Department of Neuroanaesthesia, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.
The Copenhagen Muscle Research Centre, Department of Anaesthesia, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.
Acta Physiol (Oxf). 2017 Sep;221(1):74-80. doi: 10.1111/apha.12863. Epub 2017 Mar 22.
To evaluate whether muscle vasodilatation plays a role for hypotension developed during central hypovolaemia, muscle oxygenation (S O ) was examined during (pre)syncope induced by head-up tilt (HUT). Skin blood flow (SkBF) and oxygenation (S O ) were determined because evaluation of S O may be affected by superficial tissue oxygenation. Furthermore, we evaluated cerebral oxygenation (S O ) and middle cerebral artery mean blood flow velocity (MCAv ).
Twenty healthy male volunteers (median age 24 years; range 19-38) were subjected to passive 50° HUT for 1 h or until (pre)syncope. S O and S O (near-infrared spectroscopy), MCAv (transcranial Doppler) along with mean arterial pressure (MAP), heart rate (HR), stroke volume (SV), cardiac output (CO) and total peripheral resistance (TPR) (Modelflow ) were determined.
(Pre)syncopal symptoms appeared in 17 subjects after 11 min (median; range 2-34) accompanied by a decrease in MAP, SV, CO and TPR, while HR remained elevated. During (pre)syncope, S O decreased [73% (71-76; mean and 95% CI) to 68% (65-71), P < 0.0001] along with MCAv [40 (37-43) to 32 (29-35) cm s , P < 0.0001]. In contrast, S O increased [63 (56-69)% to 71% (65-78), P < 0.0001], while S O [64% (58-69) to 53% (47-58), P < 0.0001] and SkBF [71 (44-98) compared to a baseline of 99 (72-125) units, P = 0.020] were reduced.
We confirm that the decrease in MAP during HUT is associated with a reduction in indices of cerebral perfusion. (Pre)syncope was associated with an increase in S O despite reduced S O and SkBF, supporting that muscle vasodilation plays an important role in the circulatory events leading to hypotension during HUT.
评估在中枢性低血容量期间发生的低血压是否与肌肉血管舒张有关，通过头高位倾斜（HUT）诱导的晕厥（pre-syncope）期间检查肌肉氧合（S O ）。测定皮肤血流（SkBF）和氧合（S O ），因为 S O 的评估可能受到浅层组织氧合的影响。此外，我们评估了脑氧合（S O ）和大脑中动脉平均血流速度（MCAv ）。
20 名健康男性志愿者（中位年龄 24 岁；范围 19-38 岁）接受被动 50°HUT 1 小时或直至（pre-syncope）。使用近红外光谱法（NIRS）测定 S O 和 S O ，经颅多普勒超声（TCD）测定 MCAv ，同时测定平均动脉压（MAP）、心率（HR）、每搏量（SV）、心输出量（CO）和总外周阻力（TPR）（Modelflow ）。
17 名受试者在 11 分钟后出现（pre-syncope）症状（中位数；范围 2-34），伴有 MAP、SV、CO 和 TPR 下降，而 HR 仍然升高。在（pre-syncope）期间，S O 降低[73%（71-76）至 68%（65-71），P <0.0001]，同时 MCAv[40（37-43）至 32（29-35）cm/s，P <0.0001]。相比之下，S O 增加[63%（56-69）至 71%（65-78），P <0.0001]，而 S O [64%（58-69）至 53%（47-58），P <0.0001]和 SkBF[71（44-98）与基线 99（72-125）单位相比，P=0.020]降低。
我们证实 HUT 期间 MAP 的降低与脑灌注指数的降低有关。（pre-syncope）与 S O 增加有关，尽管 S O 和 SkBF 降低，但支持肌肉血管舒张在 HUT 期间导致低血压的循环事件中发挥重要作用。
