Purpose

To determine if the menstrual cycle and oral contraceptives (OC) influence responses to acute orthostatic stress and if these factors are clinically relevant to the diagnosis of initial orthostatic hypotension (iOH).

Methods

Young, healthy women were recruited, including OC users (n = 12) and non-users (NOC; n = 9). Women were tested during the low hormone (LH; placebo pills; days 2–5 natural cycle) and high hormone (HH; active dose; days 18–24 natural cycle) menstrual phases. Changes in mean arterial pressure, cardiac output, heart rate, the 30:15 heart rate ratio and cerebrovascular resistance indices within 30 s of standing were examined.

Results

There were no effects of OC or menstrual cycle on hemodynamic responses during standing (all p>0.05). In the LH phase, OC users had a greater fall in mean middle cerebral artery blood velocity (MCA_V) compared to NOC (p<0.05). However, this was reversed in the HH phase, where OC users had a reduced fall in mean MCA_V (p<0.05). Interestingly, 8 women (OC and NOC) had drops in systolic/diastolic blood pressure meeting the criteria for iOH, and 7 of those 8 women displayed this drop in a single phase of the menstrual cycle.

Conclusion

Our results indicate that chronic versus acute OC use (i.e., long-term use observed via LH phase versus short-term use observed via HH phase) have opposing effects on cerebral blood velocity during standing. Further, our results highlight that multiple assessments across the cycle may be necessary to accurately diagnose iOH, as most women met the diagnostic criteria during a single menstrual phase.

中文翻译：

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口服避孕药的使用和月经周期影响对站立的急性脑血管反应

目的

确定月经周期和口服避孕药 (OC) 是否影响对急性体位性应激的反应，以及这些因素是否与初始体位性低血压 (iOH) 的诊断具有临床相关性。

方法

招募了年轻、健康的女性，包括 OC 使用者 (n = 12) 和非使用者 (NOC；n = 9)。在低激素（LH；安慰剂药丸；第 2-5 天自然周期）和高激素（HH；活性剂量；第 18-24 天自然周期）月经期对女性进行测试。检查站立30秒内平均动脉压、心输出量、心率、30:15心率比和脑血管阻力指数的变化。

结果

OC 或月经周期对站立期间的血液动力学反应没有影响（所有 p > 0.05）。在 LH 阶段，与 NOC 相比，OC 使用者的平均大脑中动脉血流速度 (MCA _{V ) 下降幅度更大 (p<0.05)。然而，这在 HH 阶段是相反的，其中 OC 用户的平均 MCA V}下降减少(p<0.05)。有趣的是，8 名女性（OC 和 NOC）的收缩压/舒张压下降符合 iOH 标准，这 8 名女性中有 7 名在月经周期的一个阶段出现这种下降。

结论

我们的结果表明，慢性与急性 OC 使用（即，通过 LH 期观察到的长期使用与通过 HH 期观察到的短期使用）对站立期间的脑血流速度具有相反的影响。此外，我们的结果强调，可能需要跨周期进行多次评估才能准确诊断 iOH，因为大多数女性在一次月经期就符合诊断标准。