetic activation and involuntary muscle contraction significantly reduced the drop in systolic BP upon standing (-20 to -28 mm Hg) compared to no intervention (-34 mm Hg).
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